Laser Kerf & Offset Calculator
Calculate beam waist spot size, empirical cut kerf width, and LightBurn kerf offset compensation. Eliminate loose finger joints, dowel slop, and dimensional tolerance errors across laser optics.
1. Optical & Material Parameters
Standard 40W-150W CO2 glass tube laser. Long infrared wavelength cuts non-metals (acrylic, wood, leather) cleanly.
Vaporization charring widens the slot. Higher air assist pressure reduces soot blooming and yields a tighter kerf.
Empirical 10-Line Kerf Measurement Test
Cut 10 identical rectangular strips (e.g. 10 strips of 10 mm = 100.0 mm total nominal). Push all cut pieces together firmly with digital calipers. The difference between nominal and measured width divided by 10 cuts yields exact machine kerf.
Calculated Optical Metrics
Derived from 10-line caliper audit
LightBurn & LaserCAD Offsets
In LightBurn layer settings, set Kerf Offset to 0.09 mm (positive offsets grow parts, negative shrinks inner cavities).
The Physics of Laser Spot Formation and Cut Kerf
1. Gaussian Beam Diffraction Limit
The minimum focused beam waist diameter $d_0$ of a TEM00 laser mode is determined by diffraction optics:
Where $\lambda$ is laser wavelength (1.064 µm for fiber vs 10.6 µm for CO2), $M^2$ is beam propagation quality factor, $f$ is lens focal length, and $D$ is the raw collimated beam entrance diameter. Shorter wavelengths and larger entrance apertures produce vastly tighter focal points.
2. Thermal Bloom & Assist Gas Ejection
The actual kerf is always larger than the optical spot $d_0$ due to thermal lateral conduction into the substrate, oxidation burning (when using O2 assist), and molten liquid boundary layer shearing.
- Short Focal Lenses (1.5" - 2.0"): Yield razor-sharp spot size (0.08 - 0.12 mm) for intricate engraving and thin veneer cutting, but possess tiny depth of focus.
- Long Focal Lenses (2.5" - 4.0"): Offer deep Rayleigh range (3 - 6 mm) enabling straight vertical cut walls without beveling on thick 10mm+ acrylic and timber.