Appendix B · Glossary

The words this manual uses, and the ones customers use back at you.

Air assist — a jet of air at the cut point. Blows away smoke and debris and starves a flame of the still air it needs. ⛔ Epilog's manual says to use it whenever vector cutting.

Anodised aluminium — aluminium with a hard coloured surface layer. The laser removes that layer and reveals bright metal underneath, so you are marking, not cutting. Fast, permanent, and the reason pet tags and name plates are such good jobs.

Cast vs extruded acrylic — two ways of making the same plastic. Cast engraves a bright frosted white; extruded engraves grey and muddy but flame-polishes better on a cut edge. ⭐ For engraving, always cast.

Class 2 / Class 4 — laser safety classifications. An enclosed Epilog is a Class 2 product. Open the door and remove the rear manifold for pass-through and you have a Class 4 open-beam hazard, with completely different rules. See Safety.

Compound object — several shapes behaving as one. Imported logos usually arrive this way, which is why you cannot colour part of one until you Break Apart (Ctrl+K).

Cycles — how many times a process repeats. ⭐ Two lighter passes often beat one heavy pass on thick material.

Defocus — deliberately moving focus off the material surface, so the beam's waist sits inside the material. Epilog suggests about 0.080″ closer to the lens for 1/4″ acrylic and thicker.

Dithering — turning shades of grey into a pattern of dots, because a laser fires or it does not. The algorithm you choose is the biggest factor in how a photo engraving looks. See Dithering Comparison.

DPI — dots per inch, the engraving resolution. ⚠ More is not better: past a point the dots merge and the image goes muddy. See DPI Test Sheet.

Fiducial — a mark placed so a camera can find it, used to work out where something really is.

Frequency — how rapidly the laser pulses. Matters most on cutting and on fiber work.

Galvo — a laser that steers the beam with mirrors instead of moving a head on rails. Very fast, fixed field, and the only machine that runs 3D Engraving.

Kerf — the width of material the beam removes. A part cut exactly to size comes out slightly small; a hole comes out slightly large. See 6.5.

Process — one operation with one set of settings. ALPS makes one process per distinct colour in your artwork. This is the central idea of the whole application.

Raster vs vector — raster sweeps back and forth filling an area, like a printer; vector follows a line. Engraving is raster, cutting is vector.

Rotary — an attachment that turns a round object under the head so you can engrave around it.

Score — following a line with the beam on, but only marking the surface rather than cutting through.

Thou — one thousandth of an inch (0.001″). 40 thou is about 1 mm. Used throughout this manual because it is the unit the accuracy conversation happens in.

Two-layer plastic — a coloured surface over a differently-coloured core. Engrave through the top and the core shows. ⚠ Wants less power than feels right.

Vector file — artwork stored as shapes rather than pixels (svg, dxf, pdf, ai). ⭐ Can be cut and scales without losing quality. A photograph or a PNG cannot be cut, only engraved.