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Beautiful MakerBot Printable Sarrus Linkage

Image of Sarrus Linkage Mark III - Thingiverse

Wow, just wow. Check out this Sarrus Linkage by fdavies on Thingiverse.

He says,

I printed all this on a ‘repstrap’ that I built mostly from old printers (old dot matrix printers had really great hardware). It uses a pinchwheel extruder heavily inspired by the work of Nophead on reprap.org.

I did design all these parts to print in a 100 mm cube, both so that they would not be too big for a Cupcake, and so that it could print itself.

Why three units? Well, ABS plastic is only so strong, and not very stiff. With just two units at right angles, the bottom one would have to withstand significant torque (twisting) from the weight of the extruder (when I put one on), and would let the top axis tilt out of the horizontal,

Why did i make it as three (mostly) identical subassemblies, rather than as a monolithic entity?

1. I am still not 100% sure that this will be the final configuration, so I want to be able to reconfigure if necessary.
2. The warping of large objects that is plaguing the reprap community means that it is better to make several small pieces that you connect together rather than one big piece. This is why the spine and armature are broken up.

What is a Sarrus Linkage?

The Sarrus linkage, invented in 1853 by Pierre Frédéric Sarrus, is a mechanical linkage to convert a limited circular motion to a linear motion without reference guideways. The linkage uses two perpendicular hinged rectangular plates positioned parallel over each other. The Sarrus linkage is of a three-dimensional class sometimes known as a “space crank”, unlike the Peaucellier-Lipkin linkage which is a planar mechanism.

Wikipedia Link

Tagged with 7 comments
 

7 Comments so far

  • Labrat
    December 13, 2009 at 5:58 am
     

    Think you can put up a video of this in action? As neat as a still of this looks, in motion I bet it looks awsome!

     
  • murray
    December 13, 2009 at 7:52 pm
     

    Saw a program on teev recently covering some researchers in the US who’re designing ambulating robots that have limbs and joints that use this principle. They’re the size of a cockroach and the chassis, members and linkages are stiff folded paper.

     
  • Ryan P
    December 13, 2009 at 8:01 pm
     

    awesome stuff. One issue is the notion that 100mm^2 parts are makerbot printable. Anyone accomplished this? At least with ABS it’s really warping. Plus the machine might need tweeking to make sure it doesn’t hit it’s limits on ever turn.

     
  • mccoyn
    December 14, 2009 at 10:00 am
     

    What is the purpose of the spines on these linkages? Do they carry any weight from the carriage?

    I recently bought parts for a Mendel. I spent $50 on steel rods and $50 on bearings. If this thing is smooth, accurate and fast it could really cut down on cost.

     
  • mycroftxxx
    December 15, 2009 at 5:58 pm
     

    The spines? Are you referring to the thin internal members on the hinge assembly or the long and straight pieces inside the larger assembly that cover the belts? The thin internal members on the hinge-pieces are for stiffening and strength and are thin (rather than each hinge piece being a flat panel) to reduce print times and materials cost without sacrificing strength. The long, straight modular pieces inside of the assembly (actually called “spines”) are an attempt at reinforcement against compression of the whole assembly and torsion. There is a little question as to how necessary they are. One earlier assembly actually did away with the spine on a non-motorized section, and there’s been talk of trying out the whole X-Y table without them.

     
  • =ml=
    December 15, 2009 at 7:08 pm
     

    The aesthetics remind me of the Eagle Transporter in Space 1999: http://www.starstore.com/acatalog/replica-eagle-l.jpg

    Go!

    =ml=

     
  • mccoyn
    December 18, 2009 at 1:59 pm
     

    I was referring to the long internal beams that pass through the whole assembly. I guess you have to have them somewhere, at least for the fixed spans so they might as well go inside the mechanism.

     
 

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