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Issue link: https://pf.epubxp.com/i/131829
as the voltage lines develop and current fows to the part, making it even more challenging to get powder into the recessed areas and adding more flm to the more exposed surfaces. All of this may create some challenge if the part is grounded. If the part is not earth-grounded, the Faraday cage effect and flm-build uniformity are going to be much bigger challenges. Inconsistent flm is the result, and rejects are much higher where the ground is good. Earth ground should be measured with an ohmmeter, and the reading should be less than 1 mega-ohm. Keep in mind that all it takes to maintain good earth ground is a clean contact point and good path to ground, variables that all coaters should have complete control over at all times. Assuming that the earth ground is good, coating thickness is controlled by the use of a standard set of operating variables that affect flm build: • Gun-to-target distance • Electrostatic settings (voltage and micro-amps) • Flow rate and powder velocity • Number of strokes or dwell time in front of the gun. setting on fow rate and average distance (6 inches for manual guns and 12 inches for automatic guns), and make two to three passes. Use medium to slow strokes with some overlap of your pattern. For complex shapes, reduce the amperage and voltage, and coat diffcult areas frst. Observe the spray pattern to see how much velocity you have (high velocity is bad), and note how much overspray is generated. If the overspray is low and the coverage is good, you are fne. Increase the fow if you need more powder, and decrease the fow if you have a lot of overspray. Establish a standard setup and be consistent. Maintain a smooth spray pattern by making sure that you have right ratio of fow air to secondary air. A fnal word to the wise: Be diligent with your racking. Carefully hung parts on clean hooks will yield the best results. Stable hanging patterns, parts hung in dense patterns but not too close, and good access to the spray pattern will enhance flm build control and effciency. n To develop an optimum set of controls, you need to do some experimentation and verifcation. Try full voltage and amperage to start with, a medium-to-low Find a Powder Coating Equipment Supplier LearnMORE Looking for the coatings or equipment discussed here? Access hundreds of suppliers by category at short.pfonline.com/PCSupp. Like PF on Like Products Finishing on Facebook, and enter to win a Products Finishing Fan Pack! FRONT THE FAN PACK INCLUDES: Products Finishing logo t-shirt Products Finishing drink coozie Products Finishing golf balls BACK Find us on Facebook at Products Finishing Magazine. We will choose a monthly random winner. pfonline.com 37