First layer adhesion: why prints lift and how to test the bed

If your first layer keeps lifting at the corners, nine times out of ten it is either a dirty bed or the bed is too cold for the material you are running. The other one time, the nozzle is sitting too far from the plate. Everything else is a distant third.

Get those three right and most prints stick without a brim, a raft, or a layer of glue stick. This article walks you through how we check each one on a printer that has come in for repair, and the simple test print we run before we hand it back.

What a good first layer actually looks like

A healthy first layer is squished. The lines should sit slightly flattened against the plate, touching each other with no visible gap between them. You should not see the round profile of the extruded strand. If you can see daylight between adjacent lines, the nozzle is too high. If the surface looks like polished plastic and the corners curl up, the nozzle is too low and the plastic has nowhere to go.

Run a finger over a cooled first layer. It should feel smooth and uniform, not ribbed.

What causes poor first layer adhesion

There are really only a handful of root causes, and they show up in predictable ways.

A dirty bed. Fingerprints, hand cream, old release agent and stray bits of filament all kill adhesion. PEI in particular hates skin oil. If the print sticks fine in the middle of the plate but lifts in the spot where you always grab it, that is a contamination problem, not a calibration one.

The bed is too cold for the material. PLA usually wants 55-65 deg C. PETG likes 70-80 deg C. ABS and ASA need an enclosure and a bed at 100-110 deg C, otherwise the corners contract faster than the middle and peel off the plate. Running PETG at PLA temperatures is a common cause of mystery lifting.

Nozzle too far from the bed. Even half a millimetre too high and the filament lands as a round noodle instead of a flattened ribbon. It cools before it bonds.

The bed is not flat, or not level relative to the gantry. Mesh bed levelling hides a lot of sins, but it cannot compensate for a warped plate or a gantry that is tilted front to back.

Material problem. Damp filament hisses and pops at the nozzle and lays down a foamy, weak first layer. PETG and nylon are the worst offenders. If you can hear it, dry it.

Drafts and cold air. A window open behind a Bambu or a Prusa will pull heat off the corners of an ABS print and lift it off the bed before the second layer goes down.

How we test the bed

Before touching the slicer we check the hardware. A straight edge across the plate at room temperature will show any obvious warping. Most aluminium plates are flat enough. Glass is almost always flat. Cheap spring-steel sheets can develop a slight dish in the middle after a year of being pulled off and flexed.

Next, the gantry. With the printer powered off and the steppers free, we lift the X axis to the top of its travel and lower it gently onto the bed. If one side touches before the other, the Z motors are out of sync, or one lead screw has lost steps at some point. On a Creality Ender style printer you can just lift the gantry by hand to reset it. On a CoreXY machine that is not an option.

With the bed heated to its target temperature we run an auto-level (mesh probe) and look at the mesh values. A healthy bed shows variation of less than about 0.3 mm across the whole plate. Much more than that and you are asking the firmware to do a lot of work on every print.

What to try first, in order

Work through these before anything else. They are free and they fix most cases.

1. Wash the plate. Warm water and washing-up liquid, rinse, dry with a clean cloth. Not isopropyl alcohol on its own — that just moves the oil around. For really stubborn contamination, isopropyl after washing-up liquid is fine. 2. Set the bed temperature for the material, not for the previous print. PLA at 60, PETG at 75, ABS at 105 are sensible starting points. 3. Run the printer's first-layer or bed-level calibration. On Bambu that is the built-in routine. On a Prusa MK4 it is the first-layer calibration in the menu. On Creality with a CR-Touch, it is auto home then auto level. 4. Print a single-layer test square. Watch the corners. 5. Adjust Z offset live, while it prints. Lower until the lines just start to merge into a solid sheet with no gaps and no ridges.

If you have done all five and it still lifts, the problem is usually the plate surface itself or the material.

A first layer adhesion test print

We use a 100 mm x 100 mm square, one layer thick, no infill, with the skirt disabled. Print it in the actual material you are about to use, at the actual bed and nozzle temperature, on the actual plate.

Look for four things. First, the corners should stay glued down for the whole print. Second, the lines in the middle should touch each other with no gaps. Third, the surface should be uniform — no shiny patches next to matte ones, which would indicate uneven squish. Fourth, the print should release cleanly when the plate has cooled to room temperature. If you need a scraper, the squish is too aggressive.

A 100 mm square takes a few minutes and tells you more about your printer than any benchy.

Can I fix this myself?

Usually, yes. First-layer problems are calibration and cleaning, not repair. You do not need any new parts and you do not need to open the electronics. If you are comfortable changing the bed temperature in your slicer and adjusting a Z offset, you have everything you need.

The times it stops being a DIY job are when the bed itself is warped beyond what mesh levelling can fix, when a Z motor or lead screw is failing, when the heater cartridge or thermistor in the bed is reading wrong, or when a probe (BLTouch, CR-Touch, inductive) is faulty and giving inconsistent mesh readings. Those are bench jobs.

Glue, hairspray and other crutches

A thin layer of PVA glue stick on glass is a perfectly reasonable adhesion aid, especially for PETG, which can otherwise weld itself to a PEI sheet and tear chunks out of it. Hairspray works on glass too. Neither is a fix for a poorly calibrated machine — they are a compromise for awkward materials. If you need glue to get PLA to stick to a clean PEI sheet, something else is wrong.

Never use glue stick on a textured PEI sheet. It fills in the texture and is a misery to clean off.

When to mail it in

If you have washed the plate, set the temperature correctly, run the calibration, adjusted the Z offset and it still will not lay down a clean first layer, the problem is likely mechanical. Warped plates, failing probes, dead bed thermistors and Z axes that bind in one spot are all things we see regularly and can fix on the bench.

We are a UK mail-in workshop. Send us the printer with the plate you have been using and a sample of your filament, and we will run the same first-layer test print we have described here, find the underlying fault and report back before doing any paid work. Get in touch at /contact.html and we will send you the postage details.