PLA Not Sticking To PEI: Here’s A Quick Fix

A good first layer is the key to a successful print. Getting the base layer in is crucial to supporting the full build. And, there’s nothing worse than watching a print slide out of place halfway through. While painter’s take and glue sticks will keep it in place, that’s messy and a hassle. That’s likely why you switched to PEI. But, what if your PEI surface also isn’t adhering to the filament? 

PEI is quickly becoming the gold standard print surface for 3D printing, but what happens when your print materials don’t stick? If your PLA is not sticking to a PEI surface, chances are, you can solve the issue by cleaning it and by adjusting first-layer (Live-Z) calibration. 

Why is PLA Not Sticking to PEI Sheet? 

In most cases, PLA has difficulty sticking to a dirty PEI sheet. However, there are some other reasons you might run into issues. Plus, because you don’t need a PLA smoothing spray or coat of glue with PEI, you shouldn’t try to add it. Cleaning and caring for your PEI sheet should be more than enough. 

• Dirty or greasy PEI sheet 
• Bed temperature is too cold 
• Bed height/nozzle height problems 
• Leveling issues 
• Cooling Issues 

Dirty or greasy PEI sheet 

A dirty or greasy PEI print surface is the most common reason your PLA won’t stick to the sheet. However, this will vary depending on other factors. For example, someone with a perfect setup can likely get away with less cleaning. If you don’t have heat and Z-offset calibrations perfected, your printer will be a bit more sensitive. 

Unfortunately, even a thin layer of oil from your hands can prevent PLA from sticking to PEI. Increasing the temperature of the bed might correct this. However, it’s also easy enough to thoroughly clean your PEI sheet between usage. You’ll also want to ensure you’re using gloves to handle the sheet between usage. 

Bed temperature is too cold 

Wetting refers to the plastic filament’s ability to stick to the surface. If the bed temperature is too cold, the PLA filament will cool too quickly. Then, rather than adhering to the PEI, it will simply sit on top. This is affected by several different factors such as the size of the build surface. The temperature of the bed and the enclosure are important for getting your filament to stick. It’s also important as you print beyond the base layer – because large differences between the top and bottom of the print will cause the plastic to peel. 

Bed height/nozzle height problems

Ideally, there should be as little space between the nozzle and the bed during the base layer as possible. Z-offset calibrations are used to reduce that distance as much as possible – or to calibrate the nozzle for a new bed. For example, if you add a PEI sheet or change the factory bed for a heated bed – your issue could very easily be calibration problems. Here, the nozzle is likely too far away from the bed – which can result in your PLA not sticking. 

Leveling Issues

Leveling issues create similar problems to bed height and nozzle problems. For example, if your bed is slightly less than level, the filament might be too far away to stick on one side. Then, your full build is unlikely to stick to the plate. In most cases, this should be one of the first issues you check. 

Cooling Issues

In some cases, the thermal settings in your printer could be causing issues. For example, if the fan is too fast, it could be causing the filament to cool too rapidly. In most cases, you have to balance fan speed to create an optimum between allowing the filament to stay molten long enough for the base to stick while still cooling it rapidly enough to set the second layer. If the filament takes too long to cool, the full print might be compromised because the filament won’t retain shape. So, it’s best to reduce fan speed slowly to achieve best results. 

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How To Make PLA Stick On PEI

If your PLA isn’t sticking to the bed, there are plenty of changes you can make. We’ll start with the most common solutions first. 

Clean the PEI Sheet 

If grease or dirt builds up on your PEI sheet, PLA will not stick. As we discussed earlier, this can be mitigated. For example, if you have a heated bed or a good nozzle setup, you will have more tolerance for dirt and grease. Normally, it’s a good idea to clean your PEI sheet between every print. This prevents dust, dirt, or grease from contaminating the print surface. 

How do you clean the PEI sheet? Expert users normally use either hot water and dish soap or 91% Isopropyl alcohol. Here, it’s a good idea to use rubber gloves so you can avoid re-contaminating the surface. And, use gloves when removing your build from the printer to reduce the number of times you have to clean it. 

