i made robotic arm with HS422 servos.
when force is oposing the position of servo, it is making a buzzing sound.
i guess that is normal. servo is trying to stay at position.
can it be damaged ?
What you’re hearing is dubbed “servo strain”.
All the servos that I’ve dealt with make that sort of sound, although it varies between different servos.
This sound is completely normal.
However, any time that servos are being strained, it is not wise to hold them in that position for very long.
I’m told (and, have experienced) that servos heat up inside, with no, or very little, outward indication of their internal temperature.
Prolonged strain on a single servo can cause temporary loss of holding ability, and even permanent servo damage.
The rule of thumb is to use the recommended, or better yet, stronger than recommended servos for your application.
If you don’t experience your arm falling during the times that you hear the servos straining, then I wouldn’t worry about it.
Perhaps you could use a helper spring on the arm to assist the servo and releive some of the strain. Jim sells these load springs and has a few examples of it’s use.