A Photo-Worthy Finish
August 14, 2011 | 9:08 pm CDT

Tips and techniques to get the best finish from spray guns — and train employees on how to use them.

While it is best not to judge a book by its cover, a custom woodworking project will certainly be judged by the quality of its finish. Therefore, it is critical to have well-trained finishers who know how to achieve a consistent, high-quality finish. CWB contacted several spray gun manufacturers for advice to help make the finishing operation in your shop spot-on.

Q. How can a finisher make sure he gets the best spray pattern, consistently, from his spray gun?

A. Matt Carlson, vice president of marketing, DUX AREA Inc.: Spray pattern quality is the result of the right blend of air and coating under a specific set of conditions. To ensure consistency from day to day, it is very important that the operator record all of the variables associated with the desired outcome — and then try to repeat them as closely as possible or make adjustments if those variables change.

For instance, the temperature of the coating will affect its viscosity, which in turn affects its ability to be atomized. If the operator does not, or cannot, control the temperature of the coating, he will need to make adjustments in other areas, such as fluid pressure and/or atomizing and fan air pressures.

The best way to achieve consistency is to use equipment that allows you to record your settings and then return to them very easily. For instance, be sure to use regulators with accurate pressure gauges that are easy to read — and record the pressure settings used under different conditions and with different materials in a log book. Use a spray gun that allows you to identify the exact position of the needle (via the fluid control knob) and the fan control. Many guns have unmarked knobs, so it can be difficult to know if you have the needle set in the same position. A gun with good fluid control knob markings and an immediate visual reference for the fan setting is best.

Finally, operator training is critical. Two operators can pick up the same gun and get completely different results. Distance to target, speed of gun movement and direction of the spray (i.e., head on or at an angle) all will impact the consistency of the final product. If your operators are all trained together on proper technique, you’re much more likely to see similar results from shift to shift.

A. Ken Ehrenhofer, training manager, EXEL NA: A finisher needs to make sure his spray finishing equipment is always operating at peak efficiency. In order to do this, I always say to start with the inputs.

First, make sure the paint is of the correct viscosity. Second, make sure it is properly filtered and regulated for a clean and consistent fluid delivery. Third, make sure the atomizing air is clean and dry and regulated to the correct setting for optimum atomization and transfer efficiency.

After the inputs are correct, the spray finisher must make sure his air cap and tip are clean. Soaking in solvent does not always get the job done, due to an increasing number of sprayers using two-component finishes. The tips and air caps need to be immersed in an ultrasonic cleaner or chemical bath to remove cured materials. Gun covers and hose covers are available to help keep equipment in top operating condition.

Consistency only comes from doing the same thing the same way everyday. Logging in the information as to pressures and settings, the spray operator is able to duplicate his efforts each day and achieve the same results. I refer to this as “controlling the variables.” Once the variables are under control, the finishing system is under control and you will get the same result day after day.

A. Jim Brooks, North American sales manager, Anest Iwata USA Inc.: All spray equipment needs to be maintained. Regular cleaning and maintenance is the best way to ensure that the spray pattern remains as constant as the day the gun came out of the box.

Q. What are the key steps to training a new employee to become a good spray finisher?

Carlson: Most companies unfortunately skip straight to spray technique training when bringing a new operator on board. This is understandable, since many new operators are brought in under emergency circumstances where the employer just needs to get the product out the door. Because so many different things can affect finish quality, a proper training regimen should start with a comprehensive overview of the entire coating system.

For example, it is important for operators to understand how the coating should be stored so they can identify problems that may lead to coating contamination or breakdown. They should know how the coating is delivered (i.e., via pump or pressure pot) and how to properly maintain and configure this equipment to ensure a consistent flow of clean coating material. An understanding of how regulators work and how to properly adjust the fluid flow rate is critical, as is proper care and cleaning of hoses and fittings. A failure in any one of these areas could create problems that an uninformed operator might blame on the spray gun.

With an understanding of how the entire system works, the operator can then focus on the final adjustments that can be made at the gun. As described earlier, using a log book to record past gun settings, under similar circumstances, can be a huge help to new operators. It gives them a starting point from which they can begin to experiment on their own.

Over time, with the help of more experienced operators, they’ll learn to make the smaller adjustments necessary to fully optimize the gun in any situation. Just make sure they record those changes — so the next “new guy” will have the benefit of their knowledge.

Ehrenhofer: Training a new spray finisher in the art of spray finishing is not an easy task. It takes a knowledgeable person to teach the speed of the spray gun, the distance to the target and the flow rate of the paint, just to mention a few of the tasks. Some other things to look out for include:

• Setting fluid delivery and flow rate.
• Setting atomizing air for optimum results.
• Spraying the difficult, hard-to-reach areas, edges and recesses first.
• Spray the flat surfaces last.
• Perform wet film thickness tests to make sure the correct film thickness is achieved.
• Mount a laser distance detector on the spray gun to assist in teaching the operator to keep the gun at the correct target distance.
• Have the trainee start by practicing on waste material. This will make him/her more comfortable during these practice sessions.
• Have the trainee watch other sprayers for technique.

Brooks: One of the best things to help a new finisher perform at a high level is to make sure he understands the material that he is spraying. Also, the finisher needs to develop a consistent spray technique, so he achieves the same results each time.

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