This is a bit of a longer post, but I would like to give a bit more than just a short overview of each program. This way you have enough information to decide which software you want to spend time learning. So without dragging this introduction on any further, here are my top 5 picks for free CAD software for 3d printing.
Tinkercad is extremely popular, and that for a good reason. It is browser-based with a simple, friendly interface that lets you get started right away, no matter your skill level. If you do not have any experience with CAD programs, or want to make a quick and simple part, you can not go wrong here. It is also ideal for 3d printing, as the models are saved in STL format, making slicing super easy.
To create the model, you can choose from a list of predefined shapes, ranging from simple things like a box to figurines and many other fun shapes. Once you drag the shapes into the workspace, you can change their dimensions, rotate them, and subtract them from each other. To create a simple bracket, for example, you would create a box for the overall shape and then subtract cylinders for where you want screw holes. You can also add a radius to your edges to make them nice and smooth. This way of modeling is straightforward and intuitive, but while you can do many things with it, if you want to create more complex objects and assemblies, it can get a bit tedious and restrictive.
If your projects are more complex and you are looking for a CAD program that is fully loaded with every feature you could want, look no further than Fusion 360 from Autodesk. While usually, Fusion is a paid program, there is a fully-featured free version for startups and hobbyists.
Fusion 360 is a fully parametric modeling program. This means that you first start with a 2d sketch, where you add your dimensions and the 2d shape, and then extrude it to create a 3d object. After you created that object, you can do further modifications like subtracting things or adding chamfers, threads, and many more things. After that, you can go back to the first sketch, change a dimension, and the model will dynamically update everything you did after that. This way of working is extremely powerful, especially with very complex models, and can save hours of work. Apart from just extruding straight out, there is also the possibility to create lofts, sweeps, coils, ribs, and many more, though it would take too long to explain them all. In short, no matter what you need to do, there is a way to do it.
Once you are ready for 3d printing, Fusion 360 allows you to export the model as an STL file, or send it directly to other programs like Meshmixer for further processing, or Cura for slicing. All these features make Fusion an excellent choice for intermediate and professional users that do not mind a bit of a learning curve.
If you are not a fan of being at the mercy of big cooperations, FreeCAD offers similar features as Fusion 360, in an open-source format. With parametric modeling and many different workspaces for various applications, FreeCAD is a favorite of many as it gives you access to professional features completely free of charge.
The workflow is very similar to Fusion 360, with most of the features being the same, just a bit of a different interface. FreeCAD does have some features, though, that are not present in Fusion 360. They are, however, not relevant to 3d printing, as they revolve around things like PCB design, where Autodesk has other programs that cover these areas. The only criticism for FreeCAD is that due to the many features that are developed by different people, the interface can be a bit inconsistent and complicated. This results in a bit of a steeper learning curve.
In conclusion, FreeCAD is extremely powerful and will satisfy even the most demanding users, provided you are willing to put in the time to learn about all the little things. Considering that FreeCAD is entirely free for anyone, this is truly amazing.
SketchUp has been around for a while and is also quite popular, especially for architectural design. It can be used quite well for 3d printing as well, though, by just installing a plugin to enable STL export. While modeling, there are many tools to create 2d sketches, which you then can extrude to 3d objects. You can then further modify these parts by subtracting parts, smoothing over or chamfering corners, and many more things.
SketchUp also features a marketplace where you can get many premade models to speed up your design process. Another strong suit of SketchUp is the many plugins that are available to extend the functionality of the base program. So no matter if you want to 3d print a model for your house renovation or a phone stand, SketchUp has you covered.
Well known amongst 3d animators and many others, Blender can also be used for 3d printing. It is based on moving individual points, edges, and faces of your model, and adding more if you need them. This way of working allows you to easily create shapes that do not have to be square or geometric. Amongst other things, there is also a sculpting workspace, which allows you to create very organic shapes by raising and lowering parts of the model, just like sculpting with clay.
You do have to be careful, however, to create a manifold model, which means that it is “watertight”. This is because you can easily delete faces in Blender, creating an opening in the model. If you try to slice such a model, you will either get an error or something that does not look anywhere close to what you modeled. Once you keep that in mind, though, and get over the quite steep learning curve, Blender is an excellent option if you want to create more organic shapes, which are hard to achieve with the more geometrically oriented programs previously mentioned.