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A guide to ISO 2768, the standard that sets default permissible deviations for dimensions that carry no individual tolerance.

ISO 2768 General Tolerances: Tables, Classes, Current Status

<h3>Key Takeaways</h3><ul><li>The surface texture symbol has three forms: plain means any process is permitted, a bar across the “V” means material shall be removed, a circle means material removal is not permitted.[1]</li><li>ISO 1302:2002 has been withdrawn, and ISO 21920-1:2021 is its replacement.[1][2]</li><li>The current symbol carries a bar above it. ISO 21920-1 added that bar specifically to distinguish its symbols from the ISO 1302 ones, so the bar tells you which rulebook applies.[1]</li><li>Newer and older drawings place important information in differing locations around the symbol.</li></ul><h2>Introduction</h2>A surface finish symbol or surface roughness symbol tells the machinist which process is allowed, how rough the surface may be, which way the tool marks should run, and how much stock to leave for a later operation.This guide covers the symbol seen on engineering drawings: the current ISO form, the ISO 1302 form that a large share of drawings in service were drawn to, older styles you will find on legacy drawings, and the North American ASME form. It focuses on reading and writing the callout. For the Ra numbers themselves, see the companion <a href="https://www.wevolver.com/article/surface-finish-chart-ra-rq-and-n-grade-conversions" target="_blank">surface roughness chart</a>, and for how the surface roughness values are captured, see the <a href="https://www.wevolver.com/article/measuring-surface-roughness-a-comprehensive-guide" target="_blank">measuring surface roughness guide</a>.<h2>The Surface Texture Symbol and Its Three Forms</h2><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1791407006426-Main+image.png" style="width:100%px" class="fr-fic fr-dib" alt="Surface finish symbols old and new" />The surface finish symbol comes in three main variantsThe basic graphical symbol is two straight lines of unequal length, inclined at approximately 60° to the line representing the surface being specified.[1] It looks like an elongated check mark or square-root sign.Adding a bar across the “V” of the symbol means material removal is required; adding a circle means material removal is not permitted.[1] Those two marks change what the shop is allowed to do.<div><table><tbody><tr><td>Form</td><td>Meaning</td><td>Text abbreviation</td><td>What the shop may do</td></tr><tr><td>Plain symbol</td><td>Any manufacturing process permitted</td><td>APA (any process allowed)</td><td>Machining or non-machining, the shop chooses</td></tr><tr><td>Symbol with a bar across the V</td><td>Material shall be removed</td><td>MRR (material removal required)</td><td>Must machine, grind, hone or otherwise cut the surface</td></tr><tr><td>Symbol with a circle in the V</td><td>Material removal is not permitted</td><td>NMR (no material removed)</td><td>Must leave the as-formed surface: cast, forged, rolled, injection molded</td></tr></tbody></table></div>The three-letter abbreviations exist for written text such as reports and contracts, where you cannot draw the symbol.[1]To carry any complementary requirement, a horizontal line is added to the longer arm of the symbol.[1] A circle over the kink of the complete symbol (where the top right of the “V” meets the horizontal line) means the requirement applies to all surfaces around the workpiece outline shown on that view.[2] But this is no longer used in the latest ISO standard.[1]A surface texture requirement is indicated only once for a given surface, and where possible on the same view that carries the size or location dimensions and their tolerances. The symbol must touch the surface or connect to it by a reference line and leader terminating in an arrowhead, pointing at the surface from outside the material.[1]<h2>What Each Value Around the Symbol Means</h2>This is the part engineers get wrong most often, because the values included on the surface finish callout (and their position) depend on the surface finish standard being used.<h3>ISO 21920-1</h3><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1791407061637-New+ISO+example.png" style="width:100%px" class="fr-fic fr-dib" alt="An example ISO 2190-1 surface texture callout" />A callout for Ra 2 roughness with perpendicular lay to be achieved by grinding; material removal is requiredThe current ISO standard for surface finish specifications requires, at a minimum, the graphical symbol described above in one of its three forms, a symbol to indicate the parameter being used (Ra, Rz, etc.), and a numerical value.[1] Everything else is optional and defaults if omitted.Information on the callout can include:[1]<ul><li>Manufacturing process (above the horizontal line, to the left)</li><li>Lay (above the horizontal line, to the right)</li><li>The R-parameter and its specified value (below the horizontal line)</li><li>Various optional modifiers relating to the R-parameter (below the horizontal line)</li><li>Profile direction relative to surface lay (to the right of the “V” of the symbol)</li></ul>For an evaluation-length R-parameter such as Ra, the (optional) elements must be placed in a specific syntactical order, namely: tolerance type, parameter symbol, tolerance limit value, tolerance acceptance rule, S-filter type and nesting index, L-filter type and nesting index, evaluation length, F-operator association method and nesting index, method of profile extraction, an other-requirements placeholder, manufacturing process, surface lay and direction of lay, and profile direction relative to the lay.[1]A minimal indication is just the symbol, the parameter and the limit, and ISO notes that the complete indication “might be rarely used in practice.”[1] Parameters with defined defaults include Rz, Ra, Rp, Rv, Rq, Rmax, Rt, and Pt.[1]Recommended reading: <a href="https://www.wevolver.com/article/surface-finish-standards" target="_blank">Surface Finish: Parameters, Standards, and How to Specify It</a><h3>ISO 1302</h3><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1791407228917-Old+ISO+examples.png" style="width:100%px" class="fr-fic fr-dib" alt="Old ISO surface texture symbols" />Three no-longer-current callouts: multidirectional lay, all-surface application, and machining allowance of 3 mm Under ISO 1302:2002, the final version of the old standard, some values are found in different places. And since ISO 1302 was only replaced in 2021, drawings with ISO 1302 are still very common.As with the current ISO standard, the R-parameter and its value is found under the horizontal line and the manufacturing process (if specified) is found above the line.[2]But differences include:[2]<ul><li>Lay (to the right of the “V”)</li><li>Machining allowance (to the left of the “V”)</li><li>Circle symbol indicating that the requirement applies to all surfaces around the workpiece outline shown on that view (where the “V” meets the horizontal line)</li></ul><h2>Historical ISO standards</h2><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1791407616438-Historical+ISO+examples.png" style="width:100%px" class="fr-fic fr-dib" alt="Historical surface finish symbols " />Older drawings may put the Ra value or an obsolete N-grade directly above the V of the symbolSurface finishing as a serious engineering practice has existed for almost a century, and common surface symbols entered usage in the 1960s.[3]Drawings outlive standards. On older drawings, the roughness is often given as a roughness grade number rather than an explicit Ra value, a convention that goes back to the 1971 ISO recommendation and its table of grade numbers.[4] Those grade numbers are mapped to Ra values in our <a href="https://www.wevolver.com/article/surface-finish-chart-ra-rq-and-n-grade-conversions" target="_blank">surface roughness chart</a>.The 1971 recommendation that preceded ISO 1302 already used the same basic check mark, the same bar for material removal required and the same circle for material removal not permitted.[4]However, between 1971 and 1992, values were found in different locations around the symbol,[2] notably:<ul><li>The R-parameter and its specified value (directly above the “V”, defined as “position x” in old standards)</li></ul>Recommended reading: <a href="https://www.wevolver.com/article/surface-finish-chart-ra-rq-and-n-grade-conversions" target="_blank">Surface Finish Chart: Ra, Rq, and N-Grade Conversions</a><h3>ASME Y14.36</h3>North American engineering drawings follow the American Society of Mechanical Engineers rather than ISO. The relevant standard is ASME Y14.36M, currently in its 2018 edition, reaffirmed in 2024.[5]Differences between the ISO and ASME standards are fairly minor. Callouts following ASME Y14.36 closely resemble those following the withdrawn ISO 1302.Notable placements include:[5]<ul><li>Lay (to the right of the “V”)</li><li>All-around modifier: Circle symbol indicating that the requirement applies to all surfaces around the workpiece outline shown on that view (where the “V” meets the horizontal line)</li><li>All-over modifier: Variant of the above, two concentric circles indicating that the requirement applies to all surfaces of the part (where the “V” meets the horizontal line)</li></ul>American drawings also commonly work in microinches where ISO drawings work in micrometers; ASME allows either.[5]<h2>Lay Direction Symbols in Full</h2>Lay is the predominant direction of the surface pattern, ordinarily determined by the production method used.[6] It is the direction of the tool marks, and it is specified separately from any roughness value because two surfaces with an identical Ra value can behave completely differently depending on which way the grooves run.That matters most on seals, bearings, and sliding contacts, where the grooves either guide fluid along the joint or across it. On a honed cylinder bore, the crosshatch pattern is specified as lay because the direction of the marks does work that no single roughness value can describe.ISO and ASME standards use equivalent lay symbols. However, the current ISO standard defines the first three according to an intersection plane indicator and datum feature indicator in the top right of the callout, whereas older ISO standards and ASME define them by the plane of projection.[1][5]The mapping below is taken directly from the current ISO standard.[1]<div><table><tbody><tr><td>Symbol</td><td>Meaning</td><td>Typical process</td></tr><tr><td>=</td><td>Parallel to direction</td><td>Shaping, planing, some milling</td></tr><tr><td>⊥</td><td>Perpendicular to direction</td><td>Shaping, planing across the view</td></tr><tr><td>X</td><td>Crossed in two oblique directions relative to the direction</td><td>Honing, crosshatched bores</td></tr><tr><td>M</td><td>Multidirectional</td><td>Lapping, blasting, polishing, superfinishing</td></tr><tr><td>C</td><td>Approximately circular relative to the centre of the surface to which the symbol applies</td><td>Facing and turning on a lathe</td></tr><tr><td>R</td><td>Approximately radial relative to the centre of the surface to which the symbol applies</td><td>Some grinding and facing operations</td></tr><tr><td>P</td><td>Lay is particulate, non-directional, or protuberant</td><td>Powder coating, electro-deposited and sprayed finishes</td></tr></tbody></table></div><h2>ISO Standard Changes</h2>ISO 1302:2002 has been withdrawn and replaced by ISO 21920-1, whose first edition is dated 2021-12.[1] The new standard sits in a three-part series: Part 1 covers indication on drawings, Part 2 covers terms, definitions, and parameters, and Part 3 covers specification operators.[1] Note that ISO 21920-1 is already at stage 90.92, “International Standard to be revised.”[1]Some changes from the old to the new ISO standard have already been discussed, such as the removal of the machining allowance value and the all-surfaces application symbol. Below are three other notable changes in the new standard:<h3>1. Bar above symbol</h3>ISO 21920-1’s graphical symbols carry a horizontal bar above the main symbol: “The bar above the symbol is to distinguish this symbol from the ones used in ISO 1302 and those used for indication of areal surface texture specifications.”[1]The bar is a version stamp. So if the symbol has it, you can read the callout under ISO 21920-1 rules; if it does not, it should be read under ISO 1302 rules or whatever other standard has been specified.The three forms themselves are unchanged in meaning: any manufacturing process permitted, material shall be removed, material removal is not permitted.[1]<h3>2. New default acceptance rule </h3>Under ISO 1302, a limit with no rule stated meant the 16% rule, the ISO 4288 default, which allows at most 16% of measured values to violate the limit.[1][2]Under ISO 21920-1, the default is the maximum tolerance acceptance rule, which “does not allow any measured value to exceed the tolerance limit” and which is “the default case and valid with or without indication of the Tmax symbol.”[1]The same drawing value, unchanged, is harder to pass under the new default. A third option now exists too: the median rule, where the median of all measured values must meet the limit, using at least three measurements.[1]<h3>3. Element set syntax expansion</h3>ISO 21920-1 replaced the “a-to-e” scheme (where five letters were used to specify where values should appear on a callout) with a longer, ordered specification string. For an evaluation-length R-parameter such as Ra, the elements run: tolerance type, parameter symbol, tolerance limit value, tolerance acceptance rule, S-filter type and nesting index, L-filter type and nesting index, evaluation length, F-operator association method and nesting index, method of profile extraction, an other-requirements placeholder, manufacturing process, surface lay and direction of lay, and profile direction relative to the lay.[1]<h2>Conclusion</h2>Surface finish symbols are a compact, positional language, and almost all the difficulty is in the positions rather than the values. Learn the three symbol forms, learn what sits at each position, and learn the seven lay symbols, and you can read any surface texture symbol you meet.Remember that ISO 1302 is withdrawn, ISO 21920-1:2021 replaced it, and the replacement changed both the appearance of the symbol, by adding a bar above it, and the meaning of a bare limit, by making the maximum rule the default.[1][2] However, drawings drawn to ISO 1302 will stay in service for years yet, so you need to read both schemes, and the bar is how you tell them apart.When you write a callout, specify the parameter, the limit, the cutoff, and the lay where it matters, and leave everything else to defaults. When you read one, check the bar first.<h2>Frequently Asked Questions</h2>What are surface finish symbols?They are standardized graphical symbols used on technical drawings to specify the required texture of a surface profile.What does a bar or a circle on the symbol mean?A bar added to the basic symbol means material shall be removed, so the surface must be machined. A circle means material removal is not permitted, so the surface must be left as cast, forged, rolled or molded. A plain symbol means any manufacturing process is permitted.What does 32 surface finish mean?On a North American drawing a bare 32 surface geometry is conventionally read as Ra 32 µin, because American drawings commonly work in microinches.How do you specify surface finish on a drawing?Draw the appropriate symbol form, add the horizontal extension line, then place the parameter designation and its limit value below the extension line.Is ISO 1302 still current?No. ISO lists ISO 1302:2002 as withdrawn at stage 95.99 and names ISO 21920-1:2021 as its replacement.[1] You still need to be able to read ISO 1302 callouts, because many drawings in service predate the change and will not be redrawn.What is the difference between ISO and ASME surface finish symbols?The symbol shape is shared, but value positions and units differ, as described above.What do the lay symbols mean?There are seven: = for parallel, ⊥ for perpendicular, X for crossed, M for multi-directional, C for approximately circular, R for approximately radial, and P for particulate, non-directional or protuberant lay.<h2>References</h2>[1] International Organization for Standardization. <a href="https://www.iso.org/standard/72196.html" target="_blank">ISO 21920-1:2021. Geometrical product specifications (GPS) — Surface texture: Profile — Part 1: Indication of surface texture</a>. Geneva: ISO; 2021.[2] International Organization for Standardization. <a href="https://www.iso.org/standard/28089.html" target="_blank">ISO 1302:2002. Geometrical Product Specifications (GPS) — Indication of surface texture in technical product documentation</a>. Geneva: ISO; 2002. Withdrawn 2021.[3] Nugent P. <a href="https://www.qualitymag.com/articles/87804-50-years-of-quality-a-superficial-history-of-surface-finish" target="_blank">50 Years of Quality: A Superficial History of Surface Finish</a> [Internet]. Quality Magazine. 2011 Apr 1 [cited 2026 Oct 7].[4] International Organization for Standardization. ISO/R 1302:1971. Technical drawings — Method of indicating surface texture on drawings. Geneva: ISO; 1971. Withdrawn 1976.[5] American Society of Mechanical Engineers. <a href="https://www.asme.org/codes-standards/find-codes-standards/y14-36-surface-texture-symbols" target="_blank">ASME Y14.36-2018 (R2024). Surface Texture Symbols</a>. New York: ASME; 2018.[6] American Society of Mechanical Engineers. <a href="https://www.asme.org/codes-standards/find-codes-standards/b46-1-surface-texture/2019/pdf" target="_blank">ASME B46.1-2019. Surface Texture (Surface Roughness, Waviness, and Lay)</a>. New York: ASME; 2019.

