One of the vital steps to ensure that you don’t have issues regarding bed adhesion, whether it’s the material not sticking to the build plate at all or sticking way too much to the point where you can’t remove it, is to use a surface that plays well with the filament you’re using.
In this article, we will discuss whether it would be a good idea to print PETG on PEI surfaces, take you through the process of removing a stuck PETG print off your PEI sheet, and take a quick look at some of the factors that can prevent PETG from sticking to PEI properly.
Can You Print PETG on a PEI Sheet?
When it comes to printing PETG directly on a PEI sheet, the first question we have to ask is whether the PEI sheet is smooth or textured (powder coated), as each of these surfaces will behave quite differently from the other.
If you have a powder-coated PEI sheet at hand, we can say that you practically have access to the perfect surface to print PETG on, as the PETG will stick to the powder-coated PEI sheet strongly enough to ensure that poor bed adhesion never becomes an issue but also not so strong that it becomes impossible to get the plastic off the build surface, without any need to go through some extra steps to prepare the surface first.
On the other hand, in the case of using a smooth PEI sheet, the primary problem you will come across when printing PETG is the adhesion between the PETG and the PEI being way too strong, which will often lead to a scenario where it becomes impossible to separate the printed part from the build surface without damaging both the print and the build surface due to a chunk of the PEI coming off together with the printed part.
With this in consideration, while it would be best to pick up a powder-coated PEI sheet and refrain from printing PETG on a smooth PEI sheet whenever possible to avoid the risk of permanently damaging the build surface and wasting time & material on a failed print, one workaround to prevent your PETG prints from getting stuck to smooth PEI for cases where you have no other option is to apply a release agent to the build surface any time you would like to print PETG.
A release agent, in this case, refers to a thin layer of material that sits between the surface of the PEI sheet and the PETG your 3D printer puts down, which effectively acts as a bridge between the two and prevents the PETG from permanently bonding with the PEI, making it a whole lot easier to pop your PETG prints off your smooth PEI sheet as a result.
While there are many things you can use as a release agent, with Windex (window cleaner), PVA glue stick, and hairspray being some of the most commonly-used examples, our recommendation would be to go with Windex whenever possible, as it does the job perfectly without creating too much of a mess, is easy to get a hold of, and is pretty straightforward to apply by simply spraying it once on the sheet & wiping it down with a cloth to distribute it evenly across the entire print surface.
As you may predict, one downside of this workaround is the fact that the release agent will reduce the strength of adhesion between the PETG and the PEI sheet, and even though this is necessary for the PETG not to get fully stuck on the PEI sheet, it can possibly lead to bed adhesion issues that you haven’t experienced before, such as warping, due to the strong adhesion between PEI and PETG originally compensating for it.
In such a case, our recommendation would be to resolve the warping problem through other means, such as increasing the bed temperature, using a lower print speed for the initial layer, ensuring that the print bed is correctly leveled & the Z offset is optimized, and lowering the initial layer cooling fan speed, as this will be the best way to resolve both the warping and the strong adhesion problem together.
Removing a Stuck PETG Print / Residue off a PEI Sheet
Since PETG sticks extremely well to smooth PEI, as we have mentioned earlier, having a PETG print stuck on your PEI sheet in a seemingly unremovable way, whether it’s the entire print or some residue, is a common problem you can come across after switching to PETG, or a smooth PEI sheet for the very first time.
To remove a PETG print stuck to a PEI sheet without damaging either the print or the sheet, the first step we recommend taking is to remove the sheet from the print bed and to gently flex it from as many points close to the edges of the print as possible, which should eventually release some parts (usually the corners) of the print and make it easier to separate the print from the sheet without having to apply too much force.
If that doesn’t work, our following recommendation would be to scrape the print off the PEI sheet with the help of a plastic spatula (flexing the plate will be helpful here as well), such as one you can find in the kitchen, and not a metal one, as a wrong move with a metal spatula can end up with you damaging your PEI sheet while trying to get the PETG off, especially considering that you will most likely need to apply some force to get the spatula in.
In the case where you still can’t get the print off the PEI sheet, the following method we recommend trying is to pop the PEI sheet into the freezer for 30 minutes to an hour, which will weaken the adhesion between your print and the build surface, and then to flex the sheet or use a plastic spatula again, which, in most cases, causes the PETG to come off the PEI sheet cleanly.
As an alternative, you can apply some cooling spray on the PEI sheet, specifically concentrating around the edges of the print where it connects to the build surface, which will create a similar effect to the freezer method and help you separate the PETG from the PEI in a quick and convenient way, especially if you have no freezer space to fit the PEI sheet together with your print and require a swift solution that will get the job done.
