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  1. #21
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    I don't want my comments to be taken as criticism, I think it's good that you have done some homework and are earnestly trying to accomplish this rather than simply asking for answers. That said I would like to offer the following comments:

    1) Your press is way undersized for the intended purpose. It would help to use a softer Al. variety but will still likely not be able to flat blank(not by my calculations) . The photo of the large punch merely "coining" the material should tell you something.

    2) You can add shear (various flavors of this)to help reduce tonnage and it may/may not work but it will deform the part and will require a secondary operation like rollers (described by Mechanola above) to flatten. This will have to be decided whether it's worth it or not by you.

    3) If you have any sort of urethane or spring stripper have you added the tonnage for these into total tonnage?

    4) Operating near rated capacity of any piece of equipment is usually not a good idea, presses included. So it stalls or dead stops what's the big deal? Ever see a flywheel shear off the crank and go-a-rolling through the shop? I saw the aftermath once, a lot of mass in motion that destroyed all it encountered. Dangerous potential.

    5) Do you understand what Reverse Tonnage is? Failure to observe this dynamic will beat the chicken soup out of the press if it hasn't already happened. Do look it up. Your press is way undersized if you follow this.

    I have several other comments about die construction from your photos but that's not going to help you at the moment. What you want are solutions/options for this project. I don't know if you have access to a larger press but that would be my first choice. I would NOT regard this as a failure. You're new at die making and even when something isn't successful at first it's a good chance to learn what does/doesn't work (formulas too). Do post up what your options are and perhaps one of us can help.

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    Quote Originally Posted by winklershop View Post
    I built a progressive punch and die set. I tested it today and it didnt work. I calculated the tons required and it was 16 tons of shear. 3/8" 6061 aluminum is the material. I have a no. 3 Niagara punch press that's good for 19 tons. The books said clearance constant for aluminum over 1/8" is 8, so .375 divided by 8 is about 48 thousandths, divide that by two so my clearance is 24 thousandths per side.
    Not into blanking die design, but that clearance sounds huge.

    FWIW what kind of press ? Mechanical or Hydraulic ?

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    Quote Originally Posted by Mechanola View Post
    You can bring forces down by giving the punch a slant. Make the tool enter the stock not on the entire line of cut but increasingly along it. Would presumably need to pass the cut pieces between rectifying rollers afterwards. That’s the way they used to stamp blanks like that:

    Aluminum sheet, thickness 0.118"
    If punching more than one hole, why not just step the punches to enter at different shut hiegth's ?

    would keep any sideward loading off the punches.

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    If you want the blank put the shear on the die, not the punch.

    T0 is gummy, that produces a whole new set of problems.

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    " ... The books said clearance constant for aluminum over 1/8" is 8, so .375 divided by 8 is about 48 thousandths, divide that by two so my clearance is 24 thousandths per side...

    Why divide by 2? Die clearance is always 'per side', not per 'diameter'

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    Quote Originally Posted by digger doug View Post
    If punching more than one hole, why not just step the punches to enter at different shut hiegth's ?

    would keep any sideward loading off the punches.
    I would do that, and add shear to the punches (or die depending on which part is being kept). I would grind a 'vee' in the round punch, as straight shear will want to make it walk a little bit.

    Also, my die makers handbook doesn't say anything about constant clearance over xx thickness, or that I have seen. However, they do recommend 12.5% clearance per side since Dayton did a study on this along time ago proving 12.5% produced a cleaner hole with less breakout. If you tighten the clearance up (unless you are just doing an edge trim op) the material bulges around the punch then snaps back into place creating a dragging/galding effect.

    Die Makers Handbook - Jerry Arnold - Google Books
    page 40-41

    Edit: it does mention the values change when blanking, or doing very large holes/cuts. No definition of very large, but I would guess 3/8" is pretty big for punching. I did build a die one time that did some holes and blanking in 1/4" mild steel. I think we went with the "standard" 10% / side, but that was long long time ago so don't quote me- or my failing memory.

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  12. #27
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    The guys have given great feedback on this.... so I will talk presses for a moment.

