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 Energy Recovery: Regenerative Braking and Storage

admin

Servo presses can recover significant energy during the return stroke through regenerative braking. Understanding and optimizing this energy recovery can reduce operating costs by 20-40%.

## How Regenerative Energy Works

During the return stroke (BDC to TDC), the servo motor decelerates the slide. This deceleration generates electrical energy that flows back into the DC bus of the drive.

This regenerative energy can be:
1. **Dissipated** in a braking resistor (wasted as heat)
2. **Shared** with other drives on the same DC bus
3. **Returned to the grid** via an active front end (AFE) unit
4. **Stored** in a capacitor bank or battery system

## DC Bus Sharing (Most Common)

If multiple servo axes share a common DC bus (typical in multi-axis presses), regenerative energy from one axis can be used by another axis that is accelerating simultaneously.

Example: On a 4-point servo press, when two axes are decelerating (returning), their regenerative energy powers the other two axes that are accelerating (forming). Net energy consumption is significantly reduced.

## Active Front End (AFE)

An AFE unit replaces the standard diode rectifier with an IGBT bridge that can both draw power from and return power to the AC supply.

Benefits:
- Returns regenerative energy to grid (reduces energy bill)
- Maintains near-unity power factor
- Reduces harmonic distortion

Cost: AFE units cost 30-50% more than standard rectifiers, but payback period is typically 2-4 years on high-SPM presses.

## Measuring Regenerative Energy

To quantify regenerative energy on your press:
1. Install a bidirectional power meter on the press supply
2. Run press at production SPM for 1 hour
3. Record total energy consumed and total energy returned
4. Regenerative fraction = returned / (consumed + returned)

Typical values: 15-35% regenerative fraction for servo presses vs 0% for mechanical presses.

carlos_stamping

Energy recovery efficiency varies a lot between press types. On our crank-type servo press, we recover about 15-20% of the forming energy during the return stroke. On our screw-drive press, recovery is 30-40% because the deceleration phase is longer. If energy cost is a major factor in your ROI calculation, the drive type matters more than most people realize.

mike_chen_eng

Energy recovery systems are becoming standard on modern servo presses. The payback period depends heavily on your energy rates and production volume. We calculated 18 months payback at our facility with a regen unit that feeds back to the plant bus.

Key metric: measure the deceleration energy per stroke. On a 200-ton press at 40 SPM, we were recovering about 1.8 kWh per hour. Over a year of 2-shift operation, that's significant savings.

dave_toolmaker

Regenerative braking on our 400T servo press recovers about 18% of total energy consumption. The payback on the regen unit was 14 months. One thing to watch: the braking resistor is the backup for when the regen system cannot absorb all the energy. Make sure it is properly sized and ventilated. We had one overheat and trip the press because the ventilation louvers were blocked by cardboard.