How to Achieve a Clean, Perpendicular Cut on a Plastic Rod?

[downtownjapan]

Hi everyone,
I have a plastic rod that is cut/snapped between two metal clamps. I want the break in the material to be at an angle perpendicular to the rod's surface. Can anyone tell me what factors effect this operation? How can I select the best material for the plastic rod?

Thanks in advance (sorry if the question is unclear - I have tried to explain the best I could :-)

 

[Baluncore]

Why are you doing this ?

Maybe a study of shear bolt applications would be more appropriate.
You should primarily select the plastic material based on your application.
The cutting of the material is then a secondary issue. When punching holes or shearing material, the minimum energy is required when the tool edges that initiate the shear are offset by about 10% of the material thickness. That will result in a diagonal shear at about 5.7°. If the cutting edges have insufficient separation then there will be significant additional energy needed to crush the middle of the material.

The exact offset needed for minimum energy depends on the material being cut. When the offset is correct, there will be a shear across the entire cut surface. If there is a polished part then the edge separation is not optimum.

Where the shear needs to be perpendicular to the material, it is necessary to rotate the material being cut to control the angle. There should also be a relief angle of about 2° on the side of the cutters.