So I started with a simple frame to hold the rotary tool and built a basic rig to raise and lower the frame on a bolt. The bolt was turned by a Lego NXT Mindstorm motor. I have since managed to get all 3 stepper motors turning and began figuring out how to mount the stepper in place of the NXT motor. Here is the next version of the z-axis assembly. The small dot matrix printer stepper motor is geared down to a longer 3/16" bolt. Over all the idea seems to work well.
From the top
From the front
I need to redo the support plate that holds the weight. In this side shot, you can see that the gears are not 100% straight. I plan on using a wider support plate and 3 bolts (not 2) in a triangle pattern to better align the gears.
From the side
The next step is to prevent the frame from swinging around on the bolt that raises / lowers the tool. I plan on using hardened steel rods and bushings from printers to guide the frame up and down in a straight path. Unfortunately, this is where the project took a step back, as I did not do a good job of drilling the plexiglass and broke a couple of key pieces that will have to be rebuilt.
Broken :-(
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