The concept of lean manufacturing was based on the philosophy of Toyota’s Production System (TPS), developed post World War II during reconstruction of automobile industry in Japan. Lean Manufacturing refers to the process which manufactures better quality products with a lower defect rate and at a greater speed than its competitors. However, the term “lean” was promoted only in 1996 by James P. Womack and Daniel T. Jones in their book ‘Lean Thinking’. Lean manufacturing is much more flexible than its predecessors, craft production (highly skilled workers but flexible tools) and mass production (narrowly skilled professionals and expensive machinery) and combines the positive aspects of both.
Lean manufacturing is renowned for its focus on reduction of wastes to improve overall customer value. Taiichi Ohno, father of Toyota Production System identified three broad types of wastes ‘muda’, ‘muri’ and ‘mura’. However, many lean implementations are on first waste type only, with reduced corresponding benefits. Seven muda’s are storage, transportation, waiting, motion, process, defect and over production wastes. Muda or wastes is everywhere but there are varying perspectives on how to reduce these wastes and achieve efficiency.
Principles of Lean Manufacturing
- Reduction of waste – Lean manufacturing involves never ending efforts to eliminate waste using tools like 5s, one piece flow, Kanban, Kaizen, Poke-yoke and several others. They have developed an acronym for waste – CLOSED MITT, where CLOSED stands for Complexity, Labor, Overproduction, Space, Energy, Defect and MITT stands for Materials, Inventory, Time and Transport.
- Respect for human resource – Lean Manufacturing philosophy respects humanity as the biggest resource in any company is the people that work there. It also emphasizes respect for the workers at all levels, the customers and suppliers, as well as the environment
Benefits of Lean Manufacturing
- Shorter lead time
- Reduced inventory
- Pull based manufacturing
- Production in smaller batch sizes
- Line balancing or Takt timing
- Lower process time
- Cellular Manufacturing
This concept made Toyota more effective in production and gained their success. Analyst around the world believe that lean manufacturing was the need of the day as companies were operating in a highly dynamic and competitive environment in which lower production costs would make all the differences.
Lean manufacturing in comparison to JIT manufacturing
Lean manufacturing takes the concept of JIT and reexamines it from the perspective of customer value.
- The first step in the lean manufacturing process is to consider what aspects of the product add real value for the customer. Also ensures every step adds value which customer would seek.
- The second step in lean process is to remove elements from the process. This is done by closely examining every activity of the process, identifying and eliminating non-value adding elements/activities. Lean aims to add value by increasing the efficiency and whereas JIT reduces cost to make the product affordable.
- In the next step, lean manufacturing and JIT manufacturing process are identical. At this stage, after elimination of non-value adding elements process focuses on customer orders. Lean manufacturing only manufactures based on customer orders, pull system drives the production. Similarly, JIT orders based on short term requirements. Here, JIT’s driving force for efficiency is customer value rather than cost reduction unlike in the previous step
To summarize, Lean production is the set of activities that achieves quality production at minimum cost and inventory. Adopts pull system of operation. Lean manufacturing employs philosophy of doing more with less. And is a continuous process of eliminating waste.