Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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Page 165 of 331

Fig. 8. Conventional powder booth system. motor and gear reducer used in the design. Sometimes, there are clutches and ad- justable 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 os- cillators 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 adjust- ment 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. Multi-Axis Machines Both oscillators and reciprocators provide movement in one plane only. Multi- axis machines were developed to provide increased coating flexibility and meet a demand for total automation. Multi-axis machines have been successful in eliminating some or all of the manual touch-up necessary on some products. Though costly, this increased automation often will pay for itself by providing consistent part coating with minimal, if any, touch-up. The multi-axis machine design is made up of two or three reciprocators that will move the gun(s) in two or three planes. The convention used to label the three axes of motion is as follows (see Fig. 7). X = parallel to the conveyor travel Y = up and down Z = in and out 164

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