Pokayoke

PokaYoke (pronounced with the e on the end e.g. poka-yoki) is yet another Japanese word which has come into regular use within the lean manufacturing vocabulary. In essence it is an extremely simple concept that has been applied through common sense for years. Simply put it is the use of simple mechanisms that stop mistakes being made by manufacturing operators without requiring concentration by the operators.

Most often these Pokayoke's or fail-safe devises are very simple and often inexpensive visual prompts that prevents the defect in the product occurring. Either the operator is alerted that a mistake is about to be made, or the device actually prevents the mistake from being made. The important point of these types of mechanisms is that 100% of the parts are checked without the need for concentration from the operator.

The term “PokaYoke” was popularised by Shigeo Shingo through his book “Zero Quality Control: Source Inspection and the PokaYoke System”. Shingo points out that mistakes will always be made (we’re only human after all!), but if PokaYoke’s are implemented then mistakes can be prevented from becoming defects (mistakes that reach the customer).

Examples of PokaYoke devices include jigs with pegs that will only allow a component to be inserted one way round or perhaps colour coding similar parts so that they cannot be mixed up. Examples of PokaYoke’s can be found at
http://www.campbell.berry.edu/faculty/jgrout/pokayoke.shtml

By eliminating the defect at source the cost of mistakes within a company is reduced. Often quality inspection will be carried out at the end of a series of processes if the mistake was made at the start of the process then money has been invested in that part all the way along the process up to the point it is inspected therefore increasing the cost of the mistake. It is also possible (if parts are less than 100% inspected) that the defect may carry on down the production process further increasing the cost of the defect and probably leading to the need for rework.

To get the full benefit from the application of PokaYoke’s then they should all be shared with different departments and processes so that others can see then in action and be inspired to think of their own.

PokaYoke’s are an effective and relatively inexpensive way of reducing manufacturing defects and therefore the quality costs, however thought should be given as to why it was possible to make the mistake in the first place and therefore need Pokayoke's. A longer-term aim might be to eliminate the source of problem not just prevent it from occurring, this might be best achieved in the design stage.

For more information on Pokayoke techniques please contact the help desk and arrange a visit with one of our manufacturing specialists.