Frameless Direct Drive Torque Motors

What are Frameless Direct Drive Torque Motors?

Frameless direct drive torque motors are high-performance brushless motors designed as separate rotor and stator components. Unlike traditional housed motors, they are integrated directly into the host machine’s mechanical structure. This frameless design eliminates couplings, gears, and belts, reducing backlash and torsional resonances while maximizing stiffness and dynamic response.

The large through-bore available in most models provides additional design flexibility, enabling routing of cables, optics, air, or fluid systems directly through the motor center. These characteristics make frameless torque motors ideal for precision applications requiring smooth motion, high torque density, and reliability.

The Megaflux™ Motor Family

Allied Motion’s Megaflux™ frameless direct drive torque motors cover a broad performance spectrum. With 12 standard frame diameters from 60 mm to 330 mm (2.4 to 13 in.) and multiple stack lengths, the Megaflux family ensures that an optimized motor can be matched to almost any application.

• Continuous stall torque: from 0.3 Nm up to 181 Nm

• Through-bore aperture: up to 582 mm (22.9 in.)

• Voltages: standard windings available in 48, 150, and 300 VDC

• Performance focus: high torque at low speeds, zero backlash, smooth motion

Custom modifications, unique winding designs, and fully tailored solutions are also available to meet demanding application requirements.

Series Overview

The table below summarizes the key specifications of the Megaflux™ frameless direct drive torque motor series:

Typical Applications

Frameless direct drive torque motors are widely adopted in:

• Robotics and automation – for high-precision joints, collaborative robots, and pick-and-place machines.

• Aerospace and defense systems – gimbals, turrets, and stabilization platforms where reliability and accuracy are critical.

• Medical imaging and diagnostics – CT scanners, MRI tables, and robotic surgical systems requiring smooth motion with zero backlash.

• Semiconductor and electronics manufacturing – wafer handling, inspection stages, and alignment systems.

• Industrial machinery – rotary tables, indexing systems, and packaging lines needing high torque at low speed.

• Optics and photonics – telescope mounts, optical alignment stages, and laser systems.

The torque–speed comparison highlights the performance envelopes of the Megaflux™ MF0255 and MF0310 series at 150 VDC. The MF0255 motors (solid lines) provide continuous stall torque from approximately 10 to 105 Nm, with no-load speeds ranging from about 540 to 1440 RPM. The larger MF0310 motors (dashed lines) deliver higher torque, from 17 to 181 Nm, with somewhat lower no-load speeds between 235 and 1150 RPM. This chart illustrates how the MF0310 series is optimized for applications requiring higher torque at lower speeds, while the MF0255 offers a balance of torque and speed in a more compact frame.

A Breakthrough Development: Ultra-Low Speed, High-Torque Frameless Motor

In addition to the standard Megaflux™ portfolio, Allied Motion has engineered a special “monster” frameless torque motor that redefines the limits of direct drive technology. Featuring an exceptional 64 poles, this motor delivers 240 Nm peak torque and 164 Nm continuous stall torque at just 30 RPM. With a diameter of 410 mm, a torque constant of 21.95 Nm/A, and peak current of only 10.94 A, it achieves remarkable efficiency in the 52%–66% range.

The extremely high voltage constant (≈2300 V/krpm) reflects a highly precise winding design, while the motor’s relatively high inertia ensures smooth and controlled acceleration. This unique combination makes the motor ideally suited for medical imaging systems (MRI/CT), heavy industrial platforms, and ultra-precise direct drive applications where massive torque at near-zero speed is required – all without a gearbox.