Multicolored folding robot

I saw this video by 3D Printing Nerd and figured I'd give it a try because I'm interested in clever techniques. A single-extruder 3D printer like mine can only print in layers upward (with a few exceptions) and so color changes are limited to horizontal layers. Picture a layer cake with chocolate on the bottom and white on top and frosting in between. I've done a few projects with multiple colors or different filaments, like this trophy base.






These folks at Fab 365 have designed robot models which are opened up into boxes, the sides joined by living hinges. After printing it all flattened out you fold the body into a box, which wraps the colored layers onto all four sides.













By carefully choosing the layers at which to change colors you can highlight parts on each side of the body with contrasts that make them "pop". I chose to do four colors in seven layers.

Other parts that stick up like the arms and legs and head also get the multiple colors, and they end up mostly vertical.

The shoulder parts, the frame on the front, and the jet pack mount on the back are all the same height, so they all get the orange color. The little green controls on the front are just a few layers thick and contrast well with the white background.

The feet and the fingers are about the same height, so they both came out blue. So did the top of the head, unintentionally I don't know if the model was actually designed with multilayer in mind... I think not because some of the arm and leg segments are not horizontal, so the colors cut across them at an angle.

This is all previewed in the slicer software to see exactly where the different features start, and each different colored layer is given its own segment. I needed to pause the print at the start of each layer. I found some G-code on line which was supposed to do that for me: pause the print, raise the head and move it to the side so no plastic will drip on the model while I change filament. It actually didn't work except after the first layer, so I had to manually pause it for each change. Later I found out how I had implemented it in the wrong place - better luck next time.  So I'm pretty amazed that I was able to get a good result in just one try! Now that I know how this works I could use it in my own designs.





The result is quite a patchwork of color. It's Robbie the Robot from the movie "Forbidden Planet"!

The living hinges were a little weak, and the "tab A into slot B" design that was supposed to hold it together were not sized right. So I used Super Glue and it all came out fine.

As a bonus, the design includes movable arms and legs. The shoulders actually each include two nested ball-and-socket joints, so the arms can raise and lower, and also rotate, giving them an impressive range of motion. (But on my print, one joint fused and can only rotate.)  I'll remember this joint idea for some of my own designs.