    Hydraulic presses have the stated tonnage throughout the stroke. Flywheel presses have the stated tonnage at a particular location on the press-stroke which is typically between 1/32 and 1/16" from the bottom of the stroke(that's where the energy is built up). Back geared presses with both flywheels have their stated tonnage typically at 1/4" off the bottom of the stroke.

    Many manufacturers say that you should only run dies that are around 75% of this stated tonnage. Other manufactures build presses to be run at full tonnage every day. This is why I have a 45 ton Minster that weighs 11,000# and a 45 Ton Johnson that weighs 4,600#. I talked to Heim once at they said there 95 ton press should run for production jobs needing 70 tons.

    So, I don't think you had 19 tons worth of force built up when you hit the part; I'd be guessing around 12-14 tons worth.

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    Quote Originally Posted by digger doug View Post
    Not into blanking die design, but that clearance sounds huge.

    FWIW what kind of press ? Mechanical or Hydraulic ?
    this is a flywheel mechanical niagra no 3

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    Naive question here: Can you test thinner parts of the same material to get a feel for the press and die set's actual performance? If you could punch say 3/16 but not 1/4" you'd have some idea you were a factor of two off, for example. Clearly there is quite a bit of uncertainty in the aluminum's properties as well as perhaps the press's actual performance.

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    How thick a plate can you punch? Try various thicknesses. That will tell you a lot.

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    lots of great stuff here guys, thanks so much for your input

    So we should shoot for a max of 14 tons required, so we dont overwork or brake this antique Niagra no. 3 flywheel punch press.

    I like the comments about offsetting the big punch and the small punch. In my head i thought they had to be on the same plane.

    So if we offset the punches, the small punch could go through before the big punch even starts, its still going to have some deduction on the operation i would imagine. I like the idea of sharpening this small punch to a V and adding shear will reduce the amount further more. That small slug is scrap and it doesn't matter if its flat or not. How many tons do you figure this will add to the equation, its a .500 punch going into a .548 die, i will add a V shear to the punch. shouldn't deform the blank?

    Flatteners and straighteners I would like to use as a last resort. Will adding shear on the big die cause the blanks to not be flat? For this equation lets leave that out for now. (might need to come back to it)

    I am using a bridge stripper, so that only comes into play on the return stroke.

    We need everything in our favor on this one, so we need to use a aluminum with the lowest number of shear required. sounds like its going to be the 6061 T0 (O condition). It being soft, gummy....how do we overcome that situation. Nice sharp punch and dies with the right clearance, maybe lubrication?, should over come it? Is there other aluminum out there that would be better?

    Now Red James maybe have spotted another problem, regarding my clearance.

    Thank you Mike for referring to the Die Makers Handbook, i have that book and i did come across that 12.5% per side. If we use that number, my clearance should be .047" per side about double of my current .024" which Red James pointed out...now i will refer to another book that may have got me confused...Die Design Fundamentals, 2nd ed., here is a picture out of the book:

    20191118_193640.jpg
    not sure how to rotate this picture, try it here:
    https://drive.google.com/open?id=18g...WZT8TI8l3Jw0rB

    looking at the chart on the left, it gives us a factor of 8 for "aluminum over 1/8" thick"

    .375" stock thickness divided by 8 = .047"

    It the text on the right 2nd paragraph it says "When clearance "on a side" is desired, as when laying out dies having an irregular contour or for cutting out only portions of a blank, divide the answer by two."

    That sentence through me off, i think i would have been better off if i had not read that, because it doesn't apply in this case?

    Someone mentioned that my clearance sounded huge, well now double it, now its ginormous...LOL

    It also talks about where to apply the clearance, i think i did that right, in my case we are keeping the blank so the die is made on size and the clearance is applied to the punch (subtracting clearance from all radii with centers inside the punch, and from all dimensions between parallel lines. ...but what about the opposite end of the part away from the radius.

    see drawing here:

    20191118_195316.jpg


    variables in our equation:

    14 tons max goal

    shear force of aluminum, T0 11,000

    Shear perimeter of large punch: 6.718"

    Shear perimeter of small punch: 1.722" (what effect will it actually have since its going to hit before and have shear?)

