Laser and CNC materials library

A makerspace’s laser gets fed whatever turns up in the offcut bin, and the dangerous materials look just like the safe ones. This is the reference I wanted next to the machine: what you can cut, what you mustn’t and why, how to find out what a mystery sheet is, and a place to keep the settings that worked.

How to use it

Safe to cut? Search by name or trade name (Lexan, Sintra, Delrin, Dibond…) and pick your machine. Each material is rated for a CO₂ laser, a diode laser, a fibre laser and a CNC router:

Safe — it cuts or engraves well with normal extraction and a watchful eye.
Caution — possible, with care: formaldehyde from MDF and acetal, foams and thin plastics that melt and catch fire, coatings you don’t know.
Never — toxic fumes or damage to the machine. PVC and vinyl (chlorine gas and hydrochloric acid, which also corrodes the optics and rails), polycarbonate (burns and yellows), ABS (melts, hydrogen cyanide), polyethylene (melts and catches fire), fibreglass and carbon fibre (epoxy fumes, and glass or conductive dust on a router), PTFE, polyurethane and neoprene, chrome-tanned leather (chromium compounds) and faux leather.
Won’t work well — not dangerous, the machine just can’t do it (a diode laser and clear acrylic, a CO₂ laser and bare steel).

Identify a plastic. Burn tests and the copper-wire flame test are how plastics were traditionally told apart, and the burning is the hazard you are trying to avoid. The tab works through the safer ways instead: ask the supplier, read the protective film or the resin code (♺ 1–7) or ISO 11469 marking (>PMMA<), look up a trade name, and do a density float test in water, rubbing alcohol and salt water — mark whether a sliver floats or sinks and it lists the plastics with a matching density. If it is still unknown, don’t laser it.

Settings library. Add your machines — type, power and lens — then a setting per material, thickness and operation (cut, score, engrave, raster image; or profile, pocket, V-carve and drill on a router): speed, power (and minimum power), passes, line interval, frequency (fibre) or PPI (CO₂), air assist, focus offset, kerf, a star rating for how it came out, notes and a photo. Search and filter by machine, operation and rating, and switch speeds between mm/s and mm/min.

The library comes with starting points for typical 40, 60 and 80 W CO₂ and 5, 10 and 20 W diode lasers in plywood, MDF, acrylic, card, leather, felt, cork, anodised aluminium, slate and glass. They are deliberately conservative, CO₂ ones stay at or below 70% power for tube life, and every one is labelled as a starting point. Run a test grid before trusting any of them — real tubes rarely make their rated power, diode modules are often sold by electrical input rather than optical output, and plywood varies from sheet to sheet.

Copy to my machine takes a setting from one laser to another of the same type, scaled by wattage to keep the energy per millimetre about the same: a cut keeps its power and changes its speed (and takes only 85% of the gain when going to a bigger laser, so it errs towards slow); an engrave keeps its speed and changes its power, moving the speed instead when the power would pass 100% or drop below about 5%. It won’t scale between a CO₂ and a diode laser — they work at different wavelengths and materials absorb them differently. A scaled setting is marked untested.

Print test cards opens a sheet of cards — one per ticked setting — with the numbers, boxes to tick for the result and a square to stick the sample on. To make the sample itself, use the laser test patterns tool (power × speed grids, kerf comb, fit gauge, focus ramp); for router bits, CNC router feeds and speeds works out the feed from chip load, and speeds and feeds does milling and turning in metal. Kerf feeds laser-cut patterns.

Import / export. A JSON backup holds everything you have added, photos included. CSV gives one row per setting for a spreadsheet and reads it back (machines are matched by name). LightBurn export writes one machine’s laser settings as a material library (.clb): materials become folders, thicknesses sub-folders, surface work without a thickness is filed under the operation name, cuts and scores are line ("Cut") entries and engraves are fill ("Scan") entries, with speed in mm/s as LightBurn stores it. Only the fields you set are written and LightBurn fills in its defaults. .clb files from LightBurn import too. Raster image settings export as fill — set the image mode after loading.

Sources

The ratings follow what laser makers and makerspaces publish: Epilog Laser’s and Trotec’s material guides, Glowforge’s list of materials to avoid, xTool’s and other diode-laser makers' manuals, and the laser rules many hackspaces post next to their machines — which agree closely on the "never" list. Fume chemistry (hydrogen chloride from PVC, hydrogen cyanide from nitrogen-containing plastics and polyurethane, formaldehyde from urea- and phenol-formaldehyde resins and acetal) is from the materials' safety data sheets; ask your supplier for the sheet’s. Resin codes are ASTM D7611. The .clb structure is described in LightBurn’s own material library documentation. Plastic densities are typical values for unfilled, unfoamed grades; fillers, foaming and blends move them.

This is a guide, not a safety assessment for your space: your machine’s manual and your makerspace’s rules come first.

Browser support

Any current browser. Printing test cards opens a new window — allow pop-ups for the site.

Privacy

Your machines, settings and photos are kept in this browser’s local storage and never leave it; exports are files you download. Photos are shrunk to about 480 pixels before they are stored, but local storage is small (a few megabytes) — export a JSON backup now and then.