Chipping
Chipping — Nicks and saw-tooth breaks along a cut or routed edge. It changes nothing you measure and everything you see — light scatters off a broken arris and one dragged edge cheapens the whole sheet. Causes: dull tool, fast feed, or a sheet not held down along the cut line.
Laser dross
Laser dross — The laser's edge signature: material vaporised and redeposited. At the right speed it leaves a fire-polished glaze; too slow, it leaves slag and roughness in equal parts. The one cutting failure whose only variable is the parameter table.
Drill stress cracking
Drill stress cracking — When heavy hand or a hot bit gives the sheet's internal stresses a way out. The symptom is hairlines appearing hours to days after drilling, often right at assembly. One cure only: replace the part, plus a conversation with whoever ran the drill.
| Saw chipping | dull blade / fast feed / loose hold-down — check the clamp before the blade |
|---|---|
| Laser dross | speed too slow or power excess — a scrap test coupon is always cheaper than a good sheet |
| Drill whitening | rpm too high melts the rim — low speed, sharp bit, no hesitation against the sheet |
| Delayed cracking | hairlines days later at a hole — stress riser meeting solvent (cleaner counts as solvent) |
| Assembly breakage | driver torque excess — acrylic does not share metal assembly instincts; washers and a torque stop are the insurance |
Three failures, three owners of responsibility
Chipping is usually the machine and jig’s debt — blade, feed, hold-down: one of the three betrays first. Laser dross is the parameter sheet’s debt, a pure machine failure worth a maintained test-cut log. Stress cracking is the previous operation’s debt — shearing, bending, even transport stacking wrote residual stress into the sheet, and the drill bit only found the door. Assigning each failure to its owner is what drops the rework rate: the three cures do not work on each other, and mixing them wastes blades and sheets.
The test-cut log is the cheap insurance
One A4 offcut and two minutes buy three things: the daily baseline of tool condition, the earliest alarm for parameter drift, and the quality evidence for the day’s first piece. The log need not be beautiful — it needs four columns: date, machine, batch, result. In three months, when someone asks why that sheet chipped, the log points straight at the day whose blade-change row is missing. Your customer can wait; your deadline cannot.
Assembly is the last and cruellest customs post
Every credit earned in fabrication can be zeroed at the bench by one electric driver. Bolting acrylic demands three counter-intuitives: a soft washer to spread the bearing, a torque stop or final turn by hand, and hole clearance thought through. A notable share of stress-cracking cases surface days after assembly — and what hurts at the bench is not the one cracked part, but the sixty good ones in the store tightened exactly the same way.
Why does the same batch sometimes cut perfectly and always chip on other days?
Because chipping lives between the system and the sheet, not in the sheet alone. A batch varies in moisture or in how it sat stacked, which changes the microscopic grip along the cut line; and when tool wear crosses its tipping point, any incoming-material fluctuation becomes visible. Hence the first cut of the day on a scrap offcut — let the machine report safe first.
A crack appeared — is it savable?
Depends where and which. A shallow surface crack at an edge can be polished out — if it is not a stress crack. A crack that starts at a hole and crosses the sheet is internal stress finding its exit, and polishing only buys time. A delayed crack at a hole is a batch alarm: every drilled part from that batch deserves a re-check. It is the cheapest stop-loss a shop has.