Uniform Film Build

Q. We powder coat aluminum fencing in component parts and them assemble it after coating. We are having trouble with the rails that fit at the top and bottom. They are shaped like a channel that is about two inches deep. The pickets fit up into the top channel and the bottom channel has punched holes that the pickets fit into. We cannot get uniform and consistent powder coverage up inside that two-inch deep channel. Can you give us any advice on how to improve our coverage inside the channel? J.B.

A. The first thing you need to do is review your racking arrangement. A part like you describe should be held firmly so it cannot move around in front of the spray gun. The opening of the channel should be facing the spray guns. Automatic coverage should be used for the outside and some coverage on the inside of the channel. Manual operators will have to be used for most of the coverage inside the channel. They should use a moderate flow level (25-35 lbs/hr) and control the micro-amps below 25. If you have a setup where the manual work can be done first it will help with application inside the channel. With all of these adjustments in place you still may find it hard to get 100% coverage inside the recess. If you must have complete coverage inside you will need to make sure the line speed and spacing give them enough time to concentrate on getting the area done.