This is my second prototype of a Sarrus linkage type linear axis. A Sarrus linkage uses hinged joints to make linear motion. The idea is to have a linear bearing suitable for making part of an x-y cartesian assembly without needing long polished metal rods, thus getting a 3D printer that can make more of its own parts.

Notice that there is a set of 4 holes on the top armature that match 4 hole patterns on the end pieces. This means that one axis could mount on two others at right angles.

Drive system: DC motor from a cheap garage sale inkjet printer, using the timing belt from the printer. The pulley at the other end of the belt is a screw/washer/spacer combination with a skate bearing. The skate bearing is mounted in a flexure plate style mount to give tension the belt.

Optical feedback: I took a optical quadrature encoder and encoder strip from the same printer as the motor. The encoder is mounted on the moving armature, and the strip is anchored at both ends in the end blocks.

Hinges: The hinges on the Sarrus linkage are made with 1/16" diam brass rod as the hinge pins. The holes for the hinge pins were reamed out with a 1/16" drill bit.

Frank Davies