WOW this Otto is so cool a sphere! can it roll? :D

Very good design work. You should enter it in ottos inventor program.

Camilo Parra Palacio Rolling off its feet is probably quite easy. Getting back up, not so much. Knee and elbow joints would probably be necessary. Once I have finished painting it and assembled it I will do some balance tests to see how far it can tip sideways while balancing on one foot. Because the centre of gravity is higher than in the normal model, because of the position of the battery (and my other square Otto is armless too, lowering the CoG even further) I suspect rolling over will be rather easy.

Bill SCHONFELDER Done!

Ian Shatwell what is the best way to 3d print this? it looks to me it will require lots of supports or the filament will drop

Camilo Parra Palacio It does not look like new pictures can be added within comments, so I will add those in a new post. I printed the two hemispheres open side up with supports enabled, but only from the baseplate, not from printed parts. Supports were only for 60 (maybe 65) degree or more overhangs. This meant the start of the bowl and the leg horizontal sections were supported for the body, and the bowl start, arms and eyeballs for the head. The arms are obviously vital to support, as they point downwards (when the head hemisphere is printed open side up), but I think the eyeballs might have got away without it.
This meant there was no support for any of the internal mountings, but they came out fine. I snapped one of the support posts for the arduino shield at a printing layer flaw as these were originally just the cylindrical posts, so added additional bracing into the design on Thingiverse.
One of the settings within the slicer I use (Cura) is whether to print perimeter walls from the inside out, or the outside in. This was printed outside in, which is the default, but I think the bowls might be printable without supports if the perimeters are printed the other way - inside on top of the previous layer, working outwards. I will try this at some point over the next few days, also incorporating a few more tweaks - trimming back the clips that hold the sphere together and moving the bluetooth module slightly to allow more room for the connector (as mentioned as needed in the inventor competition entry) and also loosening the clips which hold the LED matrix by half a mm or so - getting the balance right between allowing to flex enough to get the clip open, and making it strong enough that it does not snap is tricky.
My printer is a TronXY X5SA Pro, which is a good mid-range printer, but certainly not one which produces flawless prints.

Correction: Cura does print walls from the inside out by default. It is the starting brim that prints from the outside in.

what about flour or cornstarch formed as support and printing the PLA around, or printing the arms, feet, hands as support and cutting them apart afterwards?

Birger T Hi. I have heard of annealing prints in salt as a post-printing technique, but never heard of doing this. I am still a newcomer to 3D printing - I normally make things in wood through either traditional techniques or with a CNC router of my own design and construction.
Do you just start with a compacted pile of flour slightly larger than you need the support to be, and the print head brushes away the excess? I cannot see how you would keep enough flour in place to support several layers up after printing the first few layers, and how would you get adhesion to the printer plate?
Alternatively, if the flour is formed into a paste and then dried, how do you get the accuracy required?

ok I see, brainless idea, i thought the PLA comes out of something like a cannula. Sorry for your time..

Birger T If it's crazy but it works, then it is not crazy. It might work if the nozzle was long and thin, but it is short and fat instead. There is also the Z stop sensor one side and the cooling fan vent the other, so for two large (compared with the nozzle) areas a couple of centimeters away from the nozzle there is only about 1-2 mm clearance.

Ian Shatwell how about a timelapse of the printing that would be cool to se :D