Laser not cutting through: finding and fixing the causes
are explained briefly when you hover over or tap them.
The laser traces the contour, but the part is still stuck. In some places it falls out, in others it does not. This is one of the most common laser problems, and usually it is not a question of power but of focus, cleanliness or material.
Check first: is the expectation realistic?
Manufacturers’ cutting-power figures are best values under ideal conditions. Some examples from the machine database:
| Machine | Manufacturer’s figure in a single pass |
|---|---|
| xTool M2, 10 W diode | lime wood up to 8 mm |
| xTool S1 20W, 20 W diode | lime plywood up to 10 mm |
| Creality Falcon2 22W, 22 W diode | product page up to 15 mm wood, manufacturer blog 10 mm lime wood |
Even one manufacturer’s figures partly contradict each other. In an independent test, another 20 W diode laser did not manage the promised 10 mm of lime wood in a single pass. In everyday use, expect less, especially with plywood containing glue layers, hardwood or MDF. If your material is at the upper end of the stated figure, several passes are normal.
Diode lasers also do not cut clear or light-transmitting acrylic. The blue light simply passes through. For that you need a CO₂ laser. More on this under Laser cutting acrylic.
Cause 1: Focus
Focus is the most common cause. If the focal point is too high or too low, the energy is spread over a larger area. The laser then engraves rather than cuts.
- Reset the focus distance every time you change material. With a focus gauge, autofocus or a focus test.
- Enter the material thickness correctly in the software if your machine uses it to calculate the focus.
- Thick material: With several passes, it helps to lower the focus slightly for each pass. In LightBurn the function is called “Z step per pass”, in xTool Studio “Focus descent”. It needs a motorised Z axis. How to set it up is explained in Lowering the focus per pass.
- Lens and laser head secure? A loose module shifts the focus during the job.
In detail in the article Laser focus.
Cause 2: Dirty lens
Smoke and resin settle on the protective lens or lens of the laser module over time. Part of the power is then no longer transmitted but heats the deposit instead. Power drops gradually, and at some point it is no longer enough.
- Check the lens with the machine switched off. Matte spots, brown edges or dots are a warning sign.
- Clean with lens cleaning wipes or cotton swabs and isopropyl alcohol, as described in the manual.
- Burned-in spots cannot be wiped away. The protective lens or lens must then be replaced.
- With CO₂ lasers, also check the mirrors in the beam path.
Good fume extraction and air assist keep the lens clean for much longer.
Cause 3: Power and speed
If focus and lens are fine, it comes down to the settings.
- Lowering the speed brings more energy per millimetre. Too slow, however, produces wide, charred edges and more fire risk.
- Setting power to the maximum does not always make sense. Many manufacturers recommend some reserve for continuous operation. Follow the manual.
- Air assist on. Without airflow, smoke stays in the kerf and swallows energy.
As a guide: a 10 W diode laser usually cuts 3 mm plywood in one to a few slow passes, while a machine with 20 to 40 W is much faster. CO₂ lasers with 40 to 55 W manage thicker boards in one pass. You will only find concrete values with a material test. Laser a test grid with different speeds and passes and note which field is cleanly cut through.
Cause 4: Material variation
The same material is not the same. Plywood in particular causes trouble:
- Glue layers vary in thickness and density. Where there is a lot of glue, the cut gets stuck.
- Knots and resin pockets in the wood need more energy.
- Moisture: damp wood cuts worse. Store boards dry.
- New delivery, new values: if old values suddenly no longer fit, it is often down to a different batch.
Laser plywood with a glue suited to lasers is more consistent than DIY-store stock.
Cause 5: Too few passes
For thick material, several passes are often better than one very slow one. Each pass deepens the cut, and the smoke can clear in between. Plan one additional pass as a reserve if the material varies.
Important: do not move the workpiece between passes. Even half a millimetre of offset produces two cut lines.
Cause 6: Support surface
The material has to lie flat with air underneath.
- Warped material: if the board bows, the focus is only right in some places. Hold it flat with pins, magnets or weights at the edge.
- Directly on a solid surface: without a honeycomb bed or pin support, smoke cannot escape downwards, and the surface reflects heat back. A honeycomb bed or a support with pins helps.
- Forgot the riser? If you raised the machine for a thick workpiece, the focus has to be reset.
Cause 7: Mechanics and laser
If everything else is fine and power still drops:
- Loose belts stop cuts from running exactly on top of each other.
- Ageing laser module or ageing CO₂ tube: lasers lose power over their lifetime.
- Power supply or cable: loose contacts at the laser module cause dropouts.
Quick checklist
- Expectation realistic for the machine and material?
- Focus reset, material thickness entered correctly?
- Lens clean, no burned-in spots?
- Air assist on and nozzle clear?
- Test grid lasered for this material?
- Material flat, dry, consistent?
- Passes increased, workpiece not shifted?
- Honeycomb bed or pin support underneath?
Next: Laser focus and Material test.