Repair of Rejected Parts

Question:

I have seen from your web site that you can solve many painting problems and identify the correct way to do them. I was really impressed. At present, I work at a company that produces wall clocks, business instruments and other parts. Many of these products are painted using UV coatings on ABS plastic materials. We have problems with dust and scratches on surfaces after painting with the UV clear coating, and the products are rejected by our QC department. We would like to know how to repair the rejected products. We thank you for your help. C. T.

Answer:

Normally, rejected metal parts are spot repaired or stripped and repainted. Plastic parts are difficult to strip because of the sensitive nature of the substrate. A better approach would be to eliminate the cause of the rejects, in this case airborne dust and scratches.

Airborne dust can be eliminated by not allowing it into the spray booth and curing section of your paint line. Spray booth and cure oven (in your case the UV enclosure) make-up air must be filtered to remove airborne contamination. In addition, both these areas must be kept under positive pressure to prevent entrance of contaminated shop air. Of course, the parts must be dust-free before entering the spray booth.

Scratches can be eliminated by more careful handling of painted parts. This will require training of the operators, unloaders and shippers. Hopefully, since you are making high quality products, your factory workers are better trained than those at my former company. At my company the entry level position for a new worker was sweeper. The next level was painter.