This is the next step in my attempt to make a Sarrus linkage based 3D printer. The idea is to have a cartesian mechanism without those long rods and bearings.
I built three of the Mark III and mounted them in a x-y arrangement as shown. They can move over a square about 105 mm wide, and someday may carry an extruder. They are driven by DC motors taken from inkjet printers. These motors are driven in a servo arrangement using quadrature optical encoders and optical strips removed from the same printers.