    Clearance .047" per side (.047" clearance all the way around the punch in the die)

    Shear x Thickness x Perimeter



    another comment just came in, rcoope, great idea, i may need to do that. i have 3 other shapes that i was successful in, that i could compare to, 1.820 diameter circles in 1/8 and 3/16 6061 t6 and a 1/4 tabbed part. i can do some calculations on those parts and see how they look.

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    After reading your post I have to ask a couple of questions:

    1) How many pieces do you need to make? You're contemplating a lot of work doing this, which is ok if you need/want to.

    2) The intended purpose of the part? Changing the type of Al to suit the press tonnage limitations may not yield the part purpose

    3) A larger press is NOT available?

    4) How flat does the part need to be?

    5) How did you determine the press tonnage capability? There is a way to approximate this if there's no documentation/markings

    You MAY be able to accomplish this with a T0 but it will behave differently than a T6 (clearance, slivers, break vs. shear %, burr height, etc.) and you may end up chasing the proper balance just to end up with a part you CAN blank out but doesn't work very well for the intended purpose of the part. If this project is more about learning something then that's fine, nothing wrong with that either. If the priority is cost per part then could sending it out for water jet be a less costly option?

    If you are determined to make this work then consider removing the .548 perforator AND the pilot in order to isolate the large punch. I would have suggested this earlier but felt your undersized press to be the bigger obstacle. If you can't obtain satisfactory results with the large punch then the smaller one doesn't matter. You can try thinner stock thickness but bear in mind that the die clearance will not be correct and likely produce a large burr. You can also experiment with adding shear to reduce the tonnage but this will shorten the punch height with each experiment and will likely produce a deformed part you'll need to flatten in a secondary operation. Try using a maximum of 2/3 material thickness shear angle if you have enough punch height.

    It's standard procedure to stagger the punch height but that's not your biggest obstacle right now. Cutting fluid is required for production running as Al likes to micro-weld itself to the cutting edge/sides of a punch, lube helps minimize this. Use whatever you have on hand in kerosene/mineral spirits (be careful of igniting it) light oil, I've even rubbed bar soap/wax on punches for try-out. Yes you have to adjust the clearance on all sides of the punch per your drawing if you intend to increase it to 12.5% PS.

    As Danil correctly pointed out, the tonnage rating is for near the bottom of the ram stroke so despite what the press MAY be rated for unless you're blanking near the bottom of the stroke you won't get the full tonnage. Die stamping is all about numbers but any variation in those numbers (material properties aren't always to specs) in a marginal application (like this) can throw it off. I hope this works out for you. I think it's chasing the solution backwards but I'm not in your shoes. Don't stand in the path the flywheel would take if it shears off the crank. Be safe, good luck.

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    3/8" is a loooong way from the 'sweet spot' of a 19 ton crank press. All else too A D D speaks the truth.

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    Thanks AD D

    1) How many pieces do you need to make? 500 a year

    2) The intended purpose of the part? Automotive accessories like aftermarket bumpers, ladders, racks, running boards, ect...

    3) A larger press is NOT available? correct, i am a home gamer and its the only one i have

    4) How flat does the part need to be? it would need to be pretty flat, parts will bolt onto this part thru the hole and pivot or bolt on in fixed position.

    5) How did you determine the press tonnage capability? There is a way to approximate this if there's no documentation/markings

    I found a thread here: Niagara #3 Punch Press

    I was trying to revive the thread to see if they can reload the pictures that have lost connection, but that was a long time ago...id be interested to know how to approximate this.

    I am doing this project for two things, learn and grow my skill set, two is if this works, the goal is to produce them cheaper than water jet because that is the current method.

    You have lots of good points here and lots of good info to consider. thanks!

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    If your doing 500 pieces a year.....get a simple 50 ton hand pumped hydraulic "H-Frame" press.

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    Quote Originally Posted by digger doug View Post
    If your doing 500 pieces a year.....get a simple 50 ton hand pumped hydraulic "H-Frame" press.
    Good point, but I wouldn't be able to beat the water jet cost at that speed. The other goal here too is the learn about this stuff.

    I'm 33 years old, been in construction industry since I was 15, and for me to pick this "hobby" up on the side, is a little insane...I get that...on top of being a self taught machinest...LOL

    It was a way for me to find a hobby that could potentially make money instead of cost money like my drag car...

