Continuous Improvement, Toyota Production System

The Seven TPS Wastes (Muda)

Taiichi Ohno, considered the father of the Toyota Production System (TPS), identified seven types of muda. In a previous post, we discussed the Three TPS wastes, namely mura, muri and muda. Click here to view the post.

To refresh:

  • MURA pertains to inconsistency, unevenness or irregularity. This type of waste can be eliminated by keeping little or no inventory.
  • MURI pertains to overburden, strain, unreasonableness or absurdity. This type of waste can be reduced by ensuring standardisation.
  • MUDA pertains to non value-adding work or waste. This type of waste can be reduced by critically reviewing work processes and then redesigning them to eliminate any non value-adding work.

Muda can be further unpacked into the following seven wastes:

  1. Transportation: When we look at all the processes in a manufacturing production line that contribute towards the creation of an end-product, transportation isn’t really one of them. Sure, transportation gets products from the production facility into the hands of the consumer and is thus a very important and necessary link in the supply chain. However, transportation doesn’t transform or add to the product. Each time the product is moved (transported), a cost is incurred, and there’s a risk of damaging the product or delaying delivery. It’s therefore important to scrutinise all transportation processes to eliminate unnecessary steps.
  2. Inventory: The existence of inventory means capital has been spent (in order to acquire the inventory), but income has not yet been realised by the sale of this inventory. Inventory is not only assembled stock items, but can be work in progress (WIP), unassembled parts, or even raw materials. It’s important to look at the various types of inventory to find where non value-adding work can be eliminated. Perhaps machine breakdowns or changeovers/setups cause large stoppages in WIP. Inventory also takes up storage space, which comes at a cost too.
  3. Motion: Not to be confused with transportation, motion pertains to workers, equipment or producers. During motion of any of these three, the risk of safety, wear or damage increases. As parts move through the production process, risk of damage, etc. can also add expenses to the production process.
  4. Waiting: Also known as work in progress (WIP), this waste is concerned with goods that are not currently being transported, nor being assembled or processed. These waiting goods are wasteful in much the same way as inventory sitting on shelves – while they are waiting; no value is being added to them. It’s not to say that we can eliminate all waiting, but that these WIP situations should be reviewed to ascertain the cause of hold-ups: can delays or waiting times be decreased? Are we producing too much? Do we have staff or machine shortages that are causing bottlenecks?
  5. Over-production: Probably the worst of all muda, over-production can, in essence, cause all of the other mudas. Over-production happens when more product (supply) is created than required by customers (demand). This creates excess inventory, which, as stated earlier, comes at an additional cost because inventory must be stored, not to mention the costs associated with the other mudas. Over-production often occurs when manufacturers produce products in batches. Though batches may make sense in terms of economies of scale, the dichotomy lies in the fact that batch creation can take longer, during which time consumer demand could change.
  6. Over-processing: This waste occurs when more work, effort or machine investment is used than is actually required/necessary to produce the product. So for instance, if one of the machines or tools used in the production process is more complex, sophisticated and expensive than it needs to be, this constitutes waste.
  7. Defects: A defective product, whether the defect is picked up by the customer, retail outlet/agent, or on your own premises during the quality control process, constitutes waste. There is waste in terms of the time required to repair, disassemble and reassemble the product. In instances where the product is defective beyond repair, or possibly in the instance of the food industry where food standards might dictate that certain defects must result in disposing of the defective product, this constitutes even more waste.

Looking at muda in these separate seven parts, helps us to really unpack and scrutinise our processes in a more thorough way than merely saying “where can we eliminate waste?”. The seven muda force us to look deeper into our processes. By suggesting the various types of waste to look out for (as above), work teams are more likely to pick up more latent wastes and come up with creative ways to eliminate or minimise them.

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This post is part of a series covering continuous improvement tools and techniques. We believe that for these techniques to be sustainable, they shouldn’t be implemented in project-based silos or once-off improvement projects. Rather, they should be implemented as part of a process-driven integrative improvement system.



  1. Pingback: For Defect Severity Levels, Less > More | The Frugal Cubicle - July 22, 2013

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