POKA YOKE
Mistake proofing a process
GROUP 12
- Sarah Manoj (GJ22CM013)
- Vishwas Vardhan (GJ22CMM028)
- Vishnu Vallem (GJ22CMM020)
- Leelasai Koripilli (GJ22GL045)
- Vishwas Logani (GJ22NS059)
INTRODUCTION
The term Poke yoke in its literal sense refers to a Japanese term ‘to mistake proof a process.’ The
Japanese word ‘Poka’ means an unfortunate mistake and the word ‘Yoke’ means to prevent. A process
is more prone to an error since it is dependent on human labor therefore the main idea of this concept
is to impose methods to recognize the possible mistakes and take relevant measures to avoid the
problem. It emphasizes that this notion of fault free process should not be an additional step to a
procedure but needs to incorporated in the existing process. In any organization, 60 – 65% of
variabilities that lead to an increase in the overall cycle time of an operation such as rejection of
material or rework due to quality issues are mainly because of errors made by humans. To ensure that
these variabilities are avoided and not repeated in the future Poka-Yoke technique is adopted by
organizations. (Pötters, Sept 2018)
It is easy to apply without a need for any high investments. One of the biggest advantages Poka Yoke is
that it is derived with the help of the worker by applying ideas which can be better for both the
management and the implementation teams.
HISTORY OF POKA YOKE
Shigeo Shingo coined the term poka-yoke to describe industrial processes meant to eliminate human
mistakes in the 1960s. Shingo popularized the poka-yoke technique in Japanese manufacturing.
Inspections that catch all bad items but do nothing to enhance the process are ineffective. Shingo was
adamant that the system's goal was to improve the process, not to identify and eliminate bad items.
Shingo contrasted the concepts of unavoidable human errors and manufacturing flaws. The goal of
poka-yoke is to build a process that allows errors to be discovered and remedied quickly, removing
problems at their source.
The Toyota Production System is focused completely on maximum efficiency and fault-free processes.
The Poka-yoke helps Toyota employees to avoid mistakes in the below manner
BENEFITS OF POKA YOKE
Poka Yoke is wide concept with different ideologies and notion to endure ideas because of its success
rate to reduce any blemishes. It prevents the defected product from reaching out to the customers and
thereby allowing a system to be more productive and profitable. (Steele, n.d.)
There are many benefits of Poka Yoke, here are some as follows –
• Worker safety within the production floor
• Encourages the employees to have continuous improvement mindset as they design ways to
make the process error-proof
• Higher levels of product and service quality.
• Improving the effectiveness of operational processes and increasing production capacity.
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APPLICATION OF POKA YOKE
There are two ways a Poka Yoke can be applied
1. Warning approach –
This approach signals the operator when a mistake occurs and provides the operator a
chance to rectify the mistake. One very common example of Poka Yoka warning approach is
in computer software when we write an email mentioning the attachment of a file and miss
to attach the file while sending out the email, a warning pops up on the screen saying that
the attachment has not been attached.
2. Control approach –
This stops the action completely when a defect occurs and requires a corrective action to be
taken immediately in order to continue with the process. A classic example is when To
ensure that you do not forget your card, an ATM machine withholds your cash until you
have removed your card.
PRINCIPLES OF POKA YOKE
Six principles govern mistake-proofing/Poka Yoke. In terms of essentially resolving mistakes, the
following are listed in order of preference:
1. Elimination ("don't do it anymore") – is the act of removing the chance of mistake from a
product or process by redesigning it such that the task or part is no longer required.
2. Prevention (or "making sure it can't be done wrong") – entails designing and engineering a
product or process in such a way that making a mistake is impossible.
3. Replacement – To improve consistency, a more reliable procedure is substituted ("used
something better").
4. Facilitation – Use of techniques and the combination of processes to make work easier to
complete.
5. Detection – is the act of identifying a mistake before it is processed further, allowing the
user to easily remedy the problem.
