Sarrus Linear Axis Mark II
by fdavies, published
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.
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all_parts.stl is for looking at the completed assembly, and how all the parts go together, it is not for printing.
The individual stl files for printing are in the .zip file.
Total printing time about 30 hours. Printed pieces: quan 1 pulley_plate quan 1 belt_plate quan 1 motor_plate quan 2 end_piece quan 2 armature quan 4 spine quan 6 hinge_plate_type_a quan 6 hinge_plate_type_b