MOTION SYSTEM TRENDS
Moving coil technology:
Benefits today (and innovations on horizon)
Moving coils have been around for many years. Now though, market pressures are causing the technology to rapidly evolve and gain in use. This technology competes most directly against pneumatic drives and moving-magnet rotary motors. BY ED NEFF | PRESIDENT • SMAC MOVING COIL ACTUATORS (MCA)
M
oving coil technology works in both rotary and linear motors. The technology has been around for a long time. Recall that within the actuator are permanent magnets generating a magnetic field; a moving coil resides in that field. Passing current through the coil generates traverse motion of it and the output shaft or shuttle. The force of that output is proportional to the coil’s turns ad the magnetic flux within the actuator (both constants) as well as the current … so more current through the coil increases output force. In brush-type rotary servo motors based on moving coil technology, the brush provides the means for current to get to the coil. In contrast, single-pole linear motors — often called voice coils — are at the heart of many speakers.
The introduction of high-strength neodymium magnets has greatly expanded the applicability of moving-coil actuators in motion applications, as actuators with these magnets output high force (or torque). The light moving mass of their coils make the actuators excel in many industrial applications because it allows for high cycle rates – to twice that of pneumatic or ball screw actuators. In addition, moving-coil actuators have: • • • •
Long cycle life — to 10 times that of pneumatic or ball screw linear actuators High repeatability over each cycle — to 10% the variance found in pneumatic devices Programmable force and torque output The ability to provide the movement for very slow speed applications.
Electric cylinders such as SMAC’s CBL series actuators use moving-coil technology with force control. They have the same size and shape as comparable pneumatic actuators.
24
DESIGN WORLD — MOTION
01b Actuators — Motion Control Trends V3 03.19.indd 24
3 • 2019
motioncontroltips.com | designworldonline.com
3/12/19 7:58 AM
