Quality Control Tools

Quality Control Tools

Production environments that utilize modern quality control methods are dependant upon statistical literacy. The tools used therein are called the seven quality control tools. These include:

1. Check sheet
2. Pareto Chart
3. Flow Chart
4. Cause and Effect Diagram
5. Histogram
6. Scatter Diagram
7. Control Chart

Check sheet
The function of a check sheet is to present information in an efficient, graphical format. This may be accomplished with a simple listing of items. However, the utility of the check sheet may be significantly enhanced, in some instances, by incorporating a depiction of the system under analysis into the form.

Pareto Chart
Pareto charts are extremely useful because they can be used to identify those factors that have the greatest cumulative effect on the system, and thus screen out the less significant factors in an analysis. Ideally, this allows the user to focus attention on a few important factors in a process. They are created by plotting the cumulative frequencies of the relative frequency data (event count data), in descending order. When this is done, the most essential factors for the analysis are graphically apparent, and in an orderly format.

Flowchart
Flowcharts are pictorial representations of a process. By breaking the process down into its constituent steps, flowcharts can be useful in identifying where errors are likely to be found in the system.

Cause and Effect Diagram
This diagram, also called an Ishikawa diagram (or fish bone diagram), is used to associate multiple possible causes with a single effect. Thus, given a particular effect, the diagram is constructed to identify and organize possible causes for it. The primary branch represents the effect (the quality characteristic that is intended to be improved and controlled) and is typically labelled on the right side of the diagram. Each major branch of the diagram corresponds to a major cause (or class of causes) that directly relates to the effect. Minor branches correspond to more detailed causal factors. This type of diagram is useful in any analysis, as it illustrates the relationship between cause and effect in a rational manner.

Histogram
Histograms provide a simple, graphical view of accumulated data, including its dispersion and central tendency. In addition to the ease with which they can be constructed, histograms provide the easiest way to evaluate the distribution of data.

Scatter Diagram
Scatter diagrams are graphical tools that attempt to depict the influence that one variable has on another. A common diagram of this type usually displays points representing the observed value of one variable corresponding to the value of another variable.

Control Chart
The control chart is the fundamental tool of statistical process control, as it indicates the range of variability that is built into a system (known as common cause variation). Thus, it helps determine whether or not a process is operating consistently or if a special cause has occurred to change the process mean or variance. The bounds of the control chart are marked by upper and lower control limits that are calculated by applying statistical formulas to data from the process. Data points that fall outside these bounds represent variations due to special causes, which can typically be found and eliminated. On the other hand, improvements in common cause variation require fundamental changes in the process.


Summary
The tools listed above are ideally utilized in a particular methodology, which typically involves either reducing the process variability or identifying specific problems in the process. However, other methodologies may need to be developed to allow for sufficient customization to a certain specific process. In any case, the tools should be utilized to ensure that all attempts at process improvement include:

• Discovery
• Analysis
• Improvement
• Monitoring
• Implementation
• Verification
  

David Garvin

David Garvin identified his “eight dimensions of quality” which he maintained covered the meaning of quality to managers, operators and customers. By accepting that customers have a different perception of quality than that of a manager, quality effort can be focused.

The eight dimensions.

1. Performance: Main operating characteristics such as power, sound, speed etc.
2. Features: The extras that supplement the main characteristics such as trim,sunroof etc.
3. Reliability: How often it breaks down
4. Conformance: How close it is to the design specification or service to the customers experience.
5. Durability: Length of life, toughness in use, service frequency etc.
6. Serviceability: Ease, cost and friendliness of service.
7. Aesthetics: Appearance and impression.
8. Perceived quality: The feel, finish and manner in which the customer is dealt with.

Thomas Pyzdek

Thomas Pyzdek, Principal of Pyzdek Consulting, Inc.holds a career in business process improvement, which spans 38 years. He is a leading quality and Six Sigma authority and the author of over 50 copyrighted works including The Six Sigma Handbook, The Handbook for Quality Management and Quality Engineering Handbook . Pyzdek was named "Outstanding writer and author" by The International Who’s Who in Quality and he received the Quality Progress Reader’s Choice award for his articles on the future of quality.
Pyzdek has provided consulting to major clients in a broad spectrum of industries. He provides consulting guidance from the executive suite to "Belts" working in the trenches. In his public seminars and client classes he has taught Six Sigma and other business process improvement methodologies to thousands.
Pyzdek is a Fellow of ASQ and recipient of the ASQ Edward’s Medal (1995) and the Simon Collier Quality Award (2004), both for outstanding contributions to the field of quality management. Pyzdek serves on numerous editorial boards, including The Quality Management Journal, Quality Engineering and International Journal of Six Sigma and Competitive Advantage. He has worked in process excellence since 1967.

