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 Slide Parallelism Adjustment: Four-Point Measurement Method

admin

Slide parallelism is one of the most critical geometric parameters on a servo press. Incorrect parallelism causes uneven die loading, part quality problems, and accelerated die wear.

## What Parallelism Means

Slide parallelism measures how flat and level the slide face is relative to the bolster. A perfectly parallel slide would have zero deviation across its entire face.

Acceptable tolerance: typically 0.02-0.05mm per 1000mm of slide width.

## Four-Point Measurement Method

This method measures parallelism at four corners of the slide, giving a complete picture of tilt in both X and Y directions.

**Equipment needed:**
- Dial indicator with magnetic base (resolution 0.001mm)
- Precision reference block (calibrated flat, 100mm ? 100mm)
- Press must be at TDC with brake engaged

**Measurement points:**
- Point A: Front-left corner (50mm from each edge)
- Point B: Front-right corner
- Point C: Rear-left corner
- Point D: Rear-right corner

**Procedure:**
1. Clean slide face and bolster thoroughly
2. Place reference block on bolster at Point A position
3. Set dial indicator on slide face directly above reference block
4. Zero the indicator
5. Move reference block to Points B, C, D and record readings

**Interpreting results:**
- Front-to-back tilt = average(A,B) - average(C,D)
- Left-to-right tilt = average(A,C) - average(B,D)
- Maximum deviation = max(A,B,C,D) - min(A,B,C,D)

## Adjustment Procedure

Parallelism is adjusted by shimming the gib or adjusting the slide guide blocks. This is a precision operation —consult the press manual for the specific adjustment mechanism.

**Rule of thumb:** 0.1mm shim change at one corner produces approximately 0.05-0.08mm parallelism change at that corner.

After any adjustment, re-measure all four points and verify the change matches expectation before proceeding.

raj_maintenance

The four-point measurement method is the standard but I prefer using a test die with built-in pressure sensors at each corner. You get parallelism data under actual forming conditions, not just static. We built a test die with 4 load cells for about $3,000 and it pays for itself every time we set up a critical job.

dave_toolmaker

For the four-point parallelism measurement, I use a granite surface plate on the bolster as the reference surface. Place four identical gauge blocks at the corners and lower the slide onto them. Measure the gap at each block with a feeler gauge. The difference between the highest and lowest reading is your parallelism error. Quick, cheap, and accurate to 0.005mm.

mike_chen_eng

Slide parallelism is one of the most critical adjustments on a servo press. The four-point method is solid, but I'd add one more step: verify the measurement points are actually on the slide surface, not on any wear pads or shims. We had a press that measured parallel but was actually tilted because the wear pads had worn unevenly.

Also: always measure at full tonnage, not unloaded. The slide can deflect under load, and you want to know the actual working parallelism, not the theoretical value.