Metal Finishing Guide Book


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Page 220 of 843

Fig. 7. Multi-axis movement. and lever as shown in Fig. 6. The motor rotates the eccentric wheel. The lever, which is attached to the wheel at some distance from the center, will translate this rotary motion to a vertical motion. Stroke length is determined by the position at which the lever is attached to the eccentric wheel and by the diameter of the wheel itself. It can be adjusted by locating the lever at different points on the wheel radius. Speed is dictated by the motor and gear reducer used in the design. Sometimes, there are clutches and adjustable belt sheaves that will provide some speed adjustment; however, neither speed nor stroke adjustment can be changed while the unit is running. Wagglers (radial oscillators) pivot the gun through an arc, where straight oscillators provide vertical gun motion in a straight line. Gun-to-part target distance is affected with radial oscillators, while straight oscillators will not have this problem. Reciprocators Reciprocators (see Fig. 6) use a variety of electronics to control both stroke and speed. In these machines, the mechanical linkage between the motor and guns is fixed; therefore, speed and stroke control must be adjusted electrically. These adjustments are sometimes made at the control panel and sometimes at the unit itself. For instance, stroke adjustment can be made by moving electrical limit switches in the unit or by adjusting an electronic feedback loop variable in the control panel. Speed control is accomplished by a variety of methods depending upon the type of motor used. For instance, those designs that use a DC motor will provide speed control by varying voltage to the motor. Reciprocators that use AC motors have variable speed-control circuits to adjust speed. Both types allow adjustment during operation. This offers some flexibility over the oscillator design when different stroke lengths and speeds are required to coat different parts during the production cycle. 215

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