Coaters receive all sorts of complaints about the finished product. While most do not result from processing, a few can be eliminated or lessened by careful observation of incoming material. Cleanliness of the outgoing product is often the result of the state of the incoming tubs. Fasteners are often shipped into the plating shop in tubs, especially if the manufacturer is nearby. This saves time and packing efforts, as well as multiple handling steps. If the manufacturer is restrained from bulk shipping to his customer (Just-In-Time or size-controlled shipments), he doesn't want containerized shipments back from the plating operation and, again, ships parts in tubs. The parts that arrive in manufacturer's tubs, or skips as they are sometimes called, number from tens to hundreds of thousands of items. Also included, at no extra cost, is a healthy dose of oil from the tapping machines, coil lubricants and sometimes heat treat oil. Additionally, chips are often present as well as a miscellaneous part or two caught in the corners from the last bunch of parts made. The usual and current plating method is to dump the parts into a processing tub (or a washer) and set the vendor tub aside for later. The parts are processed according to the type of plating or coating specified and arrive at the end of the line. Here the parts are dumped back into the tub. They arrive back at the manufacturer with oil contamination, chips and even additional dross added by the plater (cigarette butts and lunch /candy wrappers tossed into the empty tub are common miscreants). This will bring a return call and poor relationship as soon as the customer starts to use the parts.
The problem has been recognized by some manufacturers and coaters. Washing the entire tub before putting finished parts back into them for return shipping is a practice that is getting more and more attention. This, like all add-on operations, costs some in time (read that as money) to wash the container, put it in a place that minimizes recontamination, and dispose of oil-saturated wash water. Skimmers may reduce oil content of the effluent by collection, but someone has to bear the increased cost of wastewater treatment. Many manufacturers will not be receptive to increases to processing costs, especially when it does not apply to the product at all. The best policy is to see if the customer will actually "see" the situation. Photos or a visit to your plant, even as part of a routine inspection, could be used to illustrate the point. Collected samples of all foreign materials from past tubs should be retained and brought forth during discussions.
One solution that has been tried is the use of tub liners. Plastic liners, usually with perforations in the sides and bottom, allow oils to pass out from the parts. This helps somewhat but doesn't address the chip problem much. Also, loose parts still end up wedged into corners of the tub outside the liner. The main drawback is dumping the tub at the manufacturer, because the oil from the bottom falls on the finished parts. Although the dumper is the manufacturer, the complaint will still be addressed to the plater.
The best solution that I have seen so far is one that one company is doing. It ships a clean and washed tub in on top of the tub filled with the parts. The processed parts are placed in the clean tub and shipped out. Don't we wish all our customers were so sharp? This company has added up the cost of extra shipping, handling, reprocessing (cleaning), and lost goodwill and customer satisfaction and came up with the numbers to show that this was the cheaper way to do it.