When should you use the nylon shim?

For most models of Dynamixel, the horns come with a white nylon shim, meant to go between the body of the servo and the horn.

When NOT to use the shim

When you care DO about precisely modeling the dynamics of the actuator

It is difficult to determine the effects of the dry friction created by the shim during motion.

All values for moment of inertia, damping coefficient, and stiffness coefficient of the various servos have been determined without the shim present.

When to use the shim

When you want to limit vibration in the actuated segment (such as when recording strain readings).

When you DON'T care about precisely modeling the dynamics of the actuator.