Cut acrylic with kerf compensation

When acrylic parts need to fit precisely (press-fit assemblies, snap-fits, gears), you have to account for the material removed by the laser beam.

What you need

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

Steps

1. Cut an uncompensated test square

Kerf Offset: 0.

Draw a 50 × 50 mm square. This is a metric reference size; if the current Display Unit is not millimeters, convert both dimensions to the unit shown before entering them. Set the layer to Line mode at your validated cut settings, then cut it from scrap.

2. Measure the result

Use calipers. The actual part should be slightly smaller than 50 mm in each direction. Note the difference and 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.

Treat the measured radius as a starting value for that exact machine, material, thickness, focus, and cut setting.

3. Measure an interior opening

Cut an uncompensated 20 × 20 mm hole in scrap and measure it. This is also a metric reference size; convert both dimensions to the current Display Unit before entering them. Record how much larger the hole is than the design. Comparing the part and hole measurements helps you confirm the offset before making real parts.

4. Kerf Offset

Expand a Line sublayer's vector controls and set Kerf Offset in the displayed unit. The value is the path offset, usually half the measured cut width. Positive values expand outer contours and shrink nested holes; negative values reverse this. Zero disables compensation. Preview and machine output use the compensated paths; artwork stays unchanged.

Only closed Line contours are compensated. Open paths, raster and Offset Fill are unchanged. A contour that collapses or splits stops planning with an error. Compensation can extend output beyond artwork bounds, so check Preview and clearance. Avoid applying both explicit geometry offsets and kerf compensation to the same contour.

Nesting positions artwork before kerf compensation. Allow clearance for the resulting cut paths and check Preview.

5. Verify on scrap

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

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

6. Cut the real parts

Frame, preview, and cut only after the scrap verification succeeds. Measure a finished part before producing the rest of the set.

When kerf does not matter

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

Related

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