A few simple tips can keep a spray gun working effectively and productively.

Applying the finish to a workpiece is one of the final steps in the process that turns a pile of raw materials into a valued final product, whether it is a piece of furniture, a cabinet or millwork. With all the work that goes into building the piece, making sure that the finish is perfect is vitally important. Several spray gun suppliers have provided tips to help custom woodworkers improve the look of their products, while reducing time-consuming rework.

Dale Stitt, North American sales manager, Anest Iwata USA Inc.: Assuming you are using the best possible equipment already, here are other key factors:

1) Clean environment – Use a booth and change the filters often.
2) Clean and dry compressed air – Use refrigerated dryers and desiccant dryers. Install oil separators if you are using an oil-lubricated compressor.
3) Mix the paint to the recommended ratios – Nothing can hurt a paint job more than not having the proper ratios. Remember that ratios can change based on elevation, temperature and humidity.
4) Clean and lubricate your spray equipment after every use. However, as a manufacturer, we do not recommend the use of gun cleaners. Simple hand cleaning is sufficient.
5) Most importantly, follow the manufacturer’s guidelines on inlet air pressure and measure it with a regulator installed at the gun. Many finish problems and waste occur when customers don’t follow the recommended maximum air pressures. You are also at risk of being out of compliance with local HVLP regulations, if applicable.
6) Lastly, train the operators. Our distributors around the country are more than willing to train your operators on the proper use, care and maintenance of not only the spray equipment, but also the entire paint operation. A well-trained operator will improve finish quality, reduce product waste, reduce rework and scrap and improve the life of the equipment.

Paul Lenzen, sales engineer, Mattson Spray Equipment: One thing that comes to mind would be the importance of gun maintenance and lubrication for optimum performance and spray consistency. It’s very important for the spray gun operator to understand the features of his gun, as well as understand the proper cleaning and maintenance procedures to keep his gun spraying smoothly and providing the best spray pattern and most efficient atomization. If the spray gun is ignored, finish quality and material costs are greatly compromised as well as production time dollars. Keeping spare seals and gaskets on hand is another part of proper maintenance and helps avoid unwanted downtime.

Bill Boxer, senior vice president and chief operation officer, Apollo Sprayers Int’l. Inc.: Understand the importance of atomizing pressure relative to the viscosity of the finish and the coating that you’re spraying. The two relate to each other, and it’s very important. When the viscosity is correct and the correct pressure is selected, you’ll get very efficient results and a very good atomization.

You should certainly read the instruction manual from the manufacturer of the equipment as to the performance of the spray gun. The manufacturers of the coatings also generally give some guidelines as to how their coating should be utilized or how much it should be thinned. The finisher should make a test piece, look at the end result and use common sense at that point to adjust accordingly, whether it’s adjusting the atomizing pressure or the viscosity of the product. Make the two match up to get the quality you want.

Often, people will take things literally and do exactly what the equipment manufacturer says and exactly what the coatings manufacturer says and will not get the results that they want. They assume that it’s what they’ll have to live with, when in fact, some very small adjustments will make the difference between an okay finish and a superb and perfect finish.

Steve Stalker, training manager, ITW Industrial Finishing: If you are using an HVLP spray gun, and it is required by a regulatory agency the spray gun must be operated at 10 psi or less of atomizing air. The atomizing air is the air exiting the annular (center) hole of the air cap.

An air cap designed for testing compliance is available from the spray gun manufacturer. Each air cap uses its own matching “test cap.”

There are two types of test caps available and will vary with the manufacturer. On one, the gauge is connected to the air cap via a tube. If the test cap has two connections, the connection not being used must be covered or plugged. For compliance testing, use the cap connection that is toward the center of the air cap. Leave the connection coming out of the “horn” plugged. On the second type, the gauge is connected directly to the air cap.
Following are details about how tests should be done.

Additional Criteria:
1. Testing must be done at the pressure settings used while spraying.
2. Testing must be done with the spray gun adjustments set as used while spraying.
3. The gauge should be periodically checked for accuracy or use a gauge of known accuracy.
4. Do not use the test cap for spraying.
5. The air gauge should be a maximum of 30 psi, preferably 15 psi.

Test procedure:
1. Leave all pressure settings as used.
2. Leave all gun adjustments as used.
3. Replace production air cap with test air cap.
4. Attach gauge if necessary.
5. Pull trigger on spray gun to a point just prior to releasing the coating.
6. Read the gauge.

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