What Is Poka-yoke And Why It Matters In Business

Poka-yoke is a Japanese quality control technique developed by former Toyota engineer Shigeo Shingo. Translated as “mistake-proofing”, poka-yoke aims to prevent defects in the manufacturing process that are the result of human error. Poka-yoke is a lean manufacturing technique that ensures that the right conditions exist before a step in the process is executed. This makes it a preventative form of quality control since errors are detected and then rectified before they occur.

Understanding poka-yoke

Fundamentally, poka-yoke is a lean manufacturing technique that ensures that the right conditions exist before a step in the process is executed. This makes it a preventative form of quality control since errors are detected before they occur.

Of course, some process errors cannot be detected ahead of time. In this case, the poka-yoke technique seeks to eliminate errors as early on in the process as is feasible.

Although the poka-yoke technique became a key part of Toyota’s manufacturing process, it can be applied to any industry or indeed any situation where there is potential for human error.

One of the most well-known examples of poka-yoke in action is in the case of a manual automobile. The driver must engage the clutch (a process step) before changing gears. This prevents unintended movement of the car and reduces wear on the engine and gearbox.

Another example can be found in washing machines, which do not operate if the door isn’t closed properly to prevent flooding. In both cases, poka-yoke principles mean that automation is in place to prevent errors before they occur.

The six principles of poka-yoke

To reduce the prevalence of process errors, poka-yoke is based on six principles in decreasing order of effectiveness.

Elimination – the most preferable solution. It involves redesigning a product or process so that a particular step is no longer necessary.
Prevention – or engineering a product or service so that it is virtually impossible for an individual to make a mistake.
Replacement – can a more reliable process be substituted in to lessen the chances of an error occurring?
Facilitation – or the adoption of techniques to make a task easier to perform. This may involve combining certain steps.
Detection – or identifying an error before further process steps are undertaken. This allows the error to be rectified without further damage to equipment or personnel.
Mitigation – the least preferable solution. Here, the aim is to minimize the effects of errors without necessarily solving them.

When should poka-yoke be used?

Here are some common situations where the poka-yoke approach should be used:

During a hand-off step in a process when output is transferred to another employee.
For any seemingly minor error that has the potential to cause major problems later on.
Whenever the consequences of an error are costly or unsafe.
Any service process where customers are liable to make an effort that impacts output.
Any process step where human error has been identified as a driver of defects or mistakes. This is particularly important for processes that rely on an employee’s experience, skill, and undivided attention.

Poka-yoke error detection methods

To detect and prevent errors or mistakes, there are three different methods:

Fixed value method

Ideal for operations where the same process is repeated many times over. The fixed value method utilizes automatic counters and sensory devices to control the number of moves, the length of movement, and other crucial manufacturing parameters.

Motion step method

The motion step method is used for any process requiring a single worker to carry out different activities in one process. Primarily, the motion step method ensures the worker does not omit an important step or add a step that is not a part of the standard procedure.

Contact method

A broad set of methods that detect errors in shape, dimension, position, or any other physical trait via direct contact with the product itself. The contact method is useful in manufacturing characterized by intense repetition or in facilities where production is infrequent. For example, a winery that operates a bottling production line for only a few weeks each year. On that note, the method can also be used to detect errors resulting from dust, temperature, noise, and improper lighting.

A simple poka-yoke procedure

Poka-yoke is simple to implement because it is a rational approach that can be applied in almost any situation. Consider the following step-by-step process:

Start by identifying the operation or process. Consult a flowchart if possible and review process steps where errors are likely to occur.
For each of the errors identified, work backward to discover its source in the process. Some use the 5 Whys method to assist in this step.
Then, the team must brainstorm ideas that will make it impossible for the error to occur. Return to the six principles of poka-yoke and remember that elimination, prevention, and replacement are the most desirable courses of action.
If it is deemed impossible or economically unviable to prevent the error from occurring, the team should think of ways to minimize its effects. There are two options here. The first is setting functions, which are methods used to inspect process parameters or product attributes for errors. The second option is regulatory functions, which are alerts such as bells, buzzers, or lights that let workers know an error has occurred.
With the above in mind, it is time to choose, test, and implement the most suitable prevention method for each error. Most businesses can collect rapid feedback by three different inspection methods. The first is a simple inspection that is performed at the next step in the process by another worker. Feedback may also be gathered via self-inspection, where the worker verifies their own work immediately after it has been performed. The third and final inspection method involves source inspection checks. These are carried out before the step takes place to ensure conditions are correct.

Benefits of poka-yoke principles for businesses

Error prevention is an obvious advantage to poka-yoke, but what positive ramifications does error prevention have for a business?

Improved profitability

Errors on production lines decrease profitability – whether that be through line shutdowns or expensive worker injuries. But poka-yoke principles improve a company’s bottom line in other ways.

For example, hotels now require that guests insert their key-card into a slot to activate electricity in their room. Since many guests do not bother to turn the lights off after they leave, the hotel can save money on wasted electricity consumption.

Improved productivity

Preventing errors before they occur increases productivity. Online forms require that every field be filled out before submission. This reduces errors in forms resulting from incomplete or missing information, saving the company time and money in having to chase up consumers for the extra details.

ATMs also chime or flash to remind the customer to retrieve their debit card and cash. This greatly reduces the once common error of customers leaving their cards in the machine. It also saves the bank money in loss prevention, giving customer support the resources to deal with other problems.

Simplification of smaller, error-prone tasks

Small tasks with a high probability of error are particularly prevalent in some industries such as the service and hospitality industries. Cashier errors in counting change, for example, are relatively inconsequential errors in isolation that have the potential to lose a business a lot of money over the long term.

To this end, poka-yoke principles have automated the change counting process and where automation is not possible, digital interfaces verify that the cashier has given the correct amount of change. Similar systems are now in place to prevent errors in order fulfillment and delivery of orders to a table.

Key takeaways:

Poka-yoke is a Japanese quality control technique that aims to make processes error-proof.
Although having origins in the manufacturing industry, poka-yoke principles are useful in any scenario where there is potential for human error.
Poka-yoke error prevention is guided by six principles, with elimination the most desirable and mitigation the least desirable. All six principles can nevertheless improve productivity, profitability, and simplify smaller, error-prone manual tasks.