Designing a robot
These are some of the early versions of the BBR Ard1 robot components. As you can see, there's been a progression of versions for both the chassis and the controlling circuit board. The joy of having your own 3d printer is that you can design something, make a change, print it, try it and go on to make another change. The joy of the internet is that there are incredibly cost effective circuit board manufacturing companies that designers have easy access to.
First... Start anywhere!
Honest! The Ard1 design started with a couple of blocks of wood for two servos and an Arduino computer. I soon discovered that the local library had an inexpensive 3D printing service. Using free 3D design software I started printing my first 3D prototypes and the design rapidly evolved from there!
In the BAD OLD DAYS (before 3D printing) making plastic parts cost tens of thousands of dollars and you better get it right the first time!
The average person could never do something like this. But now with 3D printing, parts cost a bit of time and a few pennies each. It's easy to make a change, print it, try it, then go back and make another change if you need to and with 3D printing... if you can think it up, you can usually make it!