Print quality and tuningBeginner15 min

Bed levelling and the first layer

See what the nozzle gap does to every line, why a warped bed ruins the first layer and how a bed mesh fixes it, then diagnose real first-layer problems.

The nozzle height decides every line

Drag the slider and watch the end of seven printed lines. The plastic keeps its volume, so a lower nozzle squeezes it wider and flatter, and a higher nozzle leaves it tall, thin and barely touching.

Nozzle height above the plate0.15 mmThe slicer assumes a 0.2 mm first layer, so about 0.12 to 0.18 mm squishes it just enough.

Good squish

Each line is pressed flat against the plate and fused to its neighbours. This is the surface you are looking for.

Line width

0.53 mm

Line height

0.15 mm

Gap between lines

0.00 mm

Grip on the plate

77%

Teaching model: a 0.2 mm layer and a 0.42 mm line that keeps its volume. Real plates, materials and nozzles shift the exact numbers, so judge your own first layer by eye.

A warped bed: let the printer measure it

No bed is perfectly flat. The printer touches the bed at a grid of points and then raises and lowers Z as it moves, so every line is pressed equally. Choose a warp and compare with and without the mesh.

Shape of the warp

Warp0.40 mmProbe points5 × 5Mesh compensation on

Worst height error

0.27 mm

Of the layer height

133%

Enough to ruin some lines

Green: the nozzle height matches the bed
Red: the bed is higher than expected, so the line is squashed
Blue: the bed is lower than expected, so the line is too high

The warp is drawn about 40 times bigger than life. Real printers use smoother interpolation than the straight-line blend used here, so a dense mesh helps a little less in this demo than it would in practice.

Ways to level the bed

From the simplest to the most automatic. All of them aim at the same thing: an even gap across the whole plate.

Screws and a sheet of paper

Heat the bed, slide a sheet of paper under the nozzle at each corner and turn the knob until it drags lightly. Repeat, because each corner affects the others.

Best for: Printers without a probe, and as a first check on any printer.

Assisted tramming

The printer measures the corners and tells you how many turns each knob needs. It gets the plate parallel to the nozzle's travel before any mesh is used.

Best for: Printers with a probe and manual knobs.

Probe and bed mesh

A probe touches or senses the bed at a grid of points and the firmware corrects Z while printing. Run it hot, and tram first so the mesh only has to fix small bumps.

Best for: Most modern printers, and warped plates.

Load cell or strain gauge

The nozzle itself feels the bed with a sensor, so it measures exactly where plastic comes out, whatever the plate is made of.

Best for: Newer printers that include one. Nothing to set up by hand.

Setting the Z offset

Levelling makes the gap even. The Z offset sets how big that gap is. Do it with the first-layer test your slicer or printer provides.

1Clean the plateWash with dish soap or wipe with isopropyl alcohol. Fingerprints and oil stop lines from sticking, whatever the height.
2Heat everything to print temperatureMetal expands. Set the bed and nozzle to the temperatures of the material you will print.
3Home and tramHome the axes and make sure the plate is evenly aligned or the mesh is current.
4Print a first-layer testA single wide layer or a few large squares. Watch the first lines as they are laid down.
5Adjust live in small stepsLower the offset if lines are round with gaps, raise it if they are ridged or the nozzle scrapes. Change by about 0.02 mm at a time and wait for the next line.

Diagram of a nozzle at the right height, too high and too low above the build plate — The first layer gap: right height (tick) presses a flat line onto the plate; too high (top cross) leaves a round line that barely touches; too low (bottom cross) squeezes plastic sideways.Stemfie3D · CC BY-SA 4.0 · Wikimedia Commons

A nozzle laying the first layer on a blue-taped bed, with a cylindrical bed probe beside it — A real first layer going down. The metal cylinder beside the nozzle is an inductive bed probe: it measures the bed so the printer can level in software.Luke Jones · CC BY 2.0 · Wikimedia Commons

Diagnose your first layer

Pick what you see. Each symptom has a likely cause and a first fix to try.

What does it look like?

Likely cause

The nozzle is too high, the plastic is under-extruding, or the nozzle is partly clogged.

First thing to try

Lower the Z offset a little. If gaps remain at the right height, check the nozzle and the flow ratio.

Plate, temperature and speed

A perfect gap still needs a surface and a temperature that the plastic likes.

Build plates

Smooth PEI

Gives a very smooth, shiny bottom. Prints usually pop off when the plate cools. Keep it free of oil.

Textured PEI

Gives a matte, grainy bottom and forgives small gap errors. Often needs a slightly lower offset than smooth.

Glass

Flat and cheap but needs a thin layer of glue stick or hairspray for most materials, and is harder to get a clean release.

Typical bed temperatures

Material	Bed
PLA	50–65 °C
PETG	70–85 °C
ABS / ASA	90–110 °C
TPU	30–60 °C

Typical ranges only. Start with the numbers on the spool label or your printer maker's profile.

Print the first layer slowly (many profiles use 20 to 50 mm/s) and with a slightly thicker layer. It gives the plastic time to bond and makes small height errors matter less.

Check yourself

Pick an answer for each question.

1. The first layer shows gaps between lines and the lines peel off easily. What is the usual cause?

2. A bed mesh helps most when the bed is…

3. You see ridges and a rough first layer, with a wide flared foot at the bottom of the part. What do you do?

4. Which is the better order?

Sources (5)

Figures such as temperatures and drying times are typical ranges. Always check the label on your own spool and your printer manufacturer's guidance.