Sarrus Linear Axis Mark II

by fdavies, published

Sarrus Linear Axis Mark II by fdavies Oct 10, 2009


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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


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

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Just gotta echo cathal here, hollo crap, that IS awesome. We denfinitely do need a video.

But the use of precision hinges does negate the elimination of long studs a little. I wonder if we could get round that though... how about a ball and socket style hinge? Seeing as they need not go past 179 degrees that could work? (Or was that mk1?!)

The question is though, does it have enough travel to make itself?

could we get a video of it in action?

how big is the extension, and does it flex much with a payload?

Wow this is really cool. Any vids of it in action?

Holy crap that's awesome!