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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

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!)

Measuring Kerf​

Accurate kerf measurement procedure:

  1. Create a test file:

    • Draw a 50mm x 50mm square
    • Draw a circle (any size, for inside cut test)

  2. Cut the test:

    • Use your normal cutting settings
    • Cut completely through
    • Let material cool

  3. Measure:

    • Outer square (part): Measure with calipers
      • If < 50mm, kerf was removed outward
      • Kerf = (50 - measured) x 2
    • Inner circle (hole): Measure diameter
      • If > designed diameter, kerf was removed inward
      • Kerf = (measured - designed) / 2

  4. Average: Use the average of multiple measurements

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:

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

Illustrator:

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

Fusion 360 / CAD:

  • Offset sketch entities before export
  • Use the kerf/offset dimension