There are three type of waste that covered by lean namely, muda or non-value-adding work, muri or over loading of people or equipment that caused by mura or volatile workload. The significance of mura and muri is often misunderstood and underestimated.
The main focus of lean is not the tools, but the reduction of three types of waste which is Mura, Muri and Muda. The tools should expose problems systematically and used in the most ideal situation. As the result, the tools should maximize value by minimizing all wasteful activities.
Mura is volatile workload. It creates the ability to process at the ‘leveled demand rate’ quickly.
Muri is over loading of people or equipment and directly caused by Mura.
- Muda – The Seven Wastes
The Seven Wastes is a tool to further categorize waste, where is known as “muda” in Japan, was originally developed by Toyota’s Chief Engineer Taiichi Ohno and Shigeo Shingo. The Seven Waste consists of seven activities, plus one activity that just has been added.
Manufacture an item before it is actually required is called as overproduction waste or referred as just in case. Overproduction waste distracts the smooth flow of materials and actually degrades quality and productivity. Overproduction waste creates excessive lead times, results in high storage cost and difficulties to detect defect. It takes the focus away from what customer really wants, large batch sizes, poor people utilization and fake busy workers. As the result, it leads to higher cost on manufacturing plant, lack of customer focus, creates inventory, space utilization, hides inventory and also hide defects problems.
Waiting waste is occurring whenever items are not moving or being processed. Waiting waste may also refer to people that wait for work to be completed. In batch and queue manufacture, more than 99% of a product’s life will be spent waiting to be processed. Waiting waste is caused by poor material flow, long production run and huge distance between work centers. It makes most of a product’s lead time is tied up in waiting for the next operation and bottlenecks within operations.
Transporting or unnecessary movement of product between processes is added no value to the product but add more cost. Excessive movement and handling may cause damage and degrades of quality. Transportation waste may be difficult to reduce due to the perceived costs of moving equipment and processes closer together.
4. Inappropriate Processing
Many organizations often use expensive high precision equipment when simpler tools would be sufficient. High asset utilization is encouraged in order to recover high cost of this equipment. This often results in poor manufacturing or even plant layout because subsequent operations are located far apart.
5. Unnecessary or Excess Inventory
Any raw material, work in process (WIP) or finished goods which are not having value added may conclude as unnecessary or excess inventory. That is direct result of overproduction waste and waiting waste. Excess inventory tends to be identified and resolved in order to improve operating performance. Increases lead times, consumes productive floor space, delays the identification of problems and inhibits communication are problems caused by excess inventory.
6. Unnecessary or Excess Motion
Ergonomics are related to unnecessary or excess motion waste. Ergonomics are designing the workplace, tools, equipment, and work environment to fit the human operator. Unnecessary or excess motion occurs when individuals move more than is necessary for the process to be completed. It caused because no standard operating procedure, bad design cell and inadequate training. The primary guideline is to design the workplace to accommodate most individuals with regard to structural size of human body. There are also health and safety issues, which become a crucial problem for organizations today’s.
Defects are having a direct impact to the organization’s cost. Quality defects resulting in rework or scrap, quarantining inventory, re-inspecting, rescheduling and capacity loss are remarkable cost to organizations. Many organizations often have their total cost of defects in a significant percentage of total manufacturing cost.
8. In the latest edition of the Lean Manufacturing classic Lean Thinking, Underutilization of Employees has been added. People are organizations greatest asset, so organizations should learn to get the best out of them. It is only by has an optimal attention on employee’s creativity that organizations can eliminate the other seven wastes and continuously improve their performance.