    Here is some pictures of the punch press and my small shop.

    https://drive.google.com/folderview?...BtGgq8LRIAS_7S

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    Additional potential issues. Unbalanced loads accelerate the wear on both the press and die-sets. Your blanking load does not seem to be concentric to the die which also means it is likely not concentric to the slide(ram face).

    Presses like balanced loads. Unbalanced loads introduce other variables into the equation such as friction and binding. If your gibbs are loose or you have slop in the slide, this unbalanced load will tilt your ram-face and likely consume tonnage there and on your pins and bushings. Ever split a die-set trying to leverage only one side? That same kind of friction would occur as you cycle this part unbalanced.

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    so quick update

    I have thought of other methods of building this part...i haven't found any methods that are up to the challenge of speed. 500 parts a year, would mean they order 500 parts at one time, i have to beat $2 per part

    i am finding it very difficult to get ANY aluminum other than 6061-T6 in 3/8" x 2" wide flat bar

    so using a different aluminum is out. which means my punch press is out.

    we are looking at a total of 47 tons needed. Now if i off set the punch heights, and add shear to the half inch punch we can probably get that down to 45 tons.??

    a couple guys did mention using a H frame hyd. press...i could do it at home with a hand pump press, but very slow...i do have access to a large H frame 50 ton electric hydraulic press at work that i am considering using. my punch press can punch a part every second... compared to a hyd. press...if i attach my air feeder to my die set and attach it to the hyd. press, using the eletric control i could probably do a part every 10 seconds... so i could live with that...

    My plan is get the correct clearance in my die set. off set the punches, add shear to the small punch, attach the flat bar air feeder to the die set, make a attachment point for the hyd. press ram, and do a couple test hits.

    i haven't had the d2 hardened yet because i want to make sure this is going to work. if the test goes well, i can send the die and big punch out for hardening, re grind it sharp on the surface grinder and then we are set.


    material cost is about $0.71 each
    10 seconds per part ($100 shop rate that would be $0.27 per part in labor)

    dollar per part

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    If your math is correct then that part price does not come into effect until you amortize all the time spent making the whole setup. In other words all the research and development is not free, $100/hr shop time adds up fast. If you spend 50 hours figuring out the setup for 500 parts then that is $10 per part for the first 500. After ten years and 5000 parts you will be down to $1/part plus all the time and materials to actually make them.

    Also are you sure you are going to be happy with a part that has ragged sides and looks like hell compared to water jet?

    Not saying you shouldn't do this but maybe your time is better spent dreaming up new products?

    Good luck,
    Michael

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  32. #40
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    Development time for the die should come into the picture, as stated above, but this is your first attempt at doing this so it should serve as another guide to the learning process. Designing/building a die is the first part of the process but the "try-out" is step two and often requires modifications and/or "tweaking" things to achieve the final part. This all takes time and money to accomplish, it's not something you pick up overnight. I'm not saying this to discourage your efforts, I applaud what you're doing. However, you do need to keep in mind that visualizing and actually making something are two different things (as you now well know). If you don't want to just machine this from 1-1/2 x 3/8 bar stock but prefer the H-press route then go for it. Maybe you need to learn something more from all this.

    The ragged edges from the part can be handled by a belt sander in about 30 seconds apiece. Use the sole of an old crepe-soled shoe to keep the belt from clogging and extend the belt life. Wax might work well too. Run a thin film of light fluid (kerosene, mineral spirits, WD-40, soapy water, etc.) on the material while in the die to prevent AL. from building up on the punches. A small paint roller works well for this. Grinding hardened D-2 is not pleasant (A-2 would have been cheaper/easier) and you'll want to have anything of D-2 in a grinding vise because D-2 does NOT stick to a mag-chuck. It may seem to but it won't. Using A-2 is a better choice when AL. is the part material. Use D-2 for higher abrasion material like spring steel, Beryllium-Copper, SS, or plastics. That's for high run production numbers. For short run like yours you can even get away with just using 4140 pre-hard for a while, saving money on punch material and heat treating, especially when experimenting with punch geometry/clearance.

    Next time you're considering/planning another die just lay it out (even on paper) and post it for suggestions. There's several design habits/suggestions to follow BEFORE cutting steel that might save you time/money correcting later. Good luck.

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