Level the Print Bed

Most printers have automatic or semi-automatic bed leveling. You can run this. However, you likely want to manually level it. Here, most 3D printers have four adjustable screws on each side of the build plate. 

1. Turn the screws a few rotations to increase the distance between the bed and the print head 
2. Use your 3D Printer’s software to home (0,0,0) the printhead to the Z-coordinate and height 
3. Unlock (sometimes listed as disable) the stepper motors)
4. Use a piece of paper to calibrate the print bed so that the nozzle just allows the paper to pass between it and the print bed. You should calibrate using the screws to close the distance between the nozzle and the print bed one screw at a time. Move the nozzle to a screw and slide the paper under. It should just pass, with a faint bit of resistance. 
5. Repeat the process on all four screws and double check everything, including the middle of the plate.

Once finished, you can run a first layer test. If leveling is successful, the print should look the same across the full surface. 

Reduce Print Speed 

Reducing the print speed can achieve two things. The first is that it might allow your filament to stick to the foil better. The second is that it can give your filament more time to set if you reduce the fan speed for that same purpose. However, it’s important not to print too slowly. For example, this could cause the filament to overheat in the nozzle. Because you’d have to reduce the printing temperature to offset this – you’d likely have even more issues with the PLA sticking to the PEI. 

Adjust Temperature 

Lowering the temperature of the fan is one way to adjust the temperature of your 3D print. This is the only real way to adjust the temperature of the filament without buying a heated bed. Here, you want to slowly reduce the fan speed to see if it gives the filament more time to adhere to the PEI. It’s important not to lower the fan in big steps because the filament will stay molten too long and it will deform your build. 

If you do have a heated bed, you can more easily make these adjustments without adjusting the fan. In most cases, it’s a good idea to try setting the bed to 140 degrees. If that’s not working, you can adjust by 5 degrees in either direction. For example, if it’s still not sticking, try 5 degrees up. If the filament is staying molten too long and the build is warping, adjust 5 degrees down. 

Change the Z-Offset 

Z-height or Z-offset is the initial distance between the nozzle and the print bed. It’s normally calibrated as a fixed value during printer calibration. Some printers also allow you to set it as “first layer height” in your slicer. If your filament isn’t sticking, it’s highly possible the Z-offset is too large. You can also check how the filament is extruding, if it looks like spaghetti, the distance is too large. 

Some experts recommend trying Live-Z at –25 or even –50. However, this should depend on your bed leveling and settings. For example, if the distance is too small – the nozzle can damage the bed. It can also cause excessive vibrations and damage the build. Plus, if there’s not enough distance between the nozzle and the bed, the initial layer will be far too thin.  

Buy New PLA 

It’s always possible that you ordered a PLA sheet or film and got something else. In fact, that’s often what happens when you order from cheap shops or from overseas. Unfortunately, there’s no way to test and guarantee the quality or even type of material sold. So, if you’ve tried everything and your PLA film still isn’t doing the trick, it may be time to replace it. 

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How To Clean PEI Sheet Properly

If your print bed is levelled, your Z-Layer calibration set, and your PEI sheet maintained, you should need no other adhesion or methods. That is, after all, what you buy PEI for. 

Use Soap Under Hot Running Water 

While you don’t have to take the PEI sheet out every time, it’s important to clean it under running water. For example, alcohol, Isopropyl, and acetone are solvents. They’ll dissolve grease buildup on the PEI. You’ll then wipe some of it up and leave some of it behind. The only way to get a thorough clean is to use gloves, wash the PEI film under hot running water with dish soap, and then dry it with a soft cloth. Plain dish soap is the best degreaser for PEI.  Make sure you wear gloves. Dry it off with a soft, microfiber cloth. 

Clean the Bed 

Any time you think you might have touched the bed or contaminated it, clean it. Here, it’s a good idea to use 91%+ isopropyl alcohol. The stronger the alcohol solution, the better the solution will work. You also want to use a soft cloth or microfiber cloth. To clean the bed, pour a generous amount of isopropyl alcohol on the center of the bed. Wipe it towards the edges of the bed, being sure to push any contaminates to the edges. Wiping the bed won’t necessarily remove oil or grease. However, it will move it out of your active print zone if you clean carefully enough. Therefore, you should wipe outwards from the center, moving the cloth to the edge and then lift the cloth and move back to the middle.

