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Robot Arms Up

Are you a die-hard MAKE fan with an urge to 3D-print robot figurines? If so, this 3D-printable Maker Faire robot is for you!

I started modeling the Maker Faire robot back in May of 2012. It was originally going to be for a Makey Award and have all sorts of articulating limbs but ended up taking too long to print the parts and I had a lot of trouble creating pegs that would hold it together. I put the project on hold and picked it back up in November, with the idea of making a single-part version which would print faster and could be given away at events. After five revisions and about 30 or so messed-up looking robots, I settled on its current version.

The most challenging part of this project was designing a 3D model from a 2D logo. The 2011 version of the Makey Awards, designed by Jonathan Monaghan, provided much inspiration so I didn’t start off with a completely blank slate.

Robot macro

While printing the robots, I realized that it’s actually a very good “Hello world” test for 3D printers. Below are the elements of the model that make it a challenging test:

  • Straight, tapered, and curved walls of the legs, body, and arms. If these walls are not smooth they would indicate that there is Z-wobble, which is when the Z axis doesn’t travel straight up. Instead, it shifts around or doesn’t travel the same height after each layer, often due to low quality or off-centered lead screws.
  • Concave and convex curves show if there are any untensioned belts since the circles would have flat sides instead of a round radius due to the backlash of untensioned belts. The backlash basically makes one axis not move until the backlash catches up with the turning of the pulley. So instead of both axises moving at the same time to form a curve, only one moves and creates a flat spot.
  • Bridging where the two legs meets the body shows how well calibrated the settings are in the slicing software. There should be little sagging where the plastic bridges between the legs.
  • 
Slight overhangs shows off how well the plastic can get cooled by a fan instead of sagging due to the heat buildup.
Multiple “islands” that requires the extruder to retract the filament and move quickly to the next island to make stringless prints. Good retraction settings and a good extruder should produce stringless prints.
  • 
Fine details in the logo on the chest and back shows off how well the slicing software and hardware handle these details.

There are three versions of the robot: one with its arms up, one with arms down, and one with its arms down but has built in overhang supports that snap off. The supports use an experimental technique that I’ve been experimenting on. It basically has a 0.1mm gap between the support and the part. This forms a weak enough bond to break off the support cleanly but still support the part and keeping it dimensionally accurate. More on this in a future posts.

Download the STL files here and print out your robot army.


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