Muda is a Japanese word that translates to waste. It describes a concept of being useless, unnecessary, or idle. The concept that waste must be eliminated in a process is a driving concept of the Toyota Production System and Lean manufacturing. Waste is a non-value-added task (NVA) within a process. Some types of waste are easier to identify than others, which is why Lean Six Sigma deploys tools such as value stream mapping. By understanding a process at all levels, teams are more likely to identify various forms of waste. According to Taiicho Ohno, chief engineer for Toyota, there are seven types of waste in Lean or waste, or resources that are commonly misused and mismanaged: correction, overproduction, over-processing, waiting, transportation, inventory and motion.
Correction
Also known as waste of rework, this first type of waste in Lean often plagues organizations that are keen on traditional quality programs. In a desire to eliminate defects from the end product, organizations institute in-process quality checks that route work with defects back for correction.
While rework might be necessary in some cases, especially if materials are particularly valuable and work is worth saving rather than scrapping, it is still waste in the process that should be identified and analyzed. When rework occurs, it increases overall process time and uses additional labor and materials to create a smaller number of products or outputs.
To eliminate rework or correction, organizations must use a twofold approach. First, the root cause of the rework—that which is causing the errors—must be addressed. Is further employee training required? Could a process be changed to make it more mistake proof? In some cases, the principles discussed in later posts on process control, including a strategy called a poka yoke, can be deployed to make it more difficult to create defects than to not create defects during a process. When defects are avoided, rework is also avoided.
In addition to addressing the root cause of errors, organizations should create quality steps that reduce rework waste. This method sometimes causes a problem of culture, though; there is a feeling among leaders and staff that the first team or first team member should be held accountable for the error. One way of seeking accountability is to have that person correct his or her mistake. While reworking errors can be a good training method when time and resources allow, it isn’t always feasible and doesn’t make for an efficient daily process. Instead, employees might be more efficiently held accountable through goal-setting and metrics for the greater good of the organization as a whole.
Overproduction
Overproduction is one of the easiest forms of waste to spot, as it tends to result in what we commonly think of as waste. Overproduction means a product, part, or service was produced too fast, at the wrong time, or in too much quantity for the process.
Overproduction is most often associated with tangible outcomes from a process, though these outcomes don’t have to be final, or “end products” of said processes. Overproduction can also exist with regard to reporting, digital assets, and preparation for processes. Almost anyone working in a business environment is familiar with reporting requirements—just as almost anyone who has created reports knows the unfortunate truth that the information often goes unread. Creating reports no one reads—or creating highly detailed reports when an overview would suffice—is overproduction.
The key to eliminating overproduction is planning of forecasting if you have the luxury of data. For example, in order to improve the Just in Time (JIT) of McDonald’s, they have started the Made for You initiative to simplify the food preparation process and it is integrate with the ordering system to forecast the high selling products. Hence, the kitchen will able prepare the food based on results of the forecasting system.
Over-process
Over-processing occurs when an employee or process inputs more resources into a product or service than is valued by the customer. This could occur because of ignorance, a desire for perfection, or even excitement. Sometimes over-processing occurs because an employee hasn’t had training on the most efficient way to handle a task. Other times, it occurs because an employee or process is more thorough than is worthwhile. A goal of any process should be to do just enough useful and necessary work to ensure that customer or end-user expectations are met.
A value stream mapping or known as VSM, is a good tool for identifying any points of over-processing. Any part of the process that doesn’t provide value could be considered over-processing; when the process features a series of linked events and none provide value, it’s even more likely that over-processing is occurring.
In a true Lean process, every step of a process provides value, but it can be tricky to determine when value is not occurring. Quality is important to both the success of the process and the end customer, for example, but the customer doesn’t care, or usually even realize, that your process is imbued with quality checks throughout. They care instead that a process takes 10 minutes longer because of those quality checks—teams have to dig deep into processes, metrics, and customer voice to determine if those 10 extra minutes are providing enough added value to cover the annoyance or loss of customer because of the added time. This knowledge is all ascertained through data collection and statistical analysis tools from Six Sigma methodology.
