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POKA-YOKE

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INTRODUCTION Pronounced as POH-kah YOY-KayPoka-yoke is a Japanese word for mistakeproofing

Mechanism that prevents a mistake frombeing made which is obvious at a glance.

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No System of Barriers is

Perfect…

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No System of Barriers is Perfect… …But improvements can be made

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POKA-YOKE

A SYSTEM for organizing work

that• Excludes any risk of erroreven by the beginner• Allows everyone to operatewithout mistake• Prevents error that are aboutto occur.

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TYPES OF POKA-YOKE

Poka-yoke systems consist of three primarymethods:

1. Contact

2. Counting

3. Motion-Sequence

Each method can be used in a control system or awarning system.

Each method uses a different process preventionapproach for dealing with irregularities.

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1.CONTACT METHOD

Contact method is based on some type ofsensing device which detects abnormalities

in the product’s shape and dimension andresponds accordingly.

It functions by detecting whether a sensingdevice makes contact with a part or objectwithin the process.

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Example

An example of acontact device usinga limit switch. In

this case the switchmakes contact witha metal barbsensing it’s

presence. If nocontact is made theprocess will shutdown.

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Example

A sensor counts the number of times apart is used or a process is completedand releases the part only when theright count is reached.

In the example to the right a limitswitch is used to detect and countwhen the required amount of holes are

drilled. The buzzer sounds alerting theoperator that the appropriate amountof steps have been taken in theprocess.

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3.MOTION STEP METHOD

The motion step method is useful forprocesses requiring several different activitiesperformed in sequence by a single operator.It uses sensors to determine whether amotion or a step in a process has occurred. Ifthe step has not occurred or has occurred outof sequence, the sensor signals a timer orother device to stop the machine and signalthe operator.

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Example

In this example, each step of the machine cycle is wired to anindicator board and a timer. If each cycle of the machine is notperformed within the required “time” and “sequence”, theindicator light for that step will be turned on and the machine willstop.

MACHINE INDICATOR BOARD

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IMPLEMENTATION

Warning poka-yokethe operator is alerted when a mistake is about to bemade

Control poka-yokethe poka-yoke device actually prevents the mistake from

being made

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THANK YOU