The mounting is beautifully simple. Firstly we made a laser-cut rack-and-pinion type gear set (made at this website – http://woodgears.ca/gear_cutting/template.html – just search for “online gear generator”) with 4mm tooth spacing and 16 teeth, with a second gear with zero teeth. This produced the cog/pulley and linear rail in a single file which was then “printed” to CutePDF to create a vector-based PDF which we could then edit in Inkscape
A laser cut piece of acrylic was mounted onto the two horizontal drawer rails and the stepper motor mounted onto this. The cog and rack interfaced by simply sticking the linear rail onto the back of the lower drawer runner. With the cog on the stepper motor shaft, and the rail position adjusted to make it perfectly parallel to the horizontal rail, everything meshed together nicely.
For this prototype, the rail was held in place with double-sided tape. After a successful test run, this will probably be fixed in place using a more permanent adhesive like two-part expoy. The steppers, btw, were salvaged from an old inkjet printer and the frame made from some £3 MDF offcuts from B&Q. Justin really is taking showstring-budget-CNC to a new level!
Turning the motor shaft by hand causes the entire carriage to move across the gantry, left-to-right.
Justin promises us a video very soon, showing (at least) the x-axis being controlled by his own custom software on a PC. We can’t wait!