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21 September, 2018

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Sub-£1,000 linear drive challenges ballscrews

01 May, 2001

Sub-£1,000 linear drive challenges ballscrews

Linear Drives, the Essex-based linear motor developer, has unveiled a low-cost linear drive that, it asserts, can compete directly with conventional technologies such as ballscrews. Joint managing director Scott Pleva hails the machine as "the smallest, lightest and lowest-cost" three-phase linear servo motor.

The ThrustTube Micro uses the same patented construction as Linear Drives` larger machines - a motor block housing windings that runs concentrically along a rod containing rare-earth magnets - but instead of the usual aluminium block, a lightweight polymer is used. This block weighs just 70g, allowing it to deliver accelerations of 30G, sub-micron positional accuracy, peak forces of up to 77N, and a top speed of 30m/s. It can reach 10m/s from a 24V DC supply.

Even higher accelerations - up to 60G - are possible over shorter distances if the motor housing is fixed and the 11mm diameter rod is allowed to move.

The impetus for developing the low-cost motor came from Linear Drives` success in supplying motor-driven faders for audio mixing desks. The company has cornered this specialist market and has already supplied more than of its 18,000 aluminium-bodied motors for mixing desks. It realised that similar, untapped markets could emerge if it could cut the cost of small linear motors.

Unlike competing technologies, such as ballscrews coupled to rotary servo motors, the ThrustTube design is easily miniaturised, according to Pleva. He describes the Micro as "the world`s first injection-moulded motor". The housing is formed from a special polymer with a high strength-to-weight ratio and a thermal conductivity 80% better than that of epoxy resin, avoiding the need for a heatsink and allowing the motor to be driven harder.

Other attractions of the new motor, according to Pleva, include its linear force response, the absence of eddy current losses, its smooth cogging-free movement, wide dynamic performance, and the ability to provide stroke lengths up to 800mm.

To ease installation, the motor`s power comes via flexible cable with a zero insertion force connector. It is supplied with an integrated bush bearing.

Applications for the new motor include pick-and-place machinery, scanning systems, probe drives, semiconductor wafer handling equipment, and valve rockers for diesel engines.

List prices for the ThrustTube Micro range from £285 for a version with a 50mm stroke, to £582 for a 700mm stroke device. A matching amplifier costs £344. This produces packages that are "well and truly in the ballscrew arena" says Pleva. He adds that volume orders could push the package price below $500.

Linear Drives is also offering the ThrustTube Micro in a linear stage format with a built-in encoder and cabling.

Linear Drives has recently opened an office in the US and has been forging a relationship with a large Japanese company, details of which will be revealed soon. Pleva says that the deal will make Linear Drives the first linear motor supplier with a truly global operation.




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