Calculating the Force to Cut Sheet Metal - CR4 Discussion Thread

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Ulhas Shah Participant Join Date: Apr 2009 Posts: 4	Calculating the Force to Cut Sheet Metal 04/06/2009 12:00 PM
	Need help!! I have a sheet metal press shop having 4 power presses 10 ton to 150 ton capacity. We use different types of press tools on these machines for production. I am facing some peculiar problem in a Blanking Press Tool. Though thw part looks reasonably small, it has to be installed on 150 T Press, making it commercially not viable. We have tried routine tricks like surface grinding the press-tool, a proper maintenance of the press tool etc. to no avail. The press tool is mounted on a "Pillar Set(or Die set)" which is itself, freely working. I am not a mechanical engineer. I remeber way back about 15 years, I had come across a formula which can be used to calculate the force required to cut metal sheets by using parameters like perimeter, thickness of sheet metal, Young's Modulus etc. to provide the blanking force required on a Power Press. I have tried various combinations of search words on "Google" without any success. Can any one help me on this?
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The Jacket Associate Join Date: Mar 2007 Location: Essex, UK Posts: 27 Good Answers: 1	#1 Re: Calculating the Force required to cut Sheet Metal 04/06/2009 12:24 PM
	Cutting force = Length (in mm) x thickness of material (mm) x shear strength of the material (N/mm2). __________________ "correct me if I'm wrong, but hasn't the fine line between sanity and madness gotten finer?" - George Price
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Curious George Active Contributor Join Date: Apr 2009 Location: IL., USA Posts: 24 Good Answers: 1	#2 Re: Calculating the Force to Cut Sheet Metal 04/07/2009 10:47 AM
	http://books.google.com/books?id=9ty5NPJ0UI4C&pg=PT111&lpg=PT111&dq=shear+strength+of+c-1018&source=bl&ots=UWuqsS0rdK&sig=p4qaXf9MSko-uOjrJaCxMYU16uQ The above link should give more in depth information. You also have to consider the face of the punch. If the face is ground at an angle other than perpendicular to the side of the punch, the force is reduced. You then need to calculate the actual engagement with the material. Stripping force and the force of the punch passing through the hole will be based on 1/3 the material thickness (the shear region, ignore the break region). ie- circumference x 1/3 x coefficient of friction x force on sidewall of punch. Depending on punch geometry, this could be greater than the actual shear force. Because of the heat generated, the material wants to swell and the hole close up on the punch. Oil will obviously help to reduce friction and promote heat transfer away from the material. The specific formula you are looking for is most likely in machinery's handbook or the die makers handbook. __________________ Half of everything in life is counter-intuitive,,, I'm not sure about the other half yet...
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