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 Shut Height and Die Space: What Engineers Get Wrong

admin

Shut height and die space are the most commonly misunderstood specifications when selecting a servo press for a new application. Getting this wrong means the press cannot run the die.

## Definitions

Shut height: the distance from the slide face to the bolster face when the slide is at bottom dead center (BDC) and the slide adjustment is at maximum.

Die space: the working area of the bolster (length x width).

Stroke: the total travel of the slide from TDC to BDC.

## The Common Mistake

Engineers specify the die height and check it against the press shut height. But they forget to account for:

1. Slide adjustment range: the shut height specification is at maximum adjustment. If you need to run the die at a specific shut height, verify the adjustment range covers it.

2. Bolster plate thickness: if you are adding a bolster plate or riser, subtract its thickness from the available shut height.

3. Die cushion: if the press has a die cushion, the cushion pins take up space in the bolster. Verify the pin pattern matches your die.

4. Minimum shut height: presses have a minimum shut height as well as maximum. If your die is too short, the slide cannot reach BDC.

## Calculating Required Shut Height

Required shut height = die closed height + any riser plates + safety margin (5-10mm)

Verify: minimum press shut height < required shut height < maximum press shut height

## Die Space Considerations

For progressive dies, the die space must accommodate:
- Die length (in feed direction)
- Die width
- Feed clearance on the entry side (typically 200-300mm)
- Scrap chute clearance on the exit side

For transfer dies, also consider the transfer mechanism width.

## Servo Press-Specific Considerations

Servo presses often have a larger stroke than equivalent mechanical presses. This means:
- The slide travels further, requiring more clearance above the die
- The shut height range is wider, giving more flexibility
- But the press height is greater, which may require a pit or higher ceiling

dave_toolmaker

This is the #1 mistake I see when shops buy a new press. They check tonnage and bed size but forget to verify shut height against their existing dies. Had a customer buy a 200T servo press and then discover that 3 of their 12 dies wouldn't fit because the shut height was 20mm too short. Had to modify the dies at $5,000 each.

jim_applications

Quick rule of thumb: your press shut height range should cover your tallest die minus 50mm to your shortest die plus 50mm. That gives you adjustment room for die grinding and shimming over the die's lifetime. If you're right at the limit on day one, you'll be out of range in 2 years.

mike_chen_eng

The 50mm rule of thumb is solid advice. I would add one servo-specific consideration: programmable BDC position.

On a mechanical press, your shut height is fixed by the crank geometry and slide adjustment. On a servo press, you can program the BDC position anywhere within the stroke range. This means you effectively have a wider usable shut height window — you are not locked to a single BDC.

Practical example: we had a transfer die set where the draw station needed 380mm shut height and the trim station needed 355mm. On a mechanical press, you set shut height for the tallest station and shim the rest. On the servo press, we programmed a two-stage BDC — deeper stroke for the draw, shorter for the trim — all in one cycle. Eliminated 4 hours of shimming on die setup.

One gotcha though: if you are running near the top of your shut height range, check your slide counterbalance pressure. Running with the slide extended further than designed can cause the counterbalance to bottom out, and that will destroy your seals in about 2 weeks. Ask me how I know.

mike_chen_eng

Good breakdown. One thing I'd add on the servo press-specific side: because servo presses can be programmed to stop at any position, some engineers use this to "set" the shut height dynamically during tryout rather than relying purely on mechanical adjustment. You jog the slide to BDC, measure the actual die closed height, then fine-tune the motion profile endpoint. Saves a lot of time compared to the traditional shim-and-measure approach on mechanical presses. Also worth noting: if you're running a transfer die with a large feed pitch, check the slide tilt spec under eccentric load. A press that's fine on shut height can still cause die damage if the slide tilts more than the die can tolerate.