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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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CAD "best practices" that happen to avoid the toponaming problem? (lemmy.one)

submitted 4 months ago by MxRemy@lemmy.one to c/freecad@lemmy.ml

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Hi c/FreeCAD, totally newbie here! I'm having a ton of fun learning FreeCAD, but I have a small question. I know the toponaming problem is going away soon, and maybe that makes this kind of irrelevant, but I'd still like to know.

Sometimes when I'm watching or reading guides on avoiding the toponaming problem, the person will say something along the lines of: "actually this technique is also more professional/proper/correct anyway, real engineers do it this way." Basically that the methods that avoid the problem are also just best practices in general. But they always say that as kind of an aside, and I wish they'd say more! What makes those methods better? Does anyone have any suggestions for articles or videos about this?

For one example, there was one guide that suggested you should use a datum plane instead of referencing one of the object's surfaces. I understand the toponaming problem well enough to get why referencing a surface can cause it. However, the person in the guide used the same surface that would have been referenced, as the attachment point for the datum plane. Why does that not produce the same issue?

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[–] HewlettHackard@lemmy.ca 2 points 4 months ago* (last edited 4 months ago)

The best I have is to be careful to minimize dependencies, and minimize when I change the number of faces an object has, but of course that’s unavoidable sometimes. I don’t buy it that all CAD tools have the same problem or that this is how real professional CAD designers would work, though.

To minimize dependencies for example, instead of drawing the sketch for pad 2 directly on a face of pad 1, I might draw it on the base plane and transform the sketch to line up with pad 1’s face. The main consequence is that I need to manually move pad 2’s sketch if I change the size/position of pad 1. It’s a tradeoff, because I’m giving up some of the benefits of parametric CAD in exchange for easier fix-up.

I agree, mapping a datum plane to a face should have the same topo naming issue as just drawing on the face, so I don’t know why the guide would suggest that. The comment below about mapping datum planes to a simplified skeleton is interesting though.

The good news is that the next release (which sounds imminent) apparently improves it quite a bit.