Manufacturing industry is heavily dependent on producing error-free end products and processes. Many techniques have been devised in order to reduce error in any process. One of the recent innovations in this field has been the Poka Yoke technique. It is a combination of rules that are designed in order to make a product or a process "error-proof". These techniques are used along with proper inspection methodologies. This has caused a substantial improvement in quality check methods as well as the cycle time. Poka Yoke was developed at Toyota. It has been applied successfully to paper processes, assembly operations, machine set up, fabrication, and a whole range of manufacturing processes.

The fundamental aim of Poka Yoke is to remove defects in a product or process. There are two governing principles of Poka Yoke: To design a product or process that cannot entail a defect and to design a product or process in such a manner that if a defect should arise, it can be identified and rectified immediately. For example, orientation of a 3.5 diskette is important when inserting it into a drive; incorrect orientation is prohibited by designing the diskette with beveled corners.

Poka Yoke is proofreading method in lean manufacturing processes. Lean manufacturing is a commitment to eliminate wastage, to provide customer service and to improve the processes and products in a continual manner. This methodology was developed by the Toyota Production System (TPS). The question that Poka Yoke raises is, “How to design a process in a manner that no defect arises?” Zero defects are an important concept of Poka Yoke because it reduces cost. This in turn, would result in reduced scrap, rework, and warranty costs. Continuous elimination of waste involves a four-step cyclic process: identification of waste, search for causes, implementation of continuous improvement, and checking and measuring results.

Poka Yoke is human centered concept. It recognizes the fact that human beings make mistakes. It does not entertain any finger-pointing. The ten kinds of human mistakes that Poka Yoke recognizes are misunderstanding, forgetfulness, lack of experience, wrong identification, slowness, sloppiness, sabotage, ignorance of procedure, and unexpected circumstances.

Implementation of Poka Yoke entails seven steps:

1. Design quality processes to maintain zero defects.
2. Build a team environment.
3. Design problem-solving methodologies that seek to eliminate errors.
4. Study the root cause of any error.
5. Focus on doing it right the first time.
6. Decisions that do not add value should be eliminated.
7. Approach of continual improvement is implemented

Poka Yoke can detect an error, and either send a warning or shut down an entire process. It does so before the manufacturing process is completed so that time and efforts are saved. Contact, counting and motion sequence are the three Poka Yoke systems. Contact system detects a contact between the sensor and a part of the process, for example, limit switches in a cylinder making contact with pistons. Counting method is used when there are a fixed number of operations to be performed in a process. Motion sequence method is used to find out if the process occurs in the right flow of events. Hence there are physical contact sensing devices, energy sensing devices, and warning systems.

While Poka Yoke is not 100% effective it is one of the most useful tools developed to make a manufacturing process error-free.