Linear electric motors designed specifically for machine tools

CNC specialist NUM has launched the LMX series of brushless linear servo motors designed specifically for continuous duty cycle applications in machine tools.

Until now, says the company, most linear motors on the market have been designed for general-purpose automation involving fast A-B positioning capabilities but relatively low duty cycles. NUM has taken a more conservative design approach, waiting until the market matured before creating a linear motor expressly intended for continuous operation in the harsh environment of modern machine tools.

NUM’s new LMX series linear motors incorporate a number of features to help mitigate the effect of arduous operating conditions. Their moving coil primary section is fully encapsulated in a robust stainless steel housing, with an integrated cooling circuit designed to maximise the flow rate, which also allows the use of low specific heat capacity cooling liquids. The motors have a short pole pitch to increase force density, minimise cogging forces and reduce thermal losses.

LMX linear motors comprise a metal track with multiple embedded rare earth magnets, and a coil assembly supported by a customer-supplied guideway. A key feature of the motors is that they are designed to operate with a comparatively large air gap of 1 mm, to reduce the impact of mounting tolerances on performance characteristics. For most machine tool applications, the track is held stationary and the coil assembly is free to move – but converse mounting arrangements are also practicable, with similar performance attributes.

Suitable for use with standard 3-phase sinusoidal brushless servo drives, NUM’s LMX series linear motors are especially cost-effective when teamed with the company’s NUMDrive X or new NUM DrivePro drives. Both these families of high performance drives feature a high degree of functional integration, making them some of the smallest on the market, and offer extensive safe motion monitoring and control options to help simplify design-in.

The new NUM DrivePro drives are likely to be of particular interest to OEMs seeking maximum performance from NUM’s new LMX series linear motors. Implemented using advanced system-on-chip (SoC) technology and based on a multi-core ARM processor, the drives employ bare metal programming to eliminate operating system latency.

NUM produces a wide range of electric motors, including spindle, servo, torque, synchronous and asynchronous, and now linear. Massimiliano Menegotto, managing director and CTO of NUM Group, said: “Choosing the best kinematic solution for any machine often involves a trade-off between various technical factors. NUM can support machine designers, during the machine’s development phase, with the selection of the most appropriate solution.”