Anelok: the 2015 case 1/2: background

Paul Boddie paul at
Mon Jan 19 17:12:50 UTC 2015

On Monday 19. January 2015 17.14.12 Werner Almesberger wrote:
> So I decided to give FreeCAD a try. After all, it says it's nice and
> parametric, just what I need. It also has a nice sketcher that lets
> you "declaratively" define geometries in no time. So far, so good.
> Then came the moment when I wanted to adjust some parameter, e.g.,
> the diameter of the cylinder containing the lanyard hole. It let me
> do that without complaining, but then all the things that depended
> on that geometry were out of sync.
> To make a long story short, I don't think this mechanism is useful
> for non-trivial designs. There are plans to improve this, but that's
> not there yet and may take a good while.

I found FreeCAD to be fairly unstable and counterintuitive, but I imagine that 
CAD software is a matter of taste, anyway. (Brief flashback to using AutoCAD 
on monochrome SunOS workstations in the early 1990s!)

> However, there is a plan B: FreeCAD can also be scripted in Python.
> The workflow would now be more similar to what I had done with fped
> (edit, compile, inspect, edit, ...), but I'd still have that 3D
> engine of a real CAD to do things like those pesky cut-outs for me.
> This approach worked and I have the script to prove it:
> It's longer than the fped script but it also does more. E.g., there
> are more case details and it also generates some components, for
> easier orientation.

It looks quite clean, and it makes me consider it instead of OpenSCAD for 
future stuff. Certainly, the style is similar enough.

> This is what the model for the complete case currently looks like:
> 114.png

Very nice! I particularly like the shading. You may have mentioned this 
already, but how do you generate these nice previews?

It's interesting how Python finds its way into the CAD process. Although I 
find OpenSCAD to be sufficient for my limited needs, others have added a 
degree of Python-based preprocessing to it:


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