Conclusion: I'll give FreeCAD a try

My Model-Creation App Criteria:

1. Models to be used for manufacture via CNC mill, laser cutter, or extruder 3d printer.
2. Primarily for mechanism type designs, with artistic/sculptural features to enhance aesthetics.
3. Models to be shared with online communities, students, and family members.
4. Low-cost in the short term and long term.
5. Accessible to students, family. 

CAD fits the bill for design needs. CAD models are solid, avoiding most 3d print errors. They are dimensionally driven (parametric); once you have a feel for how much clearance is needed between a "peg" and a "hole" on your 3d printed parts, that clearance can be used in all future designs. Most CAD apps include at least a modest tool set for aesthetic features.

A separate polygonal app with compatible import/export formats will allow for additional aesthetic flexibility. Also many of the 3d printer models available online are in stl format, which is polygonal and does not import well into CAD.

For fancy formulaic shapes, a scripting app would come in handy.

Open source apps are perfect for low cost and accessibility by all. Also consider that a model format which is not open source, it can be unexpectedly purchased, application prices can go up, or the format might be discontinued. If that happens, you may find yourself locked out of the apps and unable to work in the native format of your designs. 

My selections:

FreeCAD: hopefully this can fill the traditional CAD tool set

Blender: a polygonal app

OpenSCAD: scripted modeler

I'll be sharing my FreeCAD experiences in future posts. The FreeCAD community appears lively and enthusiastic, but the app itself is definitely a work in progress.

UPDATE: FreeCAD still in development
Update: Go try Onshape!

The Best App for Creating 3d Models

Have you wondered how to choose between all the many different 3d modeling applications? What makes them different from each other? Here is some info about what is out there, and what their models are used for. 

Rendered models: 
Think Pixar movies. These are large polygonal models for rendered animations, using bones, shaders, nurbs and many many polygons. They will be rendered with fancy lighting and effects that can take a long time to compute. Computational time is not an issue here, though, within reason. 

Some Apps: 3dStudioMax, Lightwave, Maya, Blender

Real-time models: 
Think flight simulators and games. These are also polygonal models. This model type is made to look great but render fast, to be used in interactive simulations. They are streamlined for most efficient rendering; the modeler tends to know each polygon so well that they have individual names and hand-made, lovingly applied textures. The driving criteria for efficiency change with the power of the hardware, but always are a balance between efficient use of polygons and textures, a well laid-out hierarchy, and good levels of detail so the model fidelity will change with viewing distance. The model is a bundle of tricks used to make them look more detailed than they really are.

App: Creator

 

CAD models: 
Think blueprints for houses or rockets. This is a precision model, and is not made of polygons. A circle is defined by a formula, and is round no matter how far you zoom in on it. The models are solid, or "air tight". Dimensions and constraints control the shapes of the objects. Models are used to make manufacturing drawings and are sent to a shop to make, or the models are used to create CAM routines so automated machinery can produce hardware directly. 

Some Apps: ProEngineer/Creo, Autodesk Inventor, Solid Edge, Rhino, FreeCAD, Alibre
Update: Go try Onshape!

 

There is, of course, crossover. 3d printers use polygonal model formats to produce parts. The models must be closed in order to print correctly. They can be produced from CAD or from polygonal applications. Apps like Open SCAD produce solid models through scripts, rather than visually. Programmers find this more accessible, and there is capability for making some very exotic formulaic shapes that can't be done with conventional CAD tools.  Sketchup produces models by visually manipulating geometry, making numerical input optional. The models are more CAD-like, although they are not required to be "air tight" solids, and they are not numerically driven like CAD.

Apps: Sketchup, OpenSCAD, 

Sketchup model

3d print of parametric openscad models

Direct Modeling is a new CAD movement appearing from all the major CAD apps, and also the Finite Element Analysis (FEA) crowd is joining in. It appears very much like Sketchup for CAD models, regardless of the native model format. Direct Modeling reads in the files, and frees the user from the hierarchy. It is handy for modifying models that someone else made. Time will tell if it can replace traditional Parametric CAD. For now, Direct Modeling is marketed as an additional app in a suite including Parametric.

Choosing an app depends heavily on your budget and what kind of models you want to make. The price is as low as free, and goes up to the thousands with additional yearly fees for support and upgrades. There are certainly many apps that I did not include, and I'm sure there are quite a few niche apps that I don't really touch on; hopefully this will be helpful as a starting place for your search. I will be posting more articles about the direction I am going. FreeCAD looks promising.

UPDATE: Conclusion: I'll give FreeCAD a try.

UPDATE: FreeCAD still in development