While I worked for a US battery manufacturer, we ran into a couple of difficulties that were hard to track down. In one instance, the company ran into big problems with its D-size cells experiencing chronic gassing, and asked its Canadian branch plant to supply them with 50,000 to 60,000 units to meet market demand.
To fulfill the demand, the plant added a new supplier of electrolytic deposited manganese dioxide that offered a competitive price. The supplier used lead electrodes in the process, and when the material was scraped off the electrodes, some lead content came with it.
Lead in an alkaline cell gases like crazy, blowing the vents and making a mess of everything. Fortunately for the company, the problem was discovered before the US cells found their way into the consumer market. The previous supplier of manganese dioxide used carbon electrodes. When they are scraped, it does not affect the cathode performance in any way.
Lessons learned? Do not always assume processed material is always compatible with whatever you're producing. It also suggests you should periodically audit your suppliers just in case they change their process in a way that could affect your product.
The next problem occurred with the C-size line. The crimping operation was all over the map. The tooling manager suggested that the out-of-round condition of the cans was causing the problem, and that the tolerances should be tightened. This caused a lot of consternation since the cost of the cans was calculated to a fraction of a cent, and they came in as a cluster in cardboard containers.
Giving the tool manager the benefit of the doubt, I deliberately squeezed several cans out of shape -- some egg-shaped, some elliptical -- and fed them into the crimping machine. The QC Inspector was dumbfounded when each one of these distorted cans produced a perfectly gauged finished product.
When asked what my theory was, I answered that I did not have one -- I wanted to determine how much distortion would screw up the machine and was astonished to witness the opposite. My analysis later showed that when the caps were placed in the distorted cans, they were consistently locked in place, and when the crimper indexed, they were never jostled loose. As a result of this, the tolerances were relaxed, and distorted cans could be used as received -- all leading to a cost reduction.
Tooling was added to deliberately distort cans. With the increase in placement reliability, the machine rate was increased, and the overall yield was improved, providing further cost reductions for the product.
Lessons learned? Indulge your eccentricities (but not all the time). You never know what will emerge. When troubleshooting, the goal is to do anything to the process and observe the results. If matters get worse but still stay within the family group of the problem, you will have a clue as to how to fix the problem. If your action immediately improves matters, and your colleagues marvel at your astuteness, just break into the song "I Believe in Magic." Often, management will insist that procedures be written up. That took much more time than necessary.
This entry was submitted by John Mitchell and edited by Rob Spiegel.
John Mitchell was self-employed through Mitchell Research. He worked mostly in aerospace design/liaison engineering with excursions into product/quality engineering on batteries, forensic engineering analysis, and Hovercraft. He is now retired and working on vertical axis wind turbine systems and small electric vehicles.
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