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FreeCAD is an open-source parametric 3D modeler made primarily to design real-life objects of any size. Parametric modeling allows you to easily modify your design by going back into your model history and changing its parameters.

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[SOLVED] Why is FreeCAD symmetry-stupid? (lemmy.sdf.org)

submitted 1 month ago* (last edited 1 month ago) by ExtremeDullard@lemmy.sdf.org to c/freecad@lemmy.ml

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Maybe there's something I don't understand here. I'd love it if someone told me how to do the following.

Let's say I have some really complex shape in a sketch left of the Y axis: it takes me forever to get it just right. Then I need to mirror it on the right side of the Y axis and connect the two halves.

In SolidWorks, it's trivial: mirror the stuff, done. If you change the master shape on the left, the change is reflected on the right.

In FreeCAD, the best you can do is make a mirror copy of the left-hand side elements - which also makes copies of the constraints which are completely independent from the original constraints on the left-hand side - delete the stupid new right-hand side constraints and slowly, painfully constrain the right-hand side copies to the original left-hand side elements, trying to dodge the dreaded orange over-constraints all the time. It's long, it's painful, and the end-result is usually so fragile that if you change anything significant on the left-hand side, the sketch turns orange and then it's back to hunting broken constraints again.

Surely it can't be that painful. Am I missing something obvious?

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[–] ExtremeDullard@lemmy.sdf.org 3 points 1 month ago (9 children)

I'm using the daily build.

When I use the sketcher symmetry tool, here's how it works for me:

Say I create a rectangle on the left. I use the tool, it creates 4 segments on the right with 2 horizontal constraints, 2 vertical constraints, copies of the horizontal and vertical dimensions, and zero relationships with the original elements on the left. I basically have to delete all the new constraints and add symmetry constraints manually.

[–] mranderson17@infosec.pub 7 points 1 month ago* (last edited 1 month ago) (8 children)

Here's how it works for me: https://vimeo.com/1019673822

Sorry I forgot to click record cursor. But hopefully that's clear enough.

[–] ExtremeDullard@lemmy.sdf.org 3 points 1 month ago (4 children)

FWIW, this is what I get when I try to mirror a complex sketch:

https://toobnix.org/w/njayYNd5vE1HKNM3XVqYNM

Really not what I want.

[–] mranderson17@infosec.pub 3 points 1 month ago (1 children)

You didn't select "Create Symmetry Constraints". I'm not sure if it will solve the issue completely, but it will probably make some difference.

One thing I see that may come back to bite you later: You can create sketches that make multiple bodies when padded, but I'm not sure why you would want to with the example in this video. If the sketch is two identical bodies mirrored across an X/Y/Z plane use the part design mirror feature and offset the sketch's attachment not the geometry in the sketch. It works better for that and keeps your sketches simpler, and you get to use symmetry for one side of the two things you are making because the origin will be in the center of one of the objects.

Sketches where the origin of the sketch isn't the approximate center of a single closed wire are annoying later if you want to reference them in other features or sketches.

Are you making sunglasses? 😎

[–] ExtremeDullard@lemmy.sdf.org 3 points 1 month ago* (last edited 1 month ago) (1 children)

You didn’t select “Create Symmetry Constraints”.

Oh...

Damn I feel stupid. I totally missed that somehow.

Thanks a lot, you rock! I learned something new today. I guess it was worth asking the question after all 🙂

Are you making sunglasses?

No, I'm making regular frames for a friend because he saw the ones I made for myself a couple days ago and he asked whether I could print him new frames to reuse his old lenses.

One thing I see that may come back to bite you later: You can create sketches that make multiple bodies when padded

I just used that sketch for the example.

[–] mranderson17@infosec.pub 3 points 1 month ago

Ah, I see. I imagined your use of that sketch differently. Looks good!

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