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 Read a Servo Press Tonnage Monitor: Understanding the Signature

admin

The tonnage monitor is one of the most valuable diagnostic tools on a servo press. Understanding how to read the tonnage signature can help you detect die wear, material variation, and setup problems before they cause scrap or damage.

## What the Tonnage Monitor Measures

The tonnage monitor measures the strain on the press frame or slide using strain gauges. It displays force as a function of slide position (or time), creating a "tonnage signature" for each stroke.

## Reading a Normal Tonnage Signature

A typical blanking operation signature:
- **Approach phase** (TDC to material contact): near-zero tonnage
- **Elastic compression** (material contact to punch breakthrough): rapid tonnage rise
- **Breakthrough**: sharp tonnage drop (the "snap-through")
- **Return**: tonnage returns to zero

A typical drawing operation signature:
- **Blank holder contact**: initial tonnage rise
- **Drawing phase**: gradual tonnage increase as material flows
- **BDC**: peak tonnage
- **Return**: gradual decrease

## Diagnosing Problems from the Signature

**Signature shifted earlier in stroke:**
- Die is closing too early —check slide height setting
- Material thicker than nominal

**Signature shifted later in stroke:**
- Die is not closing fully —check slide height
- Material thinner than nominal

**Peak tonnage increasing over time:**
- Die wear (punch becoming dull) —check punch edge condition
- Material hardness increasing —check material certification

**Double peak in signature:**
- Two-stage forming operation —normal for some dies
- Die misalignment causing uneven loading —check die alignment

## Setting Tonnage Limits

Set upper limit at 110% of normal peak tonnage. Set lower limit at 80% of normal peak. Any stroke outside these limits should trigger an alarm and stop the press.

lisa_quality

Tonnage signature trending is one of the most underused quality tools in stamping. We overlay the current signature against the golden sample from the first article approval. Any deviation greater than 5% triggers an investigation. This approach has caught 3 die failures in the early stages before they produced scrap. The data is already there in the press controller. You just need to use it.

dave_toolmaker

We overlay tonnage signatures from the first article run with current production as our primary SPC tool. When the current signature deviates more than 5% from the reference, we investigate. This catches die wear, material variation, and setup drift before they produce bad parts. Simple but incredibly effective.