Error-proof , POKA YOKE: by MIE

error proofing


Error proofing is a structured approach to ensuring quality all the way through your work processes. This approach enables you to improve your production or business processes in order to prevent particular errors, and hence defects from happening.

This methodology is vital for lean system, where defects in the products or services are not accepted while there is no tolerance. In “fat” system defects can be easily replaced by good ones, later on count defects and repair them.

Reasons of errors

Human mistake

lack of knowledge, skills or ability

when employees have not received proper training to perform a task and their skill or knowledge is not assessed.

Mental error

These include slips and mistakes. Slips are subconscious actions. They usually occur when an experienced employee forgets to perform a task. Mistakes are conscious actions. They occur when an employee decides to perform a task in a way that results in an error.

Mechanical process errors

Some tasks are physically difficult to do and are thus prone to error. They can result in repetitive strain injuries physical exhaustion, which are both known to produce errors.


Internal distraction like emotional stress and daydreaming are good examples. External distractions include high traffic areas, load conversations, and ringing phones.

Loss of memory

Many tasks require employees to recall information that can be forgotten. In addition, aging, drugs, or alcohol use, and fatigue can cause memory loss and result in error

Loss of emotional control

Anger, sorrow, jealousy, and fear often work as emotional blinders, hampering employees’ ability to work correctly.

Measurements/ evaluations

Unfortunately measurement devices and methods are as equally prone to error as the process and products that they measure. Use one of measurement system analysis methodology to know how big it is in your system.


85% of the errors that occur in the work process are caused by tasks and technology involved in the process, said industry experts.

Sources of error in the work process are

Process step


Decision making





Materials can contribute to error in the following ways

-1 Using wrong raw materials

-2 Using expired materials

-3 Using damaged materials, from transportation or bad handling, bad storing

-4 Using wrong amount


Machines can contribute to error in the following ways

Poor machine maintenance

Using bad spare parts

Poor machine capability index

Environmental conditions

Poor lighting

Excessive heat/ cold

High noise level

Humidity level high/low


Poor administration control

Pressure due to high target

Pressure due to high competition among employees

Red-flag conditions

Errors are happening in certain types of situations, these are called red-flag conditions.

Conditions include:

-1 Lack of an effective standard

-2 Rapid repetition

-3 High volume

-4 Poor environmental conditions

-5 Adjustment

-6 Tooling change

-7 Many critical specs

-8 Many mixed parts

-9 Multiple steps

-10 Infrequent production / orders

problem solving model

1- describe the problem

2- describe the current process

3- identify the root cause

4- develop a solution and action plan

5- implement the solution

6- review and evaluate the results

7- reflect and act on learnings

Some examples from real life

Electrical plug


SIM card










well, you got the idea