Last week we discussed transfer efficiency and I left off with the idea that HLVP spray guns can shoot coating at lower or higher transfer efficiency percentages based on the sray gun setup and operator use.
Also, there are other variables that are a factor even if the gun set up for optimal T.E. The first and most obvious is your finish person’s lead and lag technique. That refers to the amount of coating that is sprayed into the air prior to or at the end of a pass when you move the spray pattern onto or off of the surface you want to coat. Some folks don’t cycle the fluid valve at the end of a pass. They just leave it open, move the gun, and reverse direction. You will waste coating if you end each pass without cycling the fluid valve. Allowing the fluid valve to remain open when the pattern is sprayed into the air is wasteful of coating as well as booth filters. The best bet is to cycle the fluid valve on or off as close as possible to the edge of the object being sprayed. That saves coating and, thus, improves T.E.
I mentioned previously that the shape or configuration of the piece being sprayed can affect T.E. For example, if you are spraying flat panels, you should have better T.E. than if you are spraying a set of dining room chairs. Do you see my point? The dining room chair is more intricate and potentially wasteful of coating simply because of the small, irregular surfaces to be coated.
Here’s another thing that will improve T.E. over the long haul. I mentioned bounce back and overspray last week. There is “sweet spot” at which the tip should remain throughout a pass relative to the surface being sprayed. Tip to surface distance is critical.
I so often tell people that speed and distance are your friends. Well, that’s positive “spin” used to avoid talking about the fact that they can also be your enemy. Distance affects the width of the pattern and the mils of coating applied per square inch of surface. The speed of the gun also affects the mils of coating applied per square inch. But distance can also affect bounce back and overspray. Find the sweet spot and train yourself to hold the gun at that distance at all times. One source I read says that you can improve T.E. by 38% by maintaining proper tip to surface distance.
Come the end of the job, come the end of the day, and come the end of the year…think of ways to improve T.E. In order to do so, T.E. needs to be on your mind when you pick up the gun. Think about these things.
• Am I using the right equipment for this job?
• Do I have my equipment set up properly to maximize T.E?
• How am I going to spray this piece for maximum T.E?
o Other things not part of the flat surface
• What pattern(s) will work best on this piece?
• When do I cycle the fluid valve on and off relative to the edge of the surface being sprayed?
All this and more will help you reduce waste. So now, are you ready for the punch line?
Remember…it is a waste of time and money to practice bad habits. Always practice to improve your skills.
In conclusion, I would like to repeat one more thing that I’ve said before. If you are the builder, think like a finisher. Ask yourself how you would build this particular piece if you were going to spray it yourself. So many times I have seen builders build something that is exceedingly difficult to spray. If only you would stop and consider building subassemblies that could be quickly assembled after they are finished. It would not only save labor costs in the spray shop, it would improve T.E.
Until next time…spray on!
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