Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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Fig. 7. Multi-axis movement. der stream decreases the velocity of the powder delivered from the applicator, slow- ing powder speed, increasing powder density, and eliminating aerodynamic is- sues that may cause coating difficulties on box-shaped parts. Since these pumps employ significantly smaller diameter feed hose, the hose is much easier to clean with compressed air purging, making these pump the preferred choice for "fast color change" systems. GUN MOTION Automatic spray devices are often accompanied by some ancillary equipment used to produce spray gun motion. Gun-motion equipment can be broken down into four general categories: oscillators, reciprocators, multi-axis machines and robots. Each of these gun-motion systems has a different design and is used to fill a specific coating requirement; however, all have one common feature. They are de- signed to move the spray gun(s) in one or more planes to coat a larger area than a fixed spray gun. Thus, the number of spray guns required to coat a given area can be reduced. This makes for a more efficient and economical system design Oscillators & Wagglers One type of gun-motion device is called an oscillator. This design is different from other movers in that it usually has a fixed stroke and speed. Some units have ad- justment of these parameters, but they cannot be used while the machine is run- ning. The main component of this type of equipment is an eccentric wheel 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 ro- tary 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 163

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