Can polycarbonate be laser cut?
Only thin sheet, and poorly: polycarbonate chars and yellows under a CO2 laser. Route or waterjet it, or switch to acrylic if the part must be laser cut.
Acrylic cuts cleanly under a CO2 laser because it breaks down into vapour and leaves a glossy edge. Polycarbonate does not. It decomposes and chars, so the cut edge comes out brown to black, rough and sooty, and the faces near the cut discolour. On film and sheet under about 1 mm (0.04") the result can be acceptable for overlays, gaskets, insulators and nameplates where some edge discolouration is allowed. Above that the edge gets worse quickly, cutting speed drops and the fume is heavy and irritating, so many shops decline polycarbonate on a laser.
The damaged edge is also a weak edge. The heat-affected layer is stressed and slightly degraded, and polycarbonate is prone to stress cracking when stressed edges meet solvents, cleaners, threadlockers or some adhesives. A laser-cut guard window can look fine at delivery and craze around the edge weeks later. Polycarbonate is chosen for impact strength (notched Izod around 600-900 J/m, against roughly 20 J/m for acrylic), and a cracked edge undoes that.
Cut polycarbonate by CNC routing, the standard method for machine guards, windows and covers: it leaves a clean edge and holds about ±0.13-0.25 mm (0.005-0.010"). Abrasive waterjet suits thick sheet with no heat, and thin gauges shear, punch and die cut well because polycarbonate is tough rather than brittle. Finish edges by sanding and buffing; flame polishing is unreliable on polycarbonate. If the part must be laser cut and does not need impact resistance (displays, light guides, signs, covers), switch to cast acrylic, which gives a clear, polished edge straight off the laser.
Laser Cutting for polycarbonate parts: where to send them
What to specify
- Material: polycarbonate grade and thickness, and any abrasion-resistant hard coat on the faces
- Cutting method: CNC routed or waterjet; write "no laser cutting" for guards, windows and structural parts
- Profile tolerance that fits routing: ±0.13-0.25 mm (0.005-0.010")
- Edge finish: as routed, sanded or buffed, and the allowed chip size
- Masking film kept on through cutting and handling, and the show face named
- For thin film parts, whether laser or die cutting is acceptable and whether edge discolouration is allowed
- Chemicals the part will see (cleaners, adhesives, threadlockers), so the shop keeps edges low-stress
Pitfalls
- Brown, charred edges on anything thicker than about 1 mm
- Soot and discolouration on the faces around the cut, not only on the edge
- Edge crazing weeks later when heat-stressed edges meet solvents or cleaners
- Expecting a laser-cut acrylic look; polycarbonate never gives a clear edge off the laser
- Switching a guard or impact part to acrylic to get laser edges; acrylic shatters where polycarbonate dents
- Flame polishing polycarbonate edges and getting bubbles and yellowing; sand and buff instead
Frequently asked questions
- Why does polycarbonate burn when laser cut?
- Unlike acrylic, which turns to vapour and leaves a polished edge, polycarbonate decomposes and chars at the cut. The result is a brown or black, rough edge with soot on the faces.
- What is the best way to cut polycarbonate sheet?
- CNC routing for accurate profiles, a fine-tooth saw for straight cuts and abrasive waterjet for thick sheet. Thin gauges shear, punch and die cut well because polycarbonate is tough.
- Acrylic or polycarbonate for laser-cut parts?
- Acrylic if the part will be laser cut: it gives a clear, polished edge. Polycarbonate if the part needs impact resistance, and then route or waterjet it instead of laser cutting.
