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Electric actuators challenge pneumatic cylinders

01 January, 2000

Electric actuators challenge pneumatic cylinders

A Japanese automation supplier is aiming to persuade European users of pneumatic cylinders to convert to electromechanical actuators.

IAI (Intelligent Actuator) claims that its new RoboCylinder actuator will outperform pneumatics in many applications yet will cost little more. The actuator incorporates a specially developed stepping motor with an optical encoder which allows it to position a load of up to 40kg with a repeatability of 0.02mm.

Acceleration, deceleration and speed can be programmed either using a PC or a handheld control. IAI claims that the RoboCylinder with consume about one third as much energy as a pneumatic compressor. The actuator is available either in a slide format (up to 1m long) or a rod format (up to 30cm).

IAI is pricing the actuators to attract users of pneumatic cylinders, with the smallest versions starting at under £700.

"We previously targeted niche markets," says Hiro Watahiki, IAI`s European export manager. "Now we`re going for volume sales."

Although IAI has had a low profile in Europe until now, it claims to have half of the Japanese market for Cartesian robot positioning systems and to be one of the top two suppliers of this technology in the US. But IAI will not have the market to itself.

Other suppliers are starting to offer electromechanical alternatives to pneumatics. Even the pneumatic giant, SMC, is gearing up to launch its own range of electrical actuators.

Hydraulic shock absorbers cut the bounce Many mechanical stopping devices store energy rather than dissipating it. The moving items bounce back causing stress that can lead to fatigue and possibly to failures.

Hepco claims to have overcome this problem with a range of hydraulic shock absorbers that match the speed and mass of the moving object bringing it to rest with no shock. Unlike cylinder cushioning or dashpots, the SH shock absorbers are said to dissipate the energy at a uniform rate, reducing stopping times. Most of the energy is dissipated as heat.

The controlled deceleration is achieved using a matrix of holes in a high pressure inner tube through which oil is metered as the piston rod moves through its stroke. As this happens, the velocity decreases steadily, requiring the use of different hole patterns to maintain constant pressure.

The oil displaced by the piston rod is held in a closed-cell, sponge-like material. Hepco claims that the shock absorbers will extend machine life, allow higher operating speeds and production levels, reduce stress levels on system components, cut noise levels, and lower design and assembly costs.

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