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sheet metal cut and die
sheet metal cut and di  
Hello Don,

Thank you for volunteering on this site - it is a great resource for people like me who know very little about machining.
I have recently been in contact with some companies regarding punch and die cutting of 0.75 mm stainless steel 304. They have got back to me with a quote that seems great.  Before I go any further, I want to nail down any potential issues affecting the quality, but I have no experience with this type of process and very little knowledge of the capabilities or limitations. I was wondering if you could suggest questions to ask these companies that do not reveal my ignorance too much!
I have included am image of the type of hole pattern I want cut in the metal. Would you feel the geometry of the holes is difficult to produce precisely with a punch and die process?
I want to get +100,000 made. What kind of repeatability is possible with this type of process?  What kind of tolerances would you usually expect in the size of the holes and the spacing of the holes?
Sorry to cram in so many question - I am really just interested in your opinion as an expert as to whether this design is possible with a punch and die process, and any potential pitfalls I should try to avoid.

Your opinion would be most appreciated!

Thank you and best regards,
Eddie

Answer
Hi Eddie,

No need to be embarrassed by those questions, they are all excellent questions. I'm no longer in stamping but I was for 18 years and if more customers asked questions like this life would have been far easier sometimes.

I would assume for those quantities you are buying a tool outright or having the cost of one rolled into the part price? Think of a stamping tool as a really big paper hole punch.  You have a male punch and a female die.  The punch is pushed through the material into the the die. There is clearance involved at a percentage of the stock thickness anywhere from 5 to 10 percent.   That's determined by many things including but not limited to the part material, the materials used in the tools, the size of the stamped feature, expected part quantities and the type of press they plan to run it in. Once the tool is built the location of the holes relative to each other isn't going to change. If the feature is a pierced hole the punch is at print size with the clearance on the die. If you were punching a shaped part the clearance would on the punch.

While those shapes are no cake walk they are far from being impossible.  Especially these days where even the smallest toolrooms have cadcam and cnc machines. I don't see any section of those shapes that is smaller than the thickness of stock.  There is a spot that's close but it shouldn't be a problem for a competent shop.

As far as tolerances any good shop should be able to nail them down right where you want them. The only issue you will see as far as repeatability is the size of the stamped holes as there could be wear on the punches, especially making 100,000 of them. Wear will also cause burrs on the bottom of the part. Basically the tolerance is set by the customer.  Price goes up relative to tolerance getting smaller :) I joke but the tighter the tolerance the more often the tool needs to be sharpened or serviced etc.

I'm sure I'm leaving things out,it's been 9 years since I've had a stamping tool in front of me. Anyway, the short answer to your last question is yes, this is a producible part. In fact if I were still in stamping I would ask you to let me quote it. If I left out something or you need to ask anything else, feel free. During the work week I may not get to answer right away but I do my best to answer the same day.

Hope I helped
-Don  

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Don Wright

Expertise

I can answer manual and CNC machining, stamping and general machining questions, general process questions and machine setup and standard G-code. Mills, lathes surface grinders etc.

Experience

I have 29 years in machining, including 4 years of trade school. The first 15 or so in old time stamping tool rooms, including mig and tig welding. During the next 13 years I added in CNC programming, solidworks, bobcad and alibre design experience.

Education/Credentials
Blackstone Valley Technical High School diploma in 1988. Basic electronics night class certificate in 1991.

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