Bed levelling in 3D printing: what it is and how to get it right

What bed levelling actually does

The print bed needs to be the same distance from the nozzle everywhere across its surface. That gap — usually 0.1 to 0.2 mm — is where your first layer gets squeezed into the plate. Too close and the nozzle drags or clogs. Too far and the filament doesn't stick and peels away mid-print.

Bed levelling sets that gap. It doesn't mean the bed has to be perfectly flat (though that helps) — it means the nozzle travels at a consistent height above the plate as it moves from corner to corner.

Why the first layer matters so much

Everything that happens above the first layer depends on it. If the first layer doesn't grip the bed properly, corners lift, parts warp, or the whole thing peels off at layer 20. A well-laid first layer looks slightly squished into the plate, with no gaps between lines and no rough texture on top.

A bad first layer is usually one of three things: strings of filament that don't bond together because the nozzle is too far away, a thin translucent layer with almost no material because it's too close, or nothing at all because the nozzle scraped it off.

Manual levelling: how to do it

On most printers with manual levelling — budget Enders, older Creality machines, basic Prusa-style kits — there are four or five knobs under the bed that you adjust to raise or lower each corner.

Heat the bed and nozzle to printing temperature before you start. The bed expands slightly when hot, so levelling cold gives you a misleading baseline. Then home all axes (G28 in the terminal, or the home button on the screen), disable the steppers so you can move the head by hand, and work through each corner. Slide a sheet of A4 paper under the nozzle at each position. You want it to just drag with light resistance — not locked in place, not sliding freely. Adjust the corner knob until that resistance feels consistent across all four.

Move to the centre last and check there too. If the bed is warped in the middle, no amount of corner adjustment will fix it — the centre gap will be different regardless.

Run a first-layer test print straight after and watch it closely. You may need two or three iterations before it feels dialled in. That's normal.

Auto bed levelling: what it does and doesn't fix

Auto bed levelling (ABL) — BLTouch, CR Touch, Klicky probes, strain-gauge sensors like those on the Bambu A1 — probes a grid of points across the bed before each print and builds a compensation mesh. The printer then adjusts Z height on the fly as it moves, correcting for an uneven or slightly tilted surface automatically.

ABL is genuinely useful. A warped PEI sheet, a slightly wonky gantry, a bed that sits 0.3 mm lower at the right corner — ABL handles all of that once it's set up.

What it doesn't fix is a wrong Z offset. The Z offset is the baseline gap between the nozzle tip and the bed surface. If that's off, ABL applies a consistent error everywhere. You still have to set Z offset correctly; ABL then handles the variation on top. Most printers let you set this through the display or by editing a firmware value. Get that right first, then let the mesh do the rest.

The best bed levelling test prints

You don't need a complicated calibration cube to check your levelling. The most useful tests are fast and easy to read.

A single-layer square is the simplest. Print a thin rectangle at 0% infill, one perimeter wide, one layer high. Watch the lines being laid down. Gaps between adjacent lines mean the nozzle is too far away. A rough or ridged texture means it's too close. If one side looks good and the other doesn't, the bed is still slightly tilted.

A first-layer grid — a pattern of parallel lines printed across the whole build plate — shows you exactly which zones are high or low. Creality's bed levelling print is widely used and works on almost any cartesian machine. Prusa Research publish a similar one tuned for the MK4.

A large flat disc or 80 x 80 mm square at one layer high is good for checking corner adhesion. If the corners start lifting during the print, the bed is either too cold for the material, the surface needs cleaning, or the nozzle is fractionally too far away.

Any of these takes under ten minutes. That's far better than discovering the problem on layer 30 of a four-hour print.

Why levelling still goes wrong after you've done it

Oils from your fingers stop PEI, glass, and textured sheets gripping properly. Wipe with isopropyl alcohol — 90% or above — before every print. Kitchen spray isn't a substitute; the conditioners in it leave a film that makes adhesion worse.

Running the wrong bed temperature for your material is another common cause. PLA grips well at 55–65 °C. PETG prefers 70–80 °C. If you're printing PETG at PLA temperatures, you'll get first-layer lifts no matter how well the bed is levelled.

If you're using a BLTouch or similar temperature-sensitive sensor, probe when the printer is fully up to printing temperature. Some sensors read differently by 0.1–0.2 mm between cold and hot. A few printers also reset stored Z offset values after a firmware update, which can make your levelling seem to disappear overnight.

Finally, the bed itself can be the problem. A thin glass plate or a worn PEI sheet can develop a noticeable bow in the middle. ABL compensates for this up to a point, but a badly warped surface is worth replacing. Replacement PEI spring-steel sheets cost a few pounds and make a real difference.

Manual vs auto bed levelling

On a budget machine printing PLA on a reasonably flat bed, manual levelling works fine once you have the knack. It takes a few minutes per session and keeps things simple.

ABL earns its place when you're printing larger parts, switching between different bed surfaces, or using materials that need precise first-layer control. It removes most of the guesswork, which is why virtually every mid-range printer now ships with some form of ABL sensor.

The one trap with ABL is that it can make you complacent about Z offset. If your first layers look consistently under-extruded or the lines aren't bonding, check Z offset before assuming it's a slicer setting.

When to get it printed instead

If bed levelling is giving you grief and you'd rather just have the part, we can print it for you. We run a Bambu A1 and a Creality K2 Plus — both with reliable automatic first-layer calibration — so what you send us comes out right. We print PLA, PETG, ABS, ASA, and a few others. Upload your file at our printing page and we'll send you a quote. No minimum order, no fuss.