Error Proofing as it is understood
and practiced today is an outgrowth of the quality movement, specifically the
Zero Defects initiative. It is a
team-based plant floor improvement strategy that focuses on production
processes and operations. Error Proofing aims to prevent errors and deviations
from standards of all kinds that can impact quality, safety, manufacturing
costs, and customer satisfaction.
In a simple context any mechanism
or device in a process that helps eliminate defects by preventing, correcting,
or drawing attention to human error as they occur. Also known as poka-yoke, from
poka (inadvertent errors) and yokeru (to avoid) - pronounced POH-kuh YOH-kay. Which
was developed and popularized by Shigeo Shingo.
Why Error proofing is much important?
Human error
is a natural occurrence. When defects
occur on a manufacturing line, there is often a tendency to blame the operator
when the error can be traced back to the operator’s interaction with the
process. The actual reason for the
error, however, is usually a lack of foresight to account for human error by
the people that designed the process, machinery, the layout of the machinery,
or the operating procedures.
Important facts to realize about human error are:
Few workers make errors intentionally, most strive to
prevent errors. Error is inherent in the nature of humans. Error-Proofing
alters the work environment to reduce human errors and improve the safety,
culture, standard of the working environment.
Defects vs Errors
Defects:
A defect is
the result of any deviation from product specification that may lead to
customer dissatisfaction. Product
specifications are set by customer requirements which are translated into
design and manufacturing requirements.
The phrase “deviation from product specifications” means the product is
not produced according to the manufacturing plan.
In other
words, a product must fall into two categories to classify as a defect:
Product has
deviated from manufacturing or design specifications.
The product
does not meet internal and/or external customer expectations.
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One Point Info:
·
Internal
customer : anyone within an
organization who at any time is dependent on anyone else within the
organization
Eg: Next
process, stockholders, employee
·
External
customer; An external customer is someone
who uses the products or services of the company but is not part of the
organization.
Eg: Customer, Supplier
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Errors:
An error is
any deviation from a specified manufacturing process. Errors can be made by machines or people and
can be caused by previous errors that have occurred. All defects are created by errors. This means that if errors can be prevented,
no defects will be created. By using
Error-Proofing, the errors that cause defects are located and eliminated.Error-Proofing
should be continuously used to locate and prevent new errors.
Error proofing approach
There are two type of approach used for error proofing
- Prevention approach
It prevents the error
from occurring or defect that being created. Simply it prevents something from
happening
Eg:
Proximity sensor, Light sensor
- Inspection/Correction approach
It detect the defects
that has created or initiated as method off corrective action or correction
done
Eg: Program offsetting, Rework
Example of Error proofing
The best and
simple example for poka yoke technique is sim card slot designed in cell phone
SIM card slot in cell phones are designed in such a way that
the user is allowed to insert SIM card in a correct way only. There is no
chance for the user to make a mistake while putting the SIM card on a cell
phone. This makes the design mistake proof.
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