Waste, or Muda, is defined in the Toyota Production System (TPS) as anything that doesn’t increase value for your customers. When waste is removed, processes are streamlined, valuable time and costs are saved and customer satisfaction is improved.
Lean manufacturing is a management philosophy derived from Toyota and their way of working to remove waste and improve customer value. Waste can include factors that might not usually be usually be thought of as waste including as overproduction, high levels of inventory, items which need to be reworked, processing or waiting times and unnecessary movement.
Exactly what value means will be different depending on your process and customer but can involve looking at key performance indicators such as throughput, productivity, cost and amount of work in progress.
What are the common wastes of Lean manufacturing?
Defects are products or services that are out of specification. They need extra effort or resources to fix and lead to increased costs and lost time, either through repairs or having to start over.
Overproduction, where production exceeds customer demand, is considered the most harmful waste as it itself creates additional waste including excess inventory and transportation.
Waiting occurs whenever items aren’t in transport or being processed. For example, employees wait for materials, equipment waits for maintenance, or work in process waits for the employee to return.
Not utilizing talent
By under-utilizing employee skills and knowledge, organizations limit their potential. Developing talent and engaging employees in process improvement can reduce waste.
Transportation occurs whenever products are transported from one location to another. This can increase the risk of damages, additional waiting time and costs.
Inventory, such as raw materials, work-in-progress or goods which are sitting idle, is considered waste as it hasn’t yet contributed value to the end customer.
Unnecessary motion can occur due to inefficient layouts or searching for mislaid items. It can also increase the risk of damage to equipment or cause employee injuries.
Excess processing is any activity that isn’t needed to produce a functioning product or service and can occur due to any unnecessary or drawn-out processes.
Changes to manufacturing processes that can be considered to reduce waste include:
- Leveling production to match demand
- Reducing end-to-end cycle time to less than customer's expectation of reasonable wait time
- Using Just-in-Time delivery schedules with suppliers
- Monitoring quality in a responsive manner
- Properly fixing all problems at the source and accepting the higher short term cost of doing this
- Reducing change over time so that batch sizes can be reduced cost effectively
- Empowering and training employees to participate in continuous improvement and increasing communication and visibility to make this easy for them
In order to completely eliminate waste, all of these process changes should be considered together – but with a wide range of parameters to consider (e.g. batch sizes, J-i-T schedules, acceptable cycles times, Kanban quantities, container sizes), making these changes without affecting other processes or adding other forms of waste can be difficult. This is why many manufacturers rely on simulation software when planning and implementing Lean projects.
"Simul8 gave us a technical way of understanding capacity, identifying bottlenecks and changing data to achieve new capacities, new goals and new logics. We never had this ability before."