Lean Manufacturing, often called lean production, or just ‘Lean’, is a streamlined manufacturing and production technique, as well as a philosophy that aims to reduce production costs, by eliminating all ‘wasteful’ processes. Put another way, Lean focuses on ‘getting the right things to the right place, at the right time, in the right quantity, to achieve perfect workflow’.
Lean defines three types of waste: Mura, Muri, and Muda.
- Mura (Unevenness): Mura exists where there is a variation in production workflow, leading to unbalanced situations, most commonly where workflow steps are inconsistent, unbalanced, or without standard procedures.
- Muri (Overburden): Muri exists where management expects unreasonable effort from personnel, material or equipment, most commonly resulting from unrealistic expectations and poor planning.
- Muda (Waste): Muda is any step in the production workflow that does not add direct value to the Customer. The original seven wastes, as defined by the Toyota Production System (TPS), were Transport, Inventory, Motion (moving more than is required), Waiting, Overproduction, Over Processing (from poor design), and Defects (the effort involved in inspecting for, and fixing, defects). Additional and new wastes are not meeting customer demand, and are a waste of unused human talent. There is further differentiation between Type 1 (necessary waste, e.g. government regulations) and Type 2 (unnecessary waste).
Based on the original Toyota Production System, Lean Manufacturing was formally defined in 1988 by John Krafcik, and later expanded upon by James Womack, Daniel Jones and Daniel Roos.
Lean Manufacturing provides a set of techniques to identify, and eliminate, waste which, in turn, improves quality, and reduces overall production time and cost. In addition, Lean Manufacturing also improves the ‘flow’ of production through the system. These techniques include:
- Value stream mapping: Analysing and planning the flow of materials and information that is required in the production process.
- 5S: This is an approach to quality and continuous improvement. The five S’s are: Sort (to clean and organise the work area), Set in Order (arrange the work area to ensure easy identification and accessibility), Shine (mess prevention and regular maintenance of the work area), Standardise (create a consistent approach for carrying out production processes), Sustain (maintain the previous four S’s through discipline and commitment).
- Fail-proofing: Prevent human errors before they occur.
- Production levelling: Ensure that each step in the production process delivers at a constant rate, so that subsequent steps can also deliver at a constant rate. No step in the production process should produce goods at a faster rate than subsequent steps, or consume goods at a slower rate than preceding steps.
Finally, Lean Manufacturing emphasises Kaizen (改善) or Continuous Improvement; the ongoing, incremental and regular technique of improving all processes, products and functions relating to production, resources, organisational management, and the supply chain.
- The Machine That Changed the World, Womack, Jones and Roos (1991)
- Lean Production Simplified, Dennis (2007)
- Kaizen (Ky'zen), The Key to Japan’s Competitive Success, Imai (1986).