Replies

1. 
   mkornell | May 23, 2011 12:35am | #1

   By "dry spots", do you mean

   By "dry spots", do you mean spots where the finish goes on dry? (aka "dry spray") You can check this by letting the whole panel dry, and then running your fingers over the affected areas. The finish will feel kind of gritty and/or it will grain off.

   To fix that, you can

   - move the gun a bit closer to the work

   - use a retarder

   - back off the inlet pressure, narrow the fan, add some material flow. Basic idea is to reduce the ratio of air to material, slightly lessen the atomization effect, allowing the finish to hit the work before becoming too dry.

   As you say you are getting a good wet coat, it probably isn't dry spray, but may be tiger striping - where the finish goes on thicker in some some parts of the spray pattern than others, causing lighter and darker bands to be created. Cause is uneven atomization or uneven spray technique, adding retarder won't make a difference.

   First, check the gun. Make sure that it produces an even and proper-shaped (elongated ellipse) spray pattern against a test piece. If the pattern isn't right, you need to deal with that before anything else - clogged nozzle or air cap, damaged needle, etc.

   Then, consider your spray technique. Constant distance from the work, gun always perpendicular, consistent overlaps and consistent speed.

   And third, the gun settings:

   - widen the fan pattern/decrease the material flow/move the gun back and use a higher percentage of overlap/more passes

   - experiment with increasing the inlet pressure

   - crosshatch the spray pattern - first spray side to side, then up and down

   - using correct needle/nozzle for the material.

   Hope that helps. How do you like that Jaguar?