Building a High Speed Punch Press

I thought that you were going to make it on manual machinery. CNC is cheating for a hobby forum, ha-ha. Nice work !
 
randyc said:
I thought that you were going to make it on manual machinery. CNC is cheating for a hobby forum, ha-ha. Nice work !
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I didn't have the heart to tell you last night. It only took about 55 minutes to run the part. It would have taken hours on a rotary table. Thank you for the kind words.
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Now for the next operation, I have cut the keyway in the bore of the cam (pictures to follow). How am I going to get the setscrews exactly on the key center line?

Anybody have an idea?

Hint: I already have the fixture built.
 
I'm not sure what set screws you are referring to but if they are used just to apply clamping pressure to the key, then the location should not be all that critical, right ? BUT if one is finicky, LOL, place a length of key stock in the keyway, clamp the cam in the mill vise with the keystock resting on the top of the vise. Indicate one edge of the key stock, move over half the width of the key and drill/tap.
 
You ARE going to post a video of this monster-munching-machine in action, right ?
 
Jim, I don't know why I haven't asked this earlier, LOL, but why a stepping motor ?

The only reason that occurs to me is that the same motor is coupled to an automatic feed mechanism. The speed of moving work through the press can be adjusted and also momentarily paused for the stamping/punching process.

The stepping motor could presumably adjust the feed without losing a ton of torque. Care to elaborate or is this proprietary information ?

I am REALLY interested in your project because I designed a (much, much, much slower) small punch press in the early seventies to cut microwave transistors from their long lead frames. I used a mechanical means of pausing the work during the punch because high torque steppers were a thing of the future.

(I worked at Fairchild Semiconductor, Microwave and Optoelectronics Division in Palo Alto. Good times !)
 
randyc said:
Jim, I don't know why I haven't asked this earlier, LOL, but why a stepping motor ?
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Good question! There were several considerations.

One of course is high torque in a small package at low RPM. The stall torque is about the same as a 3HP squirrel cage motor, and it will run at that torque all day long. In this case, it will only reach peak torque about 1% or less of the rotation so the motor is idling most of the time. It only needs to run at maximum of 600 RPM, and most likely will be used at about 200 RPM or less. The customer only thinks he needs the higher speed. In order to get this performance curve in an induction motor would have required about a 1.5HP motor, a VFD, and a 5:1 gear box or a special low speed motor. Over all the drive package footprint would have been huge compared to the stepper. It would also have required a 230 VAC supply and that is not available. The stepper is a 15 Amp, 115VAC system, per the customer, I was limited to 20 Amps of 115VAC power.

Cost was also an issue. Purchasing all of the above hardware would far exceed the $420 cost of the stepper motor and driver/power supply.

In the case of a jam, the stepper motor will decouple under excess load and cause no mechanical or electrical damage. In addition the output torque can be limited by adjusting DIP switches

There is no direct coupling between the motor control and the feed, and the motor is not under computer control. It is being run from a pulse generator to provide the step and direction input. It is just a variable speed system with no positioning control except the stop-on-top limit switch when the operator releases the run button.

In this case a missfeed will not cause an issue, the operator will just stop and clear the work area.

I looked at a lot of options, including pneumatic, electrical solenoid, and induction motor, for driving the press before I settled on the stepper.
 
Thanks for taking the time to explain, Jim.

It is obvious that you put a great deal of thought into this project and examined MANY considerations as a good designer should do ! I hope that your customer appreciates the depth of your concerns/solutions and that he is adequately compensating you for both your ingenuity AND your craftsmanship !

I'm a little puzzled about the fact that the punching operation is de-coupled from the feed and nothing is under computer control. Have you included some form of limiting mechanism to detect the proper positioning of the workpiece under the punch ?

But I am thinking of two or more operations where features that are punched must be aligned with one another. I'm beginning to infer that it does not matter (e.g. punching out washers or something, where there is no need to align the punch with a workpiece under it).

Don't want to be a pest but I wanna' see that sucker run (and understand how) ! I realize that there is a proprietary concern, of course :)
 
I can tell you that this is a hand fed, cut-to-length operation. The parts are short and are fed to a hard stop, hence the need for maximum open time. The operator only has to keep some pressure on the end of the material as it is cut on the other end. Ultimately I will completely automate the process, but the customer is not ready for that step at this time.

If this was a progressive operation I would be doing things a lot different. I have a strip out of a progressive die sitting here on the table, it has about 20 stations and 14 of them actually perform an operation. I just got that one back together the other day.
 
JimDawson said:
I can tell you that this is a hand fed, cut-to-length operation. The parts are short and are fed to a hard stop, hence the need for maximum open time. The operator only has to keep some pressure on the end of the material as it is cut on the other end. Ultimately I will completely automate the process, but the customer is not ready for that step at this time.

If this was a progressive operation I would be doing things a lot different. I have a strip out of a progressive die sitting here on the table, it has about 20 stations and 14 of them actually perform an operation. I just got that one back together the other day.
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I get it ! Thanks -
 
Here is the first test run without the front bearing housing and covers. Also my first real movie here!!!!!

 
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