The seven deadly wastes

Everything that we do that does not directly contribute to create customer value is waste. The “seven deadly wastes” that we should look out for are:

  1. Transport
  2. Inventory
  3. Motion
  4. Waiting
  5. Over-processing
  6. Overproduction
  7. Defects

You can easily memorize these seven using the acronym TIMWOOD. The quiz at the end of the first lesson has actually listed an example for each of the above in the dishwasher task. Can you still piece them together?

Detecting waste is often not easy, and sometimes outright waste is often hidden. For example, overproduction in food production is easy to spot when looking into the waste bin behind a supermarket, but where do we have overproduction in when unloading the dishwasher? Waste is also so difficult to detect, because it almost always seems necessary. It only becomes waste once we see a better way of doing things, such as when placing the cupboard next to the dishwasher instead of wastefully transporting dishes across the kitchen.

Transport is part of every manufacturing process. It includes moving items from station to station during an assembly process, moving items from a warehouse, or moving parts from another country. Transport could also be moving parts back and forth between different manufacturing centers all across the globe. Transport is very easy to spot and can often be reduced. In our dishwasher unloading example, we reduce transport by thinking about clever ways to store the different categories of items. As walking back-and-forth takes a lot of time, we literally get a lot of mileage by focusing on transport first. Transport from one facility to another often has very good reasons, however, making reducing it much harder. Getting rid of it often requires solving a lot of other problems first. For example, “reshoring” a process from China might only make sense once lean thinking has be applied elsewhere. Removing intercontinental transport is also the most rewarding, however, as huge additional benefits such as shorter lead time, lower inventory, and a reduced carbon footprint might come with it.

Inventory is necessary to make anything. Reducing the number of parts that need to be kept in stock (and ordered) can often lead to large savings. This can be accomplished by simplifying products, making them more similar, or cutting an entire line of products. Another form of inventory is “work-in-process” (WIP), essentially inventory that has been partly processed. A large amount of WIP sitting on the manufacturing floor is usually a sign of something not going optimal. WIP cost you twice: capital cost and labor already invested and missed opportunities, because things are not ready for sale. In the unloading example, reducing your inventory of dishes will help you to use more efficient storage (less transport) and improve efficiency by better stacking. Dirty dishes waiting in the sink and the dishwasher are also WIP.

Motion is everything a worker does with their body. Motion always takes time, but sometimes even hurts. Can you arrange a work cell that minimizes bending, reaching, and turning? Can you improve the design of an assembly so that it requires less motion? In the dishwasher example, problematic motions are bending down during unloading and reaching up when storing items. In practice, optimizing motion can be achieved by leveling surfaces, or rearranging the location of tools. Once this is done, motion can be further reduced by watching video footage of workers and comparing different approaches to do a task using a stop watch.

Waiting happens when workers need to wait on each other or on a machine. Waiting is often unavoidable as it is difficult to “balance” the different times steps take in an assembly line. In the dishwasher example, an example of waiting has been to unload the machine with a partner. Unless the loading and storing motions take the same amount of time, one has to wait for the other. Waiting can be reduced by systematically recording the cycle times of all steps in a process and carefully adjusting workload, splitting lines, or adding automation at critical bottlenecks.

Over-processing often arises when there are product variations with different features and it is easier to treat parts uniformly. For example, different product variations might need mounting holes at different locations. It might be easier to drill all possible holes into every part, thereby reducing inventory, than managing the different flows of parts. In the dishwasher example, overprocessing happens when dishes that are not actually dirty are washed. This might make sense when inspecting every item would take too much time. Over-processing can be reduced using appropriate process control software that tracks and routes individual parts.

Overproduction is product and WIP that need to be thrown away for one reason or another. In a more extreme view, overproduction is everything that hasn’t been sold yet. Overproduction usually arises from trying to anticipate customer need or batch processes with poor yield where making more than intended is the only way to be (relatively) sure to be able to fill an order. Overproduction can also happen when the wrong metrics were applied such as “maximize machine utilization” . In the dishwasher example, overproduction are items that have been stored, but get used right away. Here, a lot of labor could have been saved by taking them directly out of the dishwasher when using them.

Defects are parts that break anywhere during the process. This could happen during material handling, machine failure or defects in the inventory. Precautions can be taken to minimize defects, for example by cushioning storage containers, providing gloves to the workers that increase their grip, or testing parts prior to assembly. Defects can also be decreased by reducing transport, inventory, motion, over-processing and overproduction, and sometimes even slowing down (increasing waiting) might be worthwhile.