Calling All Punch Press Experts

Do you have any old toolmakers (or even old setters) "on side", who you could take out for a beer? They probably know as much as anyone about the hows and whys.

Our toolmaker is 83 years old. But he's very much part of the "that's the way we've always done it" crowd.

If you want to teach him a new trick, tell him you learned it from someone even older.

I would have to tell him I learned it from a Civil War vet.

With 20 holes, that's pretty close to a total of 2 in² to be sheared--maybe 30-40 tons?

It's a 150 ton press.

I can see that others have vastly more knowledge of this area than I do, but please allow me to naively ask: (1) what is the source of power for this 150 ton press, and is it matched well to the maximum output of the press? and (2) Quality control might well dictate that your feed stock cannot handle having more punched hole/minute than is presently the case, since the extra work equates to heat in the feed stock, along with the already pointed out distortion (problems with the holes or the pattern), and rapid wear of the punches.

Maybe they tried going faster in the past, and it just wasn't worth the extra cost in dies and punches wearing out faster.

This chart gives about 2½ tons per ¼" hole for mild steel. ("About" because they don't list 11ga).

Thanx. That's a good reference chart.

11 ga = 1/8", give or take a few thou. (My estimate, which may be a bit low, was based on shear strength being somewhat less than tensile, but I didn't look it up.)

We need tonage of the punch press. It may not be large enough to punch any more holes then it's doing.

You said it's an old shop. The operators may not know. They just operate the presses. Need to address it with the person that designed the die. Even the die maker may not have that info just made it as he was told.

Run around you getting maybe that they cover that lack of knowledge.

Ask the die maker if he has design drawings for the die. Maybe someone signed them.

It's a 150 tonne press.

I've asked everyone who is available. Their answered were incomplete. As I mentioned, I was hoping to educate myself a bit, through your all's suggestions, before I pursue it further. So far, the suggestions have all been related to the tonnage of the press vs. the material strength. I didn't know if there were other design or process issues that may come into play with this kind of part.

It could be they didn't have a 150 ton press at the time. This may have been the limit to the press they had at the time.

Thanx Joe. That was a better-than-average answer! Gives me areas to research. And that's a good site as well.

GA

GA

If there is any capital($) available you may also want to look at alternate technology. Lasers have come a long way and although I don't have one in my shop, a lot of my suppliers have them. Where I used to pay for tooling for punch press operations, there is now only the "programming" charge which is incorporated into the final part price, and for large quantities it is quite minimal. Also less $ spent on consumables vs punches and dies for stamping operation.

Laser cutting speeds in 11 Gg can get up to and beyond 110"/min cutting. You have to add about 3 seconds of pierce time for each start. That should allow you to calculate the comparative cost vs gang punching. Then it's a matter of justifying the capital expenditure.

3 seconds pierce time per start? That sounds like an instant killer in this application.

May be true in this case. If the rectangular perforated plates is all that the OP's company makes, then they may have the right "technology". If the plates is all they make, they are also in a very limited market. The idea of manufacturing flexablity has to come in some where. Why limit your product?

I'm not sure how I explained myself so poorly, as to give the impression that the plates are the only product that we make. We make more than a hundred different parts each year, depending on the success of our sales force. The part I have described is but one operation of one particular part. As I mentioned in my original question, I run a plant that includes several large punch presses. But we are fully equipped with all the other usual machines as well. But this operation, of this one part is best made in a punch press. I'm simply trying to increase the rate, and cut the cycle time at this station. Not trying to find a way to make the part a different way... just increase the rate of the current method.

But thank you for your suggestions.

Hopefully you will be able to glean some insight from this thread.

We do have a laser. It's being used for other things. A laser to make a perforated sheet is not at all appropriate. Not even close. I'm currently punching 20 holes per cycle, per few seconds, and trying to increase that. You couldn't even make a laser stop at twenty positions in that time frame, much less burn a hole at each position.

If you manage to double the output rate will the sales volume also double?

If I double my output, I will fulfill orders quicker which will free up those machines so I can use them for other parts to be made.

As part of management, you must weight the increase of production capacity against many other factors, not the least of which is: safety, quality, maintenance, tooling costs. Best wishes, good luck, but others with more specific knowledge have already given you some really great input on this one.

We do have a fully equipped tool shop. As I mentioned, our Sr. Tool Maker is over 80 years old. He's been with this company for 53 years. I'll be the first to acknowledge that wisdom comes with age and time spent on the job, but the single fact that he's been here for 53 years... that fact alone does not necessarily mean that he is a particularly creative tool maker, it just means that he has been competent and has become part of "the family" of the previous longtime management. He hasn't exactly had any kind of continuing education or exposure to evolving or new methods. I'm sure he is doing things the way he did them in the 1960's. He built the existing tool we're talking about, so he has no reason to believe it needs changing. He may be right. I need to either confirm or reject that.

