Lean Manufacturing: Application of Lean Thinking to Operations Management
The application of the Lean Thinking principles to the operations management area (i.e. both internal and external) has been traditionally identified with the term Lean Manufacturing. In a Lean Manufacturing approach, there are:
- Production processes organized in order to clearly distinguish value streams, to ensure continuity and regularity and eliminate waste;
- Production schedule finalized to synchronize production with market demand through a pull control of the physical and informational flows;
- Work organization supporting employees involvement and pursuing perfection through continuous improvement;
- Suppliers’ relationships aimed at the research of qualitative and quantitative reliability and on time delivery.
On these issues, managerial and scientific literature over the past thirty years has sought to identify practices/tools that characterize a Lean Manufacturing approach.
With reference to production processes, in order to work with operational regularity and uniformity of the mix, the following goals have to be performed:
- Reduction of the set-up time using SMED methodology;
- Application of the Spaghetti Chart to clearly detect the flows of materials and, if possible, rearrange them according to the approach of Cellular Manufacturing;
- A high quality (i.e. compliance) performance of the production process through the Six-Sigma techniques and the use of Poka Yoke (i.e. fail safe error proofing) systems;
- Optimization of the availability and reliability of equipment by implementing the Total Productive Maintenance methodology;
- Sorting and keeping clean working areas by applying all phases of the 5Ss methodology.
Usually, as a mean to understand and streamline work processes the Value Stream Mapping (VSM) methodology is employed. The goal of VSM is to identify, demonstrate and eliminate waste affecting processes. VSM can thus serve as a starting point to help management, engineers, production associates, schedulers, suppliers, and customers recognize waste and identify its sources.
With respect to production planning and control, typical Lean Manufacturing tools are Kanban for pull adjustment of flow, Visual Management for immediate control of the shop floor, the Hejiunka box for levelling and cadencing production.
It is evident that the adoption of these practices in internal operations requires a review of the ways a company relates to suppliers. We refer to issues such as the rationalization of supply network, the construction of closer and lasting relationships, the use of vendor rating programs which evaluate the total cost of ownership, the involvement of suppliers in joint improvement programs, the application of Kanban for regulating the flows of materials from suppliers.
Through the Delphi method the experts have identified 17 practices which, in their opinion, characterized a Lean Manufacturing approach. Obviously, the list contains items well-known in the literature. Some of these practices are at the core of the lean manufacturing approach while others have become known more recently. These practices are listed below, for each of them is indicated in parentheses a bibliographic reference, which should be consulted for more details:
- Shop-floor Kanban (Asay & Wisdom, 2002);
- 5Ss (Hirano, 1996);
- Value Stream Mapping (Rother & Shook, 1999);
- Ishikawa Diagram (Ishikawa, 1976);
- Heijunka Box (Liker, 2004);
- Hoshin Kanri (policy deployment) (Jackson, 2006);
- Kanban with suppliers (Lamming, 1993);
- Kaizen (continuous improvement) (Imai, 1986);
- Lean Distribution (Zylstra 2005);
- Poka-Yoke (Shingo, 1986);
- Cell Manufacturing (Suresh & Kay, 1997);
- Set-up time reduction (SMED) (Shingo, 1985);
- Six Sigma (George, 2004);
- Spaghetti Chart (Hobbs, 2003);
- Total Productive Maintenance (TPM) (Nakajima, 1998);
- Visual Control (Ortiz and Park, 2010);
- Methods time measurements (MTM) (Maynard, Stegemerten, & Schwab, 1948).