Q. Are you aware of any standards on powder coating film thickness on complex structures? We have a customer that requires 80-100 microns on a complex chassis for a mini tractor, but, due to the construction, there will be 60-300 microns in corners and other complex areas. I am looking for a standard or some studies or guidelines that can be used for “industrial” production.—C.J.
A. I searched for a written industry standard but I cannot find one in the “PCI Handbook” or other sources. Generally, on flat or simple surfaces, the film build can be held to ±0.5 mil (±12.5 microns) of powder. So, for example, if the specification is an average of 2 mils (50 microns), then the film variation would be from 1.5 to 2.5 mils (37.5 to 62.5 microns). If the part has a more complex shape, the film variation will be greater. A medium-complexity shape could cause a variation of ±1 mils (±25 microns), and a very complex part may cause a difference of as much as 2.5 mils in either direction. As a result, on a complex part, the film build could easily run from a low of 2.0 mils to a high of 7.0 mils (50 to 175 microns). The film build can be controlled to the best possible level by using accurate and consistent process controls and gun settings. Practice with scrap parts or models to perfect your settings and technique.