In lean manufacturing, “waste” is defined as anything that doesn’t add value to a product. “Value” in manufacturing is defined as anything that a customer would be willing to pay for.

So, waste is any cost incurred in a process that does not benefit the customer. Lean manufacturing is centered around eliminating waste from manufacturing processes.

What are the 8 lean tools

Lean practitioners commonly agree on 7 wastes (or muda, as they are referred to in the Toyota Production System):

  1. Transport
  2. Inventory
  3. Motion
  4. Waiting
  5. Overproduction
  6. Overprocessing
  7. Defects

These wastes were defined by Taiichi Ohno, father of the TPS. Some practitioners include an 8th waste, unutilized talent. While the first 7 wastes are directly related to manufacturing processes, the waste of unutilized talent is specific to manufacturing management.

What are the 8 lean tools

Transport waste is defined as any material movement that doesn’t directly support immediate production. An improper facility layout, poor production planning, poor scheduling can generate transport waste. Another example is poor workplace organization, which results, in unnecessary additional material transport.

Inventory waste refers to any supply in excess of process requirements necessary to produce goods or services in a Just-in-Time manner. Causes of inventory waste include inaccurate forecasting systems, inefficient processes or suppliers, long changeover times, unbalanced production processes, or poor inventory management and tracking.

Motion waste is defined as any movement of people that doesn’t contribute added value to the product. Examples include moving equipment, reaching or bending, or gathering tools more than necessary, as well as unnecessarily complicated procedures. Motion waste is often caused by ineffective plant layouts, lack of visual controls, poor process documentation, or poor workplace organization.

The waiting waste refers to as any idle time that occurs when codependent events aren’t fully synchronized. Examples of this waste include idle operators waiting for equipment, production bottlenecks, production waiting for operators, and unplanned equipment downtime. Waiting can be caused by inconsistent work methods, lack of proper equipment or materials, long setup times, low man/machine effectiveness, poor equipment maintenance, or skills monopolies.

Overproduction is defined as producing more than is needed, faster than needed, or before it’s needed. This form of waste is most commonly seen in a "push system" supply chain. Automation in the wrong places, lack of communication, local optimization, low uptimes, poor planning, and a just-in-case reward system can cause overproduction waste.

Over-processing refers to any redundant effort in production or communication that does not add value to a product or service. Over-processing waste includes endless product or process refinement, excessive information, process bottlenecks, redundant reviews and approvals, and unclear customer specifications. It is caused by decision-making at inappropriate levels, inefficient policies and procedures, lack of customer input concerning requirements, poor configuration control, and spurious quality standards.

Defect waste is defined as the loss of value do to the scrap, repair, or rework of a product that deviates from specifications. Excessive variation in production processes, high inventory levels, inadequate tools or equipment, incompatible processes, insufficient training, or transport damage due to poor layouts and unnecessary handling can all lead to quality defect waste.

The waste of unutilized talent refers to underutilizing or engaging employees in a process. This could take the form of employees performing unnecessary work when their talent could be utilized in activities that add greater value, or not utilizing employees’ critical thinking abilities and feedback in processes. Unutilized talent also includes allowing employees to work in silos, which prevents them from sharing their knowledge.

Eliminating the 8 wastes from a manufacturing value stream is the core of lean manufacturing. Lean manufacturers should focus on building processes that make these wastes obvious so that they can be addressed—and improvements can be made—immediately.

There are many tools and techniques within lean manufacturing that aim to reduce and eliminate waste. Check out our guides to kaizen and gemba walks to learn more about some of these techniques.