I had my first experience using ARC working on the development of the gearbox for my new arm design.  With the help of DJ and many others I was able to get the Stepper working correctly.  Unfortunately the gearbox being a 38:1 ratio was not fast enough to meet my expectations for the arm.  I am now printing a 16:1 two stage gearbox to try with the stepper motor I just hope the stepper motor will be able to provide the torque I need.  This is when I wish I was and engineer that knew all the correct math to figure this out without having to guess at it because it sure would save me a lot of time and filament LOL.

Smiller you have mad 3D design skills. I doubt you have to guess much before you get it right. It would not surprise me if you come up with your own robot down the road.

I just did the first test using the 16:1 two stage gearbox and was able to get the speed I was looking for it seems to have the power and torque to move the arm.  The next test will be make a joiner to the V1 arm and see if it will actually works as expected.  So now I am designing and printing the what is going to be the shoulder mount for the gearbox to complete that test.    More to come soon!

Tested the new 16:1 gearbox and it was a fail.  The PETG gears just could not take the weight of the Inmoov arm.  So at this point I just need to walk away from trying to improve this arm. It will require metal gearboxes not 3d printed ones.

Valiant efforts @smiller29 such is life when you are doing R&D and pushing the envelope! I applaud you!

@Jeremie,  Thanks but it is very hard for me to except defeat...   I have ordered a Super servo that is really high torque and I will test J1 using that and see if can handle the weight of the arm.  But at this point with so many fails my confidence is not high if this does not work I will be officially done working on a new arm design.

Agree, a valiant effort my friend

I am sure you visited https://www.thingiverse.com/gael_langevin/collections/inmoov-parts-and-derivatives

https://www.thingiverse.com/gael_langevin/designs

Like the others, I'm impressed with your design and effort. I know the feeling of a prototype fail. I feel your pain. I worked for a year on designing my full sized B9 robot arms. I had many fails as I learned where the edge was and what I needed to make the arms work as I wanted. Many times I had to upgrade my motors and the material and parts I was using to stand the stresses the heavy, swinging arms applied. I hope you don't give up if there is any way to make your dream work. I think our designs are too good to walk away from.

Please excuse this long post and my ramblings but I'd like to share a few thoughts and some experiences I've had that are similar to your project.

I know virtually nothing about 3D printing or the filaments that can be printed. However I have a friend that 3D prints in Carbon Fiber and I have used his geared claws in one of my robots (there was little stress on the gears). I've read: Carbon Fiber is a stiff and strong fiber that behaves like 6061 Aluminum, so it can be used for lightweight components that support heavy loads. This 3D printed carbon fiber can match the strength of aluminum when continuous. Another option for a super strong filament would be Polycarbonate. I read that it's considered the strongest consumer filament out there. I'm sure you probably need a certain 3D printer to use these filaments and don't want to invest in that cost. However there are companies that take your design and print in these medias for you.

I reached this point in my B9 arm prototyping. I needed more strength and more precision then I could provide in my little basement shop using my bandsaw and drill press. I hired a machinist to take my design and build a motor bracket for the elbow that brought my design all together into a working arm. He also helped me source some parts to get the bracket working with the motor. I mention this just to let you know there is always a way. I think you have a great working design but just need a little help moving forward in your prototype building. After I finally had a working arm I had about 5 failed prototyped arms lined up. I called it my "Hall Of Shame". LOL.

You mention that you have ordered a Super servo with high torque. Could you share what you have ordered? I went that route with another part of my robot. I needed to lift a part vertically that was over 10 lbs at different speeds and stop at different positions. Using a super servo like you are going to try worked well for me but it had it's issues.  *It was very expensive *It was noisy *It would leek off and not hold position when power was turned off *It had no feedback for position or speed *It didn't last very long. After a couple years of infrequent use it lost strength and eventually stopped working.  I rebuilt, got rid of the servo and used a car's power window DC worm geared motor. However Unlike you I had lots of room so I wasn't really restricted in this area.

I'd like to validate your mention of another building option. You said you may use a metal gearbox. This is a wonderful way to move a joint that needs to lift heavy weight. With the proper gear ratio it can take most of the weight off of the motor or servo. However the more torque you choose the slower the movement. I have these in my B9 robot's arm. I use high end high power Hitech servos mounted in them. They work amazing and have stood up to a lot of abuse over a long period of time. servo City has amazing servo gearboxes and you can pick any gear ratio you need. One of the great features of using these gearboxes from SC is you can pick one that has a pot mounted on it for position and speed feedback. This made controlling this servo very easy through ARC.

SerovCity Gearboxes

Happy building my friend! Good luck. I'm looking forward to seeing what pops out of your mind next! LOL.