Upper part of robot arm weak


Good day all,

I have built the robot and had some fun with it. I’ve did some various tests and I’m running in an issue that the upper motors are terribly weak. The wrist rotation motor needs only a little touch to miss steps and the elbow rotation is the worst as it will sometime jerk with only gravity when turning 45 degrees.

I’ve solved the step loss on the other motors by reducing the acceleration and increasing current a little.

However, I’ve tried everything for those motors. I’ve played with speed and acceleration values. I’ve increased or reduced current values from 10 to 100. I’ve changed the microstepping values and even the low speed optimizations.
I’ve verified with a multi meter that the current being drawn by the slush engine during these operations was enough and it seems there’s not a problem there.

Is anyone else running in these issues and how did you solve them?

Thanks a lot,


This issue usually comes from the belt tensioner. Are you able to move the wrist freely with the power to the motor disconnected?


Ive had the same problem, only the base of the robot was strong enough but the rest of the robot is very weak and require alot of current to the stepper to not miss steps too much. I did fix it however by buying new motor stepper with precision gearbox with 1:30 ratio and i did a redesign of the arm. I now use a nema 23 in the shoulder with a gearbox. It can around 2kg now. I also made a reverse kinematic resolver wich can take x,y,z position with tool orientation and go and make the robot go there, but there are no precise speed control yet (jacobian matrix) because slushengine speed control is only taking rounded value it seems


I wpuld recommand going for chris annin AR2 robot arm if you want a good DIY arm. It has precise control, reverse kinematics solver, trajectory planer, good carrying weight, etc… i regret not going or his model in the first place


I’ll have a look at both options.