Picking or selecting order

[descatia]

When you are putting assembly constraints between two objects, does the order of selection matter?
Is a constraint between A and B exactly the same as the constraint between B and A?

Is there any criteria for selecting the first object?

 

[itsmyjob]

in V5 I do not think it matter that much... in 3D Experience it does!

Eric N.
indocti discant et ament meminisse periti ​

 

[weavedreamer]

A tidbit of V5 trivia:
One observation is that the first object in an Offset Constraint 'pulls' the second object to it, as if the first object were fixed. Using a Fixed Component constraint on the second object does negate this.

 

[itsmyjob]

the part's movement after a constraint definition depends on pre-existing constraints if any.

Eric N.
indocti discant et ament meminisse periti ​

 

[MarkAF]

Yes, the order of picking constraints in Assembly Design does have an impact, at least in some cases. Most easily to see is the Offset constraint. The offset between two planar elements can be either positive or negative depending on the order picked, and also the polarity of the first element. What I mean by polarity (have I got that right?) is which direction is the positive normal vector facing, from the face. For a solid body, positive polarity is is facing outward from the solid. For a geometry only element, i.e. a plane, polarity is more an artifact of its creation relative to the features it was created from. Creating a plane 20mm offset from a face in one direction will be the same plane as -20mm offset from the face in the opposite direction, but with opposite polarity.

The result of this is that when creating constraints in 3D, you should pay attention to the results but the desired result can be achieved sometimes by changing the sign of the offset value (+20mm vs. -20mm). If you were making constraints via a macro, then the order of selection might be a key factor.

With some experimentation, paying attention to these points, you can figure it out.

Hope that helps clarify a little bit.

Mark