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Suggest and Design a progressive die to make a blank with a 2 mm thick steel sheet as shown in Fig. The ultimate shear strength of the material is 480 MPa. Calculate press capacity assuming 75% efficiency. enter image description here

Like I know if we have to design a progressive die washer then we calculate shear force as= shear stress x Area to be sheared. area to be sheared in washer= 3.14 x (D+d) x t where D is outer diameter and d is inner diameter and t is thickness. And then press capacity is calculated as F/0.75 as 75% is efficiency

and if we need to design die a punch for a single blanking operation we calculate fore as = 3.14 x D x t x shear strength.

But I'm not able to tackle this problem as it is not similar two either of the case I described above, how do we tackle such problems, kindly looking for help. Thank you

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  • $\begingroup$ what is your question? ... you described a school assignment, but you did not ask anything ... akso, please describe what difficulty you are having $\endgroup$
    – jsotola
    Commented Oct 13, 2021 at 7:35
  • $\begingroup$ @jsotola sir basically I need to suggest a die design for my question means including shear force and a suitable die size, type with dimensions $\endgroup$
    – Rajakr
    Commented Oct 13, 2021 at 7:45
  • $\begingroup$ I don't know anything about metal punching but I would think that the force depends on the length of the cut, not the area. $\endgroup$
    – Transistor
    Commented Oct 13, 2021 at 12:07
  • $\begingroup$ Any presses I have seen have substantially more capacity than needed for a particular job. No one would design a press for a single job. $\endgroup$
    – blacksmith37
    Commented Oct 13, 2021 at 14:17

2 Answers 2

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The cutting blanks equation is,

$$F=l*t*s$$

  • L=length mm
  • t+thickness mm
  • s =shear N/mm^2

We measure the perimeter of the blank and then add the circumference of the two holes.

$\text{The straight sides are 2*70mm =140mm and 2*( 70-40-20=10)mm=20mm =160mm}$

$\text{half circles are 2*pi*20=125.66mm, inner holes 2*2*pi*15=188.49mm} $

$\text{ Total 188.49+124.66+160= 473.15mm}$

$$F= 473.15mm*2mm*S*\frac{1}{0.75}$$

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So why not calculate the cut length ie perimeter and use that with the thickness - the cut length is what you get with pi * D in your single blanking example.

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