POKA YOKE

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INTRODUCTION

QUALITY

ASSURANCE

FOOL PROOF

PREVENTION

HISTORY

Poka-Yoke was invented by Shigeo Shingo in Japan

The origin of this name came from the words “poka” which means inadvertent mistake and “yoke” which means prevent.

HISTORY

In 1961, he visited the Yamada Electric Plant and was told that one of their products had a problem. This product had 2 push buttons supported by 2 springs. They created this by taking the springs out of a large parts box, then assembled the switch. Despite the best efforts of their employees, sometimes the workers assembling this would forget to insert a spring in each push-button. The company would not know about this error until the unit already reached the customer. So the Yamada Electric Plant would have to dispatch an engineer in order to disassemble the product, insert the missing spring, and reassemble the product again. This would be very costly and embarrassing for the company.

HISTORY

Shingo created a solution to completely eliminate their problem

HISTORY

He then developed this mistake-proofing concept for the next 3 decades and made the distinction between a mistake and a defect.

“mistakes are inevitable since we are just human and we cannot be expected to do everything perfectly all the time.”

COMMON CAUSES OF DEFECTS

Current processes are unreal and incorrect - the process that they follow may not be fit for the job or in some cases there are steps in the process that was overlooked.

Variation in the process is too much and unnecessary - Too much variation may cause confusion which causes defects in the process.

COMMON CAUSES OF DEFECTS

The Variation in Raw Materials is Disproportionate - variation may cause confusion and the materials used may be interchanged thus causing it to be disproportionate.

Accuracy of Measuring Device - products require that the measurements are accurate because the products made should all be of the same size. If measuring device is not accurate, defects are made.

COMMON CAUSES OF DEFECTS

Human Mistake or ErrorEmployee's can be the cause of errors. It may be caused by poor training or by ignorance of regulations. Some may be caused by poor memory, lack of focus or making conclusions out of incomplete information given to them - deciding on their own.

WHAT IS POKA YOKE?

The term ‘Poka Yoke’ is also known as “mistake-proofing” or “fail-safing”. The concept of Poka Yoke is to eliminate defects, in order to eradicate wastes and be able to help workers use their time and mind for other productive tasks. The concept refers to techniques/ methods which aim to lessen errors in production and/ or their negative effects. Its method involves prevention, correction, and detection of errors in production. The ideal process of Poka Yoke is to make sure that the process of production is properly prepared before actually performing the production. If it is not possible to prevent defects before production, Poka Yoke acts as a detecting tool to eradicate defects as soon as possible.

CATEGORIES OF POKA YOKE

PREVENTION

DETECTION

CATEGORIES OF POKA YOKE - PREVENTION

Stop something from occurring a mistake or a problem. It is to stop any abnormality in the process so that there will be no errors. There are 2 approaches for the prevention based Poka Yoke namely Control Method and Warning Method.

CATEGORIES OF POKA YOKE - PREVENTION

CONTROL METHOD

Senses the abnormality in the process and it shuts down the operation. This is to avoid and prevent any errors in happening in the operation.

CATEGORIES OF POKA YOKE - PREVENTION

WARNING METHOD

Avoids any errors too by simple lighting up the warning signal. Although it is not like the control method that stops the operation, warning method continues the operation, but it lets the people know that there is something wrong in the operation so that it can be taken out from the process.

CATEGORIES OF POKA YOKE - DETECTION

It is not always possible to prevent the errors, we also have the detection, but it happens during the early process of the operation so that it can be fixed at once. This is to further lessen the cost of damage in the operation of products. There are 3 approaches for the detection based Poka Yoke namely Contact Method, Fixed Value Method, and Motion Step Method.

CATEGORIES OF POKA YOKE - DETECTION

Contact Method: This method uses a direct mechanism in the operation to know if there are any defects in the process. It comes direct contact with the defect and notifies that there is an error or problem.

Fixed Value Method: This method is also known as Odd Part Out. It has a specific number of rate, moves, and length of movement to know if there is a defect in the operation process.

Motion Step Method: This method is to ensure that all the steps in the process will be followed and no steps will be added.

WHAT MAKES A GOOD POKA YOKE DEVICE?

Simple and inexpensive, being useable by any operator, being placed close to where the mistakes occur, and being part of the process.

METHODS OF POKA YOKE

The three basic methods for using poka yoke recognized by Shigeo Shingo are contact method, fixed-value or constant number method, and motion step or sequence method.

