Clean Can be Lean, Part II
Edward Kanegsberg
A key premise for a process step to be lean is that it be value-added. Previously, we highlighted three process issues: rework, scrap, and latent failure. All illustrate ways in which inadequate or inappropriate cleaning can result in costly processes or costly consequences, the antithesis of lean manufacturing.
Cleaning isn’t always lean. Sometimes, a cleaning step is a “motherhood” process; you don’t really need it. This leads management to suspect that no cleaning step is really necessary. Lean principles can be applied to the cleaning process itself. For each process, the following questions can be asked:
a. Is each step value-added? If a step does not provide value, then it provides cost without benefit and should be eliminated. To determine the value, consider the cost of NOT performing the step. If eliminating a step makes the process less reliable, then it is most likely a value-added step. You can then still ask the question, “Can I obtain the same benefit at a lower cost by modifying this step?”
b. Is the order of steps appropriate? Sometimes in manufacturing processes, later steps can completely undo the benefits provided by an earlier step. With cleaning processes, ask “Is this the right time to perform this cleaning step?” Obviously, if the next step in the process requires removal of contaminants, this is the time to remove them. Sometimes, however, it can make good sense, both technically and economically, to perform a cleaning step before it is really needed. In these cases, make sure that the intervening steps don’t countermand the cleaning step.
c. How clean is clean enough? The answer to this question can vary greatly during the manufacturing process, depending on what is needed to perform the next step or next series of steps. Not only does over-cleaning cost more in labor and time, there are the costs of additional cleaning chemicals and waste disposal. In addition, since a cleaning step alters the surface of the part (ideally only by removing an unwanted contaminant), there is the potential of surface damage, removing MORE than just the contaminant.
Note: An expanded version of this article, with examples, was presented
at CleanTech2005, during National Manufacturing Week, March, 2005,
Chicago, IL.
