Hello pzh11001 I have tested the belts first but beleve me this is to much „soft”and rubber and the joins had oscilations when they moved small way with relative height speed. I replaced belt in all joins where I could. Yes, the sprockets are not ideal in this case but are better compared to the belts. Especilly the chains have very good stiffness. Please, look at Annin’s project where they use sprocket gear as well. I think that polygonal effect is quite small in general construction and in my opinion this is less worst choice in case need to choice between stiffness and some linear and smooth movement. I have tested my robot in many cases of movement and worst issue I have found in whole construction of home made robots is the play in the joins. In my post above I presented my second version of construction robot arm. In the begining when builded my first arm I used belts and replaced these with chains in second version and it was a good decision. The chains needs to be lubricated for it’s proper work and they don’t stuck when rotating – beleve me. I tensioned chains quite hard and have no play in joins at all then. I think my construction is not rigit enaugh to stop rotating sprockets :-) Now I work with third version of robot arm where I updated J4, J5 and J6. The arm is testing with 4 kg weight metal plate. The biggest problem is the rigit. With belts this is imposible to manipulate that weight. Regards

Thanks, All arms has been designed to be able to assemble whole construction with use as less as possible machined parts. Whole construction is based on laser cut alumunium 3mm thick metal sheets. Laser cut parts I needed to order from outsource. Where I need to have more strength then I used double, triple or more aluminium plates connected together. I don’t use any maschined bearing hubs or shafts. I bought those as standard and popular parts for supply. The frame is quite robust with less play as possible in joints. Unfortunately, the reduction gears aren't heigh precision so I used in axis 1 and 4 non loose gears with chain (axis 1) an belt (axis 4). Regards

Hello, I send some pictures. Axis 1 Motor nema 34, gear ratio 1:14 (two steps of chain gear 06B1 type) Axis 2 Motor nema 34, gear ratio 1:40 (1:10 planetary gear and 1:4 in chain gear) Axis 3 Motor nema 24, gear ratio 1:36 in planetary gear + chain gear get 1:45 in total Axis 4 Motor nema 24, gear ratio 1:5 (only belt HTD3 15mm width) Axis 5 and 6 Motor nema 17, planetary gear with 1:4 ratio + reduction on belt gear 1:5 HTD3 15mm width, 1:20 in total reduction ratio I used chain in gears because belt was wery softly and rubbery and robot arms were shaking when they stopped or moved slowly. The planetary gears aren't height precision but in case I would like to reduce play in joints I decided to use belt gears together with planetary. Drivers: J1 and J2 - DM556 J3, J4, J5 and J6 - DM542 Control: teensy 3.5 has been added because Arduino wasn't able to proper control arm in case of line and circle interpolation (big oscilations and loosing steps). Now (after teensy added) is much better because the movements are realy smooth but it stil loosing steps.