Overview

One of the basic tenets of kanban (and for that matter the entire Lean philosophy) is that once you implement, you should continuously improve the kanban by reducing the kanban quantities. However, the only way to reduce the quantities, without jeopardizing the customer is to improve the process or reduce your buffers. To improve the process you must reduce scrap, downtime, or changeovers. To initially illustrate this point, we presented four graphs in Chapter 4 that showed the impact of these process improvements on the calculated quantities. (Figures 9-1 to 9-4 show these same graphs.) Reducing the buffer requires you to address your safety stock and to reduce supplier lead-times.

Accordingly, we have developed this chapter to discuss how to improve these three process areas and to discuss options for reducing buffers. Our first recommendation, however, is to assess your process and determine which of the three process areas will make the most significant improvement in the kanban quantities. A simple way to make this determination is to incrementally change each factor in your original kanban calculations to see how the replenishment interval changes.

Figure 9-1: Impact of Reducing Scrap on Kanban Quantities.

Figure 9-2: Impact of Reducing Downtime on Kanban Quantities.

Figure 9-3: Impact of Reducing Changeover Times on Kanban Quantities.

Figure 9-4: Impact of Reducing All Three Factors on Kanban Quantities.

Once you have determined where to focus, then we recommend you develop a systematic plan for improving the kanban. This plan should also include long-term goals...