admin
## Why Coins Require Special Setup
Coin blanking (cutting coin blanks from strip) requires:
- Very tight dimensional tolerance: +/-0.01mm on diameter
- Burr-free edges (burrs cause problems in coin striking)
- High SPM: 300-600 SPM for production efficiency
- Consistent material flow to prevent edge cracking
## Material
Coins are typically blanked from:
- Cupronickel (75% Cu, 25% Ni) — most common
- Brass (70% Cu, 30% Zn)
- Stainless steel (some modern coins)
- Bimetallic (two-material coins require special tooling)
## Die Setup
**Die clearance:** 4-6% of material thickness per side for coin blanking. Tighter than general blanking to minimize burr.
**Punch material:** Carbide (K10 or K20 grade) for long life at high SPM. HSS punches wear too quickly above 300 SPM.
**Stripper:** Spring-loaded with controlled force. Too much stripper force causes material distortion.
## Press Motion Profile
For 400 SPM coin blanking:
- Approach: 600mm/s
- Contact: 200mm/s at 5mm above material
- Blanking: 150mm/s through material
- Return: 800mm/s
The fast return is critical for high SPM — most of the cycle time is in the return stroke.
## Quality Control
- 100% vision inspection for diameter and edge quality
- Weight check every 1000 blanks (weight variation indicates thickness variation)
- Die wear monitoring: check burr height every 50,000 strokes