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    Default Suggestion on stamping mold design

    Dear specialist friends, I hope you can help me on this topic.

    Although being a Mech. Engineer, I've never looked deep on forming and stamping technology. I just acquired recently for my workshop an old eccentric stamp press (120 punches/minute) and I am looking forward to produce some parts.

    However, since I have my own CNC and proper software, I am not willing to spend money requesting a new mold. Therefore I would like to ask you guys some hints on how would be the best mold architecture for this specific part (picture attached), numbers of steps, materials to use, and so on. Any hints are welcome, as I am practically starting to re-learn it from zero.

    The part is made from any suitable stainless steel sheet and has 1mm thickness, outside diameter 136mm and inside diameter 100mm. About 10000 parts/year.

    stamped-part.jpg

    Thank you in advance!

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    Are you starting from strip stock then? That is, you get a roll of 1mm stainless, start feeding through the die, and finish with your parts, some scrap circles and the remaining skeleton of the strip? If you are getting 136mm blanks it would be a different die.

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    Hi fcol:
    This is a deceptively difficult part to make, so if you're just starting out in this industry I think you have chosen a fair headache as your first part.

    The basic problem is that you have to make a deep draw and then cut out the middle, all without wrinkling or tearing the part where it transitions from the flat plate to the pipe section.
    A huge amount of material has to flow through that transition, so it can sometimes be a multistage process with intermediate annealing steps.
    Deep draws are very slow in stainless and require a lubricant and a press that will partly constrain the blank around the periphery while still letting it flow into the form, so it's not a whack like a punch press does; it's a slow stretch.
    We are talking about 10 seconds per part, not half a second per part.

    The correct tool is a hydraulic drawing press not a punch press.
    Here's a link to a Youtube video showing the process.
    YouTube

    Basically you'd draw a flat rimmed dome that's a bit more than half the dome diameter deep, then trim the center out and trim the rim to get the final part
    You could also spin these parts rather than deep drawing them, but then you'd need a spinning lathe.


    I'd find something less difficult and more suited to the tool you have, for my first project.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME.
    Vancouver Wire EDM -- Wire EDM Machining

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    Quote Originally Posted by implmex View Post
    Hi fcol:
    This is a deceptively difficult part to make, so if you're just starting out in this industry I think you have chosen a fair headache as your first part.

    The basic problem is that you have to make a deep draw and then cut out the middle, all without wrinkling or tearing the part where it transitions from the flat plate to the pipe section.
    A huge amount of material has to flow through that transition, so it can sometimes be a multistage process with intermediate annealing steps.
    Deep draws are very slow in stainless and require a lubricant and a press that will partly constrain the blank around the periphery while still letting it flow into the form, so it's not a whack like a punch press does; it's a slow stretch.
    We are talking about 10 seconds per part, not half a second per part.

    The correct tool is a hydraulic drawing press not a punch press.
    Here's a link to a Youtube video showing the process.
    YouTube

    Basically you'd draw a flat rimmed dome that's a bit more than half the dome diameter deep, then trim the center out and trim the rim to get the final part
    You could also spin these parts rather than deep drawing them, but then you'd need a spinning lathe.


    I'd find something less difficult and more suited to the tool you have, for my first project.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME.
    Vancouver Wire EDM -- Wire EDM Machining
    Have you ever made a stamping die?

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    Quote Originally Posted by fcol View Post
    Dear specialist friends, I hope you can help me on this topic.

    Although being a Mech. Engineer, I've never looked deep on forming and stamping technology. I just acquired recently for my workshop an old eccentric stamp press (120 punches/minute) and I am looking forward to produce some parts.

    However, since I have my own CNC and proper software, I am not willing to spend money requesting a new mold. Therefore I would like to ask you guys some hints on how would be the best mold architecture for this specific part (picture attached), numbers of steps, materials to use, and so on. Any hints are welcome, as I am practically starting to re-learn it from zero.

    The part is made from any suitable stainless steel sheet and has 1mm thickness, outside diameter 136mm and inside diameter 100mm. About 10000 parts/year.

    stamped-part.jpg

    Thank you in advance!
    You need to find a competent die designer local to you to design the die you need.

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    I am immensely thankful for all the help. That is incredibly kind.

    Yes @TGTool, I will be looking to acquire also a feeding line for the spool.

    Thanks @implmex, I am sad to hear that it is probably too difficult for stamping dies. I've already briefly showed the part to a specialist and he mentioned that it could be done, but using multi stages. Maybe he was wrong?

    I understand the necessity of lubrication and also the issue of trimming the inner part before or after drawing. But I thought it could be done on 2-3 steps, since it is not too deep, the circles are symmetric and the sheets are not too thick.

