DFM Design Guide · 05
A-grade and B-grade faces must be marked on the drawing - cosmetic grade determines gate location, and gate location determines the whole mold design direction.
Surface-Quality Zoning
05-A · Surface-Grade Definitions
| Grade | Definition | Rule |
|---|---|---|
| A-grade cosmetic face | Primary visible face; gloss or matte; no tolerance for process marks | No gate allowed · mirror-polished cavity |
| B-grade face | Non-primary face (back, internal cavity, mating face) | Gate allowed (relief form must be noted) |
05-B · Artwork Sharp-Corner Risk
Failure Scenario
Decorative relief had multiple sharp-tapered corners. About 30% of ceramic CIM samples developed micro-cracks at the sharp tips after sintering; reliability testing failures started right there.- Relief base surface: flat is preferable to curved
- Sharp corners in the depth direction: R ≥ 0.125mm fillet, to remove the stress concentration
- Minimum line width: ≥0.3mm, with a line-width-to-depth ratio ≤1:1
- Alternative: flat surface + laser engraving, avoiding all forming-related risk