Waiting
Waste of waiting refers to any idle time in a process, whether that idle time is for machinery or people. In other words, an employee or machine is working below capacity or is not working at all due to waiting on inputs from another part of the process. Waiting occurs when steps in the process are not properly coordinated, when processes are unreliable, when work is batched too large, during rework, and during long changeovers between staff or machines.
You can eliminate waste of waiting within many processes by balancing machinery, people, and production. The process will only perform as fast as the slowest link; beefing up the production of a single element does nothing for the whole, so teams must work to balance and improve the entire process. The bottleneck issue can be identified during Gemba Walk and VSM process.
Transportation
Waste of transportation is similar to waste of motion except transportation involves the movement of outputs, products, or resources. It is sometimes also referred to as waste of conveyance. For example, in a doll-making facility, if the glue that binds doll eyes to doll faces is kept in an inventory room and carried, as needed, to the process, there might be waste of transportation.
If an expense report is printed and then carried to a manager for approval who then routes it in an inner-office envelope to a director, who then carries it to the accounting department, the waste of transportation is occurring. This is especially true because appropriate technology used correctly and efficiently lets organizations handle expensive reporting via computer with little conveyance at all.
Physical transportation is often easier to locate and address than digital transportation. A spaghetti diagram, process map, or value stream map can help you identify areas where waste of conveyance might exist. Spaghetti diagrams work well in physical transportation situations, and process maps help you identify transportation in digital settings.
Once you identify waste of transportation, you can eliminate it by making changes in the process, layout, or inventory requirements for the work. If transportation waste isn’t due to poor process design or work-area layout, it might be related to another form of waste. transportation is often seen in processes that involve a lot of correction, because work is transferred back and forth between staff or areas. By addressing the waste of correction, you often also address the waste of transportation.
Inventory
Waste of inventory is similar to waste of overproduction; in fact, overproduction can cause a waste of waiting and inventory. Waste of inventory occurs when materials or inputs stack up before a step in the process; this phenomenon is also called a bottleneck.
While inventory waste can occur in any process, it is especially common in processes that operate in batches. Traditional lean wisdom says to avoid batch process – processes that involve creating a certain number of products or outputs before pushing them down the line. Reducing batch size lowers lead times—the time it takes to deliver the end product. It also reduces the amount of inventory that occurs before each step of the process.
While Lean mindsets usually push a batching-is-bad mentality, you can’t always avoid it—and reduced lead times on individual outputs aren’t always a primary goal of a process. Consider a baker who is preparing an order of one dozen cupcakes. He could prepare the order as a batch, or he could prepare each cupcake separately. Obviously, mixing the ingredients and baking the cupcakes as a batch makes more sense. Decorating them as a batch also works well—the baker might frost all of the cupcakes, add piping to all the cupcakes, and then top all the cupcakes with a candy. Batching works for the baker 12th because the first cupcake is not going to leave the bakery before the is finished—they all move together because they are considered a unit.
You can also reduce waste of inventory by understanding a process and basing inventory decisions on historic metrics. A baker doesn’t whip cream for seven pies if he or she only intends to make two.
Motion
Waste of motion has to do with how employees themselves move during a process. This type of waste is often relevant to people-powered processes in manufacturing, warehousing, shipping, delivery, or industrial fields, but waste of motion can even crop up in processes that are automated or known as Jidoka in Lean.
Streamlining company processes eliminates waste of motion, and data must be collected and analysed to identify unnecessary movement. A common tool used in manufacturing and similar environments to track movement is known as a spaghetti diagram. Begin with a basic, bird’s eye drawing of the workspace. Include furniture, computer stations, machinery, doors, and walls. Observe an actual process, tracking any and all movements with a line on the diagram.
When drawn correctly, the diagram looks like a string of spaghetti fell onto your page. Once the process is complete, you can look at the diagram to see where the movements cross paths multiple times or go out of the way unnecessarily. This helps you find opportunities for streamlining the movement in a process—sometimes, it’s as simple as moving furniture or resources around to reduce unnecessary movement. It’s worth noting that a spaghetti diagram only reveals a snapshot of movement in time; sometimes, it is worthwhile to complete more than one such diagram at different times of day or with different employees to reveal an overall picture of a process and possible waste.