    Yes @SIP6A, I understand it is a complex, but I am also willing to lately approach this die using explicit FEA (my field of expertise), which would be also my master thesis. So if it is not impossible, I would give a try... even if it takes time.

    Again, thank you very much guys. Really nice

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    Hi fcol:
    There are several ways to go about this, but a stamping die would be my last choice.

    Not to say it couldn't be made to work, but I don't think the part could ever be successfully made in one hit, given the amount of material flow needed to get from a flat blank to a short tube with a flat flange.
    To me, the right angle transition from the flange to the tube kind of defines the safest way forward, and that to me, means a deep draw.
    Stainless work hardens and galls, so it responds poorly to a fast whack when you're trying to coax it to flow.

    A progressive die to stamp it in stages is not simple to build, and is, in my opinion, still a poor way forward, especially considering that a drawing die would probably be less work and less risk, with a more certain outcome.

    Of course, that's just my opinion...you may well hear others.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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    I think before going into die particulars, we need to know what is expected of the drawn end. Can it somewhat ragged or smooth and well defined or something in the middle. Are the parts to tumbled or otherwise finished that would smooth cut edges?

    Tom

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    Quote Originally Posted by implmex View Post
    Because that was the stupidest bunch of shit I have seen posted in a long time.

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    Hi again SIP6A:
    You wrote" Because that was the stupidest bunch of shit I have seen posted in a long time."

    Well that's interesting, what makes you say that?
    Do you take exception to my belief that the part should be drawn and trimmed?
    Do you think I'm wrong when I say drawing stainless is slow compared to more ductile metals?
    Do you disagree that the little we know of his tooling, his knowledge and his experience makes this a more challenging part than maybe he is aware of?
    Would you choose a part like this for your first kick at the can and commit to make 10K parts per year, never having done it before?

    Will you share how YOU would do it?

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining


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    Research Minster, they make punch presses

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    I need to qualify my opinion/experience by saying that almost all of the dies I designed/built/maintained were stamping dies. I did maintain a few deep draws for Elkay Mfg. a long time ago. Deep draw design has rules unto itself and has little in common with piercing, embossing, and forming dies. My opinion here is certainly NOT the last word. I don't really consider the OP part to be deep draw as the part height is considerably less than the diameter. It is a part that would be easier in a progressive die with several stations, perhaps 8 as a guess-ti-mate. Material tearing, pucker, wrinkling, and wall thinning are factors that do require a deliberate design approach. I wouldn't attempt this without a lot of reading just for a starting point. I've maintained many dies that had similar parts and it's certainly possible in a stamping press but in one hit might be a bit ambitious. There are several other die makers/designers on the board, perhaps one will post and I'll get to learn something too. I've been out of die making/designing for over a decade so my opinion is dependent upon my fading memory.

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    Quote Originally Posted by implmex View Post
    Hi again SIP6A:
    You wrote" Because that was the stupidest bunch of shit I have seen posted in a long time."

    Well that's interesting, what makes you say that? Because ​It's the stupidest bunch of shit I have seen posted in a long time. It's painfully obvious that you don't know what your talking about.
    Do you take exception to my belief that the part should be drawn and trimmed? YES
    Do you think I'm wrong when I say drawing stainless is slow compared to more ductile metals? YES
    Do you disagree that the little we know of his tooling, his knowledge and his experience makes this a more challenging part than maybe he is aware of? I am aware of his lack of skill that's why I told him to bring in a qualified die designer.
    Would you choose a part like this for your first kick at the can and commit to make 10K parts per year, never having done it before? When I was in my first year of my Tool and Die apprenticeship I helpt build a three station progressive die to make a part not dissimilar to what he posted. Hobbyist have absolutely no business building any stamping die. When a die explodes in a press those heat treated steels come out the front at about 700 miles an hour. I see by your profile that your a dentist. How do you feel about me pulling a tooth out of your head. It can't be hard I've read all about it.

    Will you share how YOU would do it? I would build a three station progressive die. And yes a progressive die is appropriate for 10000 per year Just because you went to collage and can do one thing means that if somebody didn't go to college it can't be difficult and take any skill to do.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

    ..........

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    Ding, ding, ding. End of round one everyone back in your corner.

    One critical parameter has not be stated. How big is the press? I consulted with my die maker friend on this, his estimate for a progressive die is 150 ton. We both agree that this does not come under the heading of deep draw. This is more of a forming operation.

    If this is done in a prog die, then I see these moves:
    1. pilot holes
    2. tie strips to hold the part to the skeleton.
    3. blank center
    4. first form to generate a cone (~45 degree)
    5. second form to generate cone (~85-89 degrees)
    6. form to size
    7. pinch shear center
    8. blank part

    Some of the moves may not be needed in the opinion of the die designer.

