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

How to Specify Servo Press Accuracy: Key Parameters Explained

admin

When purchasing a servo press or evaluating a used machine, understanding accuracy specifications is essential. Manufacturers use different terms, and not all specifications are equally important for your application.

## Key Accuracy Parameters

### 1. Slide Parallelism (Flatness)
The deviation of the slide face from a perfect plane, measured across the full bolster area.

- Typical specification: 0.02-0.05mm per 1000mm
- Why it matters: affects part flatness and die loading uniformity
- How measured: dial indicator on 9-point grid across slide face

### 2. BDC Repeatability
The variation in slide position at bottom dead center, stroke to stroke.

- Typical specification: ?0.01-0.02mm
- Why it matters: directly affects part thickness consistency
- How measured: dial indicator at BDC over 100 consecutive strokes

### 3. Slide Perpendicularity
The deviation of slide motion from vertical, measured over full stroke.

- Typical specification: 0.02-0.05mm per 300mm stroke
- Why it matters: affects part geometry in deep drawing and bending
- How measured: precision square and dial indicator

### 4. Tonnage Accuracy
The accuracy of the tonnage monitoring system.

- Typical specification: ?2-5% of reading
- Why it matters: affects process control and die protection
- How measured: calibrated load cell comparison

### 5. Position Resolution
The smallest position increment the press can control.

- Typical specification: 0.001-0.01mm
- Why it matters: affects motion profile precision
- Determined by encoder resolution and drive interpolation

## Specifications to Ask For

When requesting a quote, ask for:
1. Slide parallelism at rated load (not just unloaded)
2. BDC repeatability at rated SPM
3. Tonnage monitor accuracy certificate
4. Encoder resolution and position control resolution
5. Frame deflection at rated tonnage (affects effective BDC position)

## Red Flags in Specifications

- Parallelism specified "unloaded" only —loaded parallelism is always worse
- BDC repeatability specified at low SPM only —repeatability degrades at high SPM
- No tonnage monitor accuracy certificate —indicates basic system

jim_applications

When specifying press accuracy, the most important number is BDC repeatability under load, not the static spec. Ask the manufacturer for repeatability data measured with a test die at 50% and 80% of rated tonnage. The numbers will be worse than the static spec and that is the reality your parts will see. We require vendors to demonstrate loaded repeatability during acceptance testing.

mike_chen_eng

On BDC repeatability specification: always ask for the spec at production SPM, not just at slow speed. We evaluated a press that claimed 0.01mm repeatability, but that was measured at 5 SPM. At our production speed of 45 SPM, actual repeatability was 0.04mm. Still acceptable for our application, but important to know before signing the purchase order.

dave_toolmaker

Press accuracy specs should always be verified with your actual tooling, not just the manufacturer test block. We had a press that met all accuracy specs during acceptance but produced out-of-tolerance parts with our die. The issue was die compliance. The die was not rigid enough and deflected under forming load. Press accuracy and die rigidity are both part of the equation.