CNC specialist NUM has launched a series of brushless linear servo motors designed specifically for continuous duty cycle applications in machine tools.
Until now, 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 maximize 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, minimize 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. According to Massimiliano Menegotto, Managing Director and CTO of NUM Group, “Choosing the best kinematic solution for any machine often involves a tradeoff between various technical factors. NUM can support machine designers, during the machine's development phase, with the selection of the most appropriate solution."
Related Glossary Terms
- computer numerical control ( CNC)
computer numerical control ( CNC)
Microprocessor-based controller dedicated to a machine tool that permits the creation or modification of parts. Programmed numerical control activates the machine’s servos and spindle drives and controls the various machining operations. See DNC, direct numerical control; NC, numerical control.
- linear motor
Functionally the same as a rotary motor in a machine tool, a linear motor can be thought of as a standard permanent-magnet, rotary-style motor slit axially to the center and then peeled back and laid flat. The major advantage of using a linear motor to drive the axis motion is that it eliminates the inefficiency and mechanical variance caused by the ballscrew assembly system used in most CNC machines.
1. On a saw blade, the number of teeth per inch. 2. In threading, the number of threads per inch.