Precise surface finishing requires precise notation

Surface finish symbols express a parameter, a limit, a process, and a lay direction in a callout the size of a check mark.

Surface Finish Symbols: How to Read a Drawing Callout

<h2>Key Takeaways</h2><ul><li>The surface finish chart below converts between Ra in micrometers, Ra in microinches, and ISO N-grades.</li><li>For most machined surfaces, Rq (RMS) is about 11% higher than the Ra value, but you cannot obtain an accurate Rq from Ra alone.</li><li>N-grades come from ISO 1302, which ISO records as withdrawn and replaced by ISO 21920-1:2021. But they still appear on drawings, so you still need to read them.</li></ul><h2>The Surface Finish Chart</h2>This is the core conversion table, with the first three columns taken directly from ISO 1302.[1] Ra is the reference column, because every other unit here is derived from it or maps onto it.<div><table><tbody><tr><td>N-grade</td><td>Ra (µm)</td><td>Ra (µin)</td><td>Typical Rq/RMS (µin)</td><td>Notes</td></tr><tr><td>N1</td><td>0.025</td><td>1</td><td>1.1</td><td> </td></tr><tr><td>N2</td><td>0.05</td><td>2</td><td>2.2</td><td> </td></tr><tr><td>N3</td><td>0.1</td><td>4</td><td>4.4</td><td> </td></tr><tr><td>N4</td><td>0.2</td><td>8</td><td>8.9</td><td> </td></tr><tr><td>N5</td><td>0.4</td><td>16</td><td>17.8</td><td>Finest as-machined finish[2]</td></tr><tr><td>N6</td><td>0.8</td><td>32</td><td>35.5</td><td> </td></tr><tr><td>N7</td><td>1.6</td><td>63</td><td>69.9</td><td> </td></tr><tr><td>N8</td><td>3.2</td><td>125</td><td>138.8</td><td>Standard as-machined finish[2]</td></tr><tr><td>N9</td><td>6.3</td><td>250</td><td>277.5</td><td> </td></tr><tr><td>N10</td><td>12.5</td><td>500</td><td>555</td><td> </td></tr><tr><td>N11</td><td>25.0</td><td>1000</td><td>1110</td><td> </td></tr><tr><td>N12</td><td>50.0</td><td>2000</td><td>2220</td><td> </td></tr></tbody></table></div>The Rq column is computed as Ra × 1.11 for reasons explained below.Note that the microinch and micrometer columns are the conventional rounded pairs, not exact conversions.<h2>How to Read This Surface Finish Chart</h2>Ra, Rq, Rz, and Rt are all roughness parameters computed from the same measured roughness profile, so one measurement can report several of them at once.<h3>Ra</h3>Ra is the arithmetic mean of the absolute height deviations of the roughness profile from the mean line, measured over the evaluation length.[3] ASME B46.1-2019 gives the discrete form used by digital instruments as:[3]Ra = (|Z1| + |Z2| + |Z3| ... |ZN|) / NWhere each Z value is a measurement of an absolute deviation (either a peak or a valley) from the mean line. N represents the total number of measurements taken.The abbreviations on older drawings all mean the same measurement:<div><table><tbody><tr><td>Abbreviation</td><td>Stands for</td><td>Notes</td></tr><tr><td>Ra</td><td>Roughness average</td><td>Current ISO and ASME designation</td></tr><tr><td>CLA</td><td>Center line average</td><td>Older British usage. Numerically identical to Ra in µin</td></tr><tr><td>AA</td><td>Arithmetic average</td><td>Older American usage. Same measurement</td></tr><tr><td>Rq</td><td>Quadratic mean</td><td>A different calculation, not a different name. See below</td></tr><tr><td>RMS</td><td>Root mean square</td><td>The same as Rq</td></tr></tbody></table></div><h3>Rq</h3>Rq, sometimes written as RMS, is the square root of the mean of the squared height deviations. Squaring before averaging weights large peaks and valleys more heavily than Ra does, so Rq always reads slightly higher than Ra on the same surface profile.[4]For most machined surfaces, Rq is approximately 11% higher than Ra, giving the rule of thumb Rq ≈ Ra × 1.11.[5] That factor is exact only for an idealized sinusoidal profile—a surface that rises and falls with perfectly consistent repetition. Real surfaces depart from it, and the rougher and less regular the surface, the less reliable it becomes. In other words, you cannot get an exact Rq value from your Ra value; you need data from the measured profile to calculate it.<h3>N-grades</h3>N-grades, defined by ISO 1302, compress a roughness specification into a single number from N1 to N12, and each step roughly doubles Ra.[1]However, ISO 1302:2002 has been withdrawn and replaced by ISO 21920-1:2021.[1][6]So N-grades are a notation from a superseded standard. They have not vanished from drawings, which is why the chart includes them, but a new drawing is better served by an explicit Ra value with its cutoff stated. If you are updating drawing templates, note that ISO 21920-1 also changed the default acceptance rule to the maximum rule.[6]<h3>Rz</h3>Ra and Rz describe different things. Ra averages every deviation from the mean line, while Rz averages the most extreme deviations from each sampling length, so it is more sensitive to pronounced peaks and valleys.[4] Two surfaces with the same Ra value can have very different Rz values depending on whether the roughness profile is uniform or punctuated by isolated scratches and burrs. One value cannot be converted from the other.Recommended reading: <a href="https://www.wevolver.com/article/ra-vs-rz-understanding-surface-roughness-parameters-in-engineering" target="_blank" rel="noopener noreferrer">RA vs RZ: Understanding Surface Roughness Parameters in Engineering</a><h3>Cutoff λc</h3>A surface roughness value is incomplete without its filter cutoff, and this is the single most common reason two parties measuring the same part disagree.The cutoff separates roughness from waviness. ASME B46.1-2019 demonstrates the effect on one measured profile: at a 0.8 mm cutoff it reports Ra 0.057 µm, at 0.25 mm it reports 0.044 µm, and at 0.08 mm it reports 0.028 µm.[3]When the drawing does not state a cutoff, B46.1-2019 gives guideline values selected from the measured Ra.[3]<div><table><tbody><tr><td>Ra (µm)</td><td>Cutoff λc (mm)</td><td>Evaluation length L (mm)</td></tr><tr><td>up to 0.02</td><td>0.08</td><td>0.40</td></tr><tr><td>0.02 to 0.10</td><td>0.25</td><td>1.25</td></tr><tr><td>0.10 to 2.0</td><td>0.80</td><td>4.0</td></tr><tr><td>2.0 to 10.0</td><td>2.5</td><td>12.5</td></tr><tr><td>over 10.0</td><td>8.0</td><td>40.0</td></tr></tbody></table></div>Most machined work falls in the 0.10 to 2.0 µm band, which is why a 0.8 mm cutoff and a 4.0 mm evaluation length is the common default. The sampling length equals the cutoff when a filter is used.[3]<h3>Lay</h3>Lay, the predominant direction of the surface pattern, is specified separately from the roughness number.[3] It is called out with its own symbol set, including R for radial and C for circular. Surface finish symbols indicate lay, the parameter, the limit, and the cutoff together on the drawing.Recommended reading: <a href="https://www.wevolver.com/article/surface-finish-standards" target="_blank" rel="noopener noreferrer">Surface Finish: Parameters, Standards, and How to Specify It</a><h2>Ra Values by Manufacturing Process</h2><img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzkwODIwNzIxODI3LXNodXR0ZXJzdG9ja18xOTcyNjAxNTM3LmpwZyIsImVkaXRzIjp7InJlc2l6ZSI6eyJ3aWR0aCI6OTUwLCJmaXQiOiJjb3ZlciJ9fX0=" style="width:100%px" class="fr-fic fr-dib" />Grinding can produce a fine surface finishDifferent processes can achieve different levels of surface smoothness. However, which exact finish a manufacturing process can reach depends on the material, the tooling, the machine, and the parameters.<div><table><tbody><tr><td>Process</td><td>Typical Ra (µm)</td><td>Quality band</td></tr><tr><td>Lapping</td><td>0.1 to 0.2[7]</td><td>Very fine</td></tr><tr><td>Honing</td><td>0.2 to 0.4[7]</td><td>Fine</td></tr><tr><td>Grinding</td><td>0.4[7]</td><td>Fine</td></tr><tr><td>CNC turning</td><td>3.2[2]</td><td>Medium to fine</td></tr><tr><td>CNC milling</td><td>3.2[2]</td><td>Medium</td></tr><tr><td>Rough machining</td><td>25[5]</td><td>Rough</td></tr><tr><td>Sand casting</td><td>50[5]</td><td>Rough</td></tr></tbody></table></div>Within any one process, the finish is driven by the details. In <a href="https://www.wevolver.com/tag/cnc-machining" target="_blank" rel="noopener noreferrer">CNC machining</a>, feed rate, spindle rpm, tool nose radius, rigidity and tool wear all affect the achievable finish, which is why the same nominal operation on two machines will not give you the same surface texture.Secondary operations are equally important. Honing refines a bore beyond what boring alone reaches, deburring removes the burrs left at cut edges, and bead blasting produces a uniform matte non-directional texture. Powder coating and similar coatings add a layer that inherits and modifies the texture underneath.Bulk-forming processes sit at the coarse end, and the surface roughness values of processes like forging and rolling are usually a starting condition to be machined away rather than a finish to be met.<h2 id="isPasted">The Price of Lower Ra Values</h2>Surface finish generally becomes more expensive as the required Ra decreases. Rough machining can achieve relatively high Ra values with standard cutting tools and short cycle times, while finer finishes require slower feeds, sharper or more specialized tooling, and better machine stability.