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Quick Answer: Focus Position Rules
Thin (<3mm): Surface / -0.5mm | Medium (3-10mm): -10% to -25% depth | Thick (>10mm): -15% to -33% depth
Calculate the optimal focus position for laser cutting based on material type, thickness, and assist gas. Focus position significantly affects cut quality, edge roughness, and dross formation.
Select parameters to get focus position recommendation.
Focus tuning
Send the material, thickness, assist gas, and focus-position result before running parameter trials.
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Save this exact setup as a local link, compare matched machines, or unlock a PDF brief when a result panel supports export. Use the export buttons on result panels when a calculator supports result files.
| Material | Gas | 1-3mm | 4-8mm | 10-20mm |
|---|---|---|---|---|
| Mild Steel | O₂ | 0 to -0.5mm | -0.5 to -1mm | -1 to -3mm |
| Mild Steel | N₂ | -0.5 to -1mm | -2 to -3mm | -3 to -5mm |
| Stainless Steel | N₂ | -1mm | -2 to -4mm | -4 to -6mm |
| Aluminum | N₂ | -1 to -2mm | -3 to -5mm | -5 to -8mm |
Negative values = focus below material surface. Values are starting points - optimize based on cut quality inspection.
For cutting, focus is typically placed INSIDE the material (negative focus position). Thin materials (<3mm): focus near surface. Medium thickness (3-10mm): focus at 10-25% depth. Thick materials (>10mm): focus at 15-33% depth. This ensures the beam energy is concentrated where the cutting action occurs, improving cut quality and speed.
Calculate W/mm² from power and spot size
M² affects focal spot size and depth of focus
Focus position affects kerf width
Optimize assist gas parameters
Estimate production time for parts
In-depth focus position theory
Note: Focus positions are starting recommendations based on industry practices. Actual optimal settings vary by machine, lens, and specific material batch. Always verify by inspecting cut edges and adjusting in small increments (±0.25-0.5mm).
Follow this sequence to move from the current result into the next practical decision.
Check M2, beam parameter product, and profile suitability before changing process settings.
Confirm whether the beam intensity supports cutting, welding, or marking.
Estimate weld depth and interaction mode after power density is known.
Transfer tuned settings between machines, wavelengths, or power classes.
Estimate cut width, compensation, and nesting spacing.
Estimate consumable life after process parameters are set.