1, list
The format of the list can be varied. Although this method is simple, it is practical and effective, and it is mainly used for recording or spot checking.
2. Data layering method
Because in actual production, there are many factors that affect the quality change. If these factors are not distinguished, it is difficult to get the change law. Data layering can be carried out in many ways according to the actual situation.
3. pareto chart
Pareto chart was named after the inventor of this picture, the Italian economist Pareto in19th century. Plato first used pareto chart to analyze the distribution of social wealth. He found that 80% of Italy's wealth was concentrated in the hands of 20%. Later, people found that this law was observed in many occasions, so it was called Pareto Law.
Later, Dr. Zhu Lan, an American quality management expert, extended Plato's statistical chart and applied it to quality management. Pareto diagram is a tool to analyze and find the main factors affecting quality. Its form is a double rectangular coordinate diagram, and the left ordinate indicates the frequency (such as the number of pieces, etc. ) The ordinate on the right represents the frequency (such as percentage).
The dotted line indicates the cumulative percentage, and the abscissa indicates various factors affecting the quality, which are arranged from left to right according to the degree of influence (that is, the frequency of occurrence). In fact, this method is very useful not only in quality management, but also in many other management work, such as inventory management.
4. Histogram
Histogram reflects the distribution of product quality by processing the seemingly messy data collected, and judges and predicts the product quality and unqualified rate.
Through histogram, the regularity of data can be analyzed, and the distribution state of product quality characteristics can be seen intuitively, which is convenient for judging its overall quality distribution. When making histogram, it involves the concept of statistics. The data should be grouped first, and how to group it reasonably is the key problem.
According to the principle of equal group spacing, two key figures are group number and group spacing. It is a geometric diagram, which is drawn into a series of connected rectangular figures based on the distribution of quality data collected in the production process, with the group distance as the bottom and the frequency as the high.
5, causal analysis diagram
Causality analysis chart is characterized by results, with reasons as factors, and the relationship between them is represented by arrows. Causal analysis chart is a good way to fully mobilize employees' brains, find out the reasons and brainstorm, especially suitable for quality democratic management of working groups.
When there is a quality problem and the reason is unclear, we can mobilize everyone to find the possible reasons for the problem, so that everyone can speak freely and list all possible reasons.
6. Scatter chart
This pairing data may be the relationship between feature-cause, feature-feature and cause-cause. Through observation and analysis, we can judge the correlation between two variables. This problem is also very common in practical production, such as the relationship between quenching temperature and workpiece hardness during heat treatment, and the relationship between the content of an element in the material and the strength of the material.
Although this relationship exists, it is difficult to express it with accurate formulas or functional relationships. In this case, it is very convenient to analyze with correlation diagram.
Suppose there are a pair of variables X and Y, X represents a certain influencing factor and Y represents a certain quality characteristic value. Through experiments or collection, the data of X and Y can be represented by points on the coordinate map, and the correlation between X and Y can be judged according to the distribution characteristics of the points.
7. Check the chart
It was first proposed in 1924 by Dr. W.A. shewhart of Bell Telephone Laboratory in the United States. Control chart has been an important tool for scientific management, especially for quality management since it was used.
It is a graph with control boundary, which is used to distinguish whether the cause of quality fluctuation is accidental or systematic, and can provide information about the existence of systematic causes, so as to judge whether the production process is under control.
According to the purpose, control charts can be divided into two categories. One is the control chart for analysis, which is used to analyze the change of quality characteristic value in the production process to see whether the process is in a stable and controlled state; The other is the control chart for management, which is mainly used to find out whether there is any abnormal situation in the production process and prevent unqualified products.
Seven new technologies
Seven tools of QC (new)
1, diagram
In the 1960s, it was put forward by Professor Akio Chijuku of Yingqing University in Japan. It is a chart used to analyze the complex relationship between things, such as "cause and effect" and "purpose and means". It can help people find solutions to problems from the logical relationship between things.
2. Affinity diagram
Originated by Kawakita Jiro, Japan, it is a method of sorting out a large number of collected language materials such as opinions or ideas about unknown things or unclear facts according to their mutual affinity (similarity), so as to make the problems clear, unify understanding and coordinate work, and facilitate problem solving.
3. System diagram
System diagram is a method to systematically develop the purpose to be achieved and the measures or methods to be taken, and draw a chart to clarify the focus of the problem and find the best means or methods.
4, process decision-making program diagram (PDPC)
It is a method to analyze the factors that can lead to various results and determine an optimal process to achieve ideal results with the progress of the situation.
5. Matrix diagram
Matrix diagram method is a method to find out the paired factors from the