Noob Looking for General Info on Stamping Press Machinery


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Thread: Noob Looking for General Info on Stamping Press Machinery

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    Default Noob Looking for General Info on Stamping Press Machinery

    I'm a machinist and metal fabricator, but I'm not at all familiar with metal stamping or punching. I want to punch/press (whatever the correct terminology is) quite a lot of spoon shaped items. I only need them to be punched out of Stainless Steel sheet and they will be flat. The Stainless will be 18 or 19 gauge (.04" thick).

    I guess first question is what machine can I use that's not expensive and easy to use. Is it something like a Federal 22 ton or larger Punch Press work, is that what they are used for?

    Next would be how to calculate how much tonnage I'll need to punch out the shape I want.

    Then I guess where I can read about making dies or where to have dies made? I have the ability to make and heat treat dies, just not the tolerances or shearing edges and so forth.

    Any help would be appreciated.

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    Default Re: Noob Looking for General Info on Stamping Press Machinery

    Punch press is the correct term for the machine.

    A 22 ton might work or a 100 ton might not be enough It depends on the area and tensile strength of the part that you are making.

    Yes, that's what they are used for. Punching (creating a hole), Blanking (punching out the entire part shape), and Forming/Bending. The dies can be a single operation or could be a progressive die where multiple operations are performed as the material progresses through the die.

    Rough tonnage (in pounds) can be calculated by multiplying the tensile strength x the area x the thickness.

    I have never seen a stamping die making book, but one may exist. Machinery's Handbook has the formulas that you need. If you have a milling machine and a surface grinder then you have the tools needed to make dies. A good rule of thumb is about 0.001'' clearance per 0.01 of material thickness. Harder material can take a bit more clearance, softer needs to be a bit tighter.

    I'll be happy to help you get started.

    One other thought, if you don't need thousands of parts, laser cutting is a good option also.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Noob Looking for General Info on Stamping Press Machinery

    Awesome. Thanks for the info.

    So when you say area for calculating the tonnage, do you mean the surface area of the part, or just the surface area of the edges to be cut out? Cause I can calculate the surface area, but not sure how I would do the other. In Rhino I just selected the curves to be cut and used the surface area function. Would that work?

    So what I have now is just about 7 square inches. So tensile strength of 304L SS is 70,000. So 70,000 x 7 x .04 = 19,600. So does that mean I'd need a press that can do 10 tons at a minimum?

    So for the die I'm guessing that I make a positive, then the negative is the bottom part and it goes all the way through the mold and that negative is (for my .04 thick SS) .04" bigger that the positive? Do the edges need to be sharp or anything or just the pieces flat? I assume I should use some lubricating liquid when punching. I figure I would use O2 or A2 for the mold and harden it. What Rc should I go to?



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    Default Re: Noob Looking for General Info on Stamping Press Machinery

    Yes, the surface area of the part. Your calculations are correct, so a 10 ton at a minimum, but I would go for 20 or more tons. It really sucks to stick the press on the bottom. Also as your tools dull a bit the tonnage requirement goes up, a lot. Tonnage is kind of like toilet paper, you can never have too much.

    Yes, you make a positive and a negative tool. The Die, the part with the hole in it normally goes on the bottom. The Punch is fixed to the top. These tools are bolted into a Die Set. https://www.google.com/search?q=dies...w=1697&bih=921

    The edges need to be very sharp. The normal way is to surface grind the punch and die after heat treat. Your clearance is in the normal range.

    Cutting fluid of some kind is recommended, the normal water based cutting fluids work OK. whatever you are using for a cutting fluid in your shop should work fine, doesn't take much, just a couple drops per inch or apply with a spray mist.

    A2 would be a good choice. D2 has a higher chrome content and is more abrasion resistant, is a PITA to machine, but for SS might be a better choice. Building a 2 piece die is a reasonable idea, where the cutting part is a thin (3/8 to 1/2 inch thick) sitting on top of chunk of 4140 or something. Reduces material cost and the thinner section is easier to heat treat. The punch can be built the same way, by building a punch holder out of 4140.

    When building the die, the actual on-size (cutting portion) portion of the die should be only 0.100 or so thick with relief below that. This keeps the parts from jamming in the die. Don't forget about the stripper plate for the punch, this keep the material from pulling back up with the punch. This looks like is has some pretty good illustrations. Lecture 8

    Normal heat treat is in the RC58-62 range, favoring the higher end.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Noob Looking for General Info on Stamping Press Machinery

    Thanks a bunch. Great information. I'll have this a ponder and let you know.



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