Keywordszirconia millingmilling defectszirconia chippingbur wearCAD/CAM milling tipspre-sintered zirconia
Most "zirconia defects" are born at the mill, not the furnace. A 0.5 mm undercut today is a chipped margin tomorrow.
Four defects and their causes
| Defect | Cause | Prevention |
|---|---|---|
| Chipped margin | Dull bur / dry mill | Replace bur at 15 h; mist cool |
| Steps on curve | Too-fast finishing pass | Drop to 60% feed |
| Cracks | Aggressive first pass | Rough-pass ≤2 mm depth |
Bur management that pays off
- Track bur hours per spindle; a worn bur costs more in scrap than a new one.
- Always use the green-state (pre-sintered) blank — never mill sintered zirconia dry.
Pair with the right zirconia disc and a calibrated mill for clean margins.
Tooling that pays for itself
| Operation | Tool | Speed |
|---|---|---|
| Roughing | 3.0 mm diamond | 12,000 rpm |
| Detailing | 1.0 mm diamond | 18,000 rpm |
| Marginal | 0.6 mm | 22,000 rpm |
Preventing the four defects
- Chips at the margin: leave 0.2 mm spheroids; cut them after sinter.
- Hairline cracks: keep the disc above 20 °C; cold zirconia is brittle.
- Burring: replace the bur at 40 hours, not when it fails.
- Steps on curve: drop to 60% feed on the finishing pass.