How to Level a 3D Printer Bed: Paper Method and Mesh

The point of bed leveling is not to make the bed level to the ground with a spirit level, but to make the nozzle sit the same distance from the bed at every point. If that distance differs at one corner, the first layer is either squashed there or left hanging in the air. Below we explain both manual (paper method) and automatic leveling.

Why does it matter?

If the bed is high at one corner and low at another, the first layer is squashed in one place and hangs in the air in another. This leads to problems such as first layer not sticking, elephant's foot and the nozzle scraping the bed.

When do you need to level?

• When you first set up the printer.
• After the printer has been moved or the bed has taken a knock.
• After replacing the nozzle or hotend.
• When first layers start to come out squashed on one side and torn on the other.

You do not need to level before every print. If the bed screws have not loosened, the level holds for weeks.

Preparation

1. Clean the bed and the nozzle. If there is plastic residue on the nozzle tip, the measurement will be wrong.
2. Heat the bed and nozzle to printing temperature. Heated metal expands. A level set when cold can change when hot.
3. Get a sheet of A4 paper or a 0.1 mm feeler gauge.
4. Home the printer with the "home" command.

Manual leveling: the paper method

This method is for printers that have adjustment knobs under the bed (usually at the four corners).

1. Open the "Level bed" or "Leveling" menu on the screen. This menu moves the nozzle to the corners in turn. If there is no menu, disable the motors and move the head by hand, keeping Z at 0.
2. With the nozzle over the first corner, put the paper between the nozzle and the bed.
3. Turn the knob at the corner to raise or lower the bed. The goal: feel slight drag when the paper is pulled back and forth. If the paper jams and tears, it is too close; if there is no drag at all, it is too far.
4. Do the same for the other three corners.
5. Adjusting one corner affects the others. So go around all corners at least two more times.
6. Finally check the middle of the bed. If the corners are good and the middle is too close or too far, the bed is warped.

Verify with a test print

The paper method gives an approximate result. For an exact one, print a single-layer test that covers the whole bed:

• Print five single-layer squares (four corners and the middle) or a thin pattern covering the bed.
• While printing, look at the lines of each square. They should all be flattened the same way and touching each other.
• If the lines in a square are round and separated, raise that corner a little. If they are squashed and translucent, lower it a little.
• On many printers you can also turn the knobs during the print.

Automatic bed leveling (ABL)

Many printers have automatic leveling systems such as BLTouch, CR Touch, an inductive sensor or a load cell that uses the nozzle itself. These systems measure many points on the bed and build a height map (mesh). During the print the Z axis is continuously corrected according to this map.

What you need to know about automatic leveling:

• You should still level the bed roughly. The mesh compensates for small differences, but large tilts make the layers print slightly crooked.
• You set the Z offset. The sensor measures the shape of the bed but does not know how far below the sensor the nozzle sits. This value: Z offset.
• Make sure the mesh is used. In Marlin the start G-code should have G29 (probing) after the G28 (home) line, or M420 S1 for a saved mesh. Order matters because G28 can disable the mesh.
• Take the mesh hot. The shape of the bed changes as it heats.
• In Klipper, BED_MESH_CALIBRATE measures the mesh and SAVE_CONFIG saves it.

Bed screws and springs

The springs under the bed flex and loosen over time, and the level goes off often. For a lasting fix:

• Use stiffer (often yellow) springs or silicone spacers.
• After adjusting the level, make sure the knobs do not turn from vibration.

A warped bed

If the middle of the bed is dished or raised, no corner adjustment will fix it.

• Stand a ruler or a flat piece of metal on the bed and see whether light leaks under it.
• The mesh of automatic leveling compensates for small warps.
• If you have no sensor, you can build a mesh by measuring multiple points by hand with Marlin's "Manual Mesh Bed Leveling" feature.
• If the warp is large, you need a flat glass plate or a new bed.

Common mistakes

Frequently asked questions

What can I use instead of paper?

A 0.1 mm feeler gauge gives more consistent results. Paper thickness varies between 0.08 and 0.12 mm depending on type. Whichever you use, make the final adjustment with a test print.

The leveling goes off after every print. Why?

The bed springs may be weak, the knobs may be turning with vibration or the bed carriage may be loose. Move to stiff springs or silicone spacers and check the bed wheels.