Muda is a Japanese term meaning futility, wastefulness, or uselessness. In the context of Lean manufacturing, muda is a key concept as one of three types of waste (muda, mura, and muri) identified by the Toyota Production System. Muda refers to the seven wastes commonly found in Lean manufacturing as identified by Taiichi Ohno:
- Transportation: Unnecessary movement of products. Products are more likely to become damaged or lost during transportation and if it is not necessary, will not add any value to the product or for the customer.
- Inventory: Inventory includes raw materials, WIP, and finished goods. The longer a product sits in one of these states, the more wasteful it is. It disrupts the workflow while not adding value for the facility, leads to longer lead times, and can result in damaged or defected products.
- Motion: This is not the motion of the product, but rather the unnecessary movements of workers that are wasteful or harmful. This may lead to strain injuries for workers, downtime, or equipment breaking down due to wear and tear.
- Waiting: A product not currently being processed or not in transport is considered to be “in waiting.” When it sits waiting, the workflow is interrupted and the value of the product decreases.
- Overproduction: Producing more than what is required is one of the worst kinds of waste. It can hide defects in products while taking up important storage space and making it more difficult to manage.
- Over-Processing: Offering a product or service that exceeds the requirements of a customer can be seen as over-processing. It takes longer and requires more money than required, making it wasteful.
- Defects: Products that do not meet company standards (defective) will likely need to be reworked or scrapped, wasting the resources that have already been used thus far. It adds cost to operation but does not add value for the customer.
Other wastes of Lean include Mura, the unevenness and irregularity of production levels, and Muri, overburdened employees or equipment.
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