Kerf Compensation¶

Kerf is the material removed by the laser beam during cutting. Kerf compensation adjusts toolpaths to account for this, ensuring cut parts match their designed dimensions.

What is Kerf?¶

Kerf = the width of material removed by the cutting process.

Example: - Laser spot size: 0.2mm - Material interaction: adds ~0.1mm on each side - Total kerf: ~0.4mm

Problem without compensation:

Designed:          Actual cut:
        
 50mm            50.4mm      Hole too big
            (kerf removed inward)

Designed:          Actual cut:
           
  Part           49.6   Part too small
               (kerf removed outward)

When it matters: - Precision assemblies (tight tolerances) - Interlocking parts - Gears and mechanical components

When it doesn't matter: - Decorative cutting (0.5mm tolerance) - Single-piece projects - Engraving (no kerf)

How Kerf Compensation Works¶

Kerf compensation offsets the toolpath inward or outward to account for material removal:

For outside cuts (cutting a part): - Offset path outward by half the kerf width - Result: Final part is the correct size

For inside cuts (cutting a hole): - Offset path inward by half the kerf width - Result: Final hole is the correct size

Example with 0.4mm kerf:

Original path:  50mm square
Compensation:   Offset outward by 0.2mm (half kerf)
Laser follows:  50.4mm square
After cutting:  Part measures 50.0mm (perfect!)

Kerf Compensation in Rayforge¶

Current Implementation

As of the current version, dedicated kerf compensation may not be fully implemented in Rayforge. Check the workflow transformers for "Offset" or "Kerf" options.

Workaround: Manually adjust paths in your design software before importing.

If/When implemented:

Measure your kerf:
Cut a test square (e.g., 50mm 50mm)
Measure the actual size
Kerf = (actual - designed) / 2
Configure compensation:
Add kerf transformer to workflow
Enter half the measured kerf value
Choose inside/outside mode
Apply to operations:
Enable for cutting operations
Disable for engraving

Measuring Kerf¶

Accurate kerf measurement procedure:

Create a test file:
Draw a 50mm 50mm square
Draw a circle (any size, for inside cut test)
Cut the test:
Use your normal cutting settings
Cut completely through
Let material cool
Measure:
Outer square (part): Measure with calipers
- If < 50mm, kerf was removed outward
- Kerf = (50 - measured) 2
Inner circle (hole): Measure diameter
- If > designed diameter, kerf was removed inward
- Kerf = (measured - designed) / 2
Average: Use the average of multiple measurements

Typical kerf values:

Material	Thickness	Typical Kerf
Cardboard	1-3mm	0.2-0.3mm
Plywood	3mm	0.3-0.4mm
Plywood	6mm	0.4-0.6mm
Acrylic	3mm	0.2-0.3mm
Acrylic	6mm	0.3-0.5mm
MDF	3mm	0.3-0.5mm

Variables affecting kerf: - Laser power (higher = wider) - Cutting speed (slower = wider) - Material type and density - Focus distance - Air assist pressure

Manual Kerf Compensation¶

If automated kerf compensation isn't available, compensate in your design software:

Inkscape:

Select the path
Path Dynamic Offset (Ctrl+J)
Drag to offset by half your kerf measurement
Outward for parts (to make path larger)
Inward for holes (to make path smaller)
Path Object to Path to finalize

Illustrator:

Select the path
Object Path Offset Path
Enter offset value: (kerf / 2)
Positive for outward, negative for inward
OK to apply

Fusion 360 / CAD:

Offset sketch entities before export
Use the kerf/offset dimension

Kerf Compensation Best Practices¶

When to compensate: - Mechanical parts with tolerances <0.5mm - Snap-fit assemblies - Interlocking designs (boxes, puzzles)

When to skip: - Decorative pieces - Engraving (no kerf) - Low-precision work

Tips: - Test first - Always cut a test piece to verify compensation - Consistent settings - Kerf changes with power/speed - Material consistency - Kerf varies between batches - Direction matters - Inside vs outside cuts need opposite compensation