A fabricator sent back twelve 8 mm PC panels with a hairline crack running from a corner. The sheet was fine. The cut was not — a saw blade meant for acrylic, no coolant, and a panel clamped hard against the table.
Why PC cuts differently
Polycarbonate is tougher and softer at the same time. It resists impact, but it grabs a blade, generates heat and melts behind the cut. Acrylic chips cleanly; PC smears. So the tool changes: a carbide blade with a low rake angle, a slower feed, and air or coolant at the kerf. On a CNC router, single-flute plastic bits and a climb cut keep the edge clean.
What went wrong on that batch
- Blade rake too high for PC, so the teeth pulled the sheet instead of cutting it.
- No coolant, so the kerf heated and the edge stress-cracked on cooling.
- Panels nested with 2 mm between parts — too tight, and the second edge was nicked by the first cut.
- Mask left on during cutting, trapping chips that scored the face when peeled.
The re-run used 4 mm spacing, a de-burred edge on both faces, and the mask removed only after the chips were blown off. No further cracks.
Tolerances to write into the order
Dim: ±0.5 mm under 1 m, ±1 mm above. Edge: de-burred, not chamfered, unless a chamfer is specified. For multi-wall PC, the cut must not crush the flutes — a crushed end is where water enters. Ask for the panel ends capped if the parts are exterior.
The stock-size ordering route is in polycarbonate sheet cut to size, and scheduling around cutting in polycarbonate sheet lead time.
Frequently Asked Questions
Q: Can polycarbonate be cut the same way as acrylic?
A:No. PC grabs a blade and heats at the kerf, so it needs a carbide blade with a low rake, slower feed and air or coolant. Cutting it on an acrylic setup is the usual cause of edge cracks.
Q: How much space should be left between nested PC parts?
A:At least 3–4 mm. Two millimetres is not enough; the first cut nicks the neighbouring edge and that nick becomes a crack start under load.
For a cut-to-size or stock-sheet quotation, send the panel list, thickness and destination port to oversales@rpplexiglass.com.