[5] Once conventional machining approaches its practical limit, processes such as grinding, honing, lapping, polishing, or superfinishing may be needed, adding both processing time and setup costs.[7]The relationship is not linear. Reducing Ra from 3.2 to 1.6 µm may require only a modest change in machining conditions, while reducing it from 0.8 to 0.4 µm can require a substantially different process. For this reason, specifying a finer surface finish than the function of the part requires can increase manufacturing cost without providing a corresponding benefit.<h2>Abrasive Grit to Ra</h2>Abrasive grit numbers map onto Ra only loosely, and the mapping depends on which grit scale is being quoted. The bands below are on the FEPA P-scale for coated abrasives, standardized as ISO 6344.[6]<div><table><tbody><tr><td>Grit (FEPA P)</td><td>Ra (µm), approx.</td><td>Ra (µin), approx.</td><td>Typical use</td></tr><tr><td>P40 to P60</td><td>3 to 5</td><td>120 to 200</td><td>Stock removal, weld knock-down</td></tr><tr><td>P80 to P120</td><td>1.5 to 3</td><td>60 to 120</td><td>Blending, coarse shaping</td></tr><tr><td>P150 to P240</td><td>0.8 to 1.5</td><td>32 to 60</td><td>Pre-finish smoothing</td></tr><tr><td>P320 to P600</td><td>0.3 to 0.8</td><td>12 to 32</td><td>Finishing, sealer scuff</td></tr><tr><td>P800 to P1200</td><td>0.1 to 0.3</td><td>4 to 12</td><td>Polish preparation</td></tr><tr><td>P1500 and finer</td><td>under 0.1</td><td>under 4</td><td>Pre-buff, high-gloss start</td></tr></tbody></table></div><h2>How the Measurement Is Taken</h2><img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzkwODIwNzY1NzA5LXNodXR0ZXJzdG9ja18xMzcyNjQ3NjI5LmpwZyIsImVkaXRzIjp7InJlc2l6ZSI6eyJ3aWR0aCI6OTUwLCJmaXQiOiJjb3ZlciJ9fX0=" style="width:100%px" class="fr-fic fr-dib" alt="A contact surface roughness tester" />A contact roughness tester or profilometerSurface finish measurement varies depending on the equipment used.A contact surface roughness tester drags a stylus of known tip radius across the surface at fixed speed and records height data at a set interval.[3] These instruments, generally called profilometers, produce the surface profile that every parameter in the chart is computed from.A non-contact method uses optical interaction instead: focus variation, confocal microscopy or interferometry. Optical instruments capture an area rather than a single line, which matters when the texture of a surface is directional.<h2>Conclusion</h2>A surface finish chart is a unit converter, but it cannot tell you what Rz corresponds to your Ra, because that depends on the shape of the roughness profile. Use the chart to translate between units, then specify the parameter, the limit, the cutoff, and the standard explicitly on your technical drawings. Then the number will mean the same thing to you and to whoever makes the part.<h2>Frequently Asked Questions</h2>What does a 32 surface finish mean?Ra 32 µin, equivalently Ra 0.8 µm or N6, a general engineering finish.What is the difference between Ra and Rq?Ra averages the absolute deviations from the mean line; Rq squares them first, which weights large peaks and valleys more heavily. On the same profile Rq typically reads about 11% higher, so RMS ≈ Ra × 1.11 as a rule of thumb.[5] They are two calculations on one measurement, not two measurements.Is CLA the same as Ra?Yes. Center line average is an older name for the same arithmetic average measurement.How do I convert Ra to Rz?You cannot do it reliably, as the Ra value has already “smoothed out” the extremes of which Rz is a measure.Are N-grades still valid?They come from ISO 1302, which ISO lists as withdrawn and replaced by ISO 21920-1:2021.[1][6] They remain common on existing drawings, so you still need to read them, but new drawings are better served by an explicit Ra value with its cutoff.Why do two shops measure the same part differently?Usually the filter cutoff. ASME’s own example gets Ra 0.057 µm and Ra 0.028 µm from one profile by changing the cutoff.[3]What Ra can CNC machining reach?Roughly 3.2 µm as machined, down to about 0.4 µm with further finishing passes.[2]<h2>References</h2>[1] International Organization for Standardization. <a href="https://www.iso.org/standard/28089.html" target="_blank">ISO 1302:2002: Geometrical Product Specifications (GPS) — Indication of surface texture in technical product documentation</a>. Geneva: ISO; 2002.[2] Protolabs Network. <a href="https://www.hubs.com/knowledge-base/surface-finishes-cnc-machinings/#surface-finishes-explained-as-machined" target="_blank">What are the types of surface finishes for CNC machining?</a> [Internet]. Protolabs Network; [cited 2026 Sep 30].[3] American Society of Mechanical Engineers. <a href="https://www.asme.org/getmedia/f22128e5-acad-429d-bc75-0ac4bdffdf44/b46-1-2019-11x17-poster.pdf" target="_blank">B46.1-2019: Surface texture (surface roughness, waviness, and lay): reference poster</a>. New York: ASME; 2019.[4] Keyence. <a href="https://www.keyence.com/products/microscope/laser-microscope/resources/laser-microscope-resources/how-surface-height-is-quantified-from-ra-to-rz.jsp" target="_blank">How surface height is quantified, from Ra to Rz</a> [Internet]. Keyence; [cited 2026 Sep 30].[5] Astro Pak. <a href="https://astropak.com/surface-roughness-average-ra/" target="_blank">Surface roughness average (Ra): chart, formula, and conversion calculator</a> [Internet]. Astro Pak; [cited 2026 Sep 30].[6] International Organization for Standardization. <a href="https://www.iso.org/obp/ui/#iso:std:iso:21920:-1:ed-1:v1:en" target="_blank">ISO 21920-1:2021: Geometrical Product Specifications (GPS) — Surface texture: Profile — Part 1: Indication of surface texture</a>. Geneva: ISO; 2021.[7] Grzesik W, Kruszynski B, Ruszaj A. <a href="https://link.springer.com/chapter/10.1007/978-1-84882-874-2_5" target="_blank">Surface integrity of machined surfaces</a>. In: Grzesik W, editor. Surface integrity in machining. London: Springer London; 2010. p. 143-179.[8] Whitby Abrasives. <a href="https://whitbyabrasives.ca/blogs/news/grit-to-surface-finish-ra-chart" target="_blank">Grit-to-surface-finish (Ra) chart</a> [Internet]. Whitby Abrasives; [cited 2026 Sep 30].

Surface finish can be specified in many different ways

A reference chart for converting between surface finish units, plus Ra values by manufacturing process and the relationship between surface

Surface Finish Chart: Ra, Rq, and N-Grade Conversions

Surface finishes can be altered with methods like coating and conversion

Surface finish decides whether a bearing seizes, a weld bonds, or a shaft survives its fatigue life. This guide covers what it is, its parameters, and how to specify it.

Surface Finish: Parameters, Standards, and How to Specify It

True position is an important concept in GD&T

This guide covers the true position formula, how to read the feature control frame, and how MMC and LMC generate bonus tolerance.

True Position in GD&T: Formula, Tolerance Zones, and MMC

H7 tolerance specifies a hole that is never smaller than its nominal diameter

H7 tolerance is the default hole class in the ISO system of limits and fits. This guide explains why H7 is useful for manufacturers.

H7 Tolerance Explained: ISO 286 Hole Tolerance Charts

Press fits are common when attaching bearings to shafts

A practical guide to press fit tolerance, including fit classes, interference calculations, and assembly methods.

Press Fit Tolerance: How to Specify Interference Fits

Tolerance stack up analysis looks at how dimensional variation compounds

Tolerance stack up is when dimensional tolerances accumulate, leading to more variation across a part or assembly.

Tolerance Stack Up Analysis: Worst Case vs RSS Methods

Design engineers, hardware integrators, and automotive technicians frequently need to verify whether relays are healthy or need replacement. This article provides a thorough, step-by-step approach to testing relays while explaining the underlying science and standards.

How to Test a Relay: Comprehensive Engineering Guide

Three phase circuits deliver balanced power for industrial and high demand applications, but mismatched wires can cause equipment damage or safety hazards.  These 3 phase wire color code schemes ensure correct installation, proper phase rotation, and compliance with electrical codes.

3 Phase Wire Color Code: Standards, Theory, and Practical Implementation

This article examines the anodizing process, an electrochemical surface treatment that makes metals like aluminium and titanium more durable and corrosion resistant.

The Anodizing Process Explained

Ground is the reference point that makes voltage meaningful and the return path that allows current to flow. This article explains what is ground in a circuit, discusses different types of grounds, and shows how to implement effective grounding strategies

What Is Ground in a Circuit? Understanding Grounding Concepts and Implementations

A comprehensive technical guide on vapor smoothing, covering process, materials, equipment, safety, and benefits for digital design and hardware engineers.

