First of all, thank you for your 100 likes 276 followers & over of 15k views. You rock!
We have another thing to celebrate today hehe. The problem about melting gears and malfunction due to steppers overheating is solved :) Let me explain the steps I followed to fix it.
1. I measured the temperature of steppers in action... and it went over 70ºC. PLA starts deforming at 60ºC... So I had a real problem there. Not only the gears were deforming, also the Art1Body part were deforming and causing the malfunction.
2. I appreciated that my design didn't had refrigeration holes, so the heat produced by the steppers only could be dissipated through the plastic (bad idea because it was causing the deformation). After facepalming myself I redesigned the parts that contain steppers and introducing 40mm fans into the design. In this way, the motors would have forced cooling.
3. I tested it. And it worked well, now the steppers don't reach 40ºC and it goes well! Just in case I printed the gears using ABS to prevent the deformation. The test was performed at a 10h non-stop maker faire called OSHWDEM at A Coruña (Spain).
So, check the new design at GitHub repo before print it! And if you have printed it already don't worry. Take the dremel, do some holes and glue the fans! (I did this hahaha)
Aaaand... there you have a video of Thor doing a manipulation job. I think that the next step is increase its speed, don't you?