QUALITY TOOLS : CAUSE AND EFFECT DIAGRAMS

HISTORY

• Known as Ishikawa Diagrams or Fishbone Diagrams.
• Created by Kaoru Ishikawa in 1968.
• Common uses of the Ishikawa diagram are product design and quality defect prevention to identify potential factors causing an overall effect.
• The CE Diagram is basically used to investigate a problem, exploring, identifying, and displaying the possible causes.
• To identify the relationship between the  effects in a given situation and all of the possible causes.
• To find problem sources and solutions.
• It helps determine the root causes of a problem using a structured approach.

TYPES

•        Manufacturing Industry 6 M’s    Service Industry 5 S’s                             

1. Measurement                            1. Surroundings
2. Material                                     2. Suppliers
3. Machine                                    3. Systems
4. Man Power                               4. Standard Documentation Skills
5. Method                                     5. Scope of Work
6. Mother Nature

•         Marketing Industry 8 P’s       Sales Industry 5S’s

1. Product                                      1. Samples
2. Place                                          2. Schemes
3. Price                                           3. Synchronous
4. People                                        4. Skin
5. Promotion                                   5. Search
6. Process
7. Physical Evidence
8. Packaging

PROCESS

1. Identify the problems to be corrected.
2. Identify any possible causes of the  problem.
3. Question the cause of problems in each area, seeking changes that are
    deviations from the norm.
4. Repeat for each sub-area.

 ADVANTAGES

1. Display relationships clearly and logically.
2. Show all causes simultaneously.
3. Facilitate brainstorming.
4. Stimulate problem solving.
5. Help maintain team focus.

DISADVANTAGES

1. It doesn’t solve any problems.
2. Makes all possible causes look equally plausible and equally important.
3. Does not offer any possible solutions or analysis.

FISHBONE DIAGRAMS

7 QUALITY IMPROVEMENT TECHNIQUE

• BRAINSTORMING

Brainstorming is the name given to a situation when a group of people meet to  generate new ideas around a specific area of interest. Using rules which remove inhibitions, people are able to think more freely and move into new areas of thought and so create numerous new ideas and solutions. The participants shout out ideas as they occur to them and then build on the ideas raised by others. All the ideas are noted down and are not criticized. Only when the brainstorming session is over are the ideas evaluated.

• CHECK SHEET

The check sheet is a form (document) used to collect data in real time at the location where the data is generated. The data it captures can be quantitative or qualitative.When the information is quantitative, the check sheet is sometimes called a tally sheet

• PARETO ANALYSIS

Pareto analysis is a formal technique useful where many possible courses of action  are competing for attention. In essence, the problem-solver estimates the benefit delivered by each action, then selects a number of the most effective actions that deliver a total benefit reasonably close to the maximal possible one.

• MATRIX ANALYSIS

The matrix diagram shows the relationship between two, three or four groups of  information. It also can give information about the relationship, such as its strength, the roles played by various individuals or measurements.

• CAUSE AND EFFECT DIAGRAM

Ishikawa diagrams (also called fishbone diagrams, herringbone diagrams, cause-and effect diagrams, or Fishikawa) are causal diagrams that show the causes of a specific event.Common uses of the this diagram are product design and quality defect prevention to identify potential factors causing an overall effect. Each cause or reason for imperfection is a source of variation. Causes are usually grouped into major categories to identify these sources of variation.

• SCATTER DIAGRAM

A scatter plot (also called a scatter graph, scatter chart, scattergram, or scatter diagram) is a type of plot or mathematical diagram using Cartesian coordinates to display values for typically two variables for a set of data. If the points are color-coded you can increase the number of displayed variables to three. The data is displayed as a collection of points, each having the value of one variable determining the position on the horizontal axis and the value of the other variable determining the position on the vertical axis.

• QUALITY CIRCLE GROUP

A quality circle or quality control circle is a group of workers who do the same or similar work, who meet regularly to identify, analyze and solve work-related problems. Normally small in size, the group is usually led by a supervisor or manager and  presents its solutions to management; where possible, workers implement the  solutions themselves in order to improve the performance of the organization and motivate employees

Acceptance Sampling

Acceptance sampling is done on sample’s post production to check for quality parameters as decided by the organization covering both attributes as well as variables. If the sample does not meet the required parameters of quality than that given lot is rejected, and further analysis is done to identify the source and rectify the defects. Acceptance sampling is done on the basis of inspection, which includes physical verification of color, size, shape, etc.

The major objectives of inspection are:

• To detect and prevent defects in products and process.
• To identify defected parts or product and prevent it from further consumption or usage.
• To highlight the product or process defect to appropriate authorities for necessary and corrective actions.
• Scope of inspection covers input materials, finished material, plant, machinery etc.

To sustain quality of product and services it is important to have in place robust quality control techniques.

Source: http://www.managementstudyguide.com/quality-control-techniques.htm