The company where I worked used a variety of tapes for many purposes in wire and cable manufacturing. One of the uses involves wraps for mechanical and electrical purposes, as well as laminated-metal tapes commonly used for shielding. One day, we received a visit by a supplier of such tapes.
The young salesman who showed up that day was very excited about a new tape his employer was producing for cable shielding. Rather than the conventional laminated construction, this new type of tape featured an electrodeposited aluminum coating. The advantages he touted included lower cost and lighter weight.
I asked about coating thickness. According to the product information, it was very thin. I was surprised by how thin it was. I then asked, "With a clear backing, how will an operator know which side is conductive?" As a note, laminated tapes use a tinted laminating adhesive, often blue, so you can easily distinguish the back from the front. This is an important matter, since the conductive side of a tape shield must be in contact with the drain wire.
Since I couldn’t tell much of a difference by looking at it, I noted that we should easily be able to determine the answer by using an ohmmeter or other continuity-testing device. We trotted off to the lab to do a quick test. To our mutual surprise, there was no discernible conductivity on either side of the tape. The electrodeposited coating was so thin that virtually none of the metal atoms were “holding hands.” The new tape had been manufactured and launched, apparently, without anyone recognizing this problem.
This entry was submitted by Peter M. Blackford and edited by Rob Spiegel.
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Years ago, I worked for a plant that. among other things, manufactured high current, low voltage power transformers. The secondary was wound with strip aluminum, about 3 inches wide, and .020" thick.
One day a salesman came in and suggested that we use aluminized mylar to replace the aluminum, as a weight and cost savings.
I grabbed an ohmmeter and stuck the probes on the coated plastic. Guess what? No conductivity, of course. Even if there had been, would it have carried the 20 amps or so that we needed?
Ann, your comment indicates that you think QC personel actually test parts. Too many times process and paper work are the only things checked. I was involved with a major project concerning a bearing shield. The customer kept rejecting the parts until they were in a "line down" condition and a company engineer came to our site to solve the problem.
We personally checked over a thousand rejected parts, but could not find one which was out of tolerance. However, the incoming QC would not approve the shipment because the dimensional variation, although always within tolerance, was great enough that an SPC chart indicated the process was incapable of producing good parts. It was only when the customer's engineer got hold of his plant manager and explained that all of the assemblies sitting on his idle production line could be completed with parts that had been 100% inspected and found to be within tolerance that we were able to ship the parts.
My point, if the inspection procedure is flawed, it does not matter whether the parts were inspected or not.
Tool_maker, you made me laugh. Yes, I assumed that either people or automated machine vision/inspection systems actually test parts. Having covered the latter subject for a few years, though, I did hear a lot of stories about companies not doing a very good job of either designing good inspection procedures, or of using the data their inspection systems provided.
Ann, are the automated machine vision inspection systems superior to human inspection in the ability to detect flawed parts? Or, are they used because they become part of a total automation system?
Rob, automated MV systems are always superior to the human eye in speed. Ditto for accuracy when programmed correctly. Not all MV systems are for production lines, and the type and function depends on where on the line--or where else on the floor--the system is and what type of inspection it's doing. Then variety can be surprising. That said, MV systems are often, if not usually, put in place to go with existing automated systems, so have often been an afterthought. But that's often for larger manufacturers. Some smaller manufacturers aren't very automated, if at all, but install MV systems of some sort to improve quality control.
That's good to hear the MV systems are being used for improvement and not just a matter of replacing humans with a less expensive solution. There seems to be a lot of automation replacing humans lately. It will be interesting to see how IBM's Watson does in medical diagnostics.
Rob, one of the main reasons companies, especially smaller ones, put off investing in machine vision is the initial expense and hassle. They are not necessarily less expensive than human inspection except at the large scale. The cost differential in smaller systems seems to depend to a large degree on how much money they save in product returns and wasted materials from defective products.
That makes sense, Ann. A larger company will realize the incremental savings and improvement much more quickly. This is part of a trend in U.S. manufacturing where automation and the cost savings that goes along with it is helping to make U.S. manufacturing more competitive worldwide. Newsweek has a cover story this week on the efficiency of U.S. companies.
Rob, a recent study says that a growing number of large US manufacturers are looking at onshoring: bringing production back to the US. Although this article discussing it highlights plastics, the study is about all manufacturers:
Thanks for that, Ann. In another interesting piece of news, the productivity data released yesterday for the first Q of 2012, overall productivity fell 0.5%. However, manufacturing productivity rose 5.9%. Manufacturing in the U.S. is on a tear.
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