Motion System Design

Forces of attraction

In longer travel automation projects — such as the production of high definition and plasma TVs — rolling or gliding contact between carbon and copper in cable carriers often leads to debris, abrasion, and noise.

To eliminate such problems in applications with travel lengths from 40 to 120 ft, igus inc., East Providence, R.I., developed a magnetic cable carrier that suspends its payload in a magnetic force field to virtually eliminate abrasion and noise by eliminating almost all points of contact. Called LeviChain, it is particularly suited for clean rooms, medical and measurement engineering, painting plants, industrial robots, electronics, material handling, and linear motors.

In typical cable carriers, contact occurs in three areas — where the chain glides on itself in the upper and lower run where it is attached, where the chain touches the guiding channel to guide it in a straight line, and where the chain rolls back and the radius hits the bottom of the carrier.

In the LeviChain system, these points of contact are eliminated. The only wear is on the links and radius.

The system features magnetic modules that are fixed on horizontally mounted track-like beams. Acting on iron integrated into the polymer chain, the magnets cause the carrier and its contents to float within the force field.

In addition to decreasing noise, vibration, and debris, the magnetic modules also reduce the force required to pull the chain, allowing smaller motors to move it. The magnetic force also provides complete guidance in all directions, preventing the chain from buckling or flipping sideways.

LeviChain resists the force of gravity and incurs no vibration because it is held in a constant state of tension. Both the upper and lower run operate unsupported and never touch one another, which reduces sliding friction, related abrasion, and wear. Because it always moves inside the magnetic field, emission of unreeling or gliding noise is eliminated, giving it a 41.7 dB (A) sound rating at a distance of 1 yd.

It has been successfully tested at lengths more than 131 ft at speeds of 32 ft/sec. At a constant speed, the driving force is independent of any additional load. LeviChain requires minimal force to create a high load of acceleration. A maximum additional load of 8.5 lb/yd is easily achieved. The upper and lower run of the LeviChain can move independently of each other in a defined space at high speeds and bending radii between 1.75 and 3.94 in. There is a 1-mm area between the E-chain and the magnetic modules.

For more information, visit or e-mail the editor [email protected].

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