1de9dPoke Yoke

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Poka - Yoke



This is known as µMISTAKE-PROOFING¶

From Japanese:

Yokeru (avoid)

Poka (inadvertent errors)

What is Poka-Yoke?



What does Poka ± Yoke do?

Eliminates the cause of an error at thesource.

Detects an error as it is being made;

Detects an error soon after it has been

made but before it reaches the nextoperation.



5 Elements of Production

Objects of Production (What?). Raw material, Finished

products, Semi ± finished products ± WIP.

Agents of production (Who?). People, Machines, Tools, Jigs,Incidental devices, Inspection equipments, Environment.

Methods (How?). Processing systems, Load & capacity,

processing conditions.

Space (

Where?). Left to right, Front to back, Top to bottom.

Time (When?). Process time, Production time, Task time.

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1. Errors Are Inevitable

People always make mistakes.

While we accept the mistakes as natural, we

blame the people who make them.

With this attitude, we are likely to overlook

defects as they occur in production.

They may be detected at final inspection, or worse still, by the customer.



2. Errors Can Be Eliminated

Any kind of mistake people make can be

reduced or even eliminated.

People make fewer mistakes if they are

supported by proper training and by a production system based on the principle

that errors can be avoided.



Inspection

One method of detecting errors isinspection.

There are two major types of inspection.

1. SAMPLING INSPECTION.

2. 100% INSPECTION.



Sampling Inspection

In some factories, the attitude is:

³It may take all day to inspect all

product.There may be a few defects, butsampling is the most practical way to

check´.



Sampling Inspection - Reflection

With sampling, there is a chance that an

error may go undetected.

Even if 1 part in 1000 is defective, the

customer who buys that part has a 100%defective product!



2. 100% Inspection

In the best factories, the attitude is:

³We won¶t tolerate a single defect! We willorganize production so that 100% of the

product can be easily inspected´.

³That makes the most sense´.



100% Inspection - Reflection

Even one defective product is enough to destroy a

customer¶s confidence in a company.

To stay competitive a company must supply good product in thousands.

The best way to achieve this is to organize

production to inspect 100% of the products.



Finding Defects in the Subsequent

Process Since subsequent processes are also µusers¶ of

the product being manufactured, they are also

expert at finding defects.

If products are produced in a flow, each

product is sent to the next process as soon as it

is finished and defects are therefore foundimmediately.



Two Strategies for Zero Defects

1. DON¶T MAK E IT!



1. Don¶t Make It!

Don¶t make product you don¶t need.

The more you make, the greater the

opportunity for defects.

Follow µjust-in-time¶ principles by only making

what is needed, when it is needed in the amountneeded.



2. Build Safeguards



2. Build Safeguards

The user is an expert in finding defects.

Therefore build safeguards into the

production process.

Quality can be built into products byimplementation of Poka-Yoke.



Errors & Defects

Humans make errors ± Cause. Defects arise, because errors are

made. (Effect).

It is impossible to eliminate errors from tasks performed byhumans.

Errors will not turn into defects if feedback and action at place

at the error stage.

Corrective measures can reduce occurrences of errors.

17



Causes of Defects

Process Defects

1. Process failures ± Operational or procedural.

2. Process errors ± Incorrect or imprecise.

Product Defects

1. Incomplete product.

2. Sub ± standard product.

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Levels of Defects

Level 1: Defects shipped out of factory (Taylor

Methods).

Level 2: Defects within the factory (SPC methods).

Level 3: Defects reduced (Demming/ Juran methods).

Level 4: Defects kept within production stage

(Demming/ Juran methods). Level 5: Defects nor produced (Poke ± Yoke

method).

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3 Methods of Inspection

Judgment Inspection (Taylor¶s inspection that discovers

defects). Absolute inspection that discovers defects at the end of the

process. Leads to rework cost, scrap cost.

Informative Inspection (Shewhart¶s inspection that reduces

defects). I nspection process which reduces defects at the end of the

process using inner process checks.

Source Inspection (Shingo¶s inspection that eliminates

defects). I nspection built into the operation to detect errors before its

occurrence.

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Shingo¶s Method

Zero defects.

Zero wastes.

Zero delays.

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Ask Five Questions

Why? Describe.

Why? Describe.

Why? Describe.

Why? Describe.

Why? Response.

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Inspection with Poka Yoke

Source Inspection (ZQC)

± built into process

± leads to a zero defect Systems Self Check Informative Inspections (SQC)

± built inside or outside immediate process

± reduces defects to a minimum

Successive Check Informative Inspection (SQC)

± built inside or outside sequential process

± reduces defects to a minimum

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