Painting Q&A: Benefits of Electrostatic Applicators
Optimizing manual electrostatic applicators.
Q. How can I optimize my manual electrostatic applicators to benefit my manufacturing facility?
A. Electrostatic guns have a number of benefits, including an excellent finish quality and a high transfer efficiency up to 90 percent. This high transfer efficiency rate provides cost savings for paint, reduces VOCs and hazardous air pollutants, potentially decreases permitting issues, and increases production. To take advantage of these benefits, understand what materials can be sprayed, which coatings to use and how to optimize the transfer efficiency of the manual gun.
Almost anything can be sprayed with electrostatic spray guns. As long as the charged paint “sees” a conductive grounded surface, it will attract and can be painted. Though metal is often the first material people think of, wood, plastic and rubber can also be sprayed electrostatically. Even nonconductive items can be sprayed with these guns, as long as they are placed between the applicator and a conductive grounded surface, or if they are sprayed conventionally first with a conductive primer.
To determine the correct coating to use with your electrostatic gun, consider its resistivity, which is measured with a paint probe meter. A paint probe meter measures megohms per centimeter of resistance. Between 25 and 50 megohms per centimeter is the ideal result.
To get the full benefit of electrostatic guns, there are a few items you can check. The first is proper gun setup for the ideal air pressure and fluid pressure. Too much air pressure will cause turbulence in the sprayed material, resulting in excessive overspray and reduced transfer efficiency. Use only enough air pressure to get a high-quality spray pattern, but low enough to optimize transfer efficiency. Minimize fluid to reduce bounce back of material on the substrate.
Spray pattern height is also important. The spray pattern height needs to match the part being sprayed. The tip size should be sized to the largest spray pattern height for your parts, but not bigger. Also, purchase a spray gun with a fan pattern adjustment knob, so the operator can adjust the spray pattern height to match the part size. Operator technique can affect transfer efficiency by 10–30 percent, so operators should be trained on proper spray techniques.
There are also many factors in the spray booth that can impact electrostatic gun effectiveness. First, all components in the spray booth must be properly grounded to optimize electrostatic guns, including the operator, the parts being sprayed, the electrostatic gun and other objects in the booth. Next, the spray booth and gun need to be clean. Using gun covers and clean part hangers increases the attraction of the material to the part.
Finally, spray booth air conditions impact transfer efficiency the gun. Crossdrafts, downdrafts and high -elocity air exhaust can deflect the paint away from the target. Temperature and humidity can also significantly affect efficiency, so the booth should be an enclosed environment.
If you’re not seeing the full potential of your electrostatic system, make sure that you, or someone on your team, understands what materials can be sprayed, which coatings to use and how to optimize the transfer efficiency. By doing so, you should see not only an increase in production and a decrease in material usage, but also cost savings.
Wendy Hartley is a product marketing manager for electrostatic applicators, conventional applicators and spray packages at Graco Inc. For more information, visit graco.com/finishing.
Originally published in the March 2016 issue.
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