iSixSigma

Poka-Yoke

Definition of Poka-Yoke:

Have you ever accidentally microwaved your face? No? You’ve never opened the microwave door while it was cooking and accidently exposed your face to microwave energy? I know that you haven’t, because whenever you open the door, the microwave stops running. There is a switch that triggers when the door is opened that tells the microwave to stop, and that switch is an excellent everyday example of poka-yoke.

Overview: What is poka-yoke?

Poka-yoke, a Japanese term that means “mistake-proofing,” refers to any tool or mechanism that keeps a person from being able to perform an action in an incorrect manner. Poka-yoke is used to avoid waste, typically by eliminating or minimizing quality mistakes that lead to rework and scrap as well as eliminating potential safety issues. 

Poka-yoke is an especially useful tool when you’re trying to improve upon the cost of quality, which is the concept that the longer it takes to detect an error, the more expensive it is to repair the error. The reality of being human is that our rate of success at any given task, regardless of simplicity or complexity, is never 100%. Poka-yoke does not change human nature, but it does decrease the opportunities for a failure to occur, which helps drive quality higher and decreases the stress of the working environment.

Implementing poka-yoke to eliminate unsafe errors

Poka-yoke can be implemented in many different ways. For example, in guide pins, limit switches, counters, alarms, and checklists. They can address the situation by testing the product’s physical attributes, such as shape or color. They can also address factors such as timings, movements, or process steps through monitoring or verification. 

There are many examples of poka-yoke in everyday life. For example, when parking a car, one of the steps is to place the gear into park. If the driver forgets this step and turns the engine off, the car sends out an alarm reminding you to put the car in the proper gear. This is a feature that early cars did not have, and if left in the wrong gear, unsafe consequences could occur. If in neutral and parked on an incline, the car could drift out of the parking space and into traffic. Also, the driver could damage their transmissions if they attempted to start the car while not in the correct gear.  

3 best practices for implementing poka-yoke

Keep your eyes peeled for opportunities to use it

Whenever performing a review of a process, such as a standard work analysis, remember to be on the lookout for poka-yoke opportunities. Standard work is not only about understanding cycle time components — it’s meant to be an exercise that helps you collect many different pieces of information, including points of failure that could benefit from mistake-proofing.

Be creative

There are no limits as to what the right poka-yoke solution will be for a given situation. Remember to tap the skills and creative ideas of your staff, as they may already have a great solution for you and are just waiting for a person with the empowerment to implement the poka-yoke. 

Borrow from others

Look to other processes for inspiration. These processes can originate from your competition, your suppliers, or your customers. Other processes, even ones that may create different types of products, can be a great place to find poka-yoke ideas that can be adapted for your processes. Also, remember to take a look at the everyday poka-yoke that surrounds you in daily life.

Frequently Asked Questions (FAQ) about poka-yoke

I see how this can assist with manufacturing, but how is poka-yoke supposed to assist me with my office process?

Many times, people associate poka-yoke with physical solutions, like guide pins and switches, but remember that it also includes tools like alarms and checklists, which are particularly useful in an office environment. 

An everyday example is your office calendar software. When set up to do so, the software can send out a meeting reminder to participants when the start time of the meeting is approaching. This is a poka-yoke tool that helps personnel remember to show up for a meeting on time, as every minute participants wait in a meeting for a late attendee to arrive is a loss of both time and money.

Checklists are a widely used tool in the office environment, verifying that all the pieces of the office product are in place before sending the product to the next stage. A large amount of waste can be found in the office environment when discovering the impact of when and how often an office product is sent back to a previous stage for rework. Checklists can help minimize these rework causes.

Is poka-yoke going to cost a lot of money to implement?

Solutions for poka-yoke can range from fast and cheap to implement to expensive and time-consuming to install. Many solutions will not be expensive, but you might need to perform a cost-benefit analysis to determine how to prioritize the solution. 

Consider using the PICK chart when deciding if or when to implement a poka-yoke solution, as this will help you measure both the level of improvement achieved against the cost and difficulty of implementation.

I have implemented a new poka-yoke solution, but my staff doesn’t want to use it.  What do I do?

While you might be receiving pushback simply because you’re asking personnel to change their old habits, odds are that some features of the new poka-yoke are not working as intended. 

First, determine whether the solution is indeed successful in eliminating or minimizing the defect. Then, gather feedback from the people using the tool. Does the new tool add large amounts of cycle time, leading to missed schedules? Are there ergonomic issues regarding the solution? Does the new tool unintentionally create a new opportunity for defects?

Poka-yoke

Poka-yoke is an effective method for eliminating certain defects from occurring. When a defect cannot be eliminated, poka-yoke can often assist in identifying the error earlier in the process, decreasing the cost of the rework and the potential of the error reaching the end customer. 

Often inexpensive and appreciated by personnel across an organization, poka-yoke can help decrease errors, making quality easier to manage and leading to a less stressful environment.

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