Q. I am a manufacturing engineer in my plant where we produce a line of fasteners. We are applying a dry-film lubricant on small bolts, nuts and washers using the dip-spin coating method. In many cases, we are faced with parts sticking together after curing and, as a result, 10 percent of these parts must be reprocessed. The coating is cured in a tunnel oven. I think some kind of additional process should be done before curing in order to keep parts from sticking together, but I do not know exactly what to do. Do you have any ideas? G.L.
A. Your problem is probably with the material, not the process. The dry-film lubricant should be “dry enough” so that parts do not stick together after the dip-spin coating method. The problem may be related to viscosity or solvent balance. Ask your coating supplier for help in this area.
Another possible cause for the parts sticking together is insufficient solvent flash-off time. The least-costly way to solve the problem is to adjust the viscosity of the dry-film lubricant. Again, this is related to solvent balance which your coating supplier can recommend. The most costly way is to lengthen to flash-off zone. This involves modifying the coating line.