Kerf
The width of material removed by a cutting tool — laser beam, plasma arc, saw blade, or router bit — during a cut. Kerf must be accounted for in nesting to ensure finished parts are the correct size.
What is kerf?
Kerf is the amount of material consumed (destroyed) by the cutting process itself. The word originally referred to the groove left by a saw blade, but it now applies to any cutting process that removes material:
| Cutting process | Typical kerf width |
|---|---|
| Fiber laser (thin steel, under 3mm) | 0.1–0.3 mm |
| CO₂ laser (wood, acrylic) | 0.2–0.5 mm |
| Plasma cutter (steel 6–25mm) | 1.5–4 mm |
| Waterjet | 0.8–1.5 mm |
| CNC router (wood/MDF) | Equal to bit diameter (3–12mm) |
| Bandsaw | 1–3 mm |
Why kerf matters in nesting
If kerf is ignored in a nesting layout, the cut parts will be smaller than designed — by approximately half the kerf width on each edge (since the cut line removes material equally from both sides of the cut path).
For precision parts, even 0.2mm of unaccounted kerf can cause dimensional failures. For thicker plasma-cut parts with 3mm kerf, ignoring kerf can mean parts are 1.5mm undersized on every edge.
Kerf compensation in nesting software
Nesting software handles kerf in two ways:
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Spacing compensation — The nesting tool adds a minimum gap between adjacent parts equal to the kerf width (or half kerf width if both parts are being cut). This prevents parts from being undersized due to shared cut lines.
-
Geometry offset (toolpath compensation) — More advanced CAM software offsets the entire cut path inward or outward by half the kerf width. This is typically done in CAM software after nesting rather than in the nesting step itself.
Lapas handles kerf via part spacing — you set the kerf width and minimum gap, and the optimizer ensures no two parts are placed closer than the specified distance. This is the correct approach for most nesting workflows where CAM handles final toolpath compensation.
Kerf and material utilization
Larger kerf widths reduce achievable material utilization because more space is required between parts. On a typical laser job with 0.2mm kerf, the impact is minimal. On a heavy plasma job with 3mm kerf and parts packed on a 2500×1250mm sheet, the kerf gaps can account for 3–5% of total sheet area.
Kerf and part-in-part nesting
Some nesting software supports common line cutting — where two adjacent parts share a single cut path, effectively halving the kerf loss between them. Lapas supports part spacing configuration; advanced common-line optimization is available in the Pro plan.
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