By Xavier Perrin (firstname.lastname@example.org)
In a recent issue of the newsletter of the French Supply Chain Magazine (#2600 ; 20/11/2017), I found an interesting topic for illustrating the principle of muri. Muda is a well-known concept of lean, which is translated by "non-value-added activity". Lean thinkers also learn to identify mura and muri. Mura means "unevenness of operations", and muri means "overburden equipment or operators by requiring them to run at a higher or harder pace with more force or effort for a longer period of time than equipment designs, and appropriate workforce management allow"*. This last principle could be difficult to evaluate. The following example from the newsletter could help. It is reported in an article entitled "When Flows Loosen…" that during a seminar organized by a health insurance institution and an association which promotes best practices in logistics, "Several major distributors, logistics providers, and carriers, said they would be positive for longer delivery lead times and less frequent orders, in particular for products whose shelf-life do not justify fast deliveries. Such evolution do not alter the revenue, nor quality in service, but it should be accompanied by concrete measures like consultation, anticipation, discussion, and sharing of experience." A manufacturer said: "not only it let us some leeway for our operations, but also for better service to our customer without stressing the whole supply chain."
When several actors of a supply chain invest some of their valued time for attending a seminar on that subject, it means that systematically reducing delivery lead time doesn't systematically create value. On the other hand, it can stress the resources and increase the negative consequences like bad working conditions, errors, induced variability (mura)… all that situations which eventually lead to non-value-added activities (muda).
Muri was a constant concern of Taiichi Ohno, the main contributor of lean. As he pushed a plant manager to remove a conveyor between two production workshops because this equipment created unnecessary inventories, he was highly anxious of the impact of the solution on operators' working conditions. When he came back to that plant a few months later, before even considering the solution that the plant manager started to present, his first question was about operators and their perception of that solution. He insisted on the fact that any solution which would deteriorate working condition is a bad solution (**).
It is probably because many managers ignore this key principle of lean that lean have got so bad reputation in some companies…