Of the many issues that can affect FDM 3D printing, ghosting is one of the easiest to spot. Typically manifesting itself as waves or ripples on the outside of a part — or as a certain feature reappearing in fainter form across the part’s surface — the phenomenon of ghosting has a few potential causes and can haunt virtually any 3D printer.

Ghosting sometimes goes by other names. Due to its appearance, the printing issue may also be referred to as ringing, rippling, or echoing. But however you want to describe it, ghosting is a nuisance that you’ll want to exorcize from your printing setup as soon as possible.

Fortunately, ghosting can usually be busted by making a few tweaks to your printing parameters or by performing some basic maintenance on the printer hardware. This article looks at the basics of 3D print ghosting, including its root causes and the most effective ways to get rid of it.

What is 3D print ghosting?

Ghosting is a common FDM 3D printing defect that is identifiable by the effect it has on print quality, particularly on the print surface. Simplify3D defines it as “a wavy pattern that may appear on the surface of your print due to printer vibrations or wobbling.”[1]

3D print ghosting usually appears as waves or ripples on the outer walls of the printed part, and can also produce overly rounded corners and edges. It may also manifest itself as a sort of shadow or repetition of a distinct feature on the print.

Although ghosting can affect a range of parts and surfaces, it is most commonly seen near sharp edges, details, and other places where the printhead needs to make a sharp change in direction. This is because the direction change can create vibrations which throw the printhead off track, causing it to lay down material with reduced accuracy.

Ghosting can therefore be thought of as the unwanted rippling after-effect of 3D printer vibration, and this gives us a good starting place for getting rid of the problem.

What causes 3D print ghosting?

An FDM 3D printer has a printhead that moves along the X-axis and Y-axis in order to lay down a layer of material. At certain points, the moving printhead changes direction completely, such as when it turns a sharp corner, and this sudden printer movement can cause reverberations throughout the printhead and extruder.

In short, the excess vibrations created when the printhead navigates sharp angles causes ghosting problems. Because the printer is made of many moving parts, some amount of vibration is inevitable, but it should ideally be stable and robust enough to print accurately in spite of these vibrations. So when and why do the vibrations prove too much and cause ghosting?

There are a few reasons why a 3D printer might suffer from ghosting when its hotend makes sudden changes in direction. These can include overly demanding print settings, such as very high print speeds and over-zealous acceleration settings, which make it difficult for the printhead to remain steady as it shoots back and forth across the print bed. Other causes include inadequate belt tension, loose screws and other components, and uneven or unstable surfaces underneath the printer.

Recap of common causes:

• Fast print speeds

• Improper acceleration settings

• Loose belts

• Loose screws and other components

• Unstable surface

How to solve 3D print ghosting

When ghosting starts to occur, it can affect virtually all prints fired off by the 3D printer, regardless of part shape or filament type. It is therefore a printing problem that generally requires immediate remedying.

Fortunately, since ghosting has a fairly clear and singular root cause (vibrations), it can be easier to fix than other, more nebulous 3D printing issues. The best case scenario is that the 3D printer simply needs some adjustment of print parameters via the slicer or firmware. Otherwise some hardware maintenance may be required.

These are the most common solutions for ghosting, starting with parameter adjustments and moving on to hardware maintenance.

Adjusting print settings can help prevent ghosting

Reduce print speed

Print speed is a measure of how fast the printhead moves along the X and Y axes as it puts down a layer of material. Fast print speeds are beneficial as they reduce overall printing time, but they can also reduce print quality and cause issues such as poor layer adhesion, under-extrusion, and ghosting.

While printing quickly can be tempting, especially when printing large parts or sets of multiple parts, it can be a direct cause of ghosting. This is because faster speeds mean that greater forces are required when the printhead comes to a halt in order to change direction. An average print speed for common filaments like PLA and ABS is around 50–60 mm/s; going beyond this range increases the risk of ghosting and other related issues. However, if you print significantly slower than this range and still experience ghosting, then there may be a hardware issue that needs resolving instead.

Note that both printing speed (when material is being pushed out of the nozzle) and travel speed (when no material exits the nozzle) can affect vibrations and ghosting, so it may be necessary to adjust both.

Recommended reading: 3D print speed: What it is and why it matters

Adjust acceleration and jerk settings

3D print speed is a measure of how fast the printhead would move if it were travelling constantly in a straight line. In reality, the printhead is rarely moving at the stated speed, because it must gradually accelerate from a stationary position to its full speed.

Slicing software or 3D printer firmware controls how quickly the printhead accelerates from zero to the specified print speed, in addition to how quickly it decelerates from full speed to a stop position. Smooth acceleration and deceleration is key to preventing ghosting, as it prevents the kind of uncomfortable starts and stops that can cause vibrations throughout the hardware.

If using Cura, make sure that both acceleration control and jerk control are enabled. In this context, “jerk” refers to the instantaneous change of speed undergone by the printhead when it accelerates. It is also possible to input precise values using Marlin firmware — on printers like the Ender 3, for example — by navigating to the “Motion” category within the advanced printer settings. The default acceleration value is 9000; try reducing that value to 4500 or even 3000.

