Die shut height and limit stops
Most metal stamping tools have limit stops. Sometimes they are called bump stops, safety blocks or setting blocks (see red blocks on the image on the right). As a general practice, there are four round machined blocks that are bolted to the bottom die shoe. The four blocks' heights are usually ground together to the same length.
These blocks were used to set the shut height of the tool before stamping parts. These blocks set the deepest point that the tool can travel down at the bottom of the stroke. The top die shoe should never hit these blocks. The die shut height should be set about 0.010 or more above these blocks.
When the tool is in storage, the upper unit of the tool could rest on these blocks.
These blocks also have a purpose as safety blocks. They can protect expensive tooling components in case the tool is over stroked and go deeper than intended.
There are unfortunate events when the press could go deeper. This could happen at the setting time by accidentally adjusting the RAM to go too deep. As a result, the press and the tool jams. It is not an easy task freeing the tool and the press. Many occasions the components require to be cut. Jamming could happen during production as well, even the shut height was set properly before. From impact hits and vibration, the RAM adjustment locking nuts may get loose and the RAM may go further down without being noticed. To undo a jammed tool and press is time consuming and expensive, also resulting in valuable downtime.
Die shut height rod retainer
Part No. DSHRR 2202
The Die Shut Rod Retainer unit is a dedicated device, specific to a tool. Each stamping tool should have one and installed.
Dimensions: 1.5" x 1.5" x (6.25" or custom sizes are available)
Material: Black Delrin and steel
Limit Stop: ½-13 x (custom) based on Shut Height.
Material: Steel Rod Switch: ½-13 x (custom less 0.75 than Limit Stop).
Includes a long nose 5/16-18 steel spring plunger with Nylock.
Electronic die shut height finder
Part No. EDSHF 2201
The Electronic Die Shut Height Finder can be used with any tool that already has the Shut Height Rod Retainer unit, so you may need only one Electronic Die Shut Height Finder at your facility.
Dimensions: 1.5" x 2.625" x 2.25"
Includes switch, lamp, two gator clips, and a 9V battery.
To test this unit: Turn the switch on and contact the two gator clips to each other. The lamp on the unit should lite up. If the lamp does not lite up, change the battery.
Removing the battery: Remove the rear cover plate by unscrewing the two Philips head screws. Slide the battery out and remove it from the contact base.
Die shut height rod retainer and electronic die shut height finder
Set the proper shut height for your die sets and mechanical presses to prevent jamming and costly downtimes.
Die shut height rod retainer
The Die Shut Height Rod Retainer is mounted inside the tool that consists of a limit stop that is made of a threaded rod. Its height is machined, ground 0.010 - 0.050 below the intended shut height. It is rather a safety block for storage, so the tool can rest on this rod, without the chance to go any deeper. In case the tool and press jams, this rod can be easily cut and replaced Versa four ~1.5 diameter machined blocks.
This threaded rod is retained in a non-conductive block that is bolted to the bottom die shoe. The threaded rod sits on the surface of the bottom die set and secured in the block with a lock nut.
There is another threaded rod, called "Rod Switch" and is about 0.75 shorter than the limit stop rod. At the top end, there is a long nose spring plunger, inside this threaded rod. This plunger acts as a contact switch allows some shut height deviation to prevent jamming. This threaded rod can be easily adjusted to the desired shut height, then set in place with a locking nut. It is usually 0.010 - 0.050 above the limit stop. The bottom end of the rod never gets contact with the bottom die shoe.
Die Shut Height Rod Retainer and Electronic Die Shut Height Finder
At any time when the tool is being installed and set up for production, the RAM / top die set should be lowered (at the bottom of the stroke) until it contacts with the tip of the spring plunger. The second part of the unit is the "Electronic Die Shut Height Finder". It contains a switch, a lamp, a 9V battery, and two gator clips.
FIRST TIME SET UP PROCESS
1. Attach one gator clip to the solid limit stop. This gets the electrical current into the entire die set. Attach the second clip to the other threaded rod, the one with the spring plunger. Any wire can be attached to any of the threaded rods.
2. Turn the switch on, on the "Electronic Die Shut Height Finder". The light beside the switch remains unlit for now. The RAM of the press, the shut height should be well above the intended closed height.
3. Cycle the press. Lower the RAM after each cycle, until the lamp on the "Electronic Die Shut Height Finder" lights up. Do not over stroke. The light should turn on when the top die shoe gets contact with the tip of the spring plunger. This should be the deepest operating point, closed height or shut height.
4. Tighten the locking nuts of the RAM adjustment. The tool set up is finished.
5.. Before the production starts, turn the switch off on the "Electronic Die Shut Height Finder" and remove the gator clips.