Feetech STS3215 Gears Stripped

[Tony Pratkanis]

Hello Everyone,

I've been playing around with a Feetech STS3215-based LeRobot SO101 arm (30 kg*cm servos). I've been seeing the gears strip when there is a stall of over 15% of the max torque limit (which works out to a max of 4.5 kg cm), which if I set as max torque the arm cannot move. I've burned out 3 servos, has anyone else seen this? Also, has anyone tried e.g. the Hiwonder servo or another brand of servos? I've also seen e.g. Dynamixels burn out previously, we went through a lot of those at work. I've noticed people in startups using Damiao or Robtech, which seem to be more "industrial grade" servos. Any thoughts from anyone?

Regards,

Tony 

[Charles Nolan]

G'Day Tony,

There are various solutions to gear failure.  Cushioning of the mechanism can be a solution, reducing startup impact.  

Do you have an ability to control the software defined rise time?

You may want to change to metal gears, which can be sourced at Wm Berg

, https://www.wmberg.com/

Regards,

Charles Nolan

Modular Energy Solutions

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[Tony Pratkanis]

Hello Charles,

The feetech STS3215 has metal gears within it (I opened up a burned out one to check), but I am guessing they are not big enough. Here's some details on feetech and LeRobot arms: https://robonine.com/testing-of-feetech-sts3215-servomotor-backlash-repeatability-and-torque/.

Regards,

Tony

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[Chris Albertson]

I burned up a number of servos before I decided to use a kind of multi-layer software design.    I have a driver that implements a few safety checks and then made sure all my code uses the driver.

The other thing to do is install fuses on the power lines.   Mine were metal gear servos and I’d blow the MOSFETs on the internal PCBs before I’d strip the gears.

Finally, my other trick was to greatly reduce the power supply voltage during software development. Then, if buggy software commands the servo to run into a mechanical stop, it is non-destructive.     Later, after it’s working, put the volts back up for improved performance.

If you are stripping servos during normal operations and not because of bugs like driving the arm to a collision or into a point stop, then you need better servos.