Muda
Muda is a Japanese word that means “waste.” The key point about muda is this: any expenditure of effort or resources that doesn’t add value is waste (muda) and should therefore be eliminated.
There are seven types of muda:
1. The Muda of Over-Production:
This is the production of anything (work-in-process, finished goods, etc.) in greater quantities than needed. If a plant manufactures more than it needs, it will expend manpower and resources that won’t be channeled into immediate profit. Inventory will accumulate, causing additional drains on the company’s resources.
The muda of overproduction is frequently called “the worst kind of muda.”
2. The Muda of Transport
A manufacturer’s end customers pay for only value-added processes--- they don’t pay a manufacturer to move parts around from one line to another, or from one storage facility to another. Some transport is of course necessary, but it should be minimized. This means designing production lines and materials flow paths in a way that minimizes the distances between workstations and temporary storage sites.
3. The Muda of Waiting
The muda of waiting occurs when employees cannot perform value-added work because they have to wait on incoming parts or materials, or when they are tied to a single machine or process that has a long wait time built into it. The muda of waiting can also occur when machines break down.
The muda of waiting is best avoided through the proper alignment of work processes, and consistent machine maintenance (to avoid machine downtime.)
4. The Muda of Motion
Work processes should be designed so that employees don’t have stretch, bend, or walk around to get the tools or materials that they need. Unnecessary motion is a waste, and it can also expose employees to ergonomic issues.
5. The Muda of Rework
This muda occurs when workpieces must be reprocessed or repaired because of defects. Rework increases production costs, without adding any profit.
The key to eliminating rework is build quality into each process, using tools like poka-yoke.
6. The Muda of Over-Processing
Suppose that a manufacturer of automotive components is making a particular part according to a blueprint. The blueprint calls for five threaded holes, each with a depth of 4-mm, on the surface of the component.
Now suppose that operator in charge of machining the holes makes each one 6 mm deep. Is this better than making them 4 mm deep? No. This is wasteful over-processing. The end customer paid for a 4-mm hole, not a 6-mm hole. Making the holes 6 mm deep will only increase cycle time, which eventually increases production costs--- without any accompanying increase in profits.
7. The Muda of Inventory
The muda of inventory can include any kind of excess inventory (materials, components, work-in-process, or finished products). The muda of inventory:
-Has an immediate, negative impact on the company’s cash flow, as it ties up cash for an indefinite period.
- Forces the company to spend additional funds on storage space, warehouse personnel, etc.
- Makes FIFO inventory management more difficult