MISTAKE - PROOFING (POKA – YOKE)

Mistake - Proofing emphasizes the detection and correction of mistakes before they become defects delivered to customers. It puts special attention on the one constant threat to any process: human error.

Mistake – Proofing is simply to pay careful attention to every activity in the process and to place checks and problem prevention at each step. It’s a matter of constant, instantaneous feedback, rather like the balance and direction data transmitted from a cyclist’s ears to brain, keeping his or her bike upright and on the path.

USES OF MISTAKE – PROOFING
Mistake – Proofing can be used to:
Fine – tune improvements and process designs from DMAIC projects.
Gather data from processes approaching Six Sigma performance.
Eliminate the kinds of process issues and defects needed to take a
process from 4.5 to 6 Sigma.

BASIC STEPS IN MISTAKE – PROOFING
Mistake – Proofing is best applied after completion of a through FMEA
prediction and prevention review. Then we can
Identify possible errors that might occur despite preventive actions.
Determine a way to detect that an error or malfunction is taking place or about to occur.
Identify and select the type of action to be taken when an error is detected.

DIFFERENT KIND OF ERRORS

Forgetfulness – Rail gate closing
Errors due to misunderstanding – Steps on break car with auto transmission
Errors in identification – Bill amount
Errors made by Amateurs
Wilfull errors – No cars at sight crossing in red.
In advertent errors – Crossing without noticing
Errors due to slowness – Delays, step on break
Errors due to lack of standards – To discretion
Surprise errors – Malfunction without warning
Intentional errors – Crimes
Mistake happen for many reasons, but almost all can be prevented if we take the
Time to identify when and why they happen.

The basic types of “Mistake – Proofing Device” are:

Control:
An action that self – corrects the process, like an automatic spell –checker / corrector.

Shutdown:
A procedure or device that blocks or shuts down the process when an error occurs. Example. The automatic shutoff feature of a home iron.

Warning:
This alerts the person involved in the work that something is going wrong.
Example. A seat – belt buzzer. So is a control chart that shows that a process may
be “out of control”.

Some common types of Mistake –Proofing measures include:
Color-and shape-coding of materials and documents
Distinctive shapes of such key items as legal documents
Symbols and icons to identify easily confused items
Computerized checklists, clear forms, best-in-class, up-to-date procedures and simple workflows will help to prevent errors from becoming defects in the hands of customers.

MISTAKE – PROOFING “DOS AND DON’TS”

DO’s:
Try to imagine all conceivable errors that can be made.
Use of all your creative powers to brainstorming clever ways to detect
and correct errors as part of the work process itself.

DON’TS:
Fall into the “ to error is human” mindset.
Rely on people to catch their own errors all the time.