Finger Prints on Zinc Plating

Q: We supply zinc plated components to a number of different industries. As you would imagine all of our customers want a perfect parts with zero defects. We do not do the actual plating but rely on outside vendors. Frequently, we will receive plated parts from our vendors with fingerprints spotting and dull areas. Do you have any suggestions and how we can reduce the number of rejected parts? J. T.

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A: I have been asked this question many times. In one situation a number years ago, I was shown some parts that had a beautiful set of fingerprints on the surface. My first suggestion was to dust the prints and then see if you could come up with a match to one of the operators in the plating shop. You might be able to find the culprits but it really doesn’t solve the problem.
Your e-mail doesn’t state what percentage of rejects you have but in today’s modern plating environment customers strive for zero rejects. To solve this problem, you have to work with your plating vendors. The first thing you have to do is set up standards. Quite often standards are rather subjective in other words, “in the eyes of the beholder.” I was involved in a situation a few years ago in which I was asked to solve a quality problem. The end user claimed the number of rejects had gone up dramatically while the plating shop claimed there had been no change in the reject rate over the same period of time. After many meetings and much time spent trying to sort this problem out, it was determined that the end-user had changed standards and had not told the plating vendor. To make matters worse, the standards were more or less visual and had no written or sample criteria.

I would start with preparing samples and getting your customers to sign off on the samples. These samples can then serve as standards.

You can now go to your plater and tell him that he has to produce parts that meet the quality specified by the samples. The plating vendor should do systematic inspections and parts that do not match the criteria as set by the samples must be reworked or discarded. This may well increase your costs. To offset this increased cost, you must convince your customer to pick up part of the cost.

Last but not least, you may have to find a new plating vendor. Yes, I know this is a hassle, but sometimes this is the only reasonable solution.