Quality improvement tool "poka yoke"
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03-04-2010, 06:10 PM


Shingo is well-known for his evolutionary work at Toyota and other Japanese companies, where he developed entire production systems focused on achieving zero defects in production. Behind poka-yoke is the notion that it is not acceptable to produce even a small amount of nonconforming product. To become a world-class competitor, an organization must adopt not only a philosophy but a practice of producing zero defects. Poka-yoke methods are the simple concepts for achieving this goal and are a key component of the continual improvement strategy in many leading Japanese companies today. Because of its preventive nature, poka-yoke represents what the Japanese refer to as "good kaizen", or superior continual improvement. How does poka-yoke work? Essentially poka-yoke devices are installed upon process equipment to eliminate or reduce the possibility of error. The specific devices that are employed will depend upon the nature of the process they are used on, but the most common types of poka-yoke devices are inexpensive modifications to process equipment, including such things as locator pins, limit switches and interference pins. Their purpose is to reduce the variability that exists in processing and to ensure consistent, defect-free production.Mistake-proofing is the use of process or design features to prevent errors or their negative impact. Mistake-proofing is also known as poka-yoke, which is Japanese slang for avoiding inadvertent errors. It was formalized by Shigeo Shingo .Poka-yoke is an preventive action that focuses on identifying and eliminating the special causes of variation in production processes, which inevitably lead to product nonconformities or defects poka-yoke offers a strategy for preventing defects at the source that is both cost-effective and easy to understand and apply. It is also a Valuable tool to add organization's continual improvement tool box, if applicable. While at heart a preventive action, poka-yoke is a continual improvement strategy that offers a way to move the QMS towards a higher level of Performance The poka-yoke concept was created in the mid-1980s by Shigeo Shingo, a Japanese manufacturing engineer.

TYPES OF POKA YOKE

Poka-yoke devices work because a nonconformity can only be in one of two states-it is about to occur or has already happened. Poka-yoke devices employ three basic methods to prevent product defects: We can classify the working of Poka yoke devices in to three types.

1. Shutdown. Poka-yoke devices monitor critical process conditions and shut down the process when a parameter moves out of the desirable range, indicating that a defective product has either been produced or is about to be produced.
2. Control. Poka-yoke devices are installed on process equipment and/or work pieces, making it impossible to produce defects and/or to flow a nonconforming product onto the next process.
3. Warning. Poka-yoke devices signal to a worker that a defect has been produced. The worker must intervene to correct the process (es) responsible for causing the defect, since otherwise the process (es) will output further nonconforming product
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24-09-2010, 05:09 PM


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Quality improvement tool "poka yoke"


bstract


Shigeo Shingo was one of the industrial engineers at Toyota who has been credited with creating and formalizing Zero Quality Control (ZQC), an approach to quality management that relies heavily on the use of poka-yoke (pronounced POH-kah YOH-kay) devices. Poka-yoke is Japanese for mistake-proofing. These devices are used either to prevent the special causes that result in defects, or to inexpensively inspect each item that is produced to determine whether it is acceptable or defective
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27-09-2010, 12:06 PM



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POKA-YOKE, AS A QUALITY IMPROVEMENT TOOL


abstract

Shigeo shingo defined poka-yoke as POKA- ‘Inadvertent mistake that anyone can make’ and YOKE- ‘To prevent or proof’

Poka-yoke is a tool to have “zero defects” and even reduce or eliminate quality control.

Poka-yoke is a Japanese name for “fool-proofing”.

Poke-yoke represents the intelligence of the operator by excluding repetitive actions that require a thinking process.

By this method the operator is more free creative thinking and added value activities.

