What to do when PLA is not sticking to print bed

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21 Jun, 2022

PLA filament is one of the most commonly used materials in FDM 3D printing

PLA filament is one of the most commonly used materials in FDM 3D printing

What causes 3D printing adhesion problems and how to ensure that your PLA print sticks to the print bed.

PLA (Polylactic acid) is one of the most popular 3D printing materials for fused deposition modeling (FDM); it is also widely known as one of the easiest filaments to work with. The thermoplastic material is made from plant-based starches derived from crops like corn and sugarcane and is thus biodegradable. In terms of its printing characteristics, PLA is easy to process: the filament does not require high temperatures and displays less shrinkage or warping than higher temperature materials, such as ABS. Even so, makers can still experience issues while 3D printing PLA, such as poor bed adhesion. In this article, we take a look at what could be causing your PLA to not stick to the print bed and how to fix it.

Print bed leveling

If your PLA 3D prints are not adhering well to the build platform, one of the most common causes is a unleveled print bed. If the print surface is uneven, even by a small margin, the discrepancy will lead to certain areas of your print bonding to the print bed and other areas bonding less. And, as any maker will tell you, if your first layer does not uniformly stick to the print bed, the entire print is at risk of peeling up from the build surface and warping.

There are two possible methods for ensuring you have a level print bed. Some 3D printers have auto bed leveling thanks to built-in sensors. If you are working with one of these systems, you simply have to select bed leveling in the 3D printer menu, set a distance, and your 3D printer should do the rest. Alternatively, you can manually level your print bed.[1] An easy way to do this is to align your nozzle close to the print bed and place a piece of standard A4 paper between the nozzle and the build surface. Turn the leveling knob to raise the bed until you feel slight resistance when pulling the paper out. Repeat this process in every corner of the build plate to ensure a level surface.

Print and bed temperature

One of the advantages of printing PLA is that the material doesn’t require a heated print bed and generally has good print results without one. That being said, if you are experiencing adhesion problems, printing temperatures could be a contributing factor and adjusting print and bed temperatures can make a difference. For example, if you are printing a part with a large footprint or are printing in a cold environment, a heated print bed can help to promote good adhesion for PLA prints. If you are using a heated print bed for PLA, a temperature between 50 °C and 60 °C is recommended (different filament brands should specify their optimal heated bed temperature).[2] 

Finding the right print temperature is a critical factor when 3D printing any filament: it affects the rate at which the thermoplastic melts and flows through the 3D printer nozzle. And when it comes to PLA, setting an optimal hotend temperature can lead to optimal initial layer adhesion. Compared to other printing filaments, PLA requires modest print temperatures, typically in the range of about 210 °C. However, if that temperature isn’t delivering the results you need, it could be worthwhile to tweak the nozzle temperature slightly (in 5 degree increments). Evaluate the different print temperatures with some small test prints. If adhesion is still a problem, it may be due to other factors.

Recommended reading: PLA bed temperature & print temperature settings

Bed adhesives

Using an adhesive to glue your 3D print to the build platform can be remarkably effective. While the term may sound technical, bed adhesives are simply substances that help your 3D print’s first layer stick to the print bed. Common DIY bed adhesives for PLA filament include glue sticks or hairspray. Blue painter’s tape is also a good solution for PLA (applied sticky side down), as the filament bonds to the tape’s porous texture.

There are also adhesives specifically designed for FDM 3D printing, including Magigoo products. If you are buying a 3D printer adhesive, simply check that it is suitable for PLA (some are designed for higher temperature thermoplastics). Whatever type of adhesive you are using, it is important to only apply a thin layer onto the printer bed, otherwise the adhesive can create leveling issues or affect the surface quality of the print’s bottom layer.

Gears 3D printed on green print bedPainter's tape works well as an adhesive surface for PLA because of its porous texture.

Clean print bed

An easy way to improve bed adhesion for PLA filament is to clean your 3D printer’s build plate. Print surfaces can be exposed to substances like dust, dirt, or grease from the environment they are in or from contact with human hands. These substances, as well as others—like leftover adhesive or traces of filament—can negatively impact how well your PLA print sticks to the print bed. Cleaning the bed surface before a build can therefore help to improve first layer adhesion.

There are a couple of methods for cleaning a print bed depending on what type of build plate you are using. If you are using a glass bed or borosilicate glass print bed, start by removing the plate and gently scraping off any filament or adhesive residue. From there you can wash the glass surface with window cleaner or soap and water. Finally, wipe down the glass using isopropyl alcohol (IPA) or acetone to remove any traces of grease that could inhibit adhesion. If your 3D printer has a PEI build plate, you can wash it with soap and water or IPA. With this type of material, however, limit the use of acetone to once a month.

