The 8 wastes or "Muda" of Lean with examples in production and maintenance

8 wastes of Lean manufacturing

Waste reduction (mudas in Japanese) is a central concept in the Lean philosophy which seeks to minimize them while maximizing productivity and increasing customer satisfaction.

Here are the eight types of Muda classically identified:
  1. Overproduction: Producing more than necessary or before it is necessary. This is often considered the worst waste, as it leads to other forms of waste, such as excessive inventory and unnecessary use of resources

  2. Waiting: Time wasted while waiting for the next step in the production process or for part of the job to be completed.

  3. Transportation: Unnecessary movement of products from one place to another. These movements do not add value to the product and may even cause damage or delays.

  4. Overprocessing or over-quality: Doing more on a product than the customer requires. This may include implementing additional features that customers do not like or use.

  5. Excess Inventory: Any quantity of materials, components, work-in-progress, or finished goods in inventory that exceeds what is strictly necessary to meet customer demand. Excessive inventory may lead to unnecessary costs such as purchase cost, storage cost, management cost, and also may hide other problems in the production process.

  6. Unnecessary movements: Unnecessary movements by employees during the work process. These moves do not create value and can increase production time and risk of injury.

  7. Defects: Production that does not meet quality criteria and requires repair or reworking, or is wasted outright.

  8. Non-utilization of talents: Not fully utilizing the skills and talents of employees. This waste is often overlooked, but can be very costly in terms of lost motivation, ideas and creativity.

7 Lean wastes initially, 8th Muda added later

The original seven forms of waste (muda) were identified by Taiichi Ohno, the engineer behind the Toyota Production System (TPS). These seven mudas include overproduction, waiting, transportation, overprocessing, excessive inventory, unnecessary movement, and defect production.

It was later that the eighth form of muda, the non-use of talents, was added. The idea of wasting talent was discussed and gradually incorporated by various companies and Lean practitioners in the late 1990s and early 2000s.

The reason for adding this eighth muda is the growing importance of employee engagement and involvement in continuous improvement processes. It has been recognized that the full potential of Lean can only be achieved if the knowledge, skills and creativity of employees are fully utilized.

It is also for the same reason and at the same time that "Respect for individuals" was added to the lean principles.

Examples of Lean waste in production or maintenance

Muda Overproduction

  1. Pre-production: If a company produces goods before demand is confirmed, it risks producing more than necessary.
  2. Produce for Inventory: If a company produces goods to store them "in case" they are needed later, this can lead to overproduction.
  3. Too large production batches: A company may choose to produce large quantities of goods at the same time for efficiency reasons, but this can lead to overproduction if not all of the goods produced are not needed immediately.
  4. Produce to avoid machine downtime: Sometimes, to avoid machine downtime, companies will continue to produce even when the demand is not there.
  5. Excessive preventative maintenance. This is overproduction applied to maintenance. For example, if a piece of equipment is designed to require maintenance every six months, but the maintenance team performs maintenance every three months "just to be sure", this represents overproduction.

Muda Waiting

  1. Waiting for raw materials: If a production line is stopped because the raw materials were not delivered on time, this constitutes a waiting time.
  2. Waiting for a previous step to complete: For example, if an assembly team is waiting for the manufacturing team to finish producing the necessary components.
  3. Waiting for spare parts (Maintenance): If a machine is down and the maintenance technician has to wait for spare parts to arrive, this constitutes a waiting time.
  4. Waiting for information or decisions (Maintenance): For example, if a technician must wait for approval from a supervisor to perform a specific repair.

Muda Transport

  1. Transportation Between Facilities: If a company has multiple production sites and products or components need to be regularly transported from one site to another, this represents waste/muda.
  2. Poor organization of the workspace: If the workspace is not organized efficiently, products may have to be moved longer distances than necessary. which creates transport waste.
  3. Moving Tools (Maintenance): If technicians need to regularly transport tools or equipment from one place to another is a waste.
  4. Transportation of spare parts (Maintenance): For example, if spare parts are stored in a central warehouse and must be transported to the equipment location each time a repair is necessary.

Muda Overprocessing

  1. Excessive packaging: If a product is packaged more than is necessary for its protection or to meet customer expectations, this constitutes overprocessing.
  2. Higher quality on demand: For example, if a component is polished to a mirror shine when the customer only asks and pays for a matte finish, this is overprocessing.
  3. Excessive repairs (Maintenance) : If a minor part of a machine breaks and the whole machine is replaced rather than just repairing the broken part, it may be considered overprocessing.
  4. Use of oversized spare parts (Maintenance): For example, installing a motor that is more powerful than it is is needed on a piece of equipment could be considered overprocessing.

Muda Inventory

  1. Inventory of raw materials: If a company stores more raw materials than it needs for immediate production, this constitutes excess inventory. This unnecessary inventory can be expensive in terms of storage space and can also become obsolete or deteriorate over time.
  2. Products in process: If a production step produces the parts needed for the next step faster than this one, or in too large a batch, this creates a temporary inventory between the two steps.
  3. Spare Parts (Maintenance): If a company keeps more spare parts than it has needed for routine repairs, this constitutes excess inventory. These parts can take up valuable storage space and may never be used if they don't match the failures that actually occur.

Muda Unnecessary movement

  1. Inefficient Workspace Layout: If the workspace is not logically organized, workers may have to walk back and forth unnecessarily. For example, if the workstations are not arranged according to the order of production operations.
  2. Poor Ergonomics: If workstations are poorly designed, workers may have to perform unnecessary or awkward movements, such as bending, twisting, or reaching for objects.
  3. Finding tools or parts (Maintenance): If service technicians need to spending time looking for the tools or parts they need.
  4. Difficult access to the equipement (Maintenance): If technicians have to climb, twist or move a lot to access the equipment they need to repair.

Muda Defects

  1. Improperly Machined Parts: In a manufacturing plant, parts that are improperly machined and do not meet required size, shape, or surface specifications would be considered defective.
  2. Assembly errors: If the parts are assembled incorrectly, for example if the screws are incorrectly tightened or if the components are put in the wrong order, this can lead to defects.
  3. Improper Repairs (Maintenance): If a machine is improperly repaired, such as if a spare part is incorrectly installed or if the underlying issue is not properly addressed, this may be considered a defect.
  4. Ineffective preventive maintenance (Maintenance): If preventive maintenance is not done properly, it can lead to faults later. For example, if a machine's oil is not changed in time, it can lead to excessive wear and premature failure.

Muda Non-use of talents

  1. No involvement in process improvement: If employees have ideas for improving production or maintenance processes, but are not encouraged or allowed to share them or to implement them, this is a non-utilization of talents.
  2. Insufficient Training: If workers are not trained in different tasks or machines, they could be underutilized when a need arises elsewhere in the production line.
  3. Lack of Accountability: If employees are not empowered or do not feel responsible for the quality of their work, their skills and commitment may be underutilized.
  4. No involvement in developing maintenance plans (Maintenance): If maintenance technicians have any ideas to improve maintenance plans, but are not encouraged or allowed to share or implement them, that is a muda.
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Saturday, 13 July 2024