How do you calculate tonnage of a punch press
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  1. #1
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    Default How do you calculate tonnage of a punch press

    I picked up a small punch press. It is a Molex TM 40D. (Yes I suppose I could contact the manufacturer but I thought I'd test the knowledge here.) It was designed to crimp connectors onto wire.
    The specs:
    Fly wheel weight: ~35 lbs (Using online weight calc based on dimensions) 9" OD
    Fly wheel RPM: 365 (Laser RPM meter)
    Stroke: 1"
    Motor 1/3 HP
    RPM 1750
    Total machine weight: 210 lbs on a digital scale

    I was thinking of using it to punch aluminum gas checks for lead bullets. Online
    punch calculators call for .1 to .3 tons for the sizes I'd like to do. I have the equipment to make my own dies.

    Anyone have to formula to calculate the tonnage of this little press?

    Thanks,
    MT6

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    I've never done a flypress before, so I may be totally wrong, but here's what I get-

    Firs calculate energy of flywheel-

    E= 1/2(I)(w^2)

    Iz = 1/2m(r^2) = 1/2 * (35/32.17) *(.375^2) = .153

    w = 365rpm = 38.22rad/s

    E = .5 * .153 * 38.22^2 = ~112 lb-ft.

    Next calculate force-
    F= 112lb @1' = 2688lb @ 1/24' (if stroke is 1", the wrist pin's radius must be 1/2", or 1/24', right?)

    2688/2000 = ~1.34t

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  4. #3
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    Cole, thanks for the calculation. You might be close. I just searched on e-bay and found a two ton press that appears to have a fly wheel not that much bigger than mine.

    The attached pic is the e-bay Alva Allen B-2 2 Ton Mechanical Trip Bench top punch press.

    I have sent an inquiry to Molex's customer service but haven't heard anything from them. If it is in the one ton range it would do what I need, just have to come up with the time to design and do it.
    Attached Thumbnails Attached Thumbnails 2ton-press.jpg  

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    I didn't include the motor's tq, that'd add an additional ~4.8lb-ft.

  6. #5
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    A quick way to determine press capacity is to square the diameter of the crankshaft main bearings and multiply by 3.5. This will give the capacity in tons.


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