Electronics > PCB/EDA/CAD
FreeCAD - is it just me, or bug city?
janoc:
--- Quote from: rollatorwieltje on May 21, 2019, 05:46:01 pm ---Well...
Pretty much every tutorial I see teaches you to make objects by mapping sketches to surfaces. Which seems to work fine as long as you never change a previous sketch... When you change a previous sketch the faces get renamed internally, so all following sketches lose their mapping. I don't know if this is the correct way to build parts, but if it is, it's not really what you'd expect from something that claims to be parametric. Yes, the construction is parametric, but never even think of adjusting one of the parameters afterwards. It's maybe not a bug, but I would call it unexpected behavior.
--- End quote ---
That sounds like a bug. I certainly didn't see this issue with 0.17. However, it is true that if you go back to a sketch that has been used to create e.g. an extrusion or a pocket and start to heavily modify it, all bets are off. Usually simple stuff like changing dimensions is fine. Adding fillets or changing topology (adding/removing holes) from the sketch can make the program go nuts, though.
However, I have seen similar problems also in Fusion360 - which is an order of magnitude more complex program ...
To some degree it is to be expected because while you can do all sort of things to the sketch, not all will have a meaningful result on the existing object (e.g. if redoing the original operation on the modified sketch would result in an invalid object) Then you will get regeneration errors and/or glitches.
bson:
Does it support User Parameters? I never got into FreeCAD enough to figure this out, but I just launched 0.17 (what I have installed) and don't see anything like it. I can't see how it's possible to recompute the timeline from parameterized objects without this, for example how would it know say an extrusion cut should be INTERNAL_HEIGHT+WALL_THICKNESS*2 just because I changed the wall thickness someplace? Unless it has some other method of setting inter-object parameter constraints? The FreeCAD "parameter editor" seems to be just for UI customization... If I type "height/2" into a parameter field it completely ignores without either an error or a message of any sort - it just silently discards what I typed!
janoc:
--- Quote from: bson on May 29, 2019, 07:46:42 pm ---Does it support User Parameters? I never got into FreeCAD enough to figure this out, but I just launched 0.17 (what I have installed) and don't see anything like it. I can't see how it's possible to recompute the timeline from parameterized objects without this, for example how would it know say an extrusion cut should be INTERNAL_HEIGHT+WALL_THICKNESS*2 just because I changed the wall thickness someplace? Unless it has some other method of setting inter-object parameter constraints? The FreeCAD "parameter editor" seems to be just for UI customization... If I type "height/2" into a parameter field it completely ignores without either an error or a message of any sort - it just silently discards what I typed!
--- End quote ---
Yes, it does. It is a bit non-obvious, though. Open the Spreadsheet module, create a new spreadsheet and type in your values there. Then right click each and set "alias" in the properties - that will be the variable name.
Then to refer to the values you open e.g. the dimension you want to set and click the round f(x) icon in the right corner of the entry box. That will open the expression editor. There you can then use the defined variables as e.g.:
Vars.thickness
"Vars" is the name of the spreadsheet and "thickness" is the alias of the field you have defined in the spreadsheet.
0db:
is there any opensource alternative to FreeCad?
janoc:
--- Quote from: 0db on April 14, 2020, 05:13:45 pm ---is there any opensource alternative to FreeCad?
--- End quote ---
Well, FreeCAD is open source. If you mean another CAD that is also open source, then not really, I am afraid. CAD is a very niche field requiring fairly high math skills so not many programmers are willing or able to work on it. It is also not very sexy work, unlike reinventing a Javascript UI framework for the umpteenth time ...
There are a few open source tools that may or may not do the job but none is as complete as FreeCAD:
- https://www.openscad.org/
- http://solvespace.com/index.pl
- https://librecad.org/ (this one is excellent but only 2D drafting, originally a fork of commercial QCad)
And a few obscure things that are more of interest for niche uses:
- http://implicitcad.org/
- http://www.mattkeeter.com/projects/antimony/3/
- https://brlcad.org/
There is also Blender (blender.org), but that is not really a CAD, more a mesh modeling program for 3D graphics.
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