Sketch and equal function of sketch lines

julian_julian372

Is this normal behavior for a sketch with = length function on sketch lines.

Here is a video showing the behavior.

https://youtu.be/FRVcfX6aSDg

sample document
https://cad.onshape.com/documents/1f2b8827b2283a9f1b4dbf36/w/eb922cf84b5b593fd5ff000b/e/5febb555e672116df6dd8fe3

I only came across this issue as i have a sketch vertically aligned and it does not behave the way I expected.

eric_pesty

That's not surprising to me, the equal length constraint is still respected.
Having the "other" equal lines did flip when the "driving" one flips direction might make sense in this specific case but is not something you would want to happen in a more "general" case as there would be many cases where that would cause unexpected results.
The "safe" choice is to not flip the line direction. if you did want the various points to "flip", you could use a construction line coming from a different reference that never flips.

As a general rule you want to avoid having things flip orientation like this in a layout sketch as much as possible as it will cause some unexpected results as some features do use the "direction" of the line (frames, offsets, chamfers, etc…)

julian_julian372

I have updated the document with 3 examples.
when compared to other CAD software the behavior is not as i expected.
here is onshape vs freeCADRC1
the behavior I would expect/want is how freeCAD behaves

MDesign

I concur it is unexpected behavior.

S1mon

Certainly that example looks much more logical in FreeCAD, but I have to say from years of solvers in Creo and Solidworks, anything where a dimension can reverse can be challenging.

In this particular example, adding a second concentric circle that the endpoints were constrained to would work. So would a radial sketch pattern.

Usually, there’s a way to redo constraints to work around these frustrations, but if you don’t exercise your sketches, you may be surprised by the results when they are changed (via dimensions or dependencies).

rick_randall

@julian_julian372 - To stop that reversing behavior, you could add another construction circle and constrain to the ends of the quadrant lines. Kind of hack way of doing things, but should solve the issue in this one particular case.