Laser cutting is a powerful, modern tool. It makes manufacturing faster and easier across many industries. This technology is part of the rapid growth in automated design, manufacturing, and advanced materials. However, not all materials work well with a laser cutter. Some materials simply resist the laser beam, and others can create much messier or even dramatic, bad outcomes. The following is a list of these materials and why you shouldn't use them.
ABS is a poor choice. It tends to melt and burn instead of turning into vapor when cut with a laser. The edges of the cut plastic will be melted and fused together. Burning ABS releases a range of toxic chemicals, including cyanide, phenol, and various benzene compounds. This plastic is also a fire risk because it doesn't vaporize or char much, leading to high local heat and possible ignition.
Epoxy resins are very bad for laser cutting or engraving. The finished cuts usually look bad, and the gases released are highly poisonous. While some people worry about hydrogen cyanide as a byproduct, research on typical epoxies lists other gases like H2, CO, methane, and various simple hydrocarbons. Since epoxies are a huge family of materials, it is still possible that HCN could be released. Polyester resins are sometimes mistaken for epoxies, but they are chemically different. Polyesters are generally harder to work with, but they actually cut better with a laser. You must know your material well to get good results.
Many experts advise against laser cutting polypropylene. The plastic tends to melt and fuse during cutting, which causes residues to overheat and smoke heavily. The smoke isn't particularly harmful, mostly just a minor irritant. A good filtered ventilation system can typically handle this smoke issue. You can get better cut quality and less smoke if you use effective air assistance.
Never cut PVC. When heated, PVC breaks down and releases chlorine gas and hydrogen chloride. These damaging and very toxic gases are bad for your health and the laser equipment. Even though good ventilation and filters can technically remove these byproducts, the potential harm to the machinery and the danger to the operator make this material completely unsuitable for laser cutting.
Small, desktop laser cutters should not be used to cut fiberglass. Few small machines can cut through the actual glass fibers effectively. The resins used in fiberglass are reported to "release toxic gases." Most common fiberglass uses polyester resins (GRP), not epoxy, and polyesters are generally considered more cuttable. However, polyester resins come in many forms, and you often can't easily identify the exact type. It is smart to avoid cutting fiberglass composites on small machines with modest ventilation.
Thin PC/Lexan™ is fine for cutting. When you try to cut sections thicker than 1 mm, you get significant melting, fusing, and a heat-affected area that turns yellow (discoloration). High-power machines, those in the kilowatt range, can cut thick PC successfully. Higher power encourages more material to vaporize, which means less heat transfers to the surrounding plastic from the melted residues.
The term "glued" covers a lot of materials. Plywood, which is layered wood veneer bonded with phenolic resin, generally cuts well because the glue layers are very thin. Cutting phenolics releases formaldehyde, so you must use good extraction and a carbon filter mask. MDF, another phenolic-bonded board, is also safe to cut with extraction and a filter mask. Wood parts bonded with PVA (wood glue) are safe to cut. However, materials held together with cyanoacrylate (super glue) adhesives produce intensely irritating fumes when heated. For these materials, you need extraction, a breathing mask, and closed-eye protection. If the glue needs very different cutting settings from the main material and is present in thick layers, it can be tough to find a single setting that cuts both well in one pass.