Recommended reading: How to clean 3D printer beds: Glass, PEI, adhesive

Z offset settings

Nearly as important as bed leveling is the Z offset value. This 3D printer setting determines the distance of the 3D printer nozzle to the default Z-axis value, also known as the home position. With FDM 3D printers, the home position refers to the closest position of the 3D printer nozzle to the build plate before it touches it. The Z offset setting lets users adjust this default position to move the nozzle’s starting point closer or farther from the home position.

Adjusting the Z offset can place your nozzle at an optimal distance from the build surface in order to improve first layer adhesion. It is especially useful if you are using an adhesive build surface or a secondary build plate, such as a PEI sheet. In the case of PLA thermoplastic, it can also be beneficial to have a slightly closer nozzle position, because the material adheres well when the nozzle puts slightly more pressure on the extruded plastic. If you are adjusting the Z offset, a higher value (>0) will raise the nozzle, while a lower value (<0) will lower it.

Recommended reading: Z offset: What it is and how to adjust it

Dry filament

Poor first layer adhesion may not be caused by your 3D printer hardware or settings at all. In some cases, the quality of the filament may be the culprit. Thermoplastic filaments such as PLA can absorb moisture from humid environments if not properly stored. In the 3D printing process, the water molecules absorbed by the filament are heated along with the plastic and evaporate. This can create air bubbles in the filament as it passes through the extruder, resulting in a variety of flaws, including poor adhesion, stringing, and blobbing. 

Maintaining dry PLA filament is therefore important to a successful 3D print. Proper storage techniques, like keeping filament in sealed dry boxes with desiccant packets, can keep moisture at bay. If you suspect your filament has already absorbed moisture, however, it is also possible to dry it out. Because of its low glass transition temperature, PLA can be dried out at fairly low temperatures. For instance, you can dry a spool of PLA in an oven at a temperature between 40 and 45 °C for between four and five hours. Alternatively, you can use a food dehydrator or dedicated filament dryer to remove water from the material.

Recommended reading: How to Dry Filament

Extruder deposits red filament layerGood first layer adhesion is critical to ensuring a successful 3D print.

Rafts and brims

Another reliable way to improve bed adhesion is to use a raft or brim. While mostly recommended for higher temperature filaments like ABS and PETG, rafts and brims can also offer benefits for PLA, especially if you are struggling with adhesion. Rafts and brims are added to your 3D model before printing in slicer programs such as Cura and help to anchor your print to the build plate.

A raft can be thought of as a 3D printed platform on which your model is printed. In other words, a raft is a printed structure that sits underneath your model, functioning as its base. Because the model is printed onto the 3D printed raft, it adheres to the printed structure instead of the build plate. Rafts can also help to create a level printing surface if you have an uneven or damaged print bed. 

A brim, for its part, is a printed border that touches the edge of the 3D model, similar to a brim of a hat. Brims give 3D prints a broader surface area at their base, which can help to improve adhesion. In a sense, brims anchor the edges of a print to the build platform resulting in better adhesion and greater stability. If you are using rafts or brims, it is important to note that they will need to be removed from the final part, which can add post-processing time.

Recommended reading: 3D Printing Rafts vs Brims vs Skirts: How to get started

Replace build plate

If you try all the aforementioned methods and your PLA is still not sticking to the print bed, it might be time to swap your 3D printer’s build plate for a new one. Over time, some build plates can start to warp and deform. Other defects, like damage caused from part removal, can also reduce the quality of your 3D prints. If you suspect a warped or damaged build surface is causing poor bed adhesion, try replacing your build plate.

When it comes to choosing a new build plate, there are many different materials to pick from. If you primarily use PLA filament, the best options are either glass print beds or spring steel sheets with PEI surface. Both of these surfaces are reliable and offer good adhesion with PLA. Glass build plates are easy to clean and have no risk of warping. Spring steel plates with PEI offer good adhesion properties during the printing process as well as easy part removal.

Conclusion/Key takeaways

Whether you are a beginner or experienced 3D printing user, you should know that good bed adhesion is imperative to a successful print job. PLA is fortunately one of the easiest 3D printing filaments to work with and generally sticks well to the print bed. If adhesion problems do occur with PLA, however, simply follow this troubleshooting guide. Ultimately, ensuring a level print bed, setting optimal extrusion and temperature settings, using adhesive aids and extra help in the form of rafts and brims can help you to get your PLA to stick.

References

[1] https://www.tomshardware.com/how-to/level-3d-printer-bed 

[2] https://www.wevolver.com/article/pla-bed-temperature-print-temperature-settings 

More by Tess Boissonneault

Based in Montreal, Tess is a freelance content writer and editor with over five years of experience in the technology and manufacturing fields. She has a background in media studies, and holds a master’s degree from the University of Amsterdam.

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