Unbend when subtract used with angled part impossible?

[thentunen]

Heres the case:
1. When I use subtract to a sheet metal object with a subtract part that I don't turn and twist the unbending works just fine
2. When I need to turn the boolean part in order to make the right kind of cut the unbending of the manipulated sheet metal part doesn't work anymore

Any suggestions? In case someone is interested I'm trying to make a 44 degree pipeline crossing and I would like the get the cutting measures for the cross before I start my torch.

Here is a picture of the situation.
http://img210.imageshack.us/img210/691/pipel.jpg
The pipe diameter is 508mm and thickness is 6,3mm and I ihave impaled the pipe with another pipe ( correction: with a solid part with same diameter) with the same diameter in a 44 degree angle. Can someone else get this kind of sheet metal part unbend?

 

[Ron]

I think why it may not be working is because you are cutting material away from the flange; in some case it will allow you to unbend/flatten the SMP while other times it will not...

I was also unable to get it to flatten while using a Boolean Subtract, but I was able to create a sketch and use Feature > Features > Cut > Extrude (to remove the material) and then use the Unbend to flatten the SMP.

Let me know if that allows you to do what you need.

- Ron

 

[thentunen]

Hi Ron

I tried it. Made a pipe and used the cut feature to take a piece of it out. The unbending didn't work altough the cut works and it shows what the piece looks like when bent. Is this some sort of a clitch or just a feature that hasn't had so much work done on it?I realise it's not the easiest thing to flatten ( a pipe which is cut with another pipe - flattening of this takes some calculation).

 

[Ron]

Would it be possible for you to attach the parts so I can look at them; that way I am working under the same conditions that you are.

 

[HaroldL]

FYI...
One thing you have to be sure of is that the cut in the sheet metal is normal to the surface at all points along the cut edge. Looking at the image you posted, it shows that this is not the case. If you are using a Boolean subtract the edges will be coincident or parallel to the surface(s) of the part used to make the boolean and not normal to the surface of the sheet metal being cut.

I don't think Alibre sheet metal is "smart" enough to create a cut that is normal on the curved surface without using the Unbend before the cut then Rebend to roll it back up.