Lean production is first introduced by Toyota production system in Japan that is widely adopted by manufacturers worldwide. Lean is a customer-focused approach that improves quality and speed by eliminating waste and applying value-added activities in the manufacturing process. Lean is concerned on the value that customer is willing to pay, therefore anything that does not add value is considered as waste. The whole idea of lean focuses on the relentless pursuit of perfection.
7 types of waste
Inventory – it becomes a waste when there is too much inventory and becomes a problem when there is too little inventory. Causes of this waste may include poor forecasting, lack of information sharing and ineffective inventory management.
Transportation – any unnecessary movement within the process that does not add any value to the product is a waste. For example, a product needs to be transported with extra minutes due to long distances between work centers and multiple storage locations.
Motion – it refers to unnecessary motion or movements of workers or equipment that does not add value to the product. Examples are repeated movements or bends caused by poor ergonomics – ineffective work method design, workstation layout, and workplace organization.
Waiting – it refers to any idle time in operations such as a workstation running the assembly slower among workstations. If one task takes longer than another, then the time spent waiting for the next material to be processed is wasted. Waiting incurs due to long changeovers, poor machine performance, lack of workers’ coordination, and rework time.
Overproduction – it is considered the worst type of waste because it causes other wastes to emerge and hinders the need for improvement. Overproduction is a result of unstable scheduling, large batch sizes, poor forecast, and lack of information sharing.
Over-processing – it is when a product is processed beyond what is acceptable to the eyes of the customer. Examples include too much product polishing, painting of unnecessary parts, and overly machining of materials. Also, a lack of adherence to best practices usually leads to over-processing.
Defect – defective products at customers hand will result to recall and degrade the company’s reputation, while defects intercepted in factory costs organization additional labor and overhead for rework. Sources of defects are lack of worker training, operator error, incapable suppliers, and excessive stock.
Goals of lean production;
– Zero defects
– 100% value add
– Lot size of one
– Pull of the customer
Lean conflicts with mass production in many areas.
Table 5. Comparison between mass and lean production.
Issues in lean production
Although lean production is a good method, however, it has several issues that usually occur during implementation.
– The partiality of support from top management
– The resistance of the new culture; continuous improvement
– Responsiveness for a sudden increase in demand
– Short term forecasting
– People feel stressed for no margins for error and over-focused on waste
– Establishment of supplier commitment
– Risk in supply delivery resulting in production flow interruption
Issues in mass production
Mass production (also called continuous production) lowers cost per unit but is vulnerable to supply chain risks resulting from:
– Large inventory (WIP and finish goods)
– Carrying cost
– Space requirement
– Process inflexibility/lack of customization
– Supply chain risks – obsolescence, huge discounting, decrease in demand, etc.
– Detection of errors
– Product quality
The use of mass and lean production is heavily dependent on the type of market the company is serving. Lean might be suitable for the automotive industry but not so much on canned goods (where mass production is appropriate). Whatever method used, it must align and contribute to the achievement of strategic and tactical goals of the company.
Implementing lean in manufacturing has a significant impact on lead time than traditional manufacturing.
Figure 12. Lean improvement on lead time.
5S is a systematic approach for organizing processes, tasks, or spaces so workers can do the job efficiently and safely. As with other improvement tools, 5S is first introduced by Toyota Production System (TPS) that is quickly emulated in the west and called it as lean manufacturing. 5S stands for;
Sort – eliminate anything that is not needed
Set in order – organize remaining items
Shine – clean and inspect the work area
Standardize – document standards for the above
Sustain – apply the standards regularly
The benefit of 5S implementation is the elimination of wastes resulting from a poorly organized work – wasted time looking for a tool. Other advantages include improved quality, satisfied employees, safe work environment, and reduced cost.