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 Fine Blanking: Process Requirements and Setup

admin

Fine blanking produces parts with shear-cut edges that are smooth, perpendicular, and burr-free —unlike conventional blanking which produces a rough fracture zone. Servo presses are increasingly used for fine blanking due to their precise force and position control.

## Fine Blanking vs Conventional Blanking

| Parameter | Conventional | Fine Blanking |
|-----------|-------------|---------------|
| Edge quality | 30-50% burnish | 100% burnish |
| Flatness | ?0.1mm | ?0.02mm |
| Burr height | 0.05-0.2mm | <0.01mm |
| Material utilization | Higher | Lower (V-ring area) |
| Press force | Blanking only | Blanking + blank holder + counter punch |

## Three-Force System

Fine blanking requires three simultaneous forces:
1. **Blanking force**: cuts the part (same as conventional blanking)
2. **V-ring (impingement ring) force**: clamps material around the cut line, preventing material flow
3. **Counter punch force**: supports the part from below during cutting

All three forces must be applied simultaneously and precisely. This is where servo press control is critical.

## Force Requirements

For a typical fine blanking operation on 4mm mild steel:
- Blanking force: 800-1200 kN
- V-ring force: 15-25% of blanking force (120-300 kN)
- Counter punch force: 5-10% of blanking force (40-120 kN)

## Servo Press Advantages for Fine Blanking

- **Programmable V-ring force**: adjust independently for different materials
- **Controlled blanking speed**: 5-15 mm/s for fine blanking (much slower than conventional)
- **Dwell at BDC**: 50-100ms improves edge quality
- **Data logging**: record force signature for every part (100% traceability)

## Setup Parameters

- Blanking speed: 8-12 mm/s (start slow, increase if edge quality acceptable)
- V-ring engagement: 0.5-1.0mm before blanking contact
- Counter punch pressure: set to prevent part deflection at BDC
- Clearance: 0.5% of material thickness (much tighter than conventional 10-15%)

dave_toolmaker

Fine blanking die clearance on servo presses can be tighter than on hydraulic fine blanking presses because the servo controls the punch velocity at contact. We run 0.5% of material thickness clearance on our servo vs 1% on the hydraulic. The result is a cleaner shear face with less rollover. Die life is comparable because the servo reduces impact shock.

mike_chen_eng

On fine blanking clearance: the 0.5% rule is a starting point. For stainless steel, we go down to 0.3% of thickness. For aluminum, 0.8-1.0% works better. The key is that clearance must be extremely consistent around the entire perimeter —variation of more than 0.01mm causes rollover on one side.

dave_toolmaker

Fine blanking on servo press requires tighter attention to V-ring condition than conventional fine blanking. The V-ring does the heavy lifting of holding the material flat during the cut. On our servo fine blanking setup, we inspect V-ring height every 20,000 strokes. When it wears below 80% of original height, the shear face quality degrades noticeably. Replacement is cheaper than sorting parts.