What is a servo press?

A servo press uses servo motors for precise force and position control during forming operations.

How do I calculate servo press tonnage?

Use our free tonnage calculator at servopress.club/tonnage-calculator.html

Servo Press for Coin Blanking: High-Speed Precision Setup

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

dave_toolmaker

Coin blanking dies are some of the most demanding I've built. The punch-to-die clearance is typically 3-5% of material thickness —half of what you'd use for normal blanking. The servo press's BDC repeatability is essential because any variation in penetration depth shows up as a burr height variation on the coin edge.

lisa_quality

We supply blanks to a mint. The dimensional tolerance is ?0.01mm on diameter and the burr height limit is 0.02mm. We run SPC on every 100th blank and our CPK stays above 2.0 on the servo press. On our old mechanical press, CPK was 1.1-1.3 and we were sorting 5% of production. The servo press eliminated the sorting operation entirely.