Engineering Decisions, Rants, Tips & Techniques 
3 Comments Bad Intentions
The other day, I blogged about how to heel internally to compensate for unbalanced thrust.
A similar situation arises with presses that have rams that suffer from unparallelism due to worn gibs.
Dies end up getting designed and built with heeling provisions in a feeble attempt to compensate for worn press gibs.
This falls into my “bad intentions” category of rational thinking.
If the press is broke, then fix the press.
Before my critics give me a speech on it costs too much or takes too much time, consider the following analogy:
You make a living running top fuel dragsters.
The car reaches speeds of over 300 miles per hour in a quarter mile.
One day, the brakes wear out and the parachute needs to be repacked.
The crew chief wants to replace the brake pads and repack the chute.
A decision maker says it will cost too much.
The solution? Cut a hole in the floor and have the driver stop the dragster Fred Flintstone style.
During the last 50 feet of track, of course.
Sound stupid?
This is no different than the press / die scenario.
The press gibs are measured in meters. Die wear plates are measured in millimeters.
Press force is measured in tons. Die force is measured in kiloNewtons.
Ram travel is measured in meters. Die travel is measured in millimeters.
No matter how you look at it, the press wins everytime.
There is no way that the relatively small engagement of die heel plates will overcome and correct parallelism of a larger press ram traveling at production velocities near the end of its downward stroke.
What to do?
Fix the damn press.
For those that insist on being the Fred Flintstone, do the following:
- Do NOT attach the upper shoe to the ram.
- Engage heel plates on the die 100 mm before the guide pins.
- Install gas springs for counterbalance before guide pin engagement.
Be sure the gas springs have enough travel to open the die far enough to load and unload the stamping without interference.
Or, forget your bad intentions and just fix the press.
Tim, with the upper die not attached to the RAM ? Is this similar to what an old “die barber” @GRFB called a “slap punch” set up. To save on Die Set up they used to mount Nitro between the upper Binder and Inner punch of the old double action. This way only the Binder had to be bolted up to the outer ram. The inner ram trailed behind and would catch up when the outer bottomed and “slap” the inner punch to finish the op. I don’t recall that entry in the Die Standards but maybe this would be similar??
Then we could have more fun talking about the “bad intentions” of RubeGoldbergin the automation to reach in to your Fred Flintstone die.
Yes … slap die concept.
It is not in any official die standards for a good reason: it is a bad concept even though it is functional.
would you like to swap links?