Finally, if all else fails, one more thing you can try is to stick the PEI sheet back on the print bed & warm the print bed up to a temperature value lower than the one you’ve used for printing (10-15 degrees less should do), and while this method isn’t our first recommendation as it can cause your print to deform if you end up using a bed temperature that’s too high, heating the PEI sheet up will definitely weaken the strength of adhesion and make the print easier to remove, especially in cases where the sheet cooled all the way down to room temperature before you attempted to remove the print.
On the other hand, for small bits of PETG, where pulling the plastic pieces off the PEI sheet in one piece without damaging them isn’t critical, our primary recommendation would be to take the PEI sheet off the print bed and thoroughly wash it a combination of hot water and regular dish soap (few drops should be enough) until you remove all the residue and rinse all the dish soap off the surface, which should get the job done in a quick and convenient manner.
Once you have ensured that the sheet is clean, all that’s left to do is to dry it with the help of some paper towel (avoid touching the print surface with your hands to avoid getting it dirty again, or wear single-use gloves to make things easier), and your PEI sheet will be ready to print once again.
What to Do If PETG Does Not Stick to a PEI Sheet?
Even though PETG is supposed to adhere to PEI without issues, sometimes even more than necessary, it’s also possible to come across scenarios where the first layer of your PETG print refuses to stick to the surface no matter what, which usually stems from external factors.
If you can’t get your PETG prints to stick to your PEI sheet, the very first steps we recommend taking are to remove the PEI sheet from the print bed, ensure that it has completely cooled down, and clean it thoroughly by wiping it with isopropyl alcohol, which will get rid of all the dirt and grease that can reduce the strength of adhesion between the sheet and your prints, and most likely solve the problem you’re facing right off the bat.
On the other hand, in scenarios where wiping the sheet with isopropyl alcohol doesn’t completely clean the PEI sheet, with some residue from old prints still visible on the surface, our recommendation would be to follow up with a hot water & dish soap wash, as we have mentioned in the previous section since it’s possible for soap to remove some of the things that isopropyl alcohol cannot.
Additionally, to avoid having this problem again, or at least reduce its frequency, we highly recommend wearing single-use gloves whenever you’re handling the PEI sheet, whether it’s cleaning it, removing it from the print bed, placing it on the print bed, or even taking your print off it, as touching the sheet with your bare hands can quickly contaminate the build surface, which would effectively lead to you having to clean the sheet over and over after every few prints.
In a scenario where cleaning the PEI sheet wasn’t enough to get the PETG to stick, the following step we recommend taking would be to look at the print settings that have a considerable influence on bed adhesion and to adjust them accordingly, whether it’s increasing the bed temperature, lowering the Z offset value, re-leveling the print bed, reducing the initial layer print speed, and decreasing the initial cooling fan speed, as even one of these settings tuned incorrectly can lead to bed adhesion problems on its own.
Additionally, when going through the print settings, one thing that can come in quite handy is to watch your 3D printer as it’s printing the first layer and look out for any signs that can indicate something is wrong, such as the nozzle consistently staying too high above the build surface (and the plastic not sticking to the build surface at all as a result), which would effectively point toward a Z offset problem.
Last but not least, another widely encountered problem that can lead to your PETG prints not adhering to the PEI build surface is the filament absorbing moisture, which is highly likely if you live in a humid area & you had your spool of PETG sitting around in the open for a while, especially considering that PETG is quite prone to absorbing moisture due to its hygroscopic qualities.
While it’s possible to dry your PETG and make it usable without issues again, our primary recommendation to rule out this and any other filament-specific problem, in this case, would be to pick up a new spool of high-quality PETG filament and to see whether the same issue occurs again, as ruling out the filament itself as the culprit will make the troubleshooting process much more straightforward.
Conclusion
With the condition of it being textured and not smooth, we can consider a PEI sheet to be the best build surface for printing PETG filament, as this combination will effectively ensure that the material sticks well enough to the surface without the need for any extras, but not to the point where you would end up having trouble when removing the 3D-printed part.
While this is not to say that smooth PEI won’t work for PETG, applying a release agent to the surface first, whether it’s Windex, hair spray, or glue stick, will become necessary in the case of smooth PEI, as the strength of adhesion between the two materials being way too strong can otherwise cause issues when removing the print.
As a software developer by profession, David has been particularly interested in how 3D printing works even before he picked up his first 3D printer, and completely fell in love with the hobby once he got his hands on a Prusa i3 MK2 for the first time back in 2017. Due to him enjoying both the functional and the non-functional sides of 3D printing equally, you’ll rarely see David’s 3D printer in an idle state.