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Bed adhesion · PET-G

PET-G Sticking Too Well — and Chipping Your PEI

PET-G and PEI are chemically close enough that at a hot bed temperature they do not just grip, they fuse. When you lever the part off, the weakest thing in the joint gives — and that is the PEI sheet, not the part. You get a crater in the plate and a disc of PEI stuck to your print. Drop the bed to 70–75 °C, let the plate cool completely before removing anything, and put a release layer between the two.

Stop it happeningPET-G settings

Vijay Raghav Varada

60–85 °C published bed range70–75 °C where PEI survivesRelease layer, not more gripCheaper than a new sheet
PrintStick Standard, the formula used as a release layer under PET-G
Four fixes

How to Keep the Plate

This is the one adhesion problem where the answer is less bond, not more.

01 · Bring the bed down to 70–75 °C

The published range is 60–85 °C and the top of it is where the trouble lives. At 85 °C PET-G and PEI are both soft enough to interdiffuse at the interface. At 70–75 °C the part still holds perfectly well and comes off cleanly. If your first layer fails at 70 °C, that is a Z-offset problem wearing a temperature costume.

02 · Wait for the plate to go cold

PET-G releases on its own as the plate drops through about 40 °C. Removing a part from a warm plate is where sheets get damaged — the bond is still near its strongest and you are applying a lever. On a flexible sheet, wait, then flex; on glass, wait, then the part often falls off by itself.

03 · Put a release layer in between

A thin film of bed adhesive is not there to hold PET-G down — it holds fine. It is there so the polymer bonds to the film instead of to the sheet, and the film washes off with water. This is the single reliable way to keep a PEI sheet usable while printing PET-G regularly.

04 · Or change the surface

Textured PEI is more forgiving than smooth PEI because there is less continuous contact area, though it can still take damage. Glass with a release layer is the safest combination. Garolite and BuildTak both handle PET-G without fusing. What you must not do is print PET-G on bare smooth PEI at 85 °C and hope.

What too much grip does

PET-G Takes the Sheet With It

A lifted part with a piece of the build sheet stuck to it, and a matching crater in the sheet
PET-G bonds to bare PEI hard enough that the part and the sheet come apart in the wrong place. A release layer between the two is what keeps the sheet whole.
If it has already happened

A PEI sheet with a crater in it is not repairable, but it is still usable outside the damaged area, and a release layer stops it getting worse. Do not try to sand the crater flat — you will thin the PEI locally and the next part will lift there instead. Reposition prints away from it and replace the sheet when the damage reaches where you need to print.

Working numbers

PET-G and CF-PET-G Settings

SettingPET-GCF-PET-GNote
Bed temperature60–85 °C70–85 °CAim at 70–75 °C on PEI
Nozzle temperature225–250 °C240–265 °CCF needs a hardened nozzle
Recommended surfacePEIPEI with adhesiveRelease layer on both
Part cooling30–60 %30–50 %Less than PLA; PET-G strings when cold
Drying65 °C / 4 h65 °C / 6 hMandatory for CF-PET-G
EnclosureNot neededNot neededPET-G barely shrinks
First-layer height0.32 mm0.32 mm0.8 × a 0.4 mm nozzle
AdhesiveAs a release layerStandard formulaNot for grip — for separation
Diagram of a thin interface layer between a printed part and the build plate
The part nobody expects

The Same Bottle, Doing the Opposite Job

Every other page in this guide is about holding a part down. This one is about letting it go. It is the same product either way: a thin, controlled interface between the part and the plate, which is exactly what you want when the two would otherwise bond to each other permanently.

PrintStick Standard covers PET-G and CF-PET-G along with PLA and TPU. One pass of the 30 mm felt head across the footprint, print as normal, let the plate cool, lift the part — and the plate wipes clean with water. The PEI stays where it belongs, which is on the sheet.

How PrintStick works
Standard is the formula for PET-G.In stock · ships across India with tracking · GST invoice · 50+ prints a bottle · leaks or arrives damaged, we replace it
Add Standard to cart₹1,199 · PLA, PET-G, TPUAdd Plus to cart₹1,899 · ABS, PC, Nylon
PET-G, answered

Questions About PET-G and PEI

Why does PET-G stick so hard to a PEI bed?
The two polymers are chemically compatible, so at a hot bed temperature they interdiffuse at the interface rather than simply gripping. The joint ends up stronger than the PEI layer itself, and when you lever the part off the PEI tears out with it. It is the one case where good adhesion is the problem.
What bed temperature stops PET-G damaging PEI?
70–75 °C. The published working range is 60–85 °C, and the damage concentrates at the top of it. At 70–75 °C the part holds perfectly well through the print and releases cleanly once the plate is cold. If the first layer fails at 70 °C, the cause is the nozzle gap, not the bed.
How do I get a PET-G part off without pulling out the PEI?
Wait. PET-G releases on its own as the plate cools through about 40 °C, and most parts can then be lifted by hand or will pop off a flex plate with a gentle bend. Removing a part from a warm plate is when sheets get craters, because the bond is near its strongest and a scraper is a lever.
Does a bed adhesive help with PET-G, or make it worse?
It helps, but for the opposite reason to every other material. A thin film is a release layer: the PET-G bonds to the film rather than to the sheet, and the film washes off with water. It does not reduce how well the part is held during the print — it changes what it is held by.
Is textured PEI safer than smooth PEI for PET-G?
Generally yes, because the contact area is broken up rather than continuous, so there is less surface to fuse and less leverage on any one point. It is not immunity — textured sheets do get pitted by PET-G at high bed temperatures. Keep the bed at 70–75 °C and use a release layer on either type.
Can I print PET-G on glass?
Yes, and with a release layer it is one of the most reliable combinations there is. Bare glass is smooth enough that PET-G can bond strongly to it too and take a flake of glass with it, which is a worse outcome than a damaged PEI sheet. Put a film down first.
Related

The Rest of the Guide

Keep the Plate, Keep the Part

Fracktal designs and builds its FDM machines in Bengaluru, and prints PET-G on them every week. Ask us anything about a material and a plate that are not getting on.

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