Poka-yoke

Poka-yoke was coined in Japan during the 1960s by Shigeo Shingo who was one of the industrial engineers at Toyota. Shigeo Shingo is also credited with creating and formalizing Zero Quality Control (poka-yoke techniques to correct possible defects + source inspection to prevent defects = zero quality control).

The initial term was baka-yoke, which means ‘fool-proofing’. In 1963, a worker at Arakawa Body Company refused to use baka-yoke mechanisms in her work area, because of the term’s dishonorable and offensive connotation. Hence, the term was changed to poka-yoke, which means ‘mistake-proofing’.

Ideally, poka-yoke ensures that proper conditions exist before actually executing a process step, preventing defects from occurring in the first place. Where this is not possible, poka-yoke performs a detective function, eliminating defects in the process as early as possible. This can be achieved using three rule.

Following are three rules of poka yoke:

1. Make the task more likely to to come right than wrong
2. Make errors evident right there on the spot
3. Make it possible for person to correct the error right then

Applying poka-yoke (steps)

• Identify the operation or process - based on a pareto.
• Analyze the 5-whys and understand the ways a process can fail.
  Decide the right poka-yoke approach, such as using a
  - shut out type (preventing an error being made), or an
  - attention type (highlighting that an error has been made) poka-yoke.
  Take a more comprehensive approach instead of merely thinking of poka-yokes as limit switches, or automatic shutoffs. A poka-yoke can be electrical, mechanical, procedural, visual, human or any other form that prevents incorrect execution of a process step.
• Determine which is appropriate
  - Contact - use of shape, size or other physical attributes for detection,
  - Constant number - error triggered if a certain number of actions are not made
  - Sequence method - use of a checklist to ensure completing all process steps
• Trial the method and see if it works
• Train the operator, review performance and measure success.
  

MISTAKE-PROOFING PRINCIPLES:

1. Hierarchy of Principles and Moving Upstream to Product & Process Design
   
2. Principle of Elimination
   Role of Product Design - Design out Potential Defects
   
3. Principle of Replacement
   Replace Error-Prone Product Features/Items
   Replace Error-Prone Process Steps
   
4. Principle of Prevention
   Prevent Errors with Product Design - Guidelines & Techniques
   Prevent Errors with Process Design - Guidelines & Techniques
   Poke-Yoke Devices - Sensors, Counters & Other
   
5. Principle of Facilitation
   Product Design Techniques to Facilitate Error Avoidance
   Process Design Techniques to Facilitate Error Avoidance
   Visual Controls
   
6. Principle of Detection
   Defect Detection - Poke Yoke Devices & Self-Checking
   
7. Principle of Mitigation

Joseph Juran

Dr.Joseph Juran born in Romania on 24 Dec 1904 - the chairman emeritus of the Juran Instituite and an ASQC Honorary member. Since 1924, Juran has pursued a variety career in management as an engineer, executive, government administrator, university professor, labour arbitrator, corporate director, and consultant. Specialising in managing for quality, he has authored hundreds of papers and 12 books, including Juran’s Quality Control Handbook (1951) , Quality Planning and Analysis, and Juran on Leadership for Quality.

Juran’s trilogy: This is an approach to cross functional management that is composed of three managerial processes: planning, control, and improvement

• Quality planning: This is the activity of developing the products and processes required to meet customer’s needs. It involves a series of universal steps which can be abbreviated as follows:
  *Establish quality goals
  *Identify the customers- those who will be impacted by the efforts to meet the goal.
  *Determine the customers’ needs
  *Develop product features that respond to customers’ needs
  *Develop processes that are able to produce those product features
  *Establish process controls, and transfer the resulting plans to the operating forces
• Quality control: This process consists of the following steps:
  *Evaluate actual quality performance
  *Compare actual performance to quality goals
  *Act on the difference
• Quality improvement: This process is the means of raising quality performance to unprecedented levels ("breakthrough"). The methodology consists of a series of universal steps:
  *Establish the infrastructure needed to secure annual quality improvement.
  *Identify the specific needs for improvement -the improvement projects
  *For each project establish a project team with clear responsibility for bringing the project to a successful conclusion
  *Provide the resource, motivation, and training needed by the team to:
  1.Diagnose the cause
  2.Stimulate establishment of remedies
  3.Establish controls to hold the gains