METHODS OF POKA YOKE - CONTACT METHOD

Functions by detecting whether a sensing device makes contact with a part or object within the process. It checks a physical characteristic such as size, shape, or temperature in order to identify product defects.

METHODS OF POKA YOKE - FIXED VALUE

When a fixed number of operations are required within a process or when a product has a fixed number of parts that are attached to it. A sensor counts the number of times a part is used or a process is completed and releases the part only when the right count is reached. It counts repetitions or parts or weighs an item to ensure completeness. It alerts the operator if a certain number of movements are not made.

METHODS OF POKA YOKE - MOTION STEP

Uses sensors to determine if a motion or a step in the process has occurred. If the step has not occurred or has occurred out of sequence, the sensor signals a timer or other device to stop the machine and signal the operator. This is done to ensure that the steps of the process are done in order.

INDUSTRY USES

AVIATION INDUSTRY

*Air travel is considered to be safer than road travel and all other modes of transportation in the world. *

> De-Icing Chemicals: It will make it difficult to form ice on the wings or planes when a certain freezing altitude is attained.

> Auto-Pilot: Probably one of the most popular aviation terms we know today. This device keeps the plan flying in case of inclement weather or when the pilot is I’ll-disposed of his duties during flight.

> Fuel Jettisoning: Probably on of the most important device during an emergency landing as this device prevent major fires from fuel held in the tanks of the aircraft.

SPACE AVIATION INDUSTRY

The space industry would have to be the most invested industry in the world to apply safety and precaution due to the demand of accurate procedures to be constantly carried out during space flight. Any small error in any implementation of these procedures can lead to a major disaster.

This industry therefore has developed many mistake proof devices to ensure safety and to prevent errors from ever occurring.

SPACE AVIATION INDUSTRY

Escape Capsules of the spacecraft. It is designed to aid astronauts safely return to earth in case there is an emergency during any part of the space mission. From launch, mid flight, and flight in general. A motor in the capsule fires over half a million pounds of thrust to steer the capsule away from the booster rocket. This error proofing device has saved and will save lives in case the launch of the rocket will fail.

SERVICE INDUSTRY

In the service industry error prevention is very important because there is direct and constant interaction with the customer and any failure would result in the losing a sale or a customer in general. One of the most used and evident error prevention system we see in the service industry would have to be the Queue Management Systems we see everywhere like banks, restaurants, retail stores, and the like. They are used promptly to prevent customer dissatisfaction in the establishment.

SERVICE INDUSTRY

Another prevention method in this industry would have to be the electronic waiter pads to ensure that the right order goes to the correct table at the shortest possible time.

AUTOMOTIVE INDUSTRY

Start Up/ Ignition system of cars. That the the system’s goal was to create a habit of the driver to make sure he pushes on the brakes before starting the vehicle. The vehicle is designed not to start up until the brakes are impressed upon. Same goes with turning off the engine. The Car must be in “Parked” before the keys can be removed from the vehicle.

ISSUES & CONCERNS

In real world situations, potentials of encountering defects, malfunctions, errors, and such are high. Poka yoke's, also known as “mistake-proofing” or “fail-safing”, aim is to reduce or completely rid output with these errors, it supports the business and its customers in several ways, specifically reducing error cost and increasing customer satisfaction. However, Poka Yoke’s success only considers internal factors resulting to errors when there are occurrences of external elements that can also contribute to malfunctioning/ error.

ISSUES & CONCERNS - SERVICE INDUSTRY

Queuing systems to monitor and prevent mistakes. Queuing ensures that customers are assisted in order and in accordance to the service they require. However, errors can occur when a customer fails to notice the queue. There are also customers who require more than one service, yet only taking one number which may result to confusion on the part of the service provider, this error can be in the form of vollying the customer from one department to another, which will definitely result to customer dissatisfaction

ISSUES & CONCERNS - AUTO/AVIATION IND

The common denominator for these industries would be the use of process count in ensuring fail-proof output. Counting the number of parts, as well as the number of processes, one unit of car or plane use and undergo can be a measure to avoid output malfunction or error; But error can still occur after production, even if the parts were properly installed and processes were followed. External factors such as the user’s lack of training when it comes to handling the output can cause malfunction; accidents can also happen even if the engine is running well, this can be due to the user’s inattention which he/she can later blame on the machineries. Other factors such as the product’s inadequate design or natural disasters can be considered outside factors that can cause errors.

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