6. Mitigation – is the process of attempting to reduce the impact of errors.
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TYPES OF ERROR
Errors are the output of human and environment which cause the process to be less successful and will
lead to defective outputs and outcomes.
TYPES OF ERRORS –
• Omission errors (mistake which occurs because of neglect)
• Errors which occur during the process
• Error which occurs while installing the equipment
• Parts not found
• installation of wrong item in the machine
• Equipment has wrong piece /structural error
• Errors while operating the machine
• Errors which occur while adjusting and taking measurements
Human Error types –
• Forgetfulness (Not Concentrating)
• Misunderstanding (wrong Conclusions)
• Identification error (lack of process noting methods)
• Lack of skill training (unskilled labor)
• Willfully committing error by not abiding by the rules(strike)
• Lack of concentration due to fatigue
• Lag error (more processing time for taking decision)
• Errors because of lack of proper Standards (lack of rule book)
MANUFACTURING INDUSTRY
EXAMPLES
INTERLOCKING METHOD:
• Process description: In rubber manufacturing for tyres, cooling of rubber is done post processing
raw rubber.
• Problem: Accumulation of rubber happens if the take away conveyor and cooling rack don’t
move simultaneously.
• Solution: Interlocking of these components is done to run/stop at same time.
• Key improvement: mismatch in movement of both of these components of rubber
manufacturing process should be avoided by removing the manual operation.
• Post improvement: interlocking facilitates synchronized movement of take away conveyor and
cooling rack and the process is automated. It prevents error.
Before Improvement After Improvement
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PROCESSING ERROR METHOD:
• Process description: an automobile base frame is being matched in a jig.
• Problem: the base frame might be placed backward causing an error. Human involvement is
required to monitor the correct operation.
• Solution: asymmetry can be utilized to place an additional guide pin.
• Key improvement: jig can be modified for correct positioning.
• Post improvement: additional pin provided for an available asymmetry eliminates the scope of
error dur to backward processing.
Before Improvement After Improvement
Poka-yoke systems consist of 3 different methods –
1. Contact
2. Counting
3. Motion-Sequence
CONTACT METHOD
• Process description: Lodge mixer turn on and off according the rope
• Problem: NO interlock so Rope loosening and rewinding could have impact on overall process
as the mixer keep running even after the rope gets dwindled or looses
• Solution: Hoist motor should stop when the rope gets loosen or strangled.
• Key improvement: skip Hoist motor when rope rewinds or when it loses tension
• Post improvement: Limit switch was provided to avoid the overall rewinding or differences in
rope Tension
Before Improvement After Improvement
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FIXED VALUE METHOD:
• This type of process is used when a repetitive activity needs to occur multiple times.
• In this method, the action is performed at a workstation where in a part must be added to a product
in defined number of actions.
• When the desired value is achieved, the machine automatically counts the number of times the
particular action has taken place and thus releases the product.
• A simple example would be – A metal sheet placed on a worktable needs to have a precise number
of holes at a specific distance. Here the machine will perform the action and accordingly perform the
repeated action thereby minimizing error.
Before Improvement After Improvement
MOTION SETP METHOD
It is used to check whether the worker performs every step-in order and checks whether its performed
or not sensors such as Gyro sensor and Proximity Sensor are used to get the motion in order.
Poka-Yoke Implementation
Before After
In an auto parts assembly operation, multiple Installing a door and light on each bin and wiring
models require the installation of different parts. it to the relevant model gave the assembly
According to each model’s specific requirement, operator much more clarity in selecting the
the parts are collected from different bins. This relevant bin according to the model’s
method might lead to wrong parts being requirements and the doors would only open for
collected or some even being mixed up or missed the part selected and the lights would indicate to
completely. the operator can view which parts are being
collected.
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SERVICE INDUSTRY
• Service industry is a human driven industry at large.
• Has a huge margin of error (error itself might be very small)
• These errors can lead to big problems like Loss of productivity, poor customer service, loss of
customer etc.
• These mistakes have a tendency of being most repetitive.
