As a MIM part reaches 1200-1400°C during sintering, it passes through a temperature range where the binder is completely gone and the metal particles have not yet fully bonded. At this stage, the part has essentially zero intrinsic strength — and gravity will cause it to sag, slump, or distort unless properly supported.
Setter materials for MIM sintering:| Material | Max Temp | Cost Index | Best For | Limitation |
|---|---|---|---|---|
| Alumina (Al₂O₃) | 1700°C | 1.0x | General MIM (stainless, low-alloy steel) | Reacts with titanium — do not use |
| Yttria-stabilized zirconia (YSZ) | 1600°C | 2.5x | Titanium MIM | Expensive, high density |
| Graphite | 2200°C | 0.8x | Vacuum sintering | Carbon contamination risk in H₂ atmosphere |
| Molybdenum | 1600°C | 3.0x | High-temp sintering (W-Cu, Inconel) | Oxidizes in air above 300°C |
| Silicon carbide (SiC) | 1600°C | 1.5x | H₂ atmosphere, long life | Brittle, expensive to machine |
- Support flat surfaces fully — if a part has a flat face, it should sit on a flat setter surface. Overhanging features will droop
- Avoid point contact — use continuous contact or shaped supports rather than pins or small contact points
- Allow uniform thermal exposure — open areas in the setter allow furnace atmosphere to reach all part surfaces evenly
- Compensate for shrinkage direction — the part shrinks toward its center of mass. The setter must accommodate this movement without constraint
- Use setters with anti-stick coatings — for titanium MIM, a yttria-based wash prevents the part from bonding to the alumina setter
MIM parts are placed on ceramic setters (typically alumina) during sintering. The setter shape is designed to support flat surfaces and prevent gravity sag. Parts with flat bottoms sit directly on the setter. Parts with complex geometry may need custom-shaped setters or ceramic powder bed support. The setter design is a specialized skill — a good setter can reduce distortion by 50-80%.
For high-volume production, setters are designed with multiple cavities (similar to a tray) that each part nests into, ensuring consistent positioning batch after batch. The setter design is part of the process qualification and is documented in the control plan.