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Piston air motor provides improved paint agitation

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Huco Dynatork's piston air motors enable Autoquip to build paint agitators that provide more consistent performance and with lower running costs than alternative systems using vane-type air motors.

Autoquip Inc is a leading supplier of paint finishing equipment and services for the industrial market in the USA, primarily providing robotic and automated systems for liquid paint spraying. Autoquip incorporates a piston air motor rather than the industry standard vane motor into its systems because it lends itself so well to the company's proven flow control techniques. It provides an excellent platform on which Autoquip can build systems that have both superior coating ability and exceptional cost efficiency.

The air motor is manufactured by Huco Dynatork. And, as Autoquip's Mike Elberson confirms: "By including the Huco Dynatork product we can substantially reduce compressed air usage and ensure constant rpm of the agitator blade." The result is better surface finish and lower running costs.

As Elberson explains: "Historically a vane motor has been used as the means to agitate paint and keep solids in suspension. But one of the main drawbacks of this type of motor is that it has low torque at low rpm." To rectify this, a 10:1 gear transmission is typically introduced to allow the vane motor to operate at a much higher speed than the blades. As well as making the system more complicated, the payback is excessive use of compressed air. Also additional lubrication is required.

Low running costs

He continues: "We estimate that the compressed air used by a small vane motor to rotate mixing blades between 50–100rpm, is in the region of 12–15scfm per day. And air is expensive. So based on 85 per cent compressor efficiency, the daily cost is $5.50 to $6.75 (£3.38 to £4.15)."

By including the Huco Dynatork self-lubricating piston air motor, Autoquip provides its customers with paint spraying systems that cost just $0.85 (52p) per day to run. The agitation system is also far less cumbersome, as the air motor naturally provides high torque at low speed, thereby negating the need for a geared transmission. It is also much quieter in operation and, thanks to its dedicated controller, the air motor also ensures process consistency.

The speed control of a vane agitator motor is achieved by manually adjusting the air pressure via a regulator. However, the pressure required to maintain rotational speed depends on the paint tank level, and the regulator cannot automatically sense the resultant load changes. Additionally, agitators often operate within an enclosed system where it is impossible for the supervisor to see the blade and determine the speed. The resultant inconsistency in agitation speed can cause coating quality problems and a loss of production.

Autoquip combines its air motor with a patented dual-mode air flow controller, also designed and manufactured by Huco Dynatork. Elberson explains: "This monitors the flow rate of air to the piston motor and adjusts the upward pressure as the flow changes. This provides much more consistent speed, regardless of the required mixing torque."

28 April 2010

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