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Setup & CalibrationModule 3.1~2 min read

Focusing a Diode Laser

Diode focusing is mechanically simpler than CO2 (no autofocus on most), but tighter than CO2 in tolerance. Get it wrong and your engrave looks soft on one side.

MATERIAL TOO CLOSElensfocal pointspot: wide and softThe beam lands before it hasnarrowed: weak, blurry marks.IN FOCUSlensfocal pointspot: as small as it getsAll the power in the smallestspot: crisp lines, deepest cut.MATERIAL TOO FARlensfocal pointspot: wide and softThe beam has already spreadback out: the same soft result.
The cone of light is the same in all three. Only the height of the material changes, and with it the size of the spot that does the work.

Three diode focus mechanisms

  1. Fixed-focus head with spacer: most budget diodes. Slide a known-thickness spacer (5-10mm) under the head; lower head until spacer fits snug; remove. Uses gravity + locking screw.
  2. Sliding focus knob: manually rotate the lens collar to set focus. Uses calibration mark on the head. Common on Ortur, Sculpfun.
  3. Motorized Z (rare on diodes): xTool S1, OneLaser XRF, some Atomstack. Allows software-driven focus + Z-step per pass.

The standard fixed-focus procedure

  1. Place material on the bed.
  2. Lower the head until the included spacer (typically a small acrylic or metal block) fits between the head and the material with light contact.
  3. Tighten the locking screw on the head's vertical slide.
  4. Remove the spacer. The head should NOT move.
  5. Verify with a test pulse, should mark cleanly.

Sliding-knob focus (Sculpfun-style)

  1. Lower the head physically until close to material.
  2. Rotate the lens collar, typically marked with focal-distance indicator lines.
  3. Test pulse at low power. Look at the dot, sharpest dot = best focus.
  4. Lock the collar.

Z-axis on motorized diodes

On xTool S1, OneLaser, etc.: focus is set via the controller / Lightburn's Move panel.

  1. Auto-focus probe (where present), drops the head onto material; controller stores Z.
  2. Manual: jog Z down 1mm at a time until laser dot is smallest.
  3. For multi-pass thick cuts: enable Z-step per pass in Layer Settings → Advanced.

Verify focus with a test pulse

Pulse at low power for 0.1s on a piece of cardstock or scrap wood. Inspect the dot:

  • Sharp, small, dark dot: focus is correct.
  • Soft, larger dot with halo: defocused. Re-set Z.
  • Star-shaped or distorted dot: lens is dirty or damaged.

The diode focus tolerance

Diode lenses focus to ~0.08-0.15mm spot. Depth of focus: typically ±1-2mm. Outside that, engrave detail degrades visibly.

Common focus mistakes

  • Forgetting to re-focus after material change: engrave depth seems wrong. First check: did the material thickness change?
  • Spacer ignored after first setup: drift from lid bumps and material shifts. Re-focus per session.
  • Focus on bed instead of material: common when bed is clean and material is thin.
  • Forgetting to tighten the locking screw: head slides during cutting; engrave goes soft halfway through.