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08-01-2011, 03:05 PM

ABSTRACT


The dictionary has many definitions for quality. A short definition, that is widely accepted is Quality is customer satisfaction. Quality is a relative term generally used with reference to the end use of the product. According to Edward Deming Quality should aim at customer need both present and future. The increasing need for quality resulted in formation of quality management systems (QMS) .When international organizations of standards (ISO) which comprises of National standard bodies of 95 countries put forward some quality standards for operation of quality management systems known as ISO standards. Latest ISO 9001 standards gives much importance of taking preventive actions in an organization to avoid problems related to non conformance and other unintentional mistakes . POKA YOKE or mistake proofing is quality improvement tool which avoids the occurrences of unintentional errors in a system. This concept was formulated by Dr. Shigeo Shingo, a famous Japanese manufacturing engineer. Shingo is well-known for his evolutionary work at Toyota and other Japanese companies, where he developed entire production systems focused on achieving zero defects in production.


.doc   Quality improvement tool “poka yoke”.doc (Size: 1.35 MB / Downloads: 114)

CONTENTS


CHAPTERS PAGE NO



1. INTRODUCTION TO QUALITY MANAGEMENT 1
2. CONTINUAL IMPROVEMENT 3
3. POKA YOKE 5
4. TYPES OF POKA YOKE 7
5. EVERY DAY EXAMPLES 8
6. INDUSTRIAL EXAMPLES 10
7. POKAYOKE AND INSPECTIONS 12
8. ADVANTAGES OF POKA YOKE 1
9. CONCLUSION 16
REFERENCES 17

CHAPTER 1

INTRODUCTION TO QUALITY MANAGEMENT


Since the ISO 9000 quality assurance and quality management standards were introduced in 1987, ISO 9001 and the other conformance standards have required organizations to have quality systems containing procedures for corrective and preventive action. However, even with the improved wording in Sub clause 8.5.3, Improvement— Preventive Action, many organizations face two challenges with this Requirement Understanding the difference between corrective and preventive action in quality management system (QMS) terms Identifying and implementing tools and procedures to help pursue preventive action.

One way to differentiate between them is that a corrective action is a response to a nonconformance in the QMS that needs to be fixed for the QMS to be truly effective while a preventive Action is a proactive step to prevent nonconformance from affecting The QMS and the organization in the first place. While both are important to continual improvement of the effectiveness of a QMS, preventive actions are purely continual improvement activities that constitute a strategy while corrective actions are designed to prevent slippage and maintain effectiveness with an end goal begin an improved QMS after the actions are taken. It is important to emphasize that ISO 9001:2000 places greater stress than its predecessors on preventive actions as a means of controlling or eliminating defects from production. This emphasis is highlighted by the new edition’s process approach to quality management, shifting as it does ISO 9001’s center of gravity away from assurance and towards continual improvement An effective ISO 9001:2000 QMS should deliver and sustain measurable and meaningful performance improvement.


ISO 9001:2000 views a QMS as a continual “process” rather than as a series of 20 clauses (ISO 9001:1994). This process approach-oriented standard begins with management’s responsibility to provide direction and resources, then moves on to planning and controlling the processes that deliver products and services and concludes with measurement and monitoring with a goal of improvement. In addition to the preventive action issue raised above, of particular significance is the fact that inputs to the quality management process are defined as “customer requirements”, with the output considered to be “customer satisfaction”. Further, the scope of what used to be inspection and testing in ISO 9001:1994 has been dramatically expanded to include Analysis of Data (Clause 8.4). Instead of checking the product (or service) at various stages to “verify that the specified requirements for the product are met” (Sub clause 4.10.1, Inspection and Testing—General, in ISO 9001:1994), an organization must now analyze the data resulting from measurements. As a result, there is a new, significant emphasis on being proactive and preventive— the beginning of continual improvement.


CHAPTER 2

CONTINUAL IMPROVEMENT


As mentioned earlier ISO 9001:2000 views a QMS as a continual “process” rather than as set of quality clauses. In a continual process approach priority is given to developing, implementing and improving the effectiveness of a quality management system, to enhance customer satisfaction by meeting customer requirements.

For an organization to function effectively, it has to identify and manage numerous linked activities. An activity using resources, and manage in order to enable the transformation of inputs into out puts, can be considered as a process. The application of a system of processes within an organization, together with the identification and interactions of these processes, and there management, can be referred to as the process approach. The continual improvement of processes based on objective measurement is very important.

