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# Mechanical Engineering/How much pressure is needed to cut/snap this object?

Question

Shear question
Hello Aroosh,

How are you? Thanks very much for all your answers in the past - they helped me understand a lot.
I have been trying to research something by myself and I am wondering if I could ask you a question about it. I am working on a design which involves laying a thin piece of plastic on one part, and then pressing another part down against the plastic to cut/snap that plastic into two pieces. As shown in the attached image, the plastic is laid onto Part B (and held in place) and then Part A is pressed down to cut the plastic.

I am trying to work out how to calculate how much pressure is needed when Part A is pressed down - would this be calculated from the Shear Strength of the plastic material?
I am assuming that Parts A and B need to be made of a material that is stronger than the plastic - is that correct? What type of strength is needed in Parts A and B for the operation to work? Do I just need something of greater density?

Thanks again for volunteering on this site!
Best regards,
Eddie

Hi Eddie

thx for kind words, it is my pleasure.
It really depends on how many times you want to perform this operation, more the operation harder the die.
You can use heat-treated aluminum up to heat treated steel, depends on the application.
but make sure to change your design to give both the top and bottom die a draft angle as relief for the cut part to come out of the die, use 1° to 2° for that.

Aroosh
good luck

Mechanical Engineering

Volunteer

#### Aroosh Shahbazian

##### Expertise

I`m able to answer to questions regarding CATIA designing software, (detail parts and assemblies), designing tips and methods, able to solve manufacturing problems, creating a long term plan to make any working operation more efficient than it is, cosmos FEA.

##### Experience

I have programmed and have designed auto and aircraft parts for various companies (inside and outside of the United States) since 1990, been working in aerospace industry since 1997 as mechanical engineer and ENG. MGR.

Education/Credentials
Masters in Mechanical Eng. (solid designing)