The sand table made its public debut at the Milwaukee MakerFaire last weekend and worked well.  It was very popular and I got a lot of nice comments about it.

There were a few problems...

The power cord got kicked out of the wall twice (how do you design against that?)

I started off using ball switching which would work for the first few changes, but would jam up with sand and then stop working, so I removed the ball changer and let the thing run with just 1 ball.  I will have to review my ball changing technique and see if I can come up with a better way to do it.

I tried to get Michael Dubno's RPi software working at the Faire and couldn't get it to run properly- I'll be revisiting that in the next few weeks because it generates really nice patterns and has a bunch of other great features and capabilities.  The problem seems to be in the communication between the RPi and the smoothieboard.

I may redesign the motor mounts to allow NEMA-17 motors to be used and may switch the controller to a Duet board or one of the others that uses 256:1 ustepping drivers to reduce the noise level from the mechanism.

The magnet sliding against the plywood creates some very fine dust that tends to accumulate on the X axis guide tube and can jam up the motion.  I had redesigned the magnet carriage with large holes to allow the sand to fall out, but I'm going to look at redesigning the X axis, milling a UHMW shoe for the magnet, and maybe applying a coat of polyurethane to the plywood to minimize dust generation.