Vapor Smoothing 3D Printed Parts

Precision orientation and stabilization to enable safe and efficient underwater cleaning and inspection.IntroductionUnderwater environments present some of the toughest challenges for robotics:<ul><li>In aquaculture, fouled nets can restrict water flow, increase disease risk, and even cause costly fish escapes.</li><li>In shipping, hull fouling reduces efficiency and raises fuel costs.</li></ul>Thus, reliable cleaning and inspection is fundamental. But operating in dark waters, filled with debris, is certainly no easy task.That’s where <a href="https://meox.no/en/home/" target="_blank" rel="noopener noreferrer">Meox</a>, a Norwegian robotics company, comes in. With a decade of experience in underwater systems, Meox develops robots that can clean, inspect, and handle mortality events for fish farms and shipping operators.At the core of their innovative products is the <a href="https://www.movella.com/sensor-modules/xsens-mti-3-ahrs" target="_blank" rel="noopener noreferrer">Xsens MTi-3 AHRS</a>, providing the precise orientation and stabilization needed to make underwater work possible.About MeoxFounded in Norway in 2015, Meox began by developing environmental monitoring sensors for fish farms. As demand grew for safer and more efficient ways to maintain underwater infrastructure, the company shifted its focus to robotics.Today, Meox operates with a core team of seven, supported by specialized partners. Their product portfolio includes:<ul><li><a href="https://meox.no/en/net-cleaning/" target="_blank" rel="noopener noreferrer">Axuda Ray</a> – high-performance net cleaner with patented cavitation technology. <a href="https://www.facebook.com/reel/784250530126885" target="_blank" rel="noopener noreferrer">See here the Axuda Ray in action.</a></li><li><a href="https://meox.no/en/produkt/meox-multiflex-en/" target="_blank" rel="noopener noreferrer">Multiflex </a>– a modular, multi-purpose ROV for net cleaning, hull cleaning, and underwater inspections.</li><li><a href="https://meox.no/en/inspection/" target="_blank" rel="noopener noreferrer">Vision</a> – compact inspection ROV with advanced manoeuvrability.</li><li><a href="https://meox.no/en/dead-fish-handling/" target="_blank" rel="noopener noreferrer">Scout</a> – mortality-handling robot designed to remove dead fish quickly and hygienically.</li></ul>Despite their compact size (some units measuring only 80 cm wide), these robots deliver powerful cleaning and inspection capabilities, reducing downtime and safeguarding both equipment and livestock.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1758622341166-A%26M+-+Case+Study+Meox+Axuda+Ray.png" style="width:100%px" class="fr-fic fr-dib" />The Axuda Ray from Meox cleans nets using cavitation cleaningThe Underwater ChallengesTraditional net maintenance in aquaculture required bringing heavy nets to the surface for cleaning, which is a time-consuming and costly process. Onsite cleaning with high-pressure washers improved efficiency but risked damaging net coatings and accelerating wear.Operating robots underwater also come with additional challenges:<ul><li>Navigation without GPS – underwater, operators have little or no visibility.</li><li>Harsh environments – debris, barnacles, and particles cause wear on motors and thrusters.</li><li>Precise orientation required – cleaning effectiveness depends on stable heading and positioning.</li></ul>For Meox, solving these challenges meant finding a reliable, compact, and cost-effective inertial sensor for orientation and stabilization.The Solution – Xsens MTi-3 AHRSSince 2024, Meox has integrated the Xsens MTi-3 AHRS into its net and hull cleaning robots, as well as new mortality-handling systems.The connection was made possible through <a href="https://linknordic.com/" target="_blank" rel="noopener noreferrer">Link Nordic</a>, Xsens’ distribution partner in Scandinavia, who recognized that Meox’s navigation and stability challenges could be addressed with Xsens orientation technology. Working closely with Meox, they facilitated the adoption of the MTi-3, helping Meox kick off integration quickly and effectively.The MTi-3 provides:<ul><li>Stabilization – maintaining heading and orientation during operation.</li><li>Operator guidance – giving reference points in low-visibility conditions.</li><li>Approximate positioning – when combined with depth sensors, helps locate position within circular fish cages.</li><li>Flexible deployment – used in both monitoring (full stabilization) and cleaning (heading-only stabilization).</li></ul><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1758622218588-A%26M+-+Case+Study+Meox+Multiflex.png" style="width:100%px" class="fr-fic fr-dib" />The Meox Multiflex used the Xsens MTi-3 for orientation and stabilization.According to Einar Agnalt, Development Manager at Meox, the MTi-3 stood out as the best suited solution during their testing:“We tried several sensors and the MTi-3 was the best fit. It’s small, affordable, and easy to integrate. The quaternion support made orientation reliable, which is critical underwater.”Benefits &amp; Results<ul><li>By equipping its robots with the MTi-3, Meox achieved:</li><li>Improved reliability – stable heading ensures consistent cleaning results.</li><li>Ease of integration – seamless communication protocols and quick adoption.</li><li>Compact size (12 × 12 mm) – fits easily into both small (80 cm) and large (2.4 m) robotic platforms without design compromises.</li><li>Cross-platform use – the same sensor works across net cleaners, hull cleaners, and mortality-handling robots.</li><li>Enhanced operator confidence – orientation data compensates for low or no visibility environments.</li><li>Customer value – reduced operational downtime, extended equipment lifespan, and healthier aquaculture environments.</li></ul>Looking AheadMeox continues to expand its portfolio with innovative robots for aquaculture and shipping. The company is now developing automated mortality-handling solutions and enhancing inspection capabilities, with the MTi-3 serving as a trusted orientation sensor across all platforms.Future plans include refining heading stability and collaborating with Xsens engineers to optimize sensor performance.ConclusionBy combining patented cavitation cleaning technology with Xsens MTi-3 orientation sensing, Meox has set a new standard for underwater robotics in aquaculture and shipping. Their robots help operators maintain cleaner nets and hulls, safeguard fish welfare, and reduce costs, while the MTi-3 proves the reliability of Xsens technology in the harshest conditions.This collaboration was made possible through Link Nordic, Xsens’ trusted partner in the Nordic region, who connected Meox with Xsens technology and continues to support customers across Scandinavia.

With Xsens MTi-3

Keeping Fish Farms Clean: How Meox Uses Xsens MTi-3 for Reliable Underwater Robotics

Marine scientists have long marveled at how animals like fish and seals swim so efficiently despite having different shapes. Their bodies are optimized for efficient, hydrodynamic aquatic navigation so they can exert minimal energy when traveling long distances.Autonomous vehicles can drift through the ocean in a similar way, collecting data about vast underwater environments. However, the shapes of these gliding machines are less diverse than what we find in marine life — go-to designs often resemble tubes or torpedoes, since they’re fairly hydrodynamic as well. Plus, testing new builds requires lots of real-world trial-and-error.Researchers from MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) and the University of Wisconsin at Madison propose that AI could help us explore uncharted glider designs more conveniently. Their method uses machine learning to test different 3D designs in a physics simulator, then molds them into more hydrodynamic shapes. The resulting model can be fabricated via a 3D printer using significantly less energy than hand-made ones. The MIT scientists say that this design pipeline could create new, more efficient machines that help oceanographers measure water temperature and salt levels, gather more detailed insights about currents, and monitor the impacts of climate change. The team demonstrated this potential by producing two gliders roughly the size of a boogie board: a two-winged machine resembling an airplane, and a unique, four-winged object resembling a flat fish with four fins.Peter Yichen Chen, MIT CSAIL postdoc and co-lead researcher on the project, notes that these designs are just a few of the novel shapes his team’s approach can generate. “We’ve developed a semi-automated process that can help us test unconventional designs that would be very taxing for humans to design,” he says. “This level of shape diversity hasn’t been explored previously, so most of these designs haven’t been tested in the real world.”But how did AI come up with these ideas in the first place? First, the researchers found 3D models of over 20 conventional sea exploration shapes, such as submarines, whales, manta rays, and sharks. Then, they enclosed these models in “deformation cages” that map out different articulation points that the researchers pulled around to create new shapes.The CSAIL-led team built a dataset of conventional and deformed shapes before simulating how they would perform at different “angles-of-attack” — the direction a vessel will tilt as it glides through the water. For example, a swimmer may want to dive at a -30 degree angle to retrieve an item from a pool.These diverse shapes and angles of attack were then used as inputs for a neural network that essentially anticipates how efficiently a glider shape will perform at particular angles and optimizes it as needed.<h2 dir="ltr">Giving gliding robots a lift</h2>The team’s neural network simulates how a particular glider would react to underwater physics, aiming to capture how it moves forward and the force that drags against it. The goal: find the best lift-to-drag ratio, representing how much the glider is being held up compared to how much it’s being held back. The higher the ratio, the more efficiently the vehicle travels; the lower it is, the more the glider will slow down during its voyage.Lift-to-drag ratios are key for flying planes: At takeoff, you want to maximize lift to ensure it can glide well against wind currents, and when landing, you need sufficient force to drag it to a full stop.Niklas Hagemann, an MIT graduate student in architecture and CSAIL affiliate, notes that this ratio is just as useful if you want a similar gliding motion in the ocean.“Our pipeline modifies glider shapes to find the best lift-to-drag ratio, optimizing its performance underwater,” says Hagemann, who is also a co-lead author on a <a href="https://arxiv.org/abs/2505.00222">paper</a> that was presented at the International Conference on Robotics and Automation in June. “You can then export the top-performing designs so they can be 3D-printed.”<h2 dir="ltr">Going for a quick glide</h2>While their AI pipeline seemed realistic, the researchers needed to ensure its predictions about glider performance were accurate by experimenting in more lifelike environments.They first fabricated their two-wing design as a scaled-down vehicle resembling a paper airplane. This glider was taken to MIT’s Wright Brothers Wind Tunnel, an indoor space with fans that simulate wind flow. Placed at different angles, the glider’s predicted lift-to-drag ratio was only about 5 percent higher on average than the ones recorded in the wind experiments — a small difference between simulation and reality.A digital evaluation involving a visual, more complex physics simulator also supported the notion that the AI pipeline made fairly accurate predictions about how the gliders would move. It visualized how these machines would descend in 3D.To truly evaluate these gliders in the real world, though, the team needed to see how their devices would fare underwater. They printed two designs that performed the best at specific points-of-attack for this test: a jet-like device at 9 degrees and the four-wing vehicle at 30 degrees.Both shapes were fabricated in a 3D printer as hollow shells with small holes that flood when fully submerged. This lightweight design makes the vehicle easier to handle outside of the water and requires less material to be fabricated. The researchers placed a tube-like device inside these shell coverings, which housed a range of hardware, including a pump to change the glider’s buoyancy, a mass shifter (a device that controls the machine’s angle-of-attack), and electronic components.Each design outperformed a handmade torpedo-shaped glider by moving more efficiently across a pool. With higher lift-to-drag ratios than their counterpart, both AI-driven machines exerted less energy, similar to the effortless ways marine animals navigate the oceans.As much as the project is an encouraging step forward for glider design, the researchers are looking to narrow the gap between simulation and real-world performance. They are also hoping to develop machines that can react to sudden changes in currents, making the gliders more adaptable to seas and oceans.Chen adds that the team is looking to explore new types of shapes, particularly thinner glider designs. They intend to make their framework faster, perhaps bolstering it with new features that enable more customization, maneuverability, or even the creation of miniature vehicles.Chen and Hagemann co-led research on this project with OpenAI researcher Pingchuan Ma SM ’23, PhD ’25. They authored the paper with Wei Wang, a University of Wisconsin at Madison assistant professor and recent CSAIL postdoc; John Romanishin ’12, SM ’18, PhD ’23; and two MIT professors and CSAIL members: lab director Daniela Rus and senior author Wojciech Matusik. Their work was supported, in part, by a Defense Advanced Research Projects Agency (DARPA) grant and the MIT-GIST Program.

MIT researchers used a new machine-learning method to produce two real-world underwater gliders: a two-winged machine resembling an airplane (lower right), and a unique, four-winged object (lower left). Credits:Image courtesy of the researchers.

An AI pipeline developed by CSAIL researchers enables unique hydrodynamic designs for bodyboard-sized vehicles that glide underwater and could help scientists gather marine data.

