In general, when you try to apply the TPS, the first ting you have to do is to even out or level the production. Leveling the production schedule may require some front-loading of shipments or postponing of shipments and you may have to ask some customers to wait for a short period of time. Once the production level is more or less the same or constant for a month, you will be able to apply pull systems and balance the assembly line. But if production levels – the output – varies from day to day, there is no sense in trying to apply those other systems, because you simply cannot establish standardized work under such circumstances.
So says Fujio Cho, President, Toyota Motor Corporation.
Jeffrey Liker’s book, The Toyota Way, Jeffrey explains how it’s not possible to run a lean operation using Dell’s build to order model. One day you will have many customer orders, forcing your staff to work beyond capacity. The next there will be much fewer orders (and your people will be idle).
Toyota found that to work lean, they needed to even out production.
They do this by focusing on the three M’s of waste:
1. Muda – Non-value added work
2. Muri – Overburdening people or equipment
3. Mura – Unevenness
When most people start with lean, they tend to focus on Muda because it is the easiest to identify and eliminate. Unfortunately, fixing muda by itself can cause greater stress in the organization as now spikes in customer demand forces people to work harder. People become overburdened, equipment breaks down, and people abandon the lean initiative.
As Taiichi Ohno describes it:
The slower but consistent tortoise cause less waste and is much more desirable than the speed hare that races ahead and then stops occasionally to doze. The Toyota Production System can be realized only when all the workers become tortoises (Ohno, 1988).