Cost of quality: The cost of quality, or not getting it right first time, Juran maintained should be recorded and analysed and classified into failure costs, appraisal costs and prevention costs.
Failure costs: Scrap, rework, corrective actions, warranty claims, customer complaints and loss of custom
Appraisal costs: Inspection, compliance auditing and investigations
Prevention costs: Training, preventive auditing and process improvement implementation

Juran proposes 10 steps to quality improvement:

• Build awareness of the need and opportunity to improve
• Set goals for that improvement
• Create plans to reach the goals
• Provide training
• Conduct projects to solve problems
• Report on progress
• Give recognition for success
• Communicate results
• Keep score
• Maintain momentum

Business Process Re-Engineering

Business process re-engineering is the redesign of business processes and the associated systems and organizational structures to achieve a dramatic improvement in business performance. The business reasons for making such changes could include poor financial performance, external competition, erosion of market share or emerging market opportunities. BPR is not - downsizing, restructuring, reorganization, automation, new technology, etc. It is the examination and change of five components of the business:

• Strategy
• Processes
• Technology
• Organization
• Culture

Michael Hammer defines business process re-engineering in his book Re-engineering the Corporation as: "Fundamental rethinking and radical redesign of business processes to bring about dramatic improvements in performance."

Hammer focuses on one of the key concepts of BPR, that it is fundamental and radical. The alternative business improvement methodology is Continuous Process Improvement, which emphasizes small and measurable refinements to an organization's current processes and systems. Continuous process improvement has its origins in total quality management (TQM) and Six Sigma,a program that began at Motorola.

Philip B. Crosby

Philip B. Crosby was corporate vice president of IIT for 14 years. He was the founder and chairman of the board of Career IV, an executive management consulting firm. Crosby also founded Philip Crosby Associates Inc. and the Quality College. He has authored many books, including Quality is free, Quality without tears, Let’s talk Quality and Leading: The art of becoming an executive. Crosby originated the concept of zero defects. He believed the quality professional must become more knowledgeable and communicative about the business. He also stated that the corporate management must take the cost of quality as a part of the financial system.

Four Absolutes of Quality:
The First Absolute: THE DEFINITION OF QUALITY IS CONFORMANCE TO REQUIREMENTS , NOT AS GOODNESS
The Second Absolute: THE SYSTEM FOR CAUSING QUALITY IS PREVENTIVE , NOT APPRAISAL.
The Third Absolute: THE PERFORMANCE STANDARD MUST BE ZERO DEFECT , NOT "THAT’S CLOSE ENOUGH"
The Fourth Absolute: THE MEASUREMENT OF QUALITY IS THE PRICE OF NONCONFORMANCE , NOT INDEXES.

The Fourteen Steps to Quality Improvement, according to Crosby were:

1. Make it clear that management is committed to quality.
2. Form Quality Improvement Teams with senior representatives from each department.
3. Measure processes to determine where current and potential quality problems lie.
4. Evaluate the cost of quality and explain its use as a management tool.
5. Raise the quality awareness and personal concern of all employees.
6. Take actions to correct problems identified through previous steps.
7. Establish progress monitoring for the improvement process.
8. Train supervisors to actively carry out their part of the quality improvement programme.
9. Hold a Zero Defects Day to reaffirm management commitment.
10. Encourage individuals to establish improvement goals for themselves and for their group.
11. Encourage employees to tell management about obstacles to improving quality.
12. Recognise and appreciate those who participate.
13. Establish Quality Councils to communicate on a regular basis.
14. Do it all over again to emphasise that the quality improvement process never ends.

The Crosby "Vaccine"
In the Crosby style, the "Vaccine" is explained as medicine for management to prevent poor quality. It is in five sections that cover the requirements of Total Quality Management.
Section 1 - Integrity
Treat quality seriously throughout the whole business organisation from top to bottom. That the companies future will be judged on its performance on quality.
Section 2 - Systems
Appropriate measures and systems should be put in place for quality costs, education, quality, performance, review, improvement and customer satisfaction.
Section 3 - Communication
The communication systems are of paramount importance to communicate requirements and specifications and improvement opportunities around the organisation. Customers and operators know what needs to be put in place to improve and listening to them will give you the edge.
Section 4 - Operations
Work with and develop suppliers. Processes should be capable and improvement culture should be the norm.
Section 5 - Policies
Must be clear and consistent throughout the business.