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Michael Balle

Michael Ballé: Pick to light and learning to teach Jidoka

By Michael Balle, co-author of The Gold Mine and The Lean Manager - Last updated: mardi, août 10, 2010 - Save & Share - Leave a comment

It’s not 100% pure jidoka as Art would have it because the machine itself never detected the defect – the operator still did, but I recently saw an application of “pick-to-light” in a semi-automatic assembly process: this is an automated line where operators fit parts into the machines which then assembles the product on palets, to end up with a final product.

In this process, the plant had greatly progessed by simply noting defectives on the production analysis board, reacting rapidly and building up pareto charts to help them focus on the main problem. These actions allowed them to reduce considerably the ppm (defective parts per million) coming out of the line, but not, unfortunately, the customer complaints. Customers would receive far fewer bad parts in numbers, but one-offs still got through the final inspection and regularly reached the customer, in particular platic hole-fillers (no functional impact, but part of the requirements) were often missing.

what the plant then did is instal “pick to light”: a captor was set at each location where operators had to take a part and a light. small light bulbs lit up in sequence to show which component had to bne picked up and if the operator’s hand did not break the sensor curtain, the automatic line would stop. The idea was that it would help, particularly with several variants of the product going through the same line (hence different components).

As Art points out, this enabled the supervisor to have a new look at his own process. The assumption had been that operators were forgetful and simply skipped parts, but what the pick to light process showed is that operators were frequently interrupted by having to turn around and refill the line from sidel-line parts bins (brought by a small train). They made this decision randomly, not necessarily at the end of any one part, and risked starting the cycle back further than they should. No one had previously realized beforehand quite how often operators moved away from the station during one shift.

As problem solving progressed, several other technical processes came to light – in particular issues with label printing, particularly after changing the paper roll, and so on. Stopping the process is the key to finding what goes wrong, as a starting point to the five whys.

all in all, an encouraging story. Now for the down part: the plant still hasn’t replicated this technique on any of its other eight lines. Although the technique clearly delivered, it is felt that it was “over and above” effort, and only the most advanced supervisor could handle it. In essence, although this plant is advanced enough to experiment with jidoka techniques, it’s still a far cry from being part of the culture. Considering that this plant has been operating with a pull system ( a real one, no parallel computer system) for years, this serves to reinforce Art’s earlier point.

The Jidoka challenge is not just the plant’s, but ours as well: as lean experts how determined are we at teaching Jidoka? And how good are we at it?

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