Metal Finishing Guide Book


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Page 253 of 903

Fig. 6. Gun motion devices. devices deliver a column of powder to the applicator without having to mix it with compressed air. Reducing the compressed air within the powder stream decreases the velocity of the powder delivered from the applicator, slowing powder speed, increasing powder density, and eliminating aerodynamic issues 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 designed 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 adjustment of these parameters, but they cannot be used while the machine is running. 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 ro248

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