By Thieu Mandos
At the packaging department of one of the largest lamp manufacturers, their high speed packaging line could not get a yield higher than 50 percent. The Italian manufacturer of the machine stopped its support after two years of trial and error, as it cost him already too much. The line was a source of irritation to management and the operators.
When I was assigned to the packaging line to improve the yield I didn’t know this history. The problem of the line was that in 30 percent of the cases, the products came out of their box again, direct after pushing them into a box. They fell into the machine causing a stop and damaged products. After each period of great trouble, the machine worked fine for half an hour and then the problems started again. When I turned down the speed of the line it worked fine. A little speed increase caused waves of complete breakdown followed by a short period of fine work.
At a test bench, the process of pushing the lamp in the box and pulling out the tool never failed. There were many experiments in modifying and polishing the pusher tool, nothing worked. Then there was a problem at the printing section of the line, the markings on the lamp were too bold. At that time, the problems with box-packing machine rose to an extreme level. A detailed analysis and a dose of good luck showed small damages in the marking, caused by the pusher tools.
I made the link between the wet ink and lamps sticking to the pusher. A long surfing session in Google brought the solution, Teflon-sticky-tape on the pusher! We shouldn’t polish the surface but change the tension characteristics of a material.
Polished steel has still a reasonable surface tension. You probably know the stick-slip effect between two polished surfaces. Teflon has an extremely low surface tension, preventing anything from sticking on it. The Teflon sticky tape is well known in the printing industry, as ink is very sticky and difficult to clean. The lamps were printed in the machine just before packing. When there was a continuous production flow, the ink on the lamps was still sticking to the pushers, and so they were pulled out the box. After a period of trouble, the lamps were drying in the buffer and transport, so there followed a wave of fine work, not related to the action taken. With the Teflon tape on the pusher we could pack the lamps with the ink still sticky and the line could run on its promised yield at full speed.
Thieu Mandos is a production engineer as well as a mechatronics designer with over 30 years of experience in the design and improvement of production equipment. He admires the combination of 6-sigma and KISS (keep it simple stupid) methods with which he has a lot of experience in his ham-radio hobby. In his designs, her favors multi-disciplined projects using analogies from one discipline to another.
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