Product Description:

The U9M4A is a flat armature DC servo motor from Kollmorgen’s ServoDisc Pancake DC Motors series. Built on disc-commutator technology, the unit supplies bidirectional torque in a 1.84-inch package, making it suitable for compact positioning stages, semiconductor tooling, and pick-and-place heads. Within an automation cell it couples directly to low-inertia loads so motion controllers can reach fast response without gear reductions.

During continuous operation at 25 °C the motor reaches a shaft speed of 3000 rpm when powered at the nominal current. That velocity is obtained from a bus potential of 26.8 V, allowing the device to run on typical 24–28 V motion rails. Copper windings present only 1.310 ohm of terminal resistance, so current stabilizes quickly and resistive loss is limited. With a torque constant of 6.56 oz-in/A, the controller can map commanded current directly to output torque, simplifying feed-forward tuning. The electromagnetic design provides a continuous mechanical output of 86 W, enough to drive small rotary actuators or indexing tables, while rated continuous current stays at 6.8 A and heat is drawn through the aluminum mounting face.

For short duty bursts, the allowable ceiling rises to 6000 rpm, enabling rapid index moves before settling into controlled motion. Under these transients, the armature can develop up to 360 oz-in of peak torque while the drive supplies 56 A, giving ample margin for overcoming friction or accelerating flywheels. System dynamics benefit from the very low rotor inertia of 0.0028 oz-in-sec², which lets servo loops achieve high bandwidth without overshoot. With a mass of only 4.5 lb, the motor adds minimal structural load, and its 31 oz-in stall torque at ambient allows vertical axes to hold position without excessive heating.