• Human involvement in service industry should be minimized to prevent scope of errors.
EXAMPLE 1
QR code for menu in restaurants
Now a days restaurants have installed a QR code sticker on the table itself which can be scanned by the
customer leading them to an app/website having menu of the restaurant and create an order basket.
After finalizing the dishes and respective quantities, the order can be placed along with the payment
option also available right away in the app resolving the problem of incorrect change. This reduces the
human error and also prevents waiting time eliminating the mistakes while ordering.
Implication of not implementing POKA-YOKE –
If the waiter takes the order manually, he/she might make a mistake in writing the order or
communicating the order to kitchen. Also, customers might not be attended by the waiter immediately
and has a waiting time associated.
Also, there might arise a problem in the billing and payment process due to
miscommunication/incorrect entry of the order or mismatch in the change given.
EXAMPLE 2
E-Filing of Income Tax Return
Income tax return filing is a complicated process requiring a lot of personal details and financial
documents to be filled. With the help of POKA-YOKE method, various checks are implemented in e-filing
such as –
• Personal details are correct or not (verified by uploading govt. ID)
• Uploading documents such as Form 16, Form 26AS etc and check which ITR form is applicable.
• Post uploading all docs, it calculates the liabilities/refund and proceed with filing.
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Implication of not implementing POKA-YOKE –
• Had there not been e-filing, human mistakes can occur while filling the documents details due to
manual writing.
• Miscommunication can lead to mistakes in details.
• Verification of documents can take up lot of time, slowing the process.
IMPLICATIONS OF NOT IMPLEMENTING POKA YOKE
• Delay in service delivery. –
Example – Not using electronic pre filed form in income tax returns takes a lot of time for
customer and thereby delay in processing the tax returns.
• High costs –
Example – By not using an arrow green symbol at the metro entrance gate there will be a heavy
rush at metro station as people will not be aware through which gate they have to enter and
exit; this makes operator to incur costs because passenger who cannot catch the train on-time is
a loss for company.
• A decrease in safety is an problem where workers are exposed to hazardous materials or
dangerous machinery such as when working with high-inertia machines or petrochemicals.
Example – In petrol chemical industries mixing one solvent with others will be very hazardous
and will lead to polluting the nearby environment which will create a lot of legal and regulatory
problems for the company.
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• Operators will need more training –
Processes containing poka-yoke devices automatically correct any deviation from what is
required.
Example – At diamond cutting industry, while cutting the diamonds to the required
specifications any deviation from the given dimensions will create a huge loss. If poka yoke
method is not used here the operators have to be given separate training about how to identify
dimensions exactly which is a time taking process.
• Higher quality checks are needed –
Example – For an airplane assembly line there is a chance of zero error and the time factor also
need to be considered, without implementing poka yoke there will be a considerable amount of
time which has to be put in to check quality again and again.
• Work becomes more repetitive for operators, as it prevents them work through processes
error-free which pushes them from having to go back and do it again correctly.
Example – The sense of anxiety among workers the What if scenario’s will be high if there is not
poka yoke being followed.
• The quality of processes is decreased, resulting in lower quality products. It also begins to
produce non-effective teams that cannot work in a coordinated effort to deliver error-free
products the first time.
Example – Any delay of work in one department of organization will have cascading effect on
another department which creates mis-understandings across teams.
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References
• Pötters, P. S. (Sept 2018). Total quality managment & Buisness Excellence. 1200-1212.
• Steele, C. (n.d.). Poka Yoke Definition: What is Poka Yoke? Retrieved from Go skills:
https://www.goskills.com/Lean-Six-Sigma/Resources/Poka-yoke-definition
• https://www.referenceforbusiness.com/management/Or-Pr/Poka-Yoke.html#ixzz7PDRJOFiS
• https://mag.toyota.co.uk/poka-yoke/
• https://kanbanzone.com/resources/lean/toyota-production-system/poka-yoke/
• https://www.rnaautomation.com/poka-yoke-in-manufacturing/
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