Why are fastened offsets sign (+/-) a crap shoot?

marten_hutchison

So irritating.  In an Assembly, if I Offset two mated parts i.e. in the Z axis, when I enter a distance value, its a crap shoot whether the direction (+ or -)  is right.  Invariably its wrong and I have to enter it again.  Its an irritating little time suck.  What am I missing?

john_mcclary

I agree, I still haven't learned the trick to forcing positive numbers the first time

edward_petrillo

Whatever the underlying logic might be that leads to a given sign for the offset, I doubt that I would be able to apply it correctly every time.  I'd settle for an easier way to switch from one sign to the other.  Perhaps an arrow or sign symbol next to each input field that would invert the sign of the offset with a single mouse click?

marten_hutchison

Intuitively when I'm creating a Mate, I'm selecting the two surfaces that will be in contact with each other, therefore my brain wants a positive offset to separate the mating surfaces and a negative to make them go toward each other. 

tim_hess427

My understanding is the the positive direction is based on the mate connector selected for the first component selected when creating the mate. 

The trouble I have is that the orientation of the mate connector can be hard to see clearly in big/complicated models. 

romeograham

@tim_hess427 I think you're right. 
Another way to see is that when you change the mate's z-offset to a positive number, it's the first part you selected that moves in Z+ direction relative to it's own Mate Connector .... This can be confusing becuase we conceptually think about the two parts we are mating as moving toward / away from each other. However, I think the movement is ONLY related to the first selected part's Mate Connector axis direction. It's almost as if the offset is really only affecting the first part relative to itself.

bruce_williams

@romeograham
great analysis!  very helpful

john_mcclary

@romeograham yea that makes it a bit easier to remember

3dcad

I have requested swap direction button a long time ago (similar to extrusion direction etc.) would make it a lot easier than typing again or other maneuvers..