AI shapes autonomous underwater "gliders"

Underwater or aerial vehicles with dimples like golf balls could be more efficient and maneuverable, a new prototype developed at the University of Michigan has demonstrated.Golf ball dimples cut through pressure drag—the resistance force an object meets when moving through a fluid—propelling the ball 30% further than a smooth ball on average. Taking this as inspiration, a research team developed a spherical prototype with adjustable surface dimples and tested its aerodynamics in a controlled wind tunnel.“A dynamically programmable outer skin on an underwater vehicle could drastically reduce drag while eliminating the need for protruding appendages like fins or rudders for maneuvering. By actively adjusting its surface texture, the vehicle could achieve precise maneuverability with enhanced efficiency and control,” said <a href="https://name.engin.umich.edu/people/sareen-anchal/" target="_blank" rel="noreferrer noopener">Anchal Sareen</a>, an assistant professor of naval architecture and marine engineering and mechanical engineering at U-M and corresponding author of two studies published in Flow and The Physics of Fluids.<iframe width="640" height="360" src="https://www.youtube.com/embed/De2VQYkdztM?&amp;wmode=opaque&amp;enablejsapi=1&amp;origin=https://www.wevolver.com" frameborder="0" class="fr-draggable"></iframe>These nimble vehicles could access typically hard-to-reach areas in the ocean while conducting surveillance, mapping new areas or collecting data on water conditions. The researchers formed the prototype by stretching a thin layer of latex over a hollow sphere dotted with holes, resembling a pickleball. A vacuum pump depressurizes the core, pulling the latex inwards to create precise dimples when switched on. Turning off the pump makes the sphere smooth again. <img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1747749824433-Anchal-Sareen-Wind-Tunnel-Sphere-Morphing-500x333.jpg" style="width:100%px" class="fr-fic fr-dib" />Anchal Sareen observes a 3D printed sphere suspended in a wind tunnel during testing. Credit: Jeremy Little, Michigan Engineering.To find out how the dimples affected drag, the sphere was put to the test within a three meter long wind tunnel, suspended by a thin rod and subjected to different wind velocities. For each flow condition, the dimple depth could be finely adjusted by shifting the vacuum pump’s strength. Drag was measured using a load cell, a sensor that detects force exerted by airflow on the object. At the same time, an aerosol was sprayed into the wind tunnel while a high-speed laser and camera captured the motion of the tiny particles as they flowed around the sphere. For high wind speeds, shallower dimples cut the drag more effectively while deeper dimples were more efficient at lower wind speeds. By adjusting dimple depth, the sphere reduced drag by 50% compared to a smooth counterpart for all conditions. “The adaptive skin setup is able to notice changes in the speed of the incoming air and adjust dimples accordingly to maintain drag reductions. Applying this concept to underwater vehicles would reduce both drag and fuel consumption,” said Rodrigo Vilumbrales-Garcia, a postdoctoral research fellow of naval architecture and marine engineering at U-M and contributing author to the studies.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1747749851147-Rodrigo-Vilumbrales-Garcia-Wind-Tunnel-Setup.jpg" style="width:832px" class="fr-fic fr-dib" />Rodrigo Vilumbrales-Garcia, makes preparations for a wind tunnel before conducting experiments with the 3D printed sphere. Credit: Jeremy Little, Michigan Engineering. The smart morphable sphere can also generate lift, allowing for controlled movement. Often thought of as the upwards force responsible for keeping planes in the air, lift can work in any direction as long as it is perpendicular to the direction of the flow.To achieve this, researchers designed the inner skeleton with holes on only one side, causing the sphere to develop one smooth and one dimpled side when activated. This created asymmetric flow separation on the two sides of the sphere, deflecting the wake toward the smooth side. By Newton’s third law, the fluid applies an equal and opposite force toward the rough side, effectively pushing the sphere in the direction of the dimples. Dimples on the right generate force to the right while those on the left push left. This enables precise steering by selectively activating dimples on the desired side.The team tested the new sphere in the same wind tunnel setup with varying wind velocity and dimple depth. With the optimal dimple depth, the half rough/half smooth sphere generated lift forces up to 80% of the drag force. The lift generation was as strong as the <a href="https://www.youtube.com/watch?v=2OSrvzNW9FE&amp;t=73s" target="_blank" rel="noreferrer noopener">Magnus effect</a>, but instead of using rotation, it was created entirely by modifying the surface texture.“I was surprised that such a simple approach could produce results comparable to the Magnus efect, which requires continuous rotation,” said Putu Brahmanda Sudarsana, a graduate student of mechanical engineering at U-M and contributing author to the studies.“In the long run, this could benefit, for example, compact spherical robotic submarines that prioritize maneuverability over speed for exploration and inspection. Typically, these submarines would require multiple propulsion systems, but this mechanism could help reduce that need,” added Sudarsana. <img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1747749913930-Putu-Brahmanda-Sudarsana-Sphere-Calibration.jpg" style="width:100%px" class="fr-fic fr-dib" />Putu Brahmanda Sudarsana calibrates the morphable sphere at the U-M Marine Hydrodynamics Laboratory. Credit: Jeremy Little, Michigan Engineering.Looking ahead, Sareen anticipates exciting collaborations that combine expertise in materials science and soft robotics, further advancing the capabilities of this dynamic skin technology. “This smart dynamic skin technology could be a game-changer for unmanned aerial and underwater vehicles, offering a lightweight, energy-efficient, and highly responsive alternative to traditional jointed control surfaces. By enabling real-time adaptation to changing flow conditions, this innovation promises to enhance maneuverability, optimize performance, and unlock new possibilities for vehicle design,” added Sareen.

A spherical prototype with "nimble dimples" can change its surface from smooth to dimpled, cutting through drag and generating lift.

Maneuverable underwater vehicles inspired by golf balls

The exploitation of renewable power sources is an essential response to the climate crisis. Solar and wind energy are the giants of the renewable world, but their output is unpredictable and intermittent. From one week to the next, it is difficult to forecast reliably how strongly the wind will blow or how brightly the sun will shine. This is a problem for national electricity grid operators, which are responsible for dynamically balancing the energy supply with the load.&nbsp;There is, though, a renewable energy source which is naturally very predictable: tidal power. The relative distances and positions of the sun, moon and Earth all affect the size and magnitude of the Earth’s two tidal bulges. At a local level, the magnitude of tides is influenced by the shape of the shoreline, as well as by weather conditions. Because the tides are driven by planetary movement, their timing can be precisely predicted, enabling power system operators to plan confidently for a tidal power generator’s contribution to the grid.&nbsp;This helps explain the growing interest in Orbital Marine Power, a UK-based innovator in tidal power generation. Succeeding where many tidal turbine manufacturers have failed, Orbital has developed a unique floating structure with turbines on each of two retractable legs. Its system off the coast of Orkney in Scotland generates a nominal 2MW output which helps the UK’s national grid to reduce its reliance on fossil fuel power sources.&nbsp;The north Atlantic is an unforgiving operating environment for electrical and electronics systems, however – and this is why Orbital relies on a robust <a href="https://www.movella.com/products/sensor-modules" target="_blank" rel="noopener noreferrer">Xsens MTi </a>inertial motion sensor to keep the floating turbine structure stable. &nbsp;The <a href="https://www.movella.com/products/sensor-modules" target="_blank" rel="noopener noreferrer">MTi motion sensor</a> is incorporated in the system as part of a Gable IMU (Inertial Measurement Unit) from Gable Technologies, which created an EtherCAT interface to integrate Xsens sensors seamlessly into industrial applications such as Orbital’s tidal power generator. This combination takes advantage of the accuracy of Xsens sensors, ensuring reliable performance in even the harshest conditions.Free from the seabed: the key Orbital innovationThe breakthrough that the Orbital design team made came from its observation of previous attempts to fix tidal turbines to the seabed: many companies that adopted this approach ran out of money, strained by the massive cost of hiring construction vessels and building a fixed underwater structure.&nbsp;The floating structure of the Orbital O2 generator eliminates these construction costs, and uses a simpler mooring system to hold the hull in place. On each side of the hull is a retracting leg featuring a turbine: this part of the structure can be lowered to the depth at which the most energetic tidal flows are to be found, or raised to protect the structure when extreme weather is forecast. &nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1740729489392-Picture1.jpg" style="width: 100%px;" class="fr-fic fr-dib">For the turbines to work effectively, the structure needs to be stable both in its geoposition, and in its attitude: excessive movement – roll or pitch – reduces the flow through the turbines, and thus affects total power output. It must maintain this stable position in extremely challenging conditions: floating in a narrow channel between islands, where the tidal flows are particularly strong, the Orbital hull is exposed to wind, saves, salt water ingress, and sunlight.&nbsp;Stable station keeping– maintaining a fixed position and attitude – in all conditions calls for an array of sensors, including a Doppler sensor to measure the speed of the tidal flow, load gauges on both legs, a GPS satellite sensor for geopositioning, and various weather sensors such as anemometers.&nbsp;Alongside these, the job of continuously measuring the hull’s pitch and roll, as well as low-frequency vibration, is performed by an Xsens MTi motion sensor. MTi sensors’ accuracy and performance are renowned – these devices are used in many applications which measure motion with millimetre precision, more than enough for the Orbital application.&nbsp;Angel Rua Santaclara, Orbital’s Powertrain Manager, was convinced that the performance of the MTi sensor would meet the tidal power generator’s needs, backed by the comprehensive magnetic calibration capability provided in the MT Software Suite from Movella. &nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1740729511338-Picture2.jpg" style="width: 100%px;" class="fr-fic fr-dib">But he says that equally important was the sensor’s ability to operate reliably in the harsh marine environment. He says: ‘The interior of the hull is dry by design – this facilitates repair and maintenance. But inevitably a floating marine structure is always going to be exposed to salt water and a humid atmosphere, and so every electrical and electronic component we use has to be rigorously specified to withstand these harsh conditions.&nbsp;‘That’s why Orbital’s first instinct was to use the specialist motion sensors that are marketed to the oil and gas industry for use in rigs and drilling platforms. But we found that they are over-specified for our requirements – for instance, they can handle operation at great depths. That meant they were also hugely expensive. We were glad to discover the <a href="https://www.movella.com/products/sensor-modules" target="_blank" rel="noopener noreferrer">MTi motion sensor</a> family, because it gives us the performance we need. The Gable IMU has an IP67-rated enclosure, which means that it can survive the damp atmosphere in the generator and repeated contact with salt water. The sensor has operated reliably ever since it was installed in our generator off the coast of Orkney.’Promising future for tidal power generationAngel Rua Santaclara says that having proved the feasibility of tidal power generation with the installation of the O2, the company is preparing to scale up its operation, building more generators for use in UK waters and elsewhere. He says, ‘Tidal power has its part to play in a carbon-free future for the electricity grid, and it can be deployed anywhere that has strong tidal flows. Our design, including the sensor systems for controlling the motion of the hull, is now proven, and we are looking forward to offering our design all around the world.’&nbsp;

