Application Digest

Specify linear motors for smooth, direct drives

Nicolas Wavre, General Manager, ETEL SA

Because advances in electronics and magnet quality have outpaced improvements in mechanical power transmission subsystems, ball screws or gearing have become limiting factors for engineers trying to improve servo-actuator performance. With a linear motor, however, load is driven directly by the magnetic field. This characteristic eliminates the need for a mechanical transmission system.

A promising area of activity is the command of X and Y tool machines. Replacing conventional ball screws and gearboxes by using direct drives with linear servo motors provides a considerable increase in performance. With the increase in bandwidth, it is possible to suppress elasticity, backlash, hysteresis, and maintenance by a factor of five to ten.

The technology used by ETEL is based on the permanent magnet synchronous motor, also known as a brushless dc motor. Motors with strokes to 50 mm are single phase, while motors with strokes exceeding 50 mm are polyphase. The power stages are IGBT or MOSFET configurations. Commutation frequencies run from 20 to 100 kHz, depending upon power, while control electronics can be analog, digital, or a combination of both.

High-force linear motors with fully integrated water cooling are drastically improving grinding machines, pc-board drilling, and wire bonding equipment in the chip-manufacturing industry.

To speak with an applications engineer from ETEL, call: +41 38 61 18 58 or FAX +41 38 61 24 19.

Ten reasons to consider metal belts

David Huntley, Belt Technologies, Europe

Design engineers who specify metal belts have options not available with other products or materials. Used for conveying, timing, indexing, positioning, power transmission, and automated manufacturing operations, metal belts offer many features and benefits.

High strength-to-weight and durability are also inherent to metal belts. Available in a variety of alloys, metal belts can withstand sustained exposure to temperature extremes, vacuum, and hostile environments.

Unlike the links of a chain, a metal belt does not generate component friction. As a result, a metal belt doesn't require lubrication. Spring steels with a high modulus of elasticity will not stretch, a characteristic that makes metal belts ideal for precision positioning.

Some other advantages of metal belts:

Smooth operation: Free from the pulsation of chordal action, metal belts precisely translate the control system motion profile.

  • Accurate and repeatable: Metal timing belts can be fabricated with a pitch accuracy of plus or minus 0.013 mm station-to-station.

  • Precise construction: Edges are smooth and dimensions are tightly toleranced.

  • Good conductivity: Metal belts can transmit energy in the form of heat, cold, and electricity.

Because metal belts experience no static buildup, they can be useful in the manufacture of ICs, SMDs, and other electronic components. Further, metal belts do not generate particulates, making them ideal for food and pharmaceutical processing. They are also clean-room compatible.

To speak with an applications engineer at Belt Technologies, Europe, dial: +44 91 383 1830.

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