Why Is My Laser Not Cutting All the Way Through?

A Troubleshooting Guide for Home Laser Users

Nothing is more frustrating than seeing your laser finish a job—only to discover the material didn’t cut all the way through. Don’t worry! This is one of the most common issues new laser users face, and it’s usually easy to fix.

Let’s walk through the most likely causes and how to solve them.

1. Your Focus Might Be Off

Problem:
If the laser beam isn’t focused properly on the surface of your material, it loses power and precision.

Fix:

• Make sure your laser is focused at the surface of the material, not above or below it.

• Use the focusing tool that came with your laser (a spacer or gauge).

• For thick materials, consider adjusting the focus midway or doing multiple passes at different heights.

 2. Your Power or Speed Settings Are Wrong

Problem:
If the power is too low or the speed is too high, the laser won’t have time to burn all the way through.

Fix:

• Increase power to 100% for cutting (if your laser supports it safely).

• Reduce speed—slower cuts = deeper burns.

• Try multiple passes at moderate speed for thick or dense materials.

Pro Tip: Start with test cuts on scrap material using different settings to dial in your sweet spot.

3. You Need Air Assist

Problem:
Without air assist, the laser can leave scorched edges, debris buildup, or poor penetration.

Fix:

• Use an air assist system (even a small air pump helps).

• Aim the nozzle at the cut zone to blow away smoke and debris.

• Clean air means better beam contact and deeper cuts.

4. Your Lens or Mirrors Might Be Dirty

Problem:
Dirt, soot, or residue on your lens or mirrors reduces laser power reaching the material.

Fix:

• Turn off your machine and clean the lens with proper lens wipes or isopropyl alcohol.

• Clean mirrors or protective glass (if your laser has them) weekly or more often.

5. The Material Might Be Too Thick or Hard; or for a Diode laser, the wrong color.

Problem:
Your laser might simply not be powerful enough for certain materials or thicknesses.

Fix:

• Check your laser’s wattage and compare it to what you're trying to cut.

• For low-powered diode lasers (5–10W), limit cuts to:

  • ~3mm basswood or plywood

  • ~2–3mm acrylic

• Use multiple slow passes with focus adjustment for thicker jobs.

• For Diode lasers don't use clear, White, or Blue based acrylics.

6. Mechanical Issues (Belt Tension, Frame, Z-axis)

Problem:
Loose belts or a misaligned frame can reduce laser precision or cause skipped steps.

Fix:

• Check belt tension—tighten if too loose.

• Ensure your laser bed and gantry are level.

• Make sure nothing is slipping on the Z-axis (if applicable).

7. Electrical or Firmware Settings

Problem:
Some machines have firmware or software limits on power output.

Fix:

• Check LightBurn or LaserGRBL device settings to confirm you’re not limiting max power (e.g., S-value too low).

• Update firmware if needed.

• Make sure your laser mode (M4) is set correctly for cutting in GRBL.

TL;DR

• Check focus—it’s the #1 cause of incomplete cuts.

• Increase power, slow down speed, and use multiple passes.

• Add air assist to blow debris away.

• Clean your lens regularly.

•  Check for loose belts, dirty optics, or underpowered lasers for the material.

• Use the correct material for your laser.