The available CAD programs with OpenSource license can't really keep up with paid products of other manufacturers, nevertheless the thought to get along without license motivates me and therefore to rely on open source software. Starting with OpenSCAD, I later ended up with FreeCAD and Blender.

OpenSCAD

Objects are described in OpenSCAD using a simple scripting language. That means, each object is a function with certain parameters e.g. a cube with 15mm edge length:"cube(15)" or a sphere with 10mm radius:"sphere(10)" . To merge multiple objects into one, they can be joined with "union()", or subtracted from each other with intersection().

Current OpenSCAD version: 2021.01 (found: 2021-07-16)

One advantage of the script language is that variables can be used for the described elements and thus they can be adjusted centrally.

Having written certain scripts from time to time, it was not difficult for me to get started with OpenSCAD. Nevertheless, describing 3D objects via a script is more complicated than via a GUI for most tasks, which led me to FreeCAD.

FreeCAD

Starting from simple geometric shapes, to complex designs: FreeCAD is a free CAD program with all the essential features. Admittedly, as a beginner I found it a bit difficult to use, but for constructions FreeCAD is still my first choice.

Current FreeCAD version: 0.21.2 (found: 2024-01-08)

Simple shapes or sketches

Currently, I don't even begin to use all the features of FreeCAD. For simple shapes like cubes, cylinders, or spheres I use the workspace: Part

Constructions I usually start with a sketch in the "Part Design" area , which I later upholster.

The sketch can first be simply drawn and later supplemented with lengths, angles, distances or constraints, making it an exact design.

Back in the Part workspace, different parts from sketches or cylinders and cubes can be marked and subtracted from each other or edges rounded.

Blender

Blender is an incredibly powerful program and in addition to modeling 3D objects, it can also render video sequences and even includes a video editing program. Not being a regular user of Blender, it always takes me time to get the hang of it. Although the GUI has been optimized several times, it is still not really clear to me, this fact is probably due to the many possibilities that Blender has to offer.

Current Blender version: 4.1.1 (found: 2024-04-17).

Currently, I use Blender mostly to modify existing STL files a bit, see as an example my glasses.

Details about the adaptation to my glasses: Why I didn't have to buy new glasses.

Conclusion

For constructions FreeCAD or OpenSCAD is suitable, Blender is suitable for modeling objects. The cost of the open source programs is not the license fees, but the possibly longer learning curve.

• OpenSCAD certainly can't be seen as a replacement for a CAD application, even though everything possible can certainly be implemented somehow via the scripting language.
• For my purposes, the features of FreeCAD are enough, yet I guess there are certainly CAD programs with more features and a more intuitive user interface.
• Blender is probably less lacking in features, but I found the operation anything but self-explanatory at first. Equipped with the knowledge of certain keyboard shortcuts, Blender can nevertheless certainly be operated very efficiently by an experienced user.