Helping Maintain Stable Position in Fast-Moving Waters

Orbital's Breakthrough Design for Tidal Power Generator Using Xsens Technology

<h2 id="isPasted">Introduction</h2>Object detection is one of the foundational tasks in industrial automation. Whether confirming the presence of a component, tracking products on a conveyor, or verifying pallet positions in a warehouse, sensors provide the information that machines need to make decisions in real time.In real-world applications, however, reliable detection is never as straightforward as it seems. Production environments are filled with variables that can complicate sensing. Parts to be detected may vary in color, shape, or surface finish. Some could be highly reflective, while others could absorb most of the incident light. Environmental factors like dust, oil mist, and changing lighting can further affect performance. Present-day productivity demands require high-speed operation, which makes it difficult to maintain consistent detection.This article explains how time-of-flight (ToF) sensing addresses the limitations of conventional photoelectric sensors in challenging industrial applications. It uses OMRON’s E3AS-HF as an example to showcase how manufacturers can achieve more reliable long-range object detection across varying targets and environmental conditions.<h2>Conventional Photoelectric Sensors and Their Challenges</h2>Photoelectric sensors are electronic devices used to detect the presence or distance of an object without making physical contact. Traditional photoelectric sensors are highly effective in many simpler applications and are widely used in the industry. They can be classified based on their working principles.<h3>Light-Quantity Methods</h3>Sensors using light-quantity methods detect an object by projecting a light beam and monitoring whether it is interrupted or by measuring changes in the amount of light reflected. Types of light-quantity methods include:Through-Beam SensorsThrough-beam sensors separate emitter and receiver units positioned opposite each other. Detection occurs when an object blocks the beam. This approach offers long sensing distances with strong detection margins but requires access to both sides of the target.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1783531257736-1783531257736.jpeg" width="740" height="185" class="fr-fic fr-dii" />Fig. 1: Through-beam sensor operationRetroreflective SensorsRetroreflective sensors combine emitter and receiver in a single housing. They use a reflector to return the light beam. While the installation is simple, alignment and reflector placement become important to consider.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1783531204831-1783531204831.jpeg" width="740" height="185" class="fr-fic fr-dii" />Fig. 2: Retroreflective sensor operationDiffuse-Reflective SensorsDiffuse-reflective sensors detect light reflected directly from the target. They are easy to install but are more sensitive to variations in color, reflectivity, and finish.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1783531328615-1783531328615.jpeg" width="740" height="185" class="fr-fic fr-dii" />Fig. 3: Diffuse-reflective sensor operationIn all these cases, performance depends to some degree on how much light reaches the receiver. Dark or low-reflectivity objects return weaker signals, while glossy or metallic surfaces can reflect light away from the sensor. Dust, oil mist, and ambient light can further reduce detection margins.<h3>Distance-Setting Methods</h3>Distance-setting methods use triangulation to estimate the position of a target by analyzing the angle formed between the incident light from the emitter and the reflected light reaching the receiver. Because they estimate distance rather than relying just on light intensity, they can better distinguish targets and support more precise position-based detection.Their usable sensing range, however, is typically shorter than that of through-beam sensors, and performance is still influenced by target surface properties, measurement distance, and mounting constraints.<h2>When Detection Conditions Become More Demanding</h2>For many applications, conventional photoelectric sensors remain the most practical and cost-effective solutions. Problems arise when the target material varies, installation space is limited, or operating conditions change frequently.A production line may need to detect matte-black rubber, polished metal, painted surfaces, and irregularly shaped parts, often at different angles and distances. To maintain stable performance under such conditions, engineers need to adjust thresholds, reposition sensors, or switch to different sensing technologies for different stations.By determining how far away an object is rather than relying primarily on the amount of reflected light, TOF sensors can deliver more consistent results across a wider range of materials and operating conditions.<h2>ToF Sensing: A More Reliable Way</h2>Unlike conventional reflective photoelectric methods, which can be highly dependent on the intensity of reflected light, ToF sensing determines distance by measuring the time it takes for emitted laser light to return from the target. As light travels at a known speed, that elapsed time can be converted directly into distance. This makes detection less affected by target color, reflectivity, and surface finish while still requiring sufficient returned light for stable measurement. For example, a matte black rubber component and a polished metal part may reflect very different amounts of light, but as long as enough light returns to be measured, the sensor can determine how far away each object is.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1783531381762-1783531381762.jpeg" width="740" height="277" class="fr-fic fr-dii" />Fig. 4: ToF sensor operationToF sensing still presents engineering challenges. The returning signal can be extremely weak, particularly when detecting dark objects at long distances. Ambient light and electrical noise can obscure the signal, and temperature changes can affect the characteristics of optical components over time. Therefore, achieving stable measurements requires more than simply measuring elapsed time. It depends on high-speed sampling, precise signal processing, and compensation techniques that maintain accuracy under changing conditions.When properly implemented, ToF sensing provides a practical solution to detect a wide range of objects with greater consistency. It can also simplify installation by allowing sensors to be mounted farther away from the target while still maintaining reliable operation. This combination of robustness and flexibility has made ToF sensing increasingly attractive for applications in the automotive industry, logistics, manufacturing, and more.<h2>OMRON E3AS-HF ToF Laser Sensor <iframe id="69c3e8ca390acc4f20b8c5ed" width="250" class="specs-iframe" height="440" src="https://wevolver.com/iframe/specs/omron-industrial-automation-e3as-hf-tof-laser-sensors?iframe=true" frameborder="0" scrolling="no"></iframe></h2>The <a href="https://www.mouser.com/new/omron-electronics/omron-ia-e3as-hf-tof-laser-sensors/">OMRON E3AS-HF</a> is a high-sensitivity ToF laser sensor designed for applications where target conditions and installation constraints can make conventional sensing methods difficult to implement. By combining long-range distance measurement with wide-angle detection characteristics, it provides greater flexibility in how and where sensors can be installed.The sensor supports a sensing range from 50 mm to 6,000 mm and is available in separate spot-beam and diffused-beam models. Depending on model type, dial position, and installation distance, beam options include approximately 2 mm (spot), 9 mm (parallel), and 40 mm (wide-area) detection.  One of the defining characteristics of the E3AS-HF is its angular performance. The sensor can detect at installation angles up to ±85° when measured at 5 m using black paper with 10% reflectance and a 200 ms response time, making it possible to mount the sensor away from moving equipment, robots, and operator pathways.The E3AS-HF brings several features that make setup and maintenance easy. An OLED display provides direct access to settings and measured values, while a bottom-mounted status indicator remains visible when the sensor is installed in elevated or hard-to-reach locations. IO-Link is supported as standard on applicable models, enabling remote parameterization, diagnostics, and condition monitoring.Table 1: Key specifications of OMRON E3AS-HF<div><table><tbody><tr><td>Specification</td><td>OMRON E3AS-HF</td></tr><tr><td>Sensing range</td><td>50 mm to 6,000 mm</td></tr><tr><td>Beam types</td><td>Spot beam and diffused beam</td></tr><tr><td>Light source</td><td>Class 1 red laser (660 nm)</td></tr><tr><td>Response time</td><td>2 ms, 10 ms, 50 ms, or 200 ms</td></tr><tr><td>Outputs</td><td>NPN or PNP digital outputs, 4–20 mA analog output</td></tr><tr><td>Communication</td><td>IO-Link v1.1 (COM3, 230.4 kbps)</td></tr><tr><td>Operating temperature</td><td>–30°C to 55°C</td></tr><tr><td>Environmental ratings</td><td>IP67, IP69K, IP67G, ECOLAB</td></tr><tr><td>Display</td><td>OLED with five language options</td></tr></tbody></table></div>The E3AS-HF combines the sensing range typically associated with larger photoelectric systems with the flexibility of an all-in-one sensor. Its 6 m maximum range allows the sensor to be mounted away from conveyors, robot arms, and other moving equipment, while the selectable response times let engineers balance speed and measurement stability for different applications.Support for both digital and analog outputs, along with IO-Link communication, makes the sensor easy to integrate into modern automation architectures. At the same time, the rugged housing and broad operating temperature range allow it to be used in environments that involve washdowns, cutting oil, dust, and low temperatures.<h2>Design Features Behind Stable Detection</h2>The E3AS-HF combines a number of design elements to ensure consistent measurements across diverse materials, surfaces, and environmental conditions.<h3>High-Speed Sampling and Signal Accumulation</h3>When measurement distances increase, the amount of light returning to the sensor can get extremely small. This is especially true for detecting dark targets such as black rubber or painted metal. To extract useful information from these weak signals, the E3AS-HF accumulates approximately 10 million data points via ultra-fast sampling at 10 billion times per second to improve measurement stability.<h3>Avalanche Photodiode-Based Photodetection</h3>The sensor uses an avalanche photodiode (APD), which offers significantly higher sensitivity than conventional photodiodes. Even when a faint amount of light is reflected from the target, the APD can amplify the weak signal, allowing the sensor to measure the distance reliably.<h3>Inbuilt Heating and Real-Time Temperature Compensation</h3>Optical components are known to change their characteristics as temperatures shift. Since this is their natural behavior, it cannot be avoided but only compensated for. The E3AS-HF uses APD-based photodetection with real-time temperature correction to reduce characteristic variation. Separately, an integrated heater and temperature sensor support low-temperature operation.<h3>Automatic Mutual Interference Prevention</h3>In industrial settings, multiple sensors are often installed close to one another. Emitted laser pulses can interfere, causing false detections. The E3AS-HF is built to handle this challenge by automatically selecting a different emission pattern, which avoids interference without requiring any manual settings. Manual configuration is available too if needed.<h3>Adjustable Beam Characteristics</h3>The sensor is available in spot-beam and diffused-beam versions, with an adjustable beam diameter to match the application. The sensor, when set at a narrow beam, can detect small targets, while at a wider beam, it spreads over larger areas.<h3>Environmental Protection and Antifouling Design</h3>A contaminated lens reduces signal quality over time. To withstand demanding industrial environments, the sensor features an antifouling coating on the lens and carries IP67, IP69K, and IP67G ratings, along with ECOLAB approval for resistance to cleaning agents. It also supports operation from –30°C to 55°C, with an integrated heater and temperature sensor that enables operation down to –30°C (warm-up may be required at temperatures below –10°C). <iframe width="640" height="360" src="https://www.youtube.com/embed/ISediMEzlp0?&amp;wmode=opaque" frameborder="0" class="fr-draggable">        </iframe><h2>Industrial Application Scenarios</h2>OMRON’s E3AS-HF is a versatile ToF laser sensor suitable for a broad range of automation tasks.<h3>Automotive Manufacturing</h3>Automotive production lines include a mix of painted body panels, machined metal components, and dark plastic parts, each exhibiting different optical properties. The E3AS-HF can verify part presence, identify vehicle body types, and confirm the position of painted panels, even when the sensor is mounted at an angle or far from moving robots and tooling.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1783531531444-1783531531444.jpeg" width="740" height="223" class="fr-fic fr-dii" />Fig. 5: Automotive applications of OMRON E3AS-HF ToF sensors. Source: OMRON<h3>Logistics and Warehousing</h3>In warehouses and distribution centers, sensors are used to detect pallets, cartons, and moving shuttles. Because package colors and surface finishes can vary, maintaining stable detection with intensity-based methods can be difficult. The E3AS-HF’s distance-based operation and automatic mutual interference prevention make it well-suited for pallet detection, conveyor tracking, and automated storage and retrieval systems.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1783531553492-1783531553492.jpeg" width="740" height="223" class="fr-fic fr-dii" />Fig. 6: Logistics and warehousing applications of OMRON E3AS-HF ToF sensors. Source: OMRON<h3>Manufacturing and Assembly</h3>General manufacturing applications often involve object positioning, height verification, and counting tasks. The E3AS-HF offers accurate distance measurement with selectable beam characteristics, allowing engineers to select a sensing area for small features or larger surfaces. Its analog current output and scaling function can also be used to detect subtle height differences over a narrow measurement range.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1783531571754-1783531571754.jpeg" width="740" height="223" class="fr-fic fr-dii" />Fig. 7: Automotive applications of OMRON E3AS-HF ToF sensors. Source: OMRON<h2>Toward More Flexible Industrial Sensing</h2>As production environments become more automated and product variation continues to increase, sensors are expected to perform reliably under a wider range of conditions. Differences in color, reflectivity, shape, and installation geometry can all affect detection performance, particularly when sensing methods depend heavily on the amount of light blocked/returned by the target.ToF sensing offers a different approach compared to traditional photoelectric sensors by measuring distance directly. This makes detection less dependent on the target’s appearance and more on the quality of the sensors deployed.For engineers designing systems that detect diverse targets and require reconfigurability, <a href="https://www.mouser.com/new/omron-electronics/omron-ia-e3as-hf-tof-laser-sensors/">OMRON’s E3AS-HF</a> offers a practical way to maintain more consistent sensing performance.

