Let's Make Robots!

The Karpetbeest, a printable Jansen walker

walk gracefully under wind or other power
AttachmentSize
a set of parts, print finished succesfully1.09 MB
fresh out of the oven1.1 MB
closeup of the support structure skeinforge makes1.12 MB
locally grown produce1.49 MB

This is a mm scale model of Theo Jansen's Strandbeests suitable for printing with RepRap 3D printers - a work in progress.

Update April 2012: Finally, I finished a six-pairs-of-legs blue specimen for the show at ŠKUC gallery. It walks if you push it around the carpet! A 2m PVC electrician tube is provided to make this more comfortable. :) Rotating joins between printed parts are made with 3mm plastic filament, melted a little into a ball on each side. That works so well I only wish it could be used for everything!

Lots of hexnuts on M3 threaded rod keep the printed backbone parts of the bot nicely parallel and equally spaced. I tried with hotglue and thick copper wire first, but it was hard to get a good bond inside the hole and many of them came unstuck after a while.

Crankshaft pins are held in little holes with superglue. They like to break off and are now the weakest link. I will try epoxy next, and if that doesn't help, switch from straight pins to U or clamp shaped ones which will not "pull out of the hole". Some redesign of the printed part will be necessary for that. Or maybe the plastic filament would work here too, and I'm just not brave enough to try?

The model is built in Blender with lots of boolean modifiers using python scripting. Blender lets me see the motion and assembly before printing and because it's a script it's easy to adjust some parameters after test prints, for instance hole sizes which can be tricky to get right. The script takes Jansen's magic numbers as millimeter measurements and builds all the parts of the leg and frame in the right shapes and sizes.

I'm now (2012) testing new Blender versions with improved booleans code, which is much faster and more stable. But it still chokes sometimes on what I'm asking it to do. When finished, the generated model will be cleaner and more precise. Perhaps OpenSCAD would really be better for all this CSG...

The frame accepts skate bearings into which the crankshaft parts are glued, hopefully giving a smooth and precise circular motion and minimal friction. Hinge axes are 3mm metal pins, like the sled rails in optical drives (CD, DVD), which i've got a few lying around.

Expect more to come soon, as I progress toward a walking unpowered beest, then figure out the propulsion, and finally build a two-motor robot with 2 groups of 3 pairs == 12 legs! I'll put the design files and script up here and on Thingiverse under a free license as soon as I make sure it all fits together well, eliminate the weak spots and adjust the tolerances for good fit where needed.

a set of parts, print finished succesfully

 

 

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Hey, did you ever get this posted up to Thingiverse?

i see it's been three months since i posted this - but i made no progress with it (had no time to make robots... shame on me) so no updated version or post on thingiverse yet. but the demo linkage was in an exhibition for a month :)) vacations are coming though so hopefully won't be too long now.

i need to beef up the "link bars" ears a bit, they break too easily as they are now. and i'm still not sure how to best fix the pins either... so really looking forward to finishing this first one. if anyone wants to collaborate on design, i can send the current files in private too.

btw, i saw theo jansen himself started selling 3d printed mini-beests on shapeways in the meantime. they look very much like the gakken kit, but require no assembly! fancy...

 

 

Great project my friend,I love 3D printers and CNC. Keep up the progress :)

I'm the CNC guy from CP.

So you finally got your RepRap going, cool job!

PS: Welcome to LMR btw!

have been following your progress on Valkyrie, and was especially amazed by the TEA stepper drivers. How are they holding up?

also, how is the second track for the robot coming along?

our rapman has been going since last summer, but this is the first robot project it is going to print in whole!

hope you flew home from madrid, the bus ride was looooong... ;)

The drivers are holding up pretty well, lately one of them started to act funny ... did not get to trace the problem, but the drivers took a lot of beating so I think I will soon need to replace them. 

Second track is on it's way ... been milling like crazy this weekend will post soon. 

 

 

I'm working on a design for printable 1-part ball bearings. Those are 608's, right? I'll beam you the STL in the near future...

These are 608 skate bearing yes, because they're easy to get.

The printed bearing should be bigger I imagine, big enough to have two shaft holes on the inner rotating piece 15mm from the center, 120 degrees apart. The outer part will be static and part of the frame, like the hole now. This way we could get rid of the two crankshaft parts, quite a bit of precision gluing and have a stronger crankshaft too, because the shaft pin could go much deeper in the hole. Now they're only a mm deep and will probably need some very strong glue.

Are your bearings completely printed, including the balls, or are you using some premade balls? I try to imagine the sound a beest with eight of those would make when walking... Hehe, remains to be heard!

Do you mean something like this....... Blender 608 bearing

..... i bumped into this because i am also dabbling with blender :-)

That's a nice tutorial, most models made for printing don't look so good. :) An STL file is not much more than a list of triangles.

There are a bunch of printable bearings projects on Thingiverse - could use one of those as a starting point.