But as I mentioned, I haven't delved into this subject too deeply yet. I wanted to educate myself a bit (here) before I had the conversation of possible process improvement.

You have not described the entire process.

A typical press of this capacity runs about 30 strokes/minute or 2 seconds per stroke. Therefor a part should take somewhere around one minute of actual press stroke time to produce. Your greatest opportunity for improvement is in what happens between press strokes. If you reduce or eliminated the wasted time between strokes you will make a major improvement in productivity.

Now, my questions

• In what form is the material processed, individual sheets or from continuous coil stock? I am guessing that it is as individual sheets.
• How is the material advanced in the die, manually or by some type of automatic feeder.
• What type of press are you using. OBI, gap frame, turret press (doubtful)?
• What are the dimensions of the press bed, and in what direction are the sheets advanced through the die.

I would love to see a video of the process

(My background is 50 years as a die maker, designer and manufacturing engineer)

It's an OBI Press. I believe it's a Bliss, circa about 1950. Runs about 1.75 seconds per stroke. The material is coil stock and is advanced automatically, entering the right side and exiting on the left, where it stops after all holes are punched, and automatically chops off the part, which the operator then stacks on a cart for the next operation on a press brake.

I'm not clear on exactly which surface is called the press bed.

I'll try to remember a cord for my phone tomorrow, so I can transfer a couple pictures to my PC, and post them.

It's all fairly efficient. I'm just trying to determine if I can increase it any further. I'll be doing the same to all the operations of all our parts. I just recently completely rearranged the entire plant into a work-cell type layout. That was the first big step. My spaghetti graph looks far less intimidating now.

What you describe is a very efficient operation. Not what I had envisioned.

Now the problem is, can the feeder advance the strip to double the distance within the window of the press stroke? If not, you will have gained nothing by increasing the pitch of the feeder by doubling the number of punches.

What type of feeder are you using? There are basically three types of feeders:

• Roll feeds, mechanically coupled to the press crank
• Hitch feeds, adjustable fixed feed length, timed by the press crank angle
• Servo feed, independently programmed feed length timed by the press's crank angle

What you described is not a progressive die. Staggering punches can reduce the punching force, but it will not reduce the stripping force. I had a very bad experience in my early career with that. Picture taking apart a die with the product stuck on the punches with 50,000 pounds of compressed spring force on the stripper, ready to release at any moment

That sounds really dangerous, and could cut someone to shreds.

I am picturing it... and I see dead people.

... or at least pretty messed up.

Indeed before any process speed ramp, I would recommend re-assessing all the current safety aspects of this process. There may appear one salient reason why not to increase production speed.

I'll follow all correct procedures. I'm just trying to find out what is possible.

The best safety procedure is to keep the operator's hands and body out of the press. Any process that requires the operator to reach into the press area is inherently dangerous in spite of whatever safety devices are incorporated. The safest process is one that minimizes the operator's exposure.

Can a layman weigh in? Having been searching out punch equipment for the occasional task that needs same day availability (a simple part, but each two pieces is unique from the prior and next job as to hole placement and spacing); i learned a few things, none of which are metallurgy nor tolerances. My process can be done many ways. All will be within specification. Upfront cost on the low end at 2200.00 for a brand new Unipunch, including one punch and die set, and a third party sourced automotive shop modest bearing press manually pumped hydraulic piston. On the midlevel; a used Rotex, turret punch press, with 18 punch/dies onboard would run me 3500.00 . No power, no pneumatics, no compressor no noise in my locksmith shop / showroom. But it eats a big footprint. Either would do the job, and in the course of 3 or 4 years, the cost savings over ordering from a manufacturer would be my break even on the more expensive of the two. The larger one negates the likelihood of buying more tooling. For the square yard of space, I could make it a showpiece of American Industry, and put it in showroom, as a centerpiece of a display;hiding it in plain sight. My purpose again, is to have part same day, without drawings, approvals, production and shipping. We will keep blank stock on hand, in 3 finishes. The decision has to be between all the options available at all prices, then weighed on the economics, potential new capabilities one machine or process may offer over another, and so forth. CNC punching has constraints of machine throat, real estate of machine itself, maintenance etc. Water can cut stacked material, from my limited knowledge, so the engineers in here can address a number of modes to achieve the speed, tolerances and other challenges. Then you have to see what opportunities each may offer beyond this one piece you are referencing. i hope i have not droned on, and that the intent was to share the process i am going through now. i have one advwntage. If my decision was not the right one, i suffer the consequences. I am self employed. I just endeavor to learn from it, and make better decisions going forward, That is whati love about being the CEO. But the shareholder within, tempers the enthusiasm to try everything without due diligence. I do not have an employee who may feel his job is being replaced with a mqchine. If such is the case, your purchase will require some retraining of the guy you got. Heck, he may be bored with the old press, and get excited to play with a neat new toy!