Sunday, February 7, 2010

Seven Wastes|Waste of Waiting

In a previous post on how to implement lean manufacturing I discussed the seven wastes, within this post I will discuss the waste of waiting. A fairly obvious waste you would think, waiting for the previous operation, or the machine to finish what it is doing.

Why do people end up waiting? Generally they are waiting because the processes are not balanced, that is they don’t all take the same amount of time. Even in the best flow lines it is very difficult to have all operations perfectly balanced. But in a lot of manufacturing companies this is a major waste.

You see one machine starved of product as the previous process has not finished producing the large batch of components and the batch cannot be moved until all complete. You see people standing idle waiting for the fork truck to transport that large pallet of material. The operator on the machining centre watching the machine patiently while it completes its eight minute cycle.

Just go and stand in the center of your company and watch what is going on, how many times do you see people just waiting, or working slowly so as not to bring attention to the fact that they do not have enough work?

When learning how to implement lean manufacturing, you learn how to make the value flow at the pull of the customer. As I have already mentioned before when discussing Just In Time (JIT), the ideal would be to have a single piece flow, the product moving through each process when required by the customer. The idea at this point is to try to balance each operation so that they take as close as possible the same amount of time. If you go into a car assembly plant and watch the operators on the line, they all have the same amount of time to complete the work before the car has moved into the next section. If the work took too long then it would not be complete before the next section began their work!

Many of the other wastes contribute to the waste of waiting, one process will often be waiting for the previous as rework is completed due to the waste of defects and so on.

As to the operator waiting for his CNC machine to cycle for eight minutes or the injection molding operator watching his ninety second cycle, many companies now will have them operating multiple machines organized in a cell to utilize their time fully. But so many still have the operators stood there waiting “in case something goes wrong!” The operator could be loading the next products into an additional fixture, working on the next operations or running additional machines, but not just waiting – do you really want to pay someone to stand and watch a machine for the bulk of their day?

So if we are going to learn how to implement lean manufacturing we need to learn how to eliminate this waste of waiting. The easiest thing here is to look at our flow and try to balance it. Tools such as Heijunka can be used here to help with balancing the flow, more about the tools in future posts. Look at our scheduling within the factory, we often plan delays into the process! Look at the physical locations of machines and processes and try to bring them closer together. Reduce batch sizes to as small as possible, aim for single piece flow.

So if you are learning how to implement lean manufacturing and you walk into a factory and see people waiting everywhere you look, you can be pretty sure that they have the waste of waiting as one of their seven wastes. To return to the list of wastes use this link for waste elimination.

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