Sketch changed when mirrored

glib_kotelnytskyy

I've versioned a documet that I'm having a problem with: https://cad.onshape.com/documents/d00ceaba15e3ae5795e20cc8/v/e1306259ed2b791bba55a81d/e/5b289bdfe74c787a08ec07e3

There's a sketch "Sketch 2", on a plane parallel to the "Front plane"
The angle between two lines of this sketch is as follows:


Then I've mirrored this sketch by the parallel mirror plane "Front"
And on the mirrored entity the angle between those lines is different:


How could it happen?

I've checked that all the vertical and horizontal lines on both sketches are parallel, but not the inclined lines.

NeilCooke

That's very unusual. The construction line at the bottom is shorter and I can't see the reason for it, so it may well be a bug. Please open a support ticket (help > report a bug). As a workaround, create a new sketch on a plane where the mirror should be and "use" the geometry from the first sketch.

NeilCooke

That's very unusual. The construction line at the bottom is shorter and I can't see the reason for it, so it may well be a bug. Please open a support ticket (help > report a bug). As a workaround, create a new sketch on a plane where the mirror should be and "use" the geometry from the first sketch.

MBartlett21

@NeilCooke
Would it be to do with dropping external references?
https://forum.onshape.com/discussion/8603/option-to-not-to-drop-external-sketch-references-in-feature-pattern

NeilCooke

@MBartlett21 that may well be the root cause, but in this situation, I don’t think that would have an effect. 

EDIT: I take that back. Deleting the external constraint in the lower left corner fixes the mirror. The link you shared refers to a feature pattern limitation, whereas this presents itself as more of a bug, but it's the same thing. I will add this as a test case for fixing.