Awesome design!
I am afraid the twisted belt will be the source of inconsistencies.
@Tomas_Vit How so? It is over a constant distance. I could use synchromesh if it is a problem.
Middle belt path isn’t connected in this video?
@ThantiK The left middle big pulley has a small pulley hidden in the top housing of the left top big pulley which drives the arm. This allows me to cut some slits for that belt to make it over to drive the distal arm.
I know it is confusion but it was important to the design to keep the three big pulleys tightly stacked. That just wasn’t possible without pulleys going through other pulleys. Luckily one of the pulleys I needed to go through didn’t rotate in relation to the belt direction.
Just in case you are talking about it not spinning, I was lazy.
I want to build one!
@Nicholas_Seward My experience with GT-like belts is that any non-linearity of belt’s mid-plane adds inaccuracies, frequently because of inconsistant wearing of edges. But can’t predict, how strong the effect will be in the twist.
@Tomas_Vit Hmmm. I just can’t see how that could be but it is hard to argue with experience. This is my first time using belts so I have some learning. I think I will carry on with it because it is only on the independent z axis which only monotonically increases with time. Nonlinear issues could reasonably be calibrated out.
@Nicholas_Seward In any case good luck with designing, it looks quite interesting. If you will create a Collection about it here on G+, make a notice.
Love it! You brain is wired for crazy cool 3d printer design! Let me know when you release files. I want to build one!
Brook
@Brook_Drumm It might be a while. I have no life for the foreseeable future.
Ha! I hear you! Just enjoy the fun stuff when you can!
Brook
neat design. i think i would prefer the z utilized a leadscrew though, for better accuracy and would also eliminate the need for a twist.
@Jason_Richardson That is a super idea. That will bring the part count down. However it requires a loop belt that I don’t have and screws with my tensioning scheme but that is just me being lazy. I will put some serious thought into this for the final design. I think I will carry on with the belts just to see. I just can’t convince myself that the twist will do anything bad.
I think the twist is fine. Google kuka arms… they have tons of belts that twist 
they seem to do ok- yes I know it’s closed loop but they are very predictable
Hi Nicholas, have you planning to print the parts of this mockup? I’m very interested in!
@Cosimo_Orlando Check my feed out. I just posted the assembled arm.