A big component of the Toyota Production System (TPS) is its identification of the categories of waste (or muda) in the typical production process. Getting rid of these seven wastes is the main goal of a lean production process. (Lean=No Waste.) This is the seventh in a series of posts describing each form of waste and where it can be found in everyday life.
The seven muda are Defects, Inventory, Motion, Overprocessing, Overproduction, Transportation and Waiting. This time we’ll talk about Waiting.
Waiting is probably the easiest form of waste to understand: Whenever people, equipment or processes are idle when they could instead be creating value for a customer, you are generating waiting-related waste.
In the traditional automobile factory, the production process often finds itself waiting for:
- Supplies: If supplies are not available in time to put them into a car, the process halts until they are available. (I saw this happen first-hand on a tour of a Ford truck plant, which ground to a halt in front of our eyes when a snowstorm on the East Coast stopped the flow of parts into the factory.)
- Equipment: If equipment has not been configured for the next task, the process halts until it has been reconfigured. This can take a great deal of time on the huge single-purpose machinery of traditional factories; Henry Ford’s automobile plants shut down for months when they had to be reconfigured for a new model.
- Completion of preceding steps: If the preceding step in a process is not completed in time, the subsequent step will be idle until it has caught up. Traditional factories use push-style systems that rely on guesswork and predictions to judge when steps need to be completed, and these forecasts often go wrong in the real-life chaos of the plant.
- Quality Inspection: When a production process produces a high number of defects, the product will be forced to wait for time-consuming quality inspection at various points in the process (especially at the end) to ensure that a defective product does not go out to customers.
- Rework: Similarly, when many defects find their way into a product during the production process, various parts or even the entire product must wait for extensive repair and rework to remove these defects before the product can be shipped.
- Customer Demand: If the customers do not want what the factory is producing, the factory will eventually be forced to go idle and furlough its workforce until demand picks up or the factory is retooled for a new product line.
Although it is often worthwhile to pause in a production process (to solve a problem, for instance), none of the above examples of waiting adds any value to the product for the consumer. On the other hand, ALL of the above examples of waiting add to the costs and headaches of the manufacturer. This is why waiting is generally seen as a waste by the lean perspective, and why its reduction or elimination is seen as an unequivocal gain for the production process.
Lean production techniques include a number of solutions for the problem of waiting:
- Pull-style coordination systems are used to make sure that supply deliveries and manufacturing steps are completed “just in time” for the subsequent process requiring them, and not a moment after (or before).
- Quick-change equipment procedures are used, such as the famous single-minute exchange of dies (SMED) that drastically reduced the time it took to reconfigure an automobile body panel press for its next task.
- An intolerance of defects becomes standard procedure. Any defects are quickly traced back to their source using a diagnostic technique such as the “Five Why’s,” and prevented in the future rather than being dumped downstream into subsequent processes. A lean process strives for such a low defect rate that almost no quality inspection or rework is necessary before products are shipped out to customers.
- Small batches of work are done and flexible multi-purpose machinery are used, allowing the whole process to be rapidly reshaped to match quickly-changing customer appetites. As a result, the workflow is stable, the process is responsive to its constituents, and mistaken predictions of future demand are unable to sideline the operation.
Although reducing waiting has many advantages, it is not easy. Running on the thin time margins found in lean production requires a great deal of trust in the process. Moreover, in the early stages of a lean transformation, waiting is often increased as the process stops continuously to deal with systemic problems. However, as the kinks get worked out, the opposite generally becomes true; lean production processes then become much less prone to interruption than more traditional processes and waiting becomes a negligible issue.
Taking this out of the factory and into everyday life, it isn’t hard to find examples where poorly-organized processes suffer from unnecessary waiting. Postponing necessary maintenance on household equipment can lead to long waits for repairs to be made to the car or lawnmower. Tolerating careless work in the kitchen leads the need to check and recheck food before it hits the table to make sure an important ingredient hasn’t been left out, pushing dinner later. Failing to run the dishwasher or laundry “until you get a full load” can lead to long waits for clean mugs or dress pants. And so on.
When considering the ways that waiting impacts everyday life processes and how it can be eliminated, it’s worth remembering that different forms of waste are usually connected. You cannot get rid of waiting while you still tolerate a lot of defects, because defects lead to waiting. Excess motion or transportation also lead to waiting, as do all of the other forms of waste in some way or another.
There are surprising and revealing connections that always appear when you start to scratch beneath the surface of any kind of production waste and start to get lean.