    The move is 6 inch, or 150 mm. Stock width 6 inch or 150 mm. Matl 304L special draw quality

    Die length 5 ft.

    Probably need to run in 150-200 ton 4 post press. Speed 30 strokes/minute.

    For 10,000 pieces this obviously overkill.

    This could only be done with individual dies. Registration would be from the hole instead of pilots.

    1. cut blanks from strip
    2. blank center hole
    3. first cone form
    4. second cone form
    5. finish form
    6. pinch trim
    7. blank part.

    Each die of course is going to need stripper plates in addition to the die and punch plates.

    Minimum press size is 75 ton for individual dies.

    Tomdie-drawing.jpg

    Tom

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    Let us add more only right way. spin it.
    It falls on edge of deep draw, the height looks about the same as flange, the local deformation is factor.

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    I just gotta respond to this:
    "I see by your profile that your a dentist. How do you feel about me pulling a tooth out of your head. It can't be hard I've read all about it."

    And this:" Just because you went to collage and can do one thing means that if somebody didn't go to college it can't be difficult and take any skill to do."

    Man you are really taking this personally... don't hurt yourself over this... it's just not that important.
    Just to set the record straight; I did my apprenticeship as a mold maker starting in 1974, and except for the 10 years I spent as a dentist I've been working as a full time toolmaker for close to 45 years, building everything from injection molds to assembly tooling to punch tooling to prototyping and product development across a lot of different industries, some of them quite demanding.

    So I do know my shit....admittedly I have not designed or built big complex stamping dies but I have built a fair number of small prototyping dies so I have a basic familiarity with that turf too.

    So please spare me the butthurt attitude about how I think I'm some kind of king shit superior being because I went to university...I don't swing that way and I resent your misrepresentation that I do.
    It's bullshit, and anyone who knows me at all knows that about me too.

    Moving on to the topic under discussion:
    The OP describes a punch press that certainly doesn't sound like a 150 ton Minster capable of handling a fairly big progressive die.
    I got the distinct impression from his first post that he bought his new toy on Ebay or something like that, and it's sitting in his garage waiting for him to get a chance to play on it.
    He's also going for his masters degree so he's a student with a workshop, housing probably a toy CNC and his new punch press and maybe some other goodies, probably all in that garage at home.
    The 10K parts a year are probably a fantasy based on those magic 120 hits a minute from his first post.

    If that is true, I stand by my recommendation that this is not a good part for him to try to build a progressive stamping die for and hope he can run it in his new press regardless whether he finds a die designer to design it for him.

    If he REALLY wants to try his hand at producing these parts, and has some ingenuity, I also believe a draw die and press is a more realistic thing to try to build than a progressive stamping die.
    As a bonus, a small hydraulic press is not too hard to build, is quiet and doesn't take up much space, so for his circumstances, I maintain that it would be a better choice unless I've totally misread what he's got to work with.

    Now I'll grant you, SIP6A that I didn't frame my first post very well, and it seems clear that in spite of your snark, you do have lots of experience making punch tooling that I don't have, so I'll happily learn from you and anyone else who cares to weigh in.
    But there's really no need for you and I to have a big pisser over this; so lets say we shake hands on it and start over.
    I'm game if you're game.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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    I stopped reading after the first couple of posts but Its only 5” flanged washer. A deep draw to me, is anything over 10”s in a single hit. Think floorpans, fuel tank half, hoods, pickup box sides. A dually approach’s almost 14” deep.

    On a difficulty level of 0-10, you’re looking at a 3. You have to ask yourself if you want to spend the time/money on a prog die or a couple single hit dies. Once you figure out which direction you want to go, we can move on. Do you have the cradle, straightener and the feeder for your press to run it in automatic?

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    I agree with implmex that when the OP sees the magnitude of the problem, we will hear no more of him. Says he want to use this for a Master's thesis, in what field I am not sure. If it is in manufacturing or design, then I would have expected a lot more homework before coming here for ideas. Just blanking the part from stock sheet is going to take 52,500 lbs (from Unipunch data sheet, shear strength 75,000psi, 304) and this doesn't take into account stripper spring loads. I doubt his press is 50 ton. A 50 ton OBI press is rather large for a home shop.

    Tom

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    Quote Originally Posted by Hobby Shop View Post
    I stopped reading after the first couple of posts but Its only 5” flanged washer. A deep draw to me, is anything over 10”s in a single hit. Think floorpans, fuel tank half, hoods, pickup box sides. A dually approach’s almost 14” deep.

    On a difficulty level of 0-10, you’re looking at a 3. You have to ask yourself if you want to spend the time/money on a prog die or a couple single hit dies. Once you figure out which direction you want to go, we can move on. Do you have the cradle, straightener and the feeder for your press to run it in automatic?
    An automatic press will do little good with single station die sets.

    Tom


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