Conventional photoelectric sensors used for object detection and distance measurement can struggle with dark, glossy, or irregular targets because they rely on light intensity. Time-of-flight laser sensors overcome these challenges by using distance-based sensing instead.

Industrial Object Detection with Long-Range, Wide-Angle Time-of-Flight Sensing: OMRON E3AS-HF

European automotive manufacturing is under structural pressure from multiple directions at once. Experienced metrologists are retiring. EV platforms demand entirely different inspection approaches. Global competitors have already automated. And production lines cannot slow down to wait for quality control to catch up.For many facilities, the bottleneck is not the production technology. It is the inspection workflow sitting behind it.<h2>Explore the whitepaper</h2>This whitepaper examines how automated 3D optical metrology helps automotive manufacturers close the gap between modern production and legacy quality control. It covers the real pressures driving the change, the practical limitations of coordinate measuring machines, and how optical scanning systems can be deployed directly on the shop floor.<iframe id="JotFormIFrame-261653944967372" src="https://form.jotform.com/261653944967372" frameborder="0" style="min-width:100%;max-width:100%;height:1000px;border-width:medium;border-style:none;border-color:currentcolor;border-image:initial" scrolling="yes" class="fr-draggable"> </iframe><h2>You will learn:</h2><ul><li>Why demographic decline across EU manufacturing hubs is making traditional CMM expertise harder to source and retain</li><li>How EV platforms, battery enclosures, thin-walled aluminum structures, and reflective surfaces expose the limits of point-based measurement</li><li>How optical scanners capture millions of geometrically linked data points in a single pass and compare them directly against CAD models</li><li>What it means to move inspection out of the metrology lab and into production, where feedback reaches engineers before defects compound into large batches</li><li>How stamping and casting operations can use accumulated scan data to track tooling drift and move from reactive maintenance to predictive intervention</li><li>What a full Industry 4.0 integration looks like, including MES connectivity, automated reporting, and modular robotic inspection cells deployable in two days</li></ul><h2>Why read it</h2>Traditional inspection systems were built for a stable, high-volume world with a ready supply of skilled operators. That world has changed. EV production requires validation techniques that CMMs were not designed for. Customizable vehicles mean higher part variability. Supply chains spanning dozens of countries mean dimensional deviations that go undetected in one stage create assembly problems three steps later.Late defect detection is not just a quality problem. Every rejected part costs energy, machine time, and labor. In the context of the European Green Deal, it is also a sustainability problem.This whitepaper looks at inspection as a complete production system rather than a separate step, and shows how automated optical metrology turns quality control from a bottleneck into an active part of the manufacturing process.<iframe id="JotFormIFrame-261653944967372" src="https://form.jotform.com/261653944967372" frameborder="0" style="min-width:100%;max-width:100%;height:1000px;border-width:medium;border-style:none;border-color:currentcolor;border-image:initial" scrolling="yes" class="fr-draggable"> </iframe><h2>Case study: stamping inspection at a tier-one supplier</h2>A supplier producing 782 different stamped part types for Honda, Toyota, and Nissan was running out of road with CMM-based inspection. Manual setup, slow throughput, and the requirement to work directly on a live shop floor made the existing process unsustainable.After deploying an automated 3D optical scanning system alongside the stamping lines, large sheet metal parts could be fully scanned in three minutes. Smaller parts took around one minute. Defects were caught earlier, corrective action happened faster, and scrap and rework both came down.<h2>Learn from the source</h2>Scanology develops automated 3D inspection systems used in automotive production environments across Europe and Asia. Their systems are certified to ISO 10360 standards and tested in CNAS ISO 17025 accredited laboratory conditions.This whitepaper draws on that experience to give engineers and operations leaders a practical guide to modernising their inspection infrastructure.

Why traditional inspection can no longer keep pace with modern automotive production, and what to do about it

Navigating Europe's Manufacturing Dilemma Through Automated Metrology

When we first came up with the idea to enhance our projection units with the power of blue light wavelengths, we knew we were onto something extraordinary. By solving long-standing challenges with difficult materials, extending scanning ranges, and enabling new multi-sensor configurations, blue laser vision systems are opening up application areas that were previously impractical or impossible.Today, we can confidently say that the new generation of 3D scanners delivers 2.5x better data completeness and 50% more scanning power. When paired with red laser systems in multi-sensor setups, you can also perform a simultaneous 3D scanning tasks with no interference, which can be essential for applications like  <a href="https://www.photoneo.com//bin-picking" target="_blank">bin picking</a> and <a href="https://www.photoneo.com//3d-meshing" target="_blank">3D meshing</a>.<h2>The Physics Behind the Blue Laser Advantage</h2>To understand why blue laser technology represents such a significant advancement, we need to dive into the fundamental physics of light interaction with materials. The key lies in wavelength. Blue lasers typically operate at wavelengths around 405-450 nanometers. This is significantly shorter than the 650-670 nanometer wavelengths of traditional red lasers.This shorter wavelength brings several crucial advantages.<h3>Enhanced Surface Interaction</h3>Shorter wavelengths scatter more effectively across a broader range of materials. This phenomenon means that blue light interacts more readily with surface textures and microscopic irregularities that longer wavelengths might pass through or reflect away from. The result is dramatically improved data capture on challenging materials that have historically been problematic for 3D scanning.<h3>Reduced Speckle Noise</h3>One of the most significant technical improvements blue lasers bring is the reduction of speckle noise. Speckle patterns – those granular interference patterns that appear when coherent light reflects off rough surfaces – have long been a nemesis of <a href="https://www.photoneo.com/how-to-evaluate-3d-sensing-technologies/" target="_blank">precision 3D scanning</a>. The finer speckle structure produced by blue lasers creates less interference with captured data, resulting in cleaner, more accurate point clouds.<h3>Superior Signal-to-Noise Ratio</h3>Blue laser vision systems can achieve higher signal-to-noise ratios, particularly when combined with sensors optimized for blue wavelengths. This improvement translates directly into better data quality, especially in challenging scanning conditions where ambient light or material properties might compromise measurement accuracy.<h2>Breaking Through Material Barriers</h2>Perhaps nowhere is the advantage of blue laser technology more apparent than in its ability to handle materials that have traditionally challenged <a href="https://www.photoneo.com/3d-scanning-software/" target="_blank">3D scanning systems</a>.<h3>Reflective and Metallic Surfaces</h3><a href="https://ai.photoneo.com/automotive" target="_blank">Automotive manufacturing</a>, with its abundance of polished metal components, stamped parts, and reflective surfaces, has been a particularly challenging environment for traditional 3D scanningBlue lasers excel at penetrating through surface reflections and capturing meaningful geometric data from highly reflective materials. This capability opens up new possibilities for in-line quality inspection of  <a href="https://ai.photoneo.com/automotive" target="_blank">automotive</a> components, from body panels to precision-machined engine parts.<hr />To take a deeper look into how 3D vision can transform inspection and quality control. Not only in the automotive industry. Download our free e-book today. <a href="https://ai.photoneo.com/3d-vision-automotive-quality-control-ebook" target="_blank">Go to Download</a><h3>Dark and Absorptive Materials</h3>At the opposite end of the spectrum, very dark materials that absorb most incident light have also posed challenges for red laser systems. Blue light’s high energy density and distinct absorption properties enable better data capture from difficult materials. Consequently, systems can reliably scan complex surfaces without requiring sprays or special surface preparation.<h3>Transparent and Semi-Transparent Objects</h3>One of the most exciting applications of blue laser technology is in scanning transparent and semi-transparent materials. Blue laser systems unlock complex measurements previously considered impractical with red light. A primary example is <a href="https://www.photoneo.com/case-cat/automotive/" target="_blank">automotive</a> gap and flush inspection, where the system must accurately capture the interface between transparent plastic and painted metal.<h2>Extended Dynamic Range Capabilities</h2>Blue laser technology doesn’t just improve scanning quality at traditional ranges – it extends the useful scanning envelope significantly. Several factors contribute to this <a href="https://www.photoneo.com/high-dynamic-range/" target="_blank">enhanced dynamic range</a> performance:<ul><li>Higher Power Density – Blue laser projection units can deliver significantly more optical power within the same laser safety class restrictions. This increased power density means a more useful signal reaches distant objects, enabling reliable data capture at ranges that would be marginal or impossible with red laser systems.</li><li>Improved Dynamic Range – When combined with advanced sensors and processing algorithms, blue laser systems can achieve dynamic ranges 20dB or more beyond traditional systems. This extended dynamic range means the scanner can simultaneously capture fine details on nearby objects while still maintaining signal integrity from distant surfaces – a crucial capability for <a href="https://www.photoneo.com/mixed-palletizing-3d-vision/" target="_blank">applications like palletizing</a>, where robots might need to scan objects at various heights within a large working volume.</li><li>Better Ambient Light Suppression – The spectral characteristics of blue lasers, combined with precisely matched optical filters, enable  <a href="https://www.photoneo.com/lighting-conditions-machine-vision/" target="_blank">superior ambient light suppression</a>. This capability is particularly valuable in industrial environments where natural lighting, overhead fluorescents, or other illumination sources might interfere with scanning operations.</li></ul><h2>Multi-Sensor Synergy</h2>One of the most innovative applications of blue laser technology is in <a href="https://www.photoneo.com/multi-perspective-3d-vision-automotive-industry/" target="_blank">multi-sensor scanning configurations</a>. Because blue and red wavelengths operate in distinct spectral bands, sensors using different laser colors can operate simultaneously without interference.This capability enables several powerful scanning modalities:<h3>Parallel Multi-View Scanning</h3>Scanning in succession adds time and complexity to the operation. Rather than scanning sequentially from different angles, <a href="https://www.photoneo.com/motioncam-3d-color-blue-launch-webinar-faq/" target="_blank">blue and red laser systems</a> can scan simultaneously from multiple perspectives. This parallel operation cuts scanning time in half while providing the multiple viewpoints needed for complete object reconstruction.<h3>Complementary Material Coverage</h3>Different laser wavelengths interact differently with various materials. By using both blue and red lasers simultaneously, scanning systems can optimize data capture across a broader range of surface types. This way, you can essentially combine the strengths of both technologies.<h3>Enhanced Robustness</h3>Multi-wavelength scanning provides inherent redundancy. If one laser struggles with a particular surface or material characteristic, the other wavelength often compensates. The results introduces more complete and reliable data capture.<h2>Applications Transformed by Blue Laser Technology</h2>The capabilities enabled by blue laser technology are opening up entirely new application areas and dramatically improving existing ones:<h3>Advanced Quality Inspection</h3>The improved resolution and material compatibility of blue laser systems enable quality <a href="https://www.photoneo.com/case-study/automated-inspection-of-large-objects-in-motion/" target="_blank">inspection applications</a> that were previously impractical. Weld bead inspection, surface finish analysis, and dimensional verification of complex geometries all benefit from the <a href="https://www.photoneo.com/crash-car-inspection-3d-vision-motion/" target="_blank">enhanced data quality</a> and completeness that blue lasers provide.<h3>Outdoor and Variable Lighting Applications</h3>Superior ambient light suppression makes blue laser systems viable for applications in uncontrolled lighting environments. Solar panel inspection, <a href="https://www.photoneo.com/case-cat/agriculture/" target="_blank">agricultural applications</a>, and railway maintenanc. All of these scenarios where consistent artificial lighting isn’t practical – become feasible with robust blue laser scanning systems.<h3>High-Precision Assembly Operations</h3>In electronics manufacturing and other <a href="https://ai.photoneo.com/dynamic-assembly-3d-vision-ebook" target="_blank">precision assembly operations</a>, the improved resolution and material handling capabilities of blue laser systems enable more sophisticated guidance and verification tasks. Component placement and quality verification can all be performed with higher confidence and accuracy.<h3>Large-Scale Automation</h3>The extended range capabilities of blue laser systems enable automation in larger working volumes. <a href="https://www.photoneo.com/automated-warehouse/" target="_blank">Warehouse automation</a>, large-part manufacturing, and infrastructure inspection applications all benefit from the ability to capture high-quality data across greater distances.<h2>Looking Forward: The Future of Blue Laser Technology</h2>As blue laser technology matures, we can expect to see continued improvements in several areas:<h3>Integration with Artificial Intelligence</h3>The higher quality, more complete data provided by blue laser systems creates better inputs for AI-powered analysis and decision-making systems. This synergy between improved sensing and intelligent processing will enable even more sophisticated <a href="https://www.photoneo.com/application/" target="_blank">automation applications</a>.<h3>Enhanced Multi-Modal Sensing</h3>Future sensing systems will evolve by integrating blue laser structured light with complementary modalities, such as thermal imaging, hyperspectral analysis, or advanced RGB processing. This synergy will enable comprehensive systems capable of unprecedented material analysis and geometric precision.<hr />Explore Photoneo’s Blue Laser devices – MotionCam-3D Color (Blue) for dynamic scanning in motion and PhoXi 3D Scanner Gen3 for the maximum precision in static scenes.

