Principles of lean thinking have been broadly accepted by many manufacturing operations and have been applied successfully across many. Different authors define it distinctively. Lean manufacturing is most frequently associated with the elimination of seven important wastes to ameliorate the effects of variability in supply, processing time or demand defined it as a philosophy of manufacturing that focuses on delivering the highest quality product on time and at the lowest cost. Worley (2004) defined it as the systematic removal of waste by all members of the organization from all areas of the value stream. Briefly, it is called lean as it uses less, or the minimum of everything required to produce a product or perform a service. In a nutshell, lean manufacturing can be best defined as an approach to deliver the upmost value to the customer by eliminating waste through process and human design elements. Lean manufacturing has become an integrated system composed of highly inter-related elements and a wide variety of management practices, including Just-in-Time (JIT), quality systems,work teams, cellular manufacturing etc .The purpose of implementing it is to increase productivity, reduce lead time and cost, and improve. Lean manufacturing requires that not only should technical questions be fully understood, but existing relationships between manufacturing and the other areas of the firm should also be examined in depth, as should other factors external to the firm As an integrative concept, the adoption of lean manufacturing can be characterized by a collective set of key areas or factors. These key areas encompass a broad array of practices which are believed to be critical for its implementation. They are, scheduling, inventory, material handling, equipment, work processes, quality, employees, layout, suppliers, customers, safety and ergonomics, product design, management and culture, and tools and techniques.These 14 areas are the subjects of investigation in this study and each of them will be reviewed and described now.
Scheduling - Effective schedules improve the ability to
meet customer orders, drive down inventories by allowing smaller lot sizes, and reduce work in processes. Appropriate scheduling methods are able to optimize the use of resources. Pull methods such as Kanban, and lot size reduction are commonly used to reduce storage and inventories and to avoid overproduction. Pull means to do nothing until it is required by the downstream process. Minimizing lot sizes enables a smoother production flow and maximizes productivity by eliminating production line imbalances.
Companies store inventories to enable continuous deliveries and overcome problems such as demand variabilities, unreliable deliveries from suppliers, and breakdowns in production processes. However there is a need to maintain inventories at the minimum level because excess inventories would require more valuable spaces and result in higher carrying costs. Moreover, they accumulate the risk of “products becoming obsolete”. Excess inventories are seen as “evils” because they hide problems such as defects, production imbalances, late deliveries from suppliers, equipment downtime and long setup time. Material handling is also crucial in lean manufacturing because the cost attributed to material handling is estimated between 15% and 70% of the total manufacturing operation stated that transporting parts not only does not add value to a product, it increases manufacturing lead time. Hence, it is a major waste that needs to be eliminated. A steady material flow which moves frequently in small batches will allow a faster replenishment of materials. This will then shorten lead time and increase productivity.
The level of equipment support should be given attention in lean manufacturing because some manufacturing processes rely heavily on their equipment to produce products. Unexpected machine downtime would...