Kerf compensation

Measure the material removed by the laser, then compensate with explicit offset geometry and a verified scrap test.

When the laser cuts, it removes a strip of material called the kerf. A cut centered on the design line removes material from both sides of that line, so exterior parts usually come out smaller and interior openings usually come out larger than the design.

The exact kerf depends on the machine, material, thickness, focus, power, speed, and other process conditions. Do not treat a range associated with a broad laser category as authoritative for your setup. Measure the result produced by the settings you will actually use.

Current Beam Bench behavior

Beam Bench stores and displays a per-layer Kerf value, but the current planner does not apply that value to generated job paths. It does not change the planned geometry, Preview, or generated G-code.

Do not rely on the per-layer field to compensate a part or opening. Use explicit geometry from Offset Shapes, then verify it on scrap.

Measure the kerf

Draw a simple test square and cut it from the same material with the same focus, power, speed, and air-assist setup planned for the real job.
Measure the part with calipers.
Subtract the measured dimension from the design dimension. The difference is the total kerf loss for that axis.
Divide the total loss by two to obtain a starting kerf radius.
Cut and measure an interior opening as a second check.

For example, if a 50 × 50 mm design produces a 49.8 × 49.8 mm exterior part, the total loss is 0.2 mm and the starting radius is 0.1 mm. These are metric reference values. Convert design dimensions and the radius to the unit shown by the current Display Unit before entering them; Beam Bench stores geometry internally in millimeters.

Treat the result as specific to that exact setup. Re-measure when the material, thickness, focus, or cutting settings change.

Create explicit compensated geometry

Keep the source geometry while you verify the result:

Select the contour to compensate.
Choose Tools → Offset Shapes (Alt+O).
For an exterior part contour, choose Direction: Outward. For an interior opening, choose Direction: Inward.
Set Distance to the measured kerf radius in the current Display Unit.
Leave Delete Original off and inspect the live preview before applying the offset.

After applying the offset, ensure that only the intended compensated paths are assigned to output. Keep the original geometry on a non-output layer or remove it only after the compensated path has been verified.

Verify before cutting real parts

Preview and cut the compensated exterior part and interior opening on scrap. Measure both with calipers and test the intended fit. If either result is wrong, adjust the offset and repeat the scrap test.

Do not produce the real parts until the compensated scrap result matches the intended dimensions and fit.

When it matters

Slot-and-tab assemblies: the slot and tab dimensions determine whether the parts fit.
Press-fit parts: a small dimensional error can change a snug fit into a loose or impossible one.
Gear teeth: kerf changes the effective tooth profile.

For decorative engraving and isolated shapes that do not need to fit another part, kerf often does not matter.