The print will not come off the bed — 6 causes and safe ways to remove it

Symptom: the print came out perfectly, but you cannot get it off. The scraper skids along the edge, the spring steel sheet bows into an arc, and the model still holds. Push harder and either a piece of the bed coating tears away or the print itself cracks. Sometimes an imprint of the first layer is left on the PEI surface that cannot be rubbed off.

Adhesion is always a compromise. The same energy that saves the first layer from lifting works against you once the print is finished. The bond between model and bed forms in two ways: mechanically, when the plastic works its way into the microporosity of the surface, and adhesively, when there is genuine chemical affinity between the plastic and the coating. The first mechanism releases as things cool, because the material shrinks more than the steel sheet does. The second does not release at all, and it is responsible for most ruined build surfaces. The good news is that both can be controlled without wrestling with a scraper.

The most common causes and their fixes

1. The bed was hotter than the material needs

Excess bed temperature keeps the bottom layers soft for the whole print, so the plastic has time to flow into every irregularity in the surface. Elephant's foot is a side effect of the same thing. Most often this affects PLA printed on a profile set up for PETG.

How to check: compare your setting with the manufacturer's range. The whole PLA family works in the 0–60 °C range, PETG in 60–80 °C, and TPU Flex 98A in a mere 40–60 °C.

What to do: drop into the lower half of the range. With PLA on a PEI surface, 55 °C instead of 60 °C is often enough, and the difference in how easily it comes off is immediate. You can also set the bed temperature to drop after the first few layers.

2. The PEI surface has bonded too strongly with PETG

This is the classic that has already cost many users a new sheet. PETG and a PEI coating have similar chemistry and at elevated temperature they form a bond so durable that what comes away is not the print but a crater in the coating. The chips are permanent, and every subsequent print in that spot holds even harder.

What to do: with PETG on smooth PEI, apply a thin layer of glue stick. In this application the glue is not an adhesion promoter but a release layer that physically separates the plastic from the coating. The alternatives are a textured PEI sheet instead of a smooth one, a surface with a PEO coating, or glass with hairspray. Bring the bed temperature down to the bottom of the 60–80 °C range as well. The same principle applies to HT PETG, for which the manufacturer explicitly recommends using glue, and where the bed runs at as much as 100–120 °C.

3. The adhesion agent was applied too thickly

Glue stick and hairspray work best as a thin, even layer. Applied thickly, they form a hard crust as they cool that locks around the edges of the model and bonds to it mechanically. The giveaway is white lumps stuck to the bottom wall of the print.

What to do: wash the bed with warm water, since glue stick dissolves in it completely, and apply a new layer thinly, in a single pass. Degrease the surface with isopropyl alcohol only after washing the glue off, not instead of it.

4. The first layer is pressed down too hard

Too low a Z-axis offset squeezes the plastic into the surface and increases the real contact area. The print then holds as though it had been fused on, and underneath it has a wide, transparent rim and visible indentations from the nozzle's paths.

How to check: look at the underside of a previous print. The paths should be visible as even, adjoining lines, not as one uniform, ironed-flat sheet.

What to do: raise the offset by 0.02–0.03 mm and print a test square. The goal is a first layer that adheres but still shows the pattern of the paths.

5. You are removing it at the wrong moment

Temperature decides the outcome more than force does. With the bed hot the plastic is soft and stretchy, so the model will deform rather than release. With the bed completely cold most materials come away by themselves, because shrinkage does the work for you. The exception is ABS on glass, where at full cooling it can take a piece of the surface with it.

What to do: when the print finishes, switch off the bed heating and simply wait. With a spring steel sheet, take it off and flex it only once it is cool to the touch. Do not lever the model up until you hear the characteristic crack of the layer letting go.

6. The bed surface is damaged

Scratches, scraper dents and places where the coating has chipped act as anchors: plastic flows into every crevice and sets there. That is why the problem usually builds up and localises in one area of the sheet, most often in the middle, where you print most often.

What to do: move the model to a different part of the bed and compare the result. Cover damaged coating with a thin PEI film or replace the sheet. Give up metal scrapers in favour of plastic ones and never lever a print with a blade held perpendicular to the surface.

Porima material	Bed range	Risk of bonding too strongly	Recommendation
PLA and derivatives	0–60 °C	Moderate on smooth PEI	Stay in the lower half of the range
PLA/CF	50–70 °C	Moderate	Remove only once the sheet has cooled
PETG and PETG Transparent	60–80 °C	High on smooth PEI	Glue stick as a release layer
HT PETG	100–120 °C	High	The manufacturer recommends using glue
ABS and Eco ABS	80–110 °C	High on glass	Do not let the glass cool completely
ASA	90–120 °C	Moderate	Enclosed chamber, remove after cooling
PC/ABS	100–120 °C	High	A release layer is recommended
PA (nylon)	90–120 °C	High	Release layer, heated chamber
HIPS	80–110 °C	Low	Usually comes away on its own once cool
TPU Flex 98A	40–60 °C	High	The lowest bed temperature in the catalogue, do not raise it

The bed temperature ranges come from the official FDM technical data table from the manufacturer, Porima. The risk assessment columns describe workshop practice. The full set: print temperature table.

The thermal shrinkage trick

When a print holds on despite having cooled, make use of the difference in thermal expansion between plastic and sheet. Put the removed spring steel sheet, model and all, in the fridge for a quarter of an hour, or in the freezer for really stubborn parts. The plastic shrinks faster than steel, so the mechanical bond breaks by itself, usually with an audible crack. The method works beautifully on PLA and PETG. With large flat parts it is worth waiting afterwards until the sheet is back at room temperature before you start the next print, because a cold surface will ruin the first layer.

The second method is dental floss or thin fishing line drawn under the model with a sawing motion. It gets under the edge where a scraper has no chance, and it leaves no scratches on the coating. Never use a knife or a metal blade at right angles to the surface: one such lever can permanently take a part of the sheet out of service.

Related problems

• Warping — exactly the opposite problem, the same adjustment in the other direction.
• Elephant's foot — excess bed temperature gives you a spread base and excessive adhesion at the same time.
• The first layer will not stick — the other side of the offset and bed temperature settings.
• Dimensional accuracy and shrinkage — a first layer pressed too hard changes the dimensions of the base.
• Poor surface above supports — supports that hold too well are the same problem on the scale of the model.
• Layer delamination — forcing a print off separates layers that the print itself bonded correctly.