Lean Manufacturing
By: Tompkins Associates

  The following material is the second in a series of information about lean manufacturing provided by Tompkins Inc., a total operations consulting firm based in Raleigh, N.C.

  A pull system is a lean tool focused on the reduction of work-in-process inventory (WIP). The concept was originally borrowed from American grocery stores where empty spaces on product shelves signaled the clerk to restock.

  In a traditional batch system, each batch process in the operation pushes as much product as possible to the next batch process as they are measured primarily on output. In a pull system, succeeding batch operations, where they still exist, call to the previous operation for more WIP inventory. Only a predetermined amount of WIP inventory may exist between operations. Once this amount is reached, it may be necessary to stop the preceding operation, unless it is a bottleneck operation.

  Even so, the procedure may still dictate that it be stopped. A visual signal or kanban is a tool used to promote a pull system. The kanban may be a card, an empty bin, a lamp, or a flag. The kanban signals the preceding process that more WIP inventory must be delivered to the succeeding process. Production rates determine what time constraints exist with ...

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