If these don’t work, chances are, you want to take the sheet out and clean it in the sink. 

Using Acetone 

You can occasionally use acetone for cleaning PEI sheet material. However, acetone can eat into the PEI and cause cracking. Therefore, the more frequently you use Acetone, the sooner your PEI will fully fail. To clean using acetone, apply the acetone to a soft cloth. Wipe the bed down, starting from the center or an edge and move to an outer edge. Like alcohol, acetone will break up and dissolve anything on the bed. However, it won’t remove it. If you wipe around the bed, you’ll just move contaminates around. 

Acetone dissolves PEI. The more you use it, the less sticky your PEI sheet will become. Therefore, if you’ve already cleaned your PEI sheet with acetone a lot, that could be the reason your build isn’t adhering. 

Using Abrasives 

If cleaning your PEI sheet doesn’t improve bed adhesion, you can always try using an abrasive. Here, you want to choose the abrasive based on the thickness of the PEI. For example, if you’re using a thin film, you wouldn’t want to use sandpaper. Here, scuffing or polishing pads like Scotch-Brite are a good alternative. Look for 1200-1500 grit and then gently scuff the surface of the PEI. If you use a rougher grit, you will dig out PEI – which can reduce the quality of your PEI bed. In addition, if you use sandpaper, look for 1200 grit or finer. 

If your PEI sheet is clean, it should shed water when tilted. Any oil or grease on the sheet will cause water to pool or to split around that spot. Of course, you should always avoid touching your PEI sheet to check. Instead, you should use gloves. Alternatively, you can very carefully slide your fingers under the sheet to tilt it up. 

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Other Cleaning Products to Use for Better Adhesion 

You should never have to use more than good calibration and good cleaning to get PLA to stick to PEI. However, if you have a poor quality PEI sheet, there are some extra steps you can take. 

• Glue sticks (use purple or another color glue stick, so you can see how much of the surface you’ve covered)
• ABS Juice (You should not need this if you have a quality PEI sheet. Additionally, only use it on a smooth PEI sheet. You can not clean ABS juice off PEI without damaging the PEI. 
• Acetone – Acetone will normally reduce the stickiness of your PEI. However, you can use it on non-textured, non-powder-coated sheets. Just don’t use it more than a few times over the lifetime of the sheet. 

Other cleaners are also frequently recommended. However, they all serve to decrease adhesion, not increase it. For example, window cleaner will reduce adherence. Don’t use it if you’re trying to improve adhesion. 

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Frequently Asked Questions

If you still have questions, this FAQ should help. 

Can you use a glue stick on a heated bed? 

Yes. However, you should always apply the glue stick when the heated bed is off. Afterwards, you’ll want to make sure you don’t exceed recommended temperatures. For instance, most glue sticks start to get tacky at 250 degrees. Therefore, if you’re printing PLA, glue sticks are fine with a heated bed. On the other hand, if you’re printing ABS, your bed might remain sticky with a glue stick. 

How do you remove PLA from PEI sheets? 

If you’re removing a PLA print from a PEI sheet, it should be a simple matter of letting it cool and popping it off. However, you should never attempt this while the build is warm. It will adhere and you will damage the build. Once it’s cool, simply apply pressure to one corner of the build. Alternatively, you can flex the PLA sheet. Take care to minimize touching the PLA sheet to reduce how much you have to clean it. 

If your PLA is stuck, try using a freezing spray or applying ice around the edges. Just keep in mind that freezing the PLA will weaken it. 

What happens if you print PLA too hot? 

Overheating PLA causes it to become soft and flimsy. In most cases, it will never regain its original tensile strength. In addition, overheating PLA can also cause it to bubble, which will badly affect your print. 

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Final Thoughts

A good PEI sheet should not need anything more than proper cleaning and a good Z-Level calibration. If your PLA still isn’t adhering, try cleaning the sheet again. In any case where you have to use an additional adherent to get PLA to stick, it’s probably damaging the PEI.