Ensure the printer is stable

A solid base is critical to preventing ghosting. Although vibrations are caused by printhead movement, these vibrations can be exacerbated if the printer itself is not fully stable, as this will cause even more areas of the printer to experience unwanted movement. An unsteady printer can also contribute to issues like layer shifting.

First off, the printer needs to be placed on a flat, level surface. A heavy, stable tabletop will usually suffice, as will a flat floor. Avoid flimsy tables and uneven floor surfaces like fluffy rugs or non-level floorboards. Vibration dampeners like rubber feet underneath the printer will further help in the fight against ghosting; if your model of printer does not have such feet as standard, they can be bought at a low price and attached to the base of the machine.

Parts within the printer can also contribute to a lack of stability. For example, many FDM machines contain springs that are used to assist with bed leveling. If these springs are not adequately taut — they can lose their stiffness over time — the bed can make unwanted movements while a print is in progress. Replacing the default components with stiffer springs (which cost about $3 each on Amazon) can help keep the printer more stable.

Tighten loose belts

The X/Y movement of a printhead is powered by motors, and these motors connect to the moving parts of the printhead via a system of belts. Printing works best when these belts have the appropriate amount of tension, which can be adjusted by tightening or loosening the relevant screws. You may wish to consult the documentation for your particular model of 3D printer, as this will contain instructions for making such an adjustment.

Both overly tight and overly loose belts can be a problem for a 3D printer. However, when it comes to ghosting, looseness is more often the culprit. Different printers have different methods for adjusting belt tension, but the process can usually be carried out with a screwdriver.

There are a few ways to determine whether the belt has the right degree of tension. Prusa3D advises that an X/Y belt “should be tight enough to sound like a low bass note when plucked.”[2]

Note that other components within the printer can also cause vibrations if they have become loose. It can therefore be beneficial to do a routine check for loose screws throughout the machine.

Tightening 3D printer belts can help combat ghosting

Reduce printhead weight

The weight of the printhead can directly affect ghosting, as a greater mass will create greater forces when it changes direction. This means that direct drive extruders might be more likely to create ghosting issues, as there is more hardware on the moving carriage. Bowden extruders, by contrast, have their cold end mounted onto the printer frame, so only the hotend weight must be considered.

In some cases, it is possible to cut down the moving weight of the printhead. This could be achieved by using different hardware altogether (replacing a direct drive extruder with a Bowden extruder, for example, or simply using a sleeker model of extruder) or by removing the second extruder in a dual-extrusion setup. Filament spools are not usually part of the moving carriage, but mounting them aside from the printer rather than on top of it may also reduce vibrations.

Replacing extruder hardware is a fairly drastic solution to the problem of ghosting and should therefore only be considered if there are other good reasons for doing so (such as purchasing upgrades).

Testing for ghosting

Printer users will probably be able to diagnose ghosting when they see it. Nonetheless, it can be helpful to carry out ghosting tests to measure how adjustment of print parameters or hardware affects the issue.

The best way to test for ghosting is to print a sample part that will clearly show the effects of ghosting if vibrations occur. There are a few 3D models on Thingiverse — such as this one from Ante Vukorepa — that are designed specifically to indicate the extent of ghosting. Vukorepa’s model is a cube with an indented “X” on one face and a “Y” on another; ghosting on the “X” face indicates issues on the X-axis, while ghosting on the “Y” face indicates issues on the Y-axis. (The distinction may be helpful when adjusting jerk settings, for instance, where the X and Y jerk speeds can be adjusted independently.)

A methodical way to use the ghosting test print would be to make relevant adjustments in small increments. For example, when attempting to solve ghosting by making speed adjustments, the model could be printed first at 60 mm/s speed, then at 50 mm/s, then at 40 mm/s, and so forth, to see if models printed at slower speeds show an improved surface quality.

Recommended reading: How to find free STL files

Key takeaways

Ghosting is a common 3D printing issue that can spoil the cosmetic appearance of printed parts while also compromising part strength. The problem should be dealt with promptly, as it will likely continue to affect future prints.

Ghosting can be caused by either misconfigured print settings or hardware issues, but it makes sense to investigate print settings first. For instance, it would not make sense to go to the effort of tightening your printer belts before attempting a simple reduction in print speed. Maintenance is generally only needed if adjustment of print parameters fails to solve the problem.

That being said, it is good practice to ensure that your printer is set up on a stable surface at all times, regardless of whether you are experiencing ghosting issues.

References

[1] Vibrations and ringing [Internet]. Simplify3D. 2019 [cited 2022 Aug 2]. Available from: https://www.simplify3d.com/support/print-quality-troubleshooting/vibrations-and-ringing/

[2] Ghosting [Internet]. Prusa3D. 2022 [cited 2022 Aug 2]. Available from: https://help.prusa3d.com/article/ghosting_1801