Physics Behind the Blue Laser Advantage

Why Blue Laser is Becoming the Core of High-Fidelity 3D Scanning

<h2>Executive Summary</h2>This white paper investigates the increasing need for high-precision metrology in highly regulated industries such as automotive and civil aviation. Where current metrology solutions are falling short in terms of efficiency, completeness, and scale, high-performance 3D scanning is emerging as a powerful solution. SHINING 3D’s 3D scanning systems offer myriad benefits to engineers and quality assurance (QA) teams in both the automotive and civil aviation sectors, including full-field, micron-level data capture, accelerated inspection times, repeatability, and traceability. This white paper illustrates these benefits and more in case studies from the automotive and aviation sectors, while also presenting different application areas for the technology. Finally, the white paper explores the question of integrating 3D scanning into existing QA or inspection processes with the goal of streamlining workflows and enhancing results.<iframe id="JotFormIFrame-260782481285464" src="https://form.jotform.com/260782481285464" frameborder="0" style="min-width:100%;max-width:100%;height:1000px;border:none" scrolling="yes" class="fr-draggable"> </iframe><h2> Introduction</h2>Precision has always been fundamental to manufacturing, but the way it is achieved has changed dramatically. Even as far back as the building of the pyramids in Ancient Egypt, measurement standards were used to ensure a consistent size of limestone or granite block, which resulted in a deviation of a mere 0.05% comparing all the sides of the structure. [1]In today’s era of digital transformation, smart manufacturing, and zero-defect production, metrology has evolved from a supporting function into a core, data-driven capability. Today, advanced production technologies, such as Computer Numerical Control (CNC) machining and Additive Manufacturing (AM), have brought with them new design possibilities, such as highly complex assemblies whose performance and functionality are dependent on extremely tight tolerances. The proliferation of high-precision components has introduced an array of challenges for traditional quality assurance tools like calipers, gauges, and even coordinate-measuring machines (CMMs). As many manufacturers have experienced firsthand, these tools fall short when it comes to measuring and qualifying complex surfaces with extreme precision in a scalable, repeatable way.Enter 3D metrology. 3D metrology solutions, such as SHINING 3D’s 3D scanners, have emerged as a powerful solution. Capable of capturing accurate surface data in a fast and non-contact manner, 3D metrology tools are transforming quality assurance workflows for the better and providing more exacting insights into a part’s form, fit, and function.As we’ll explore in this white paper, advanced 3D metrology solutions are becoming increasingly indispensable in industries like automotive and civil aviation, where critical components require ultra-tight tolerances in order to ensure optimal safety and performance as well as regulatory compliance. Moreover, as both sectors pursue greater efficiency through the development and production of ultra-lightweight parts, engineers are discovering that many of these parts are susceptible to deformation during handling and contact-based inspection processes. 3D metrology tools provide a safe, non-contact solution in these cases.Additionally, the integration of 3D metrology enables manufacturers to align the pace of quality control with that of production. In other words, 3D metrology solutions facilitate rapid, automated inspections that match with takt time requirements and unlock high-throughput production without compromising on precision or quality. Beyond qualification in automotive and aviation production lines, 3D metrology is also facilitating the inspection of legacy parts and supporting reverse engineering applications.In this white paper, we will first look at the limitations of traditional metrology tools when it comes to advanced production applications in automotive and aviation. From there, we will examine the benefits of 3D scanning and explore specific applications in both industries where 3D metrology is playing a game-changing role. Finally, we will illuminate the impacts of integrating 3D metrology solutions into engineering and quality assurance workflows.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzczNzk2MTU1MzkxLUZyZWVTY2FuX0NvbWJvXzkxMUdUM1RvcnVpbmdfMi53ZWJwIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width:100%px" class="fr-fic fr-dib" /><h2>The Metrology Gap: The Limitations of Traditional Contact-Based Metrology</h2>Before delving into the transformative capabilities of advanced 3D metrology, it is helpful to first understand how traditional metrology tools are falling short of modern manufacturing expectations. Though handheld instruments like calipers, gauges, and templates have long been used in quality control workflows and have the benefits of being simple to use and relatively low cost, their functionality, repeatability, and scalability are limited.These rudimentary metrology tools effectively work by measuring a part’s dimensions (calipers) or checking whether a particular feature or dimension falls within allowable limits (gauges and templates). A major shortcoming with these metrology tools is that they can only measure individual dimensions and do not provide full-field data. Moreover, these tools are used manually and therefore bring with them the risk of human error and lack of repeatability, an issue that is magnified when extreme accuracy is required. These tools are also fundamentally unsuited for the inspection of freeform geometries and compound-curved surfaces, which limits their use to simple geometric structures.Even sophisticated metrology technologies like coordinate-measuring machines (CMMs) present limitations when it comes to inspecting critical, high-precision parts in the automotive and aviation sectors. CMMs use a tactile probe to measure discrete points on a part, leveraging coordinate technology to determine dimensional accuracy in multiple axes.While CMMs are known for their high level of accuracy, the approach has workflow limitations that hinder its adoption for many applications. For one, coordinate-measuring technology is slow and can create bottlenecks in fast-paced production environments. CMMs are also limited in size, meaning that they are unsuitable for inspecting body-in-white (BIW) structures, body panels, aerospace skins, and other large structures. The fixed nature of CMMs, which must operate in a controlled, vibration-free environment, also limits how and where they can be used. Similarly, long setup times inhibit flexibility and make CMMs inefficient for high-mix production and iterative development cycles.Considering the limitations of these widespread metrology tools and the growing demand for high-precision, complex parts in demanding industries like automotive and aerospace, there is a strong need for fast, full-field, high-accuracy metrology. In many cases, 3D scanning is the answer. <img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzczNzk2MjEzNzUzLTE3NzM3OTYyMTM3NTMucG5nIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" class="fr-fic fr-dib" /><h2>The Need for High-Accuracy 3D Scanning for Metrology</h2>With technological roots dating back to the 1960s, 3D scanning is today at the cutting edge of industrial metrology. [2] On a basic level, the technology works by projecting light onto an object. Based on the way the light bounces back from the object, the scanning technology captures full-field data of the object’s surface and geometry. This data, in the form of thousands or even millions of points, can be used for metrology purposes or to reconstruct a high-fidelity digital twin of the object. Professional and industrial-grade 3D scanning solutions, such as SHINING 3D’s dynamic tracking 3D measuring system, handheld laser scanning, and high-precision inspection systems, offer several benefits over traditional metrology approaches. With micron-level repeatability, broad material compatibility, dynamic tracking, and environmental robustness, SHINING 3D’s advanced scanning tools enable manufacturers across the most demanding industries to inspect and qualify parts with confidence.One of the greatest benefits of 3D scanning is full-field, high-density data capture. While CMMs are the gold standard for point accuracy, their sparse measurements often miss global deviations. In contrast, laser scanners capture the entire surface geometry, enabling comprehensive shape and dimension analysis. This high-density data allows for the generation of chromatic deviation maps, which instantly visualize form errors like warpage or shrinkage. Instead of just checking isolated points, manufacturers can assess the entire surface profile to identify exactly where and by how much the part deviates from the CAD model.The superior data density unlocked by 3D scanning is not only transformative for quality assurance and metrology, it also plays a critical role in informing engineering decisions related to geometric dimensioning &amp; tolerancing (GD&amp;T), part analysis, reverse engineering, computer-aided engineering (CAE) validation, and tool compensation loops.SHINING 3D’s solutions offer manufacturers additional advantages, including markerless, dynamic tracking for large structures, ideal for inspecting BIW, fuselage, monocoque, and chassis structures without the setup hassle of placing markers or stickers. This, along with the elimination of any manual measurement, results in faster metrology workflows and overall fewer Advanced Product Quality Planning (APQP) bottlenecks.Moreover, scanning systems that feature blue light laser technology can scan traditionally challenging parts, such as those with dark or shiny surfaces, with a high level of accuracy. This capability extends scanning material compatibility to dark carbon fiber composite structures as well as shiny metal surfaces, and beyond, without surface preparation.In industries like automotive and civil aviation, which are bound by strict regulatory standards and frameworks, 3D scanning tools must meet stringent requirements when it comes to accuracy and repeatability. SHINING 3D solutions deliver repeatability and traceability backed by ISO 17025, VDI/VDE 2634 and ISO 10360 certifications. This is paired with a higher level of environmental robustness than sensitive metrology tools like CMMs. <img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzczNzk2MjY5NjMzLTE3NzM3OTYyNjk2MzMucG5nIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" class="fr-fic fr-dib" /><h2> </h2><h2 id="isPasted">Unlock the Full Potential of High-Accuracy 3D Scanning</h2>You’ve seen how 3D scanning is transforming inspection and quality workflows—but this is only the starting point.In the full whitepaper, explore detailed automotive and civil aviation applications, including carbon fiber monocoque validation, sheet metal deformation analysis, and aircraft damage detection. Learn how leading manufacturers are deploying high-precision 3D metrology to reduce inspection time, improve accuracy, and streamline production.Download the complete whitepaper to access real-world use cases, technical workflows, and the measurable impact of integrating advanced 3D scanning into engineering and QA processes.<iframe id="JotFormIFrame-260782481285464" src="https://form.jotform.com/260782481285464" frameborder="0" style="min-width:100%;max-width:100%;height:1000px;border:none" scrolling="yes" class="fr-draggable"> </iframe>

Manufacturing Machines

Engineers Wiki. Most Asked Questions.

ISO 2768 General Tolerances: Tables, Classes, Current Status

Surface Finish Symbols: How to Read a Drawing Callout

Surface Finish Chart: Ra, Rq, and N-Grade Conversions

Surface Finish: Parameters, Standards, and How to Specify It

True Position in GD&T: Formula, Tolerance Zones, and MMC

H7 Tolerance Explained: ISO 286 Hole Tolerance Charts

Press Fit Tolerance: How to Specify Interference Fits

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