Glossary · Setting

Laser

Passes

How often the laser traces the same path. Several passes at lower power cut thicker material more cleanly than a single pass that is too strong.

Explained in more detail

For each layer, you set in the software how often the path is repeated. Each pass removes some material until the sheet is cut through. Several faster passes often produce fewer burn marks than one slow pass, because the material cools in between and the smoke clears. With thick sheets, the focus can be lowered for each pass (Z step), usually by a fraction of the material thickness. With diode lasers, 2 to 6 passes are normal for 6 to 10 mm of wood, depending on power.

Where does the term come from?

A pass is one run of the laser over the job.

In practice

• Start with a test grid: at fixed power, test several speeds and passes until the parts drop out cleanly.
• If a part does not fall out, one more pass often helps more than a slower speed.
• Do not move the workpiece between passes, otherwise the cuts no longer line up.
• With many passes, watch for flames and smouldering spots, especially with MDF and plywood containing a lot of glue.

Not to be confused

Not to be confused with passes in UV printing, in which the print head travels over an area several times to apply ink.

Frequently asked questions

Better to use more passes or laser more slowly?

For thick wood, often more passes at higher speed, because the edges stay lighter. For acrylic with a CO₂ laser, one slow pass is usually better because the edge then looks polished.

Why does the laser not cut through?

Common causes are wrong focus, a dirty lens, missing air assist or too few passes. Check focus and lens first, then increase the passes.