As industrial automation equipment becomes smaller, faster, and more precise, rotary motion systems require higher performance within increasingly limited installation space. A Small Size DD Motor provides a direct-drive solution that eliminates the need for a conventional reduction gearbox, offering a direct torque transmission path, high dynamic response, and precise rotary motion control. From 3C electronics and semiconductor equipment to laser processing, inspection systems, and precision rotary tables, Direct Drive Motor technology offers a compact alternative to traditional geared systems. However, when applications require higher output torque and torque density, a Harmonic Servo Actuator may be a more suitable solution. This article explains the working principles, advantages, applications, and key selection factors of small DD motors, while comparing direct-drive and harmonic actuator architectures from an engineering perspective.

A traditional servo rotary actuator consists of a rotor, stator, housing, bearings, end caps, and feedback components. A frameless motor removes all redundant mechanical structures and retains only the electromagnetic conversion core. The rotor becomes a direct part of the load shaft, while the stator is integrated into the machine structure through bonding, locking, or potting.

The HATF Harmonic Servo Rotary Actuators support harmonic drives of models 11, 14, 17, 20, 25, 32, 40, 50, and 58, with rated torque from 4 N·m to 1200 N·m. They feature multi-turn absolute encoders with Tamagawa protocol: single-turn 17-bit / multi-turn 16-bit, or single-turn 23-bit / multi-turn 16-bit. Dual-encoder configurations are also available.Based on the HAS solid model, the HATF actuators add an integrated flange, allowing mounting when end-face installation is not possible. This design provides better support for axial and radial loads, while enhancing vibration and impact resistance.