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Constraints are not preserved when copying sketch items

Message 1 of 8
191 Views, 7 Replies

Constraints are not preserved when copying sketch items

Lets say that I have a rectangle and I add three lines to delimit a small part of the rectangle. Those lines are fully constrained.


Now I want to duplicate those three lines multiple times to create bounded areas for extrusion. Instead of redrawing them, I just select the 3 lines and copy then paste. After paste I drag the new items to the right and click okay. I expect the lines to be unconstrained because I have changed the x position and with that dimension missing they are still movable.




Then, in order to position the lines, I add a dimension constraint.




Notice that two of the lines are still no fully constrained. The perpendicular and coincident constraints were not copied.

I had originally used constraints instead of dimensions for the copies in order to clean up the sketch. (Equality for line lengths) After realizing that the dimensions do get copied, I copied from dimensioned items in order to reduce my work.


Now imagine that I want to copy the same three lines 20 more times. The fact that the constraints are not copied means that copy/paste does not save me any time. I have tried to use different types of constraints and nothing works.


What I expect, and what I would like is to use only constraints, as below, to make the first copy a duplicate of the second in all but x position.


Then copy and paste with only translation of the x position should maintain all of the constraints during the copy.

Surprisingly, there was one constraint that was kept for a vertical line, but all the others are gone.

If the move part of the paste is only a translation in the x direction then I do not understand why the coincident constraints with the bottom line should be removed. If the translation was in the y direction that would make sense.

The equality of line length constraints never have a reason to be removed, regardless of the new position. That would also apply to any constraints among the copied lines such as perpendicular.









Message 2 of 8
in reply to: Julie_7

In your example, I would not expect the bottom two constraints to be copied.  Constraints are between two sketch items.  If you only copy/paste one of the items, the constraint or dimension to the un-copied item will be dropped.  I don't know why the top constraint was lost, and I cannot reproduce this:

Jeff Strater
Engineering Director
Message 3 of 8
in reply to: jeff_strater

I understand that constraints are between two sketch items. When I copy one item and move the copy in a way that does not affect the constraint I do not understand why it is not still valid. I am copying in the same sketch.

What about the equality constraint on line lengths?
Or collinear constraints?

I tried making the first copy constrained by using equality and collinear to the original lines and then using that copy to create the others. My thought was that those types of constraints should still be valid for the copy.
Message 4 of 8
in reply to: Julie_7


What is your end goal?

Perhaps Pattern would be a better technique.

In any case, I recommend that you use whatever techniques you can figure out and then Attach your file here for tips by the experts.

Message 5 of 8
in reply to: TheCADWhisperer

I cannot use patterns because the offset distances are different for each instance. I use a script to update the parameters used to calculate distances depending on what is being stored in the tray.
Message 6 of 8
in reply to: Julie_7

@Julie_7 wrote:
I cannot use patterns because the offset distances are different for each instance.

Doesn’t matter.

Message 7 of 8
in reply to: TheCADWhisperer

What do you mean by "Doesn't matter"?
Is there some way to use a pattern with an array of spacing distances?
Message 8 of 8
in reply to: Julie_7


Do it the hard way and Attach your file here.

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