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Transition between the inside of a tube and a flat surface

Question asked by Christian Hellwig on May 15, 2018
Latest reply on May 15, 2018 by Christian Hellwig

Hi everybody,


I'm having a hard time getting my head around a problem and maybe some of you might be able to help me.

I've got a punch/die which looks like this:

and is inserted in this tube through the slot:

The punch goes in till the rim sits flush with the inner diameter of the tube

This results in a sharp corner in the middle of the punch, don't really know how to explain this in English but I hope you can see what I mean by the following sectional view.

In my use case (coldforming) I need kind of a better transition between the punch and the inside of the tube. So I decided to use a 40° angle, to do so I took the difference between the highest point on the punch and the inner diameter of the tube (2.55 mm) and made the base of the punch elliptical at the ends instead of round.

The same goes for the slots in the tube. Next step was to make a swept cut at the end of the punch.

Next step was to assemble both parts again.

The cross section looks fine but while panning around a little bit you can see that now there is a gap between the slot and the punch at some areas.

I will add the parts and the assembly so you may take a closer look on your own to see what I mean.


Question now is how do I get rid of the gap. I need kind of an angle at the ends of the punch to help the material flow but there must not be a gap because the material will flow in there and will so damage the part.


Thanks for your help!