Runners-Repeaters-Strangers

In assembly operations, we need a Plan For Every Part (PFEP). For each purchased component, we must specify suppliers, choose order and delivery patterns, organize all actions taken inside the plant to deliver it from the receiving dock to the assembly line.

Setting a plan for each one of the thousands of purchased items is a daunting task. It helps if you can group the items in a handful of categories. Policies by category may not be as fine-tuned as for individual items but they are an improvement over “one-size-fits-all.”

To make it easiest to do what you do the most frequently, a natural criterion for categorizing purchased components is frequency of use. Once you have sorted the purchased components by decreasing frequency of use, however, you need to set category boundaries that make sense for assembly.

Rather than using arbitrary cut-offs, we base thresholds on the proportion of the demand that can be built completely as a function of the frequency rank of components. A point on this plot means, for example, that 50% of the demand can be met using only the 100 most frequently used components.

We explain how we use this chart to categorize components as Runners, Repeaters, and Strangers. Then we show how we generate it from bills of materials and a product demand. We end with actual examples from several factories and recommendations on communicating these results.

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