Yes, I had been working toward building my own RepRap style 3D printer / CNC mill.  Got the XYZ working, steppers, stepper drivers, and Arduino for control.  Got the Marlin firmware and pronterface host-side connected and working too.

The extruder was a bit of a challenge, though I did get part of the way there.  I had an aluminum heating block and thermistor and I had milled my own nozzle, but setting up a fourth stepper motor with gears or something similar was a bit daunting.  If only I could print some of the necessary pieces…

So I broke down and bought a PrintrBot Metal Simple.  I ordered the kit, not so much because it was cheaper, but so that I could have the experience of putting it together and I would get a good familiarity with all the pieces and how they work.

Unfortunately it has pretty well derailed my efforts at getting my home-built one working, because since I have a working one, I no longer need my RepRap.  I am not sure if this is good or bad — I think it is ultimately good because I can shift focus to more robotics and more original concepts, rather than spending energy on building yet another 3D printer.  The 3D printer problem is pretty much solved and with everyone jumping on the bandwagon, the 3D printer space is getting a bit crowded anyway.

The 12-foot walking rideable robot world is still wide open, with only a few exceptions.  Most are hexapods and there are no true bipeds that I know of.

One of the things I’ve been experimenting with to reduce cost of a 3D printer system is a system of rails and pulleys, to eliminate the linear bearings and lead screws that are used in the more conventional RepRap designs.

With a table saw, a straight V shaped groove can be cut on the underside of a plank.  With a matching rail shape, an extremely simple linear slide can be made, with very good stiffness and no slop.  As long as the lateral forces are low, which they usually are with a FDM style printer, this ought to work well for very low cost.

Here is a video of an earlier attempt, using primarily particle board.  The grooves and rails were made using a table saw.

(Original video taken August 8, 2014.)

(This setup was later torn down and rebuilt because poor planning had left no way to securely attach a Z-axis above the XY table.)