Some of the waste reduction tools include zero defects, setup time reduction, and line balancing. The goal of zero defects is to ensure that products are fault free all the way, through continuous improvement of the manufacturing process (Karlsson and Ahlstrom 1996). Human beings almost invariably will make errors. When errors are made and are not caught then defective parts will appear at the end of the process. However, if the errors can be prevented before they happen then defective parts can be avoided. One of the tools that the zero defect principle uses is Poka Yoke. Poka-Yoke, which was developed by Shingo, is an autonomous defect control system that is put on a machine that inspects all parts to make sure that there are zero defects. The goal of Poka-Yoke is to observe the defective parts at the source, detect the cause of the defect, and to avoid moving the defective part to the next workstation (Feld, 2000).
Single Minute Exchange of Die (SMED) is another technique of waste reduction.During 1950’s Ohno devised this system; and was able to reduce the die changing time from 1 day to three minutes (Womack, Jones and Ross, 1990). The basic idea of SMED is to reduce the setup time on a machine. There are two types of setups: internal and external. Internal setup activities are those that can be carried out only when the machine is stopped while external setup activities are those that can be done during machining. The idea is to move as many activities as possible from internal to external (Feld, 2000). Once all activities are identified than the next step is to try to simplify these activities (e.g. standardize setup, use fewer bolts). By reducing the setup time many benefits can be realized. First, die-changing specialists are not needed. Second, inventory can be reduced by producing small batches and more variety of product mix can be run.
Line balancing is considered a great weapon against waste, especially the wasted time of workers. The idea is to make every workstation produce the right volume of work that is sent to upstream workstations without any stoppage (Mid-America Manufacturing Technology Center Press Release, 2000). This will guarantee that each workstation is working in a synchronized manner, neither faster nor slower than other workstations.
Work Standardization:
A very important principle of waste reduction is the standardization of work. Standardized work basically ensures that each job is organized and carried out in the same manner; irrespective of the people working on it. In this way if the work is standardized the same quality output will be received even if the worker is changed in process. At Toyota, every worker follows the same processing steps all the time. This includes the time needed to finish a job, the order of steps to follow for each job, and the parts on hand. By doing this one ensures that line balancing is achieved, unwanted work in process inventory is minimized and non value added activities are reduced. A tool that is used to standardize work is called takt time.
Value Stream mapping:
Value Stream Mapping (VSM) is a technique that was originally developed by Toyota and then popularized by the book, Learning to See (The Lean Enterprise Institute, 1998), by Rother and Shook. VSM is used to find waste in the value stream of a product. Once waste is identified, then it is easier to make plan to eliminate it. The purpose of VSM is process improvement at the system level. Value stream maps show the process in a normal flow format. However, in addition to the information normally found on a process flow diagram, value stream maps show the information flow necessary to plan and meet the customer’s normal demands. Other process information includes cycle times, inventories, changeover times, staffing and modes of transportation etc. VSMs can be made for the entire business process or part of it depending upon necessity. The key benefit to value stream mapping is that it focuses on the entire value stream to find system wastes and try to eliminate the pitfall (Wilson, 2009, p. 147-153). Generally, the value stream maps are of three types. Present State Value Stream Map (PSVSM) tells about the current situation, Future State Value Stream Map (FSVSM) can be obtained by removing wastes (which can be eliminated in the short time like three to six months) from PSVSM and Ideal State Value Stream Mapping (ISVSM) is obtained by removing all the wastes from the stream. The VSM is designed to be a tool for highlighting activities. In lean terminology they are called kaizen activities, for waste reduction. Once the wastes are highlighted, the purpose of a VSM is to communicate the opportunities so they may be prioritized and acted upon. Hence, the prioritization and action must follow the VSM, otherwise it is just a waste like other wastes.