Quality Control & Management Tools

In this lesson, you’re expected to learn about:
– quality control tools
– quality management tools

Several quality tools exist that can be used to analyze processes, prioritize problems, report the results, and evaluate the results of a corrective action plan.

Quality tools consist of quality control tools and quality management tools.

1) Check sheets are used for collecting data in a logical and systematic manner.

2) A histogram is a frequency-distribution diagram in which the frequencies of occurrences of the different variables being plotted are represented by bars.

3) A scatter diagram is a plot of the values of one variable against those of another variable to determine the relationship between them.

These diagrams are used during analysis to understand the cause-and-effect relationship between two variables.

Scatter diagrams are also called correlation diagrams.

4) A Pareto diagram is a special use of the bar graph in which the bars are arranged in descending order of magnitude.

The purpose of Pareto analysis, using Pareto diagrams, is to identify the major problems in a product or process or, more generally, to identify the most significant causes for a given effect. This allows a developer to prioritize problems and decide
which problem area to work on first.

5) A flowcharting tool can be used to document every phase of a company’s operation, for example, from order taking to shipping in a manufacturing company.

It will become an effective way to break down a process or pinpoint a problem. Flowcharting can be done at both the summary level and the detailed level serving different user needs.

6) One form of a cause-and-effect (C&E) diagram is used for process analysis when a series of events or steps in a process creates a problem and it is not clear which event or step is the major cause of the problems. Each process or sub-process is examined for possible causes; after the causes from each step in the process are discovered, significant root causes of the problem are selected, verified, and corrected.

The diagram is also called a fishbone or Ishikawa diagram, invented as a problem-solving tool.

7) Stratification helps the C&E diagram because it is a procedure used to describe the systematic sub-division of population or process data to obtain a detailed understanding of the structure of the population or process. It is not to be confused with a stratified sampling method. Stratification can be used to break down a problem to discover its root causes and
can establish appropriate corrective actions, called countermeasures.

8) A control chart assesses a process variation. The control chart displays sequential process measurements relative to the overall process average and control limits.

The upper and lower control limits establish the boundaries of normal variation for the process being measured.

[Optional] 7 Basic Quality Tools
1) An affinity diagram is a data-reduction tool that organizes a large number of qualitative inputs into a smaller number of major categories. These diagrams are useful in analyzing defect data and other quality problems and useful in conjunction with cause-and-effect diagrams or interrelationship digraphs.
2) A tree diagram can be used to show the relationships of a production process by breaking it down from few larger steps into many smaller steps. The greater the detail of steps, the better simplified they are.

Quality improvement actions can progress from the rightmost of the tree to the leftmost.

3) A process decision program chart is a preventive control tool that prevents problems from occurring in the first place and mitigates the impact of problems that do occur. From this aspect, it is a contingency planning tool.

The objective of the tool is to determine the impact of the “failures” or problems on project schedule.

4) A matrix diagram is developed to analyze the correlations between two groups of ideas with the use of a decision table.

This diagram allows one to systematically analyze correlations. Quality function deployment (QFD) is an extension of the matrix diagram.

5) An interrelationship digraph is used to organize disparate ideas. Arrows are drawn between related ideas. An idea that has arrows leaving it but none entering is a root idea.

More attention is then given to the root ideas for system improvement. The digraph is often used in conjunction with affinity diagrams.

6) Prioritization matrices are used to help decision-makers determine the order of importance of the activities being considered in a decision. Key issues and choices are identified for further improvement.

These matrices combine the use of a tree diagram and a matrix diagram.

7) Activity network diagrams are project management tools to determine which activities must be performed, when they must be performed, and in what sequence. These diagrams are similar to program evaluation and review technique (PERT) and critical path method (CPM), the popular tools in project management.

Unlike PERT and CPM, activity network diagrams are simple to construct and require less training to use.

Other Tools

Process mapping is flowcharting of a work process in detail, including key measurements.

Design of experiments deals with planning, conducting, analyzing, and interpreting controlled tests to evaluate the factors that control the value of a parameter (e.g., design specification tolerance).

Quality function deployment (QFD) is a structured method in which customer requirements are translated into appropriate technical requirements for each stage of product development and manufacturing. Input for the QFD process comes from listening to the voice of the customer (VOC).

The house of quality (HOQ) is a diagram that clarifies the relationship between customer needs and product features.

It helps correlate market or customer requirements and analysis of competitive products with higher-level technical and product characteristics. The diagram, which makes it possible to bring several factors into a single figure, is named for its house-shaped appearance but sometimes is referred to as QFD, a sign of the connection between the three approaches of VOC, QFD, and HOQ.

Jim Rohn Sứ mệnh khởi nghiệp