Cut acrylic with kerf compensation

Make press-fit acrylic parts that actually fit. Measure your kerf, then tell Beam Bench.

When acrylic parts need to fit precisely (press-fit assemblies, snap-fits, gears), you have to account for the laser's kerf. Beam Bench's per-layer kerf compensation handles this automatically once you know the value.

What you need

Cast acrylic in the thickness you want to cut.
Calipers.
A test cut you have already verified for power / speed (see Material Test if you have not dialed in your settings).

Steps

1. Cut a kerf test square

Draw a 50 × 50 mm square. Set the layer to Line mode at your normal cut settings. Cut.

2. Measure the result

Use calipers. The actual part should be slightly smaller than 50 mm in each direction. Note the difference, call it total kerf loss.

The kerf radius is half the total loss. For a 50 × 50 mm design that came out at 49.8 × 49.8 mm:

Total kerf loss = 0.2 mm.
Kerf radius = 0.1 mm.

3. Verify by cutting a hole

Cut a 20 × 20 mm hole in scrap. Measure the hole, it should be slightly larger than 20 mm by the same amount. (Outline cuts shrink the part; hole cuts grow the hole.)

4. Set the layer's Kerf field

Open the Cuts/Layers panel.
Find the layer you cut with.
In the quick-edit strip, set Kerf (mm) to your kerf radius.

The planner now offsets the cut path outward for outlines and inward for holes by the kerf radius. The output part lands at the designed size.

Select the shape.
Modify → Offset Shapes (Alt+O).
Direction: Inward, Distance: your kerf radius.
Apply.

This creates a new (smaller) path you can cut.

Verify it worked

Cut parts measure within ±0.05 mm of design dimensions.
Press-fits actually fit press-tight, not loose, not impossible.

When kerf does not matter

Engraving fills.
Decorative cuts where exact fit is not required.
Single shapes that do not interface with other shapes.

Kerf compensation explainer
Offset dialog
Cuts / Layers panel
Material Library panel
Resize Slots dialog: for adapting existing slot designs