Ask the Stamping Expert: What type of hydraulic clamps are best for quick-change setups?

Q: What type of hydraulic clamps do you use in your stamping presses for quick-change setups?

A: The type of clamp is insignificant; there are many suitable brands. How you use the clamp is the important thing. Before you get into a true lean die-change system, you need to do some homework.

1. Plan how to mount the stamping tools in the press using a quick-clamping system. Review and group all your stamping dies into setups of common sizes and common presses. The clamping footprints you put in place need to accommodate all the tools that run in a particular machine. This usually requires custom T-slots in the machine bolster so that you can slide clamps into place and clamp tools of varying footprints with the click of a button.

Standardize tool heights with top and bottom spacer plates as needed. All the tools should have a common feed line and press shut height. You might choose to design and build a master die shoe, permanently mounted in the press, with several patterns of hydraulic clamps built in. Your production dies mount inside this master tool so that you can choose the bolt pattern and use hydraulic clamps that drop in and lock with a one-half turn by hand.

The key is to eliminate the need for tools. The ideal situation is to slide the die in the press, drop/slide in the bottom clamps, activate the clamps, bring the ram down, drop /slide in the top clamps, activate the clamps, and open the press. Build standard heights into your design so that it can accommodate future new builds for the long term.

2. Install bolster extension arms on the press to support the tool as it is rolled in and out of the press. The arms allow you to place and pick up tools easily from the underside. They require the use of hydraulic rollers mounted in the press bed. When activated, the tool can roll right out on to the arms for pickup. The extension arms fold down out of the way during production. No tools are required for this operation.

3. Standardize the feed line height for all tools. Ideally, the raw material feed height for stamping, as measured where the material enters the die, should be the same on all your tools. This eliminates the need to move the feed up and down for tool changeovers. For existing tools, screw a subplate to the die to get the height you need. Build standard feed line heights into your design so that it can accommodate future new builds for the long term.

4. Attach the raw material support liner to the feed so it stays in place. Choose a telescoping design if possible, so you can slide it left to right to fill the gap between the feed and die. You also can back it off for setup.

5. Set the feed length and pilot release. If you install a servo feed, you can complete this step with the push of a button.

If you are accustomed to using part or scrap chutes, set the bottom spacer plate in the press first. Drop in the chutes and slide the tool over them to sandwich them between the spacer and tool. Making the spacer plate longer and wider allows for permanently mounted stop blocks, which will align the spacer and tool.

Drop a headed pin into an alignment verification hole in the tool and subplate. This will help prevent blockage of cutting scrap holes in the bottom of the die. You might also take the extra step of putting a sensor on the pin head for presence sensing. Again, the goal is to minimize or eliminate the need for tools.

A custom spacer on the top of the tool will prevent your having to adjust the press shut height. For all new tool builds, put standards in place and vary the thickness of the die shoe to achieve the standard height.

6. Stay organized for quick changeover. All these hydraulic clamps and rollers need to be inspected and maintained on a regular basis to keep them functioning as intended. Prestage all the items you need for the next changeover in advance, such as raw material, lubricant, tools, and chutes. Keep the press area clean and organized.

Assuming there is a tool in the press, a changeover should go like this: Close press and off top clamps (1 min.). Open press and off bottom clamps (1 min.). Telescope liner back and slide tool to extension arms (1 min.). Remove tool and stage next tool on arms (5 min.). Slide new tool in place and clamp (3 min.). Extend liner and set preprogrammed servo feed (2 min.). Change raw material and lubricant concurrent with the tool.