Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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Figure 3. When combined with color-on-demand technology, dense phase application equipment can provide color changes in 20 seconds or less. track very close to the part at a high speed, resulting in exceptional powder uni- formity, better standard deviation of film build, reduced over-spray, and reduced cycle time. Coupled with AFC (automatic feedback control) current limiting technology, this allowed the robot to not only contour the part quickly, but to reach back into cavities and coat them uniformly without bounce-back due to the low velocity of powder and without defects caused by too high of a current. When a powder gun is at its optimum distance from the part–the effective charging voltage of the powder is optimized and current draw is low. When the gun-to-part distance decreases, effective voltage also decreases and the current increases. This causes a defect on the powder coated surface of the part commonly known as back ionization. In the case of cavities, this can result in what is known as the Faraday Cage Effect, resulting in poor powder coverage of the surface of the cavity. Dense phase with its low powder velocity and the resulting reduced bounce back—coupled with AFC current control—makes it the perfect match for use with robots for all powder coating applications. This is especially true for those that require frequent color changes. Because dense phase pump is purge-able in both directions, the powder deliv- ery line can be cleaned quickly and effectively. When coupled with "color-on-de- mand" technology, dense phase technology provides automatic color changes in less than 20 seconds. When combined with automatic gun presets that control application parameters—such as powder flow and electrostatics (KV and AFC) for each and every part as well as each and every powder—powder coaters now have the ultimate tool for productivity and flexibility in their powder coating operations. Office furniture manufacturers in Japan have been using dense phase tech- nology, robotics and color-on-demand technology for several years now to pow- 105

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