Hollow Shaft Direct Drive Torque Motors for Machine Tools

Employing innovative optimized magnetics, TMX series direct drive motors from NUM Corporation (Naperville, IL) have an extremely low cogging torque that is almost half that of competitors’ motors. They are ideal for applications that demand very smooth and accurate rotation, especially at low speeds. Typical uses include direct drive machine tools, rotary tables and radial positioning units. NUM pioneered the development of AC brushless servo motors and has produced more than 5,000 different types. Their current range covers torques from 0.318 Nm to 160 Nm and speeds up to 8,000 rpm. They also manufacture a range of synchronous and asynchronous motor spindles with flux weakening, offering power outputs as high as 55 kW.

For direct drive applications, they have generally specified use of torque motors produced by IDAM (Drives & Mechatronics AG & Co. KG; Suhl, Germany), which specializes in direct drive technology and enjoys a tight business partnership with NUM. “However, a growing number of our customers request customized motors, and prefer to deal with a single supplier for all their CNC machine tool requirements,” explained Massimiliano Menegotto, the general manager of NUM’s main manufacturing plant in Milan, Italy. “We have developed the TMX series of torque motors specifically to address these needs. They complement those produced by IDAM and provide us with additional in-house configuration flexibility, enabling us to offer customers an even wider range of systems.”

NUM is initially launching two TMX series frameless torque motors, with stator diameters of 140 mm and 291 mm, and intends growing the range in the future. These motors’ hollow shaft rotors utilize high flux density neodymium-iron-boron (NdFeB) magnets and offer ample internal space for through-motor wiring or mechanical parts. The stator windings are fully protected against over-temperature conditions and are encapsulated within a thermally optimized enclosure that offers a choice of air-cooled and water-cooled configurations. Like all direct drive motors, the TMX series units are capable of providing continuous torque even when stalled, and are designed for direct attachment to the load. This obviates the need for gearboxes or shaft couplings, to provide highly accurate, backlash-free rotary transmission. The rotor and frameless stator are supplied as component parts and are primarily intended for applications that require total integration of the motor within the servomechanism in order to reduce weight or volume.

These TMX series motors can produce a very high S1 torque density and are available with a choice of stator and rotor lengths to best suit the motion requirements of the application. By way of example, a 140 mm diameter motor with an active length of 70 mm can produce a peak torque of approximately 82 Nm at speeds up to 1,500 rpm, and a continuous (stall) torque of approximately 50 Nm. The motors can be driven by most industry-standard servo drives, including MDLU3 and MDLUX drives that form part of the latest-generation Flexium+ CNC platform.

NUM Corporation, 603 East Diehl Road, Suite 115, Naperville, IL 60563, 630-505-7722, [email protected], www.num.com.