Metal Finishing Guide Book

2013

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troubleshooting, testing, & analysis TROUBLESHOOTING COMMON (AND SOME NOT-SO-COMMON) PROBLEMS RELATED TO PAINT, POWDER COATINGS, AND SURFACE PREPARATION BY RON JOSEPH (1944 –2011), FMR PAINT & COATINGS CONSULTANT, EXPONENT, INC., MENLO PARK, CALIF., AND KEVIN BILLER, POWDER COATING RESEARCH GROUP, CINCINNATI, OHIO (Editor's note: This section is dedicated to the memory of Ron Joseph, Metal Finishing's long-time organic coatings editor, who passed away in 2011.) MATCHING HVLP NOZZLE SIZE TO YOUR APPLICATION Q: What is the best spray gun and tip to use while spraying Imron 5000 & 6000? I am using an Iwata HVLP with a 1.3 tip, and I'm still having trouble with heavy metallics. A: First, you didn't mention the Iwata HVLP model number. The vendor recommends nozzle sizes for each spray gun model. For instance, I went online and reviewed the nozzle sizes for the LPH 2003 HVLP spray gun. If you scroll down their Web page you will find recommended fluid nozzle sizes, given in millimeters and inches. For your particular spray gun you should review the nozzle sizes Iwata has recommended. The HVLP spray gun might be perfectly adequate, but you might need to play with the fluid flow rate and air atomizing pressure. Invariably, painters use too high a fluid flow rate and the atomizing air can't adequately break up the paint stream. I suggest that you set up your spray gun from scratch. Take a piece of aluminum foil and attach it onto the spray booth wall. Turn the fluid needle, fan control knobs, and the air atomizing control valve all the way closed. Now open the air atomizing control value a quarter turn and do the same with the fluid knob. If no paint emerges from the gun, open the air a little more. Perhaps also open the fluid control knob another quarter turn. Continue opening the air atomizing valve until some paint emerges from the gun orifice. Eventually, a wet round circle of paint will deposit on the foil. At this point, start to open the fan control knob to widen the fan pattern. By opening the air valve, fan control, and fluid control knobs in small increments, you should be able to get a setting that will produce a good-looking paint finish. This will take time and patience, but the process usually works. If these steps fail, perhaps you need to change to a smaller or larger tip size. PAINT ODORS AND SPRAY BOOTHS Q: I own an upholstery company, and every so often my neighbor spray paints outside. The smell is quite horrible. When I leave my warehouse door open, the odor enters and I must close the door to keep out the obnoxious smell. Are there regulations preventing him from painting outdoors? 553

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