An important step in continual improvement of a system is implementation of preventive actions and corrective actions. More priority is given to preventive actions. corrective actions deal with actual problems—they already occurred—while preventive deal with potential problems—they have occurred yet. The corrective actions procedure is essentially a problem fixing procedure, while the preventive measures procedure is a risk-analysis process. In other words, a preventive action is targeted at a potential nonconformity, in that one will most likely occur unless an action to eliminate its cause is taken. If you truly understand it, ISO 9001:2000 makes it relatively simple to identify potential nonconformities. Objectives must be measurable and requirements must be defined for the measuring and monitoring of processes and products, making the setting of targets for these data gathering activities a natural progression with ISO 9001:2000. When a measurement trends in them wrong direction relative to the defined target, organizations will want to divert problem by taking action. This action would be preventive. The standard asks companies to record and review actions taken, and significant preventive actions should be considered for management review. On the other hand, if actions are designed not to address a potential issue and an organization merely wants to

Improve some aspect of its QMS, and then the activity is considered continual improvement. In actuality, ISO 9001:2000 does force an organization to assemble a generous tool box with which to perform continual improvement project and implimentations: quality policy, quality objectives, audit results, analysis of data, corrective and preventive actions and management review. To fully demonstrate continual improvement, companies should be able to present a clear picture of what the situation was before and after improvement actions have been taken
One tool any organization implementing preventive action procedures should explore is poka-yoke, a Japanese improvement strategy for mistake-proofing to prevent defects (or Nonconformities) from arising during production processes.


CHAPTER 3

POKA YOKE


Mistake-proofing is the use of process or design features to prevent errors or their negative impact. Mistake-proofing is also known as poka-yoke, which is Japanese slang for avoiding inadvertent errors. It was formalized by Shigeo Shingo .Poka-yoke is an preventive action that focuses on identifying and eliminating the special causes of variation in production processes, which inevitably lead to product nonconformities or defects poka-yoke offers a strategy for preventing defects at the source that is both cost-effective and easy to understand and apply. It is also a Valuable tool to add organization’s continual improvement tool box, if applicable. While at heart a preventive action, poka-yoke is a continual improvement strategy that offers a way to move the QMS towards a higher level of Performance The poka-yoke concept was created in the mid-1980s by Shigeo Shingo, a Japanese manufacturing engineer.







Fig 1
Dr. Shigeo Shingo

Shingo is well-known for his evolutionary work at Toyota and other Japanese companies, where he developed entire production systems focused on achieving zero defects in production. Behind poka-yoke is the notion that it is not acceptable to produce even a small amount of nonconforming product. To become a world-class competitor, an organization must adopt not only a philosophy but a practice of producing zero defects. Poka-yoke methods are the simple concepts for achieving this goal and are a key component of the continual improvement strategy in many leading Japanese companies today. Because of its preventive nature, poka-yoke represents what the Japanese refer to as “good kaizen”, or superior continual improvement. How does poka-yoke work? Essentially poka-yoke devices are installed upon process equipment to eliminate or reduce the possibility of error. The specific devices that are employed will depend upon the nature of the process they are used on, but the most common types of poka-yoke devices are inexpensive modifications to process equipment, including such things as locator pins, limit switches and interference pins. Their purpose is to reduce the variability that exists in processing and to ensure consistent, defect-free production.



CHAPTER 4

TYPES OF POKA YOKE


Poka-yoke devices work because a nonconformity can only be in one of two states—it is about to occur or has already happened. Poka-yoke devices employ three basic methods to prevent product defects: We can classify the working of Poka yoke devices in to three types.

1. Shutdown. Poka-yoke devices monitor critical process conditions and shut down the process when a parameter moves out of the desirable range, indicating that a defective product has either been produced or is about to be produced.
2. Control. Poka-yoke devices are installed on process equipment and/or work pieces, making it impossible to produce defects and/or to flow a nonconforming product onto the next process.
3. Warning. Poka-yoke devices signal to a worker that a defect has been produced. The worker must intervene to correct the process (es) responsible for causing the defect, since otherwise the process (es) will output further nonconforming product.

It is very important to understand the working environment of the organization to develop a poka yoke device. Clear cut idea about the potential nonconformities will help in developing a efficient poka yoke device. While developing a poka yoke device all classes of workers directly or indirectly dealing with it should also get involved. That will give a good understanding of working of the device and more specified requirements regarding the device can be obtained.


CHAPTER 5

EVERY DAY EXAMPLES


Fig 2 Fig 3


3.5 inch diskettes cannot be inserted unless diskette (fig 2) is oriented correctly. This is as far as a disk can be inserted upside-down. The beveled corner of the diskette along with the fact that the diskette is not square, prohibit incorrect orientation.

Fueling area of car has three error-proofing devices: (fig 3)
1. Insert keeps leaded-fuel nozzle from being inserted
2. Does not allow loss of gas cap
3. Gas cap has ratchet to signal proper tightness and
prevent over tightening.
Fig 4



This lawn mover will automatically stop when its handle is dropped. Thus it avoids wastage of power and also reduces the risk of accidents.

Fig 5 A Fig 5 B


In the above picture 5 A, an ordinary cooking range is shown. It doesn’t show the dials and corresponding burners, thus possibility to commit mistakes is more. The situation changes when we redesign the cooking range in which each burner and its dial are geometrically represented. Fig 5 B


CHAPTER 6

INDUSTRIAL EXAMPLES

Shingo cited an example of poka yoke in action in Zero Quality Control: Source Inspection and the Poka-Yoke System (Productivity Press, 1986).

Suppose a worker must assemble a device that has two push-buttons where a spring must be put under each button. Sometimes the worker will forget to put the spring under the button and a defect occurs. A simple poka-yoke device to eliminate this problem was developed. The worker counts out two springs from a bin and places them in a small dish. After assembly is completed, if a spring remains in the dish, an error has occurred. The worker knows a spring has been omitted and can correct the omission immediately. While the process of having the worker examine the dish involves minimal cost and interruption, it effectively functions as a form of inspection that is an important addition to prevent defects. The cost of rework at this point is Also minimal, although the preferred outcome is still to find the dish empty at the end of assembly, which avoids even the small cost of rework at this stage. Shingo’s example also demonstrates that poka-yoke performs well when the Preventive action is aimed at eliminating operator oversights and omissions. In such cases, poka-yoke devices can be an effective alternative to the usual exhortations for greater worker diligence and application. Another example would be the spot-welding of nuts on a work piece. In this case, the work piece and an inserted nut are set in a jig on a spot-welding machine and are welded together. However, it is possible that a work piece without a nut in place could be welded, thus yielding a defective piece. The poka-yoke solution in this case is to install a photoelectric detector and light source on the spot-welding machine. If a work piece without a nut attached is placed on the jig, then the welding head assumes a lower position on the work piece and interrupts the light beam, triggering the photoelectric cell. This halts the process and signals to the operator that there is a problem.

Additional examples of poka-yoke devices in action include the following.
• Guide pins of varying sizes that ensure the upper and lower portions of a stamping die are correctly aligned and centered.
• Error-detection alarms that alert workers when a defective part has been produced.
• Limit switches that ensure correct placement of work pieces in machines and processing equipment.
• Counters used to ensure that all processing operations have been completed before transferring a part to the next process.
• Checklists filled out to ensure that all components in an assembly have been installed.


CHAPTER 7

POKA YOKE AND INSPECTION

The Relationship between Poka-Yoke and Inspections, Shingo differentiated between three different types of inspection
1. Judgment
2. Informative
3. Source

1. Judgment inspections discover defects by sorting the defective pieces out from finished products. Judgment inspections gave rise to the term “inspecting quality into a product”. Shingo agreed with the consensus in modern quality management that “inspecting in quality” is not an effective approach to realizing quality and he advocated against its use.

2. Informative inspection, on the other hand, uses data gained from inspection as feedback to control and improve the process and reduce the occurrence of defects during production. Traditional statistical process control (SPC) is a type of informative inspection. In Shingo’s Zero Quality Control (ZQC) system, both successive checks and self-checks is also a type of informative inspection. Successive checks were Shingo’s response to the insight that the speed of improvements is a direct function of the timeliness with which quality feedback is obtained. Typically, work-in-process undergoes many processing steps as it is moved through a manufacturing facility, but inspections are often not conducted until the intermediate stages. Shingo’s concern was that inspections may not occur soon enough after a production process to give the timely information necessary to determine the cause of the quality problem and to prevent its recurrence in the future. Under this approach, each operation in the flow performs a quality inspection. Effective poka-yoke devices make such an inspection system possible by reducing the time and cost of inspection to near zero. Because these inspections entail minimal cost, every item may be inspected. Provided that work-in-process inventories are low, quality feedback used to improve production processes can be obtained very rapidly by the upstream operation that needs to make an improvement. While successive checks give rapid feedback, carrying out self-checks by having each worker use poka-yoke devices that allow him/her to assess the quality of his/her own work provides even faster feedback. Because operators check every unit produced, they are able to recognize what process conditions have changed when a defect is produced This insight can then be used to prevent further defects (i.e., root-cause analysis). Because of the immediate feedback capability, self-checks are preferred to successive checks whenever possible. Shingo believed that, while informative inspections and self-checks each had their place in quality management, the most significant form of inspection was source inspection.

3. Source inspections attempt to eliminate defects by determining that the conditions necessary for defect-free production exist prior to the commencement of actual production. Under a source-inspection system, poka-yoke devices are employed to ensure that the optimal conditions for error-free production exist and, in fact, prevent the production process from beginning until such a state has been realized. The spot-welding example given above showed how poka-yoke devices can be used to perform source inspections and ensure that the conditions necessary for defect-free production exist.


CHAPTER 8

ADVANTAGES OF POKA YOKE


1. Zero defects

Poka yoke devices reduced mistakes or defects almost to zero in production and other regions of company. Eg.
• Ortho-Clinical Diagnostics (Johnson & Johnson) saved $75000 annually by discovering a new use of Post-It® notes
• AT&T Power Systems (Lucent Technologies) reported net saving of $2545 per device (3300 devices)

2. Inexpensive devices
In almost all cases poka yoke devices are very cheap and the result out of them is tremendous.
• Weber Aircraft reports saving $350,000 during their first year of implementation of approximately 300 devices.
• Dana corporation has reported a $500,000 savings resulting from a $6 device
• GE Aircraft Engines spends a minimum of $500,000 on any in-flight shut-down (IFSD). Spending $10,000 to stop one IFSD yields 50:1 benefit

3. Rapid feed back.

poka-yoke is an effective technique in the improvement toolbox. When used in combination with source inspection, it permits an organization to launch preventive actions while systematically moving the QMS to a higher level of performance. That is the ultimate goal of preventive action.

4. Continual improvement

The importance of continual improvement has already been explained. Poka yoke devices are really a boost to continual improvement strategy of the company.

Some results of poka yoke on global companies are also given
• AT&T Power Systems is first US manufacturer to win the Deming prize. Average outgoing defects reduced by 70%
• A washing machine drain pipe assembly line produced 180,000 units without a single defect (6 months).
Other advantages are
5. Leads to more innovation in an industry
6. This is a preventive action
7. Helps in achieving quality objective of the organization.
8. Avoids non conformances which gives good efficiency to the production system


CONCLUSION


All organizations are spending much on quality control and quality assurance. These objectives of organizations can be achieved by applications of poka yoke devices. The concept of “zero quality control” is getting closer by these quality improvement tools. Our country should adopt such tools for effective quality control in a scenario of globalization. These tools are mostly cheaper and easy to implement in the system. This tool will be more effective and also gives rapid feed back of the system.



REFERENCES

• TOTAL QUALITY MANAGEMENT ,{GROUP OF AUTHORS } PEARSON EDUCATION 2004
• QUALITY CONTROL & TQM- PL JAIN 2003
• TQM – POORNIMA M PEARSON EDUCATION 2003
• THE INFORMED OUT LOOK
• informintl.com
• iso.org
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