It's generally a good idea in DIY(and not only DIY) projects to model your future device in 3d before start actually making something. It can save your time and resources and give you certain insights on improvements of your initial idea. Not saying that to 3D print you just need to model it in some design software.
Unfortunately, professional CAD software is expensive.
That's why when I found that DesignSpark launched free DesignSpark Mechanical modelling software I was just excited. In fact it's a limited version of SpaceClaim Engineer. Still it's quite a powerful and easy to use tool, which I consider to be the best available free CAD modelling tool.
Once you have downloaded and installed it from the download page you can start your experiments.
I've made these three video tutorials to share my experience of using common tools and some useful tricks. Videos are without narration, but I tried to make them short and understandable.
Just some common things which cannot be restored from videos:
To move camera around selected object you need to hold middle mouse button pressed and to shift camera - hold also Shift button. To select multiple objects use Ctrl. Double and triple clicks help you select closed paths and solids in 3d.
Step 1: Making a Box and Exporting It to STL for Further 3d Printing
It's about work with basic tools and dimensions, modifiers such as round and chamfer corners.
And the trick is modelling the box as the single body and then splitting it into a box and a cover. This can save your time when the shape of container is not trivial.
Step 2: Making Rotunda
Here is how to create bodies of rotation and patterns from features. This is particularly useful to create different wheels.
Step 3: Making IPhone Bumper Case
This is just to show how you can use imported geometry and sweep shapes. But you can play with gaps and walls to make it actually useable.
For this tutorial you need to download a reference model of iPhone. DesignSpark Mechanical accepts STEP and OBJ files, but I had troubles with importing STEP, so I used less precise OBJ format which loaded just great.
I used this free 3d model by silviuq12
Step 4: Bottomline
DesignSpark Mechanical is cool. I hope you'll enjoy it too. What I really miss is a mirror 3d tool, which is known to present in SpaceClaim Engineer. Nevertheless 2d mirroring is possible while sketching.
If you want to read more you can proceed to this comprehensive tutorial by DesignSpark.
Good luck in your projects!
P.S. I am participating in FormLabs contest as Form 1 3D printer is extremely welcome in my big project - Octodon - a powerful pocket-sized full-speed keyboard for handhelds. A lot of small and precise parts need to be printed during prototyping iterations, and using my own printer would significantly reduce the costs.