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Parts flipping over during mate or align constraint in assy


Parts flipping over during mate or align constraint in assy

Can anyone help me avoid having parts flipping over to the other side of a surface during an align or mate constraint in an assembly? Anyone else having this problem? This is a chronic problem with me. :(



Mine does it too. I think the issue lies in the orientation of the individual parts to their coordinate systems. In an assembly, they are reversed and when aligned/mated, they flip. Not sure tho... :?


New Member

:idea: I had a simular problem in the engine assembly tutorial. The piston was correctly attached to the connecting rod. When I constrained it to the crankshaft the piston inverted. I deleted the constraints then moved and rotated the parts to the general location I wanted them in and reconstrained them. That time it did not invert



Senior Member
Re: Parts flipping when constrained

What I've done in a lot of cases is use the Move or Rotate commands to orient or re-orient the parts to get them aligned as closely to how they're meant to go together as possible, and then apply the constraints. This isn't a problem specific to Alibre though - it affects every solid modeling program I've used. Some of it has to do with the coordinate systems the parts were originally created in (directions of the Normals, etc.), but most of it has to do with these systems being, well unintelligent. No matter how powerful they are, they're pack less intelligence than the grasshopper sitting on the bush outside your window.


Alibre Super User

This used to drive me absolutely nuts :? After some time I came to notice a rule of thumb that may be useful:

Mate and align get faces together. The question is where the rest of the body will lay. Lets think of two soda cans.

:arrow: Use mate when you want one can on top of another, like if you were making a tower. In this case, two faces will be touching each other but the rest of their corresponding bodies will be facing opposite directions.

:arrow: Use align when you want both cans to still have a face touching each other (or at least belong to the same plane), but the rest of their cylinders to be facing the same way, as they would be on a six pack.

Happy thing is that if you get it wrong and your bodies flip, you may just edit the contrain to make everything right (you do not have to kill the contrain, rotate the bodies back to original and reconstrain).


Senior Member

It would be nice to have a "FLIP" button in the constraint edit window.
Also, it would be nice if the constraint window remained open until manually closed, so that editing and additional constains could be added quickly.