Value-Stream Mapping in a Make-to-Order Environment
By Mike Rother Make-to-order, very high variety and custom-product situations are often mistakenly considered unsuitable for continuous flow processing and load leveling, since the work content involved in making each different product type varies too much. In fact, you can approximate continuous flow and achieve many of its benefits in most make-to-order processes, such as in production of custom items, stock picking in warehouses and even administrative (paperwork) processes. This is done by maintaining a First In, First Out (FIFO) flow through the processing steps and carefully regulating the quantity of work you consistently release to that FIFO chain of processing steps. In a make-to-order chain of processes, you typically have to send the schedule or production instruction to the first (leadoff) process. That scheduling information, often called a “traveler,” is then passed from one process on to the next as the material moves forward. Here is the problem: Companies tend to release maketo-order work by customer order. That is, each traveler equals one customer order. If one customer order is large then the traveler has a lot of work in it. If the next customer order is small then the amount of work in that traveler is light. Unfortunately, this means that travelers, or orders, tend to bunch up excessively between some processing steps. This leads to a loss of FIFO as individual processes select travelers based on setup efficiency and other factors. It is also very difficult to see if you are ahead or behind at any of the processing stages. Lean relies on fast response to abnormalities so that flow can quickly be reestablished, but by the time you notice that a process's in-box is overflowing, it is too late. The result is an unpredictable and unmanageable flow of work, difficulties in managing capacity, order expediting, peaks and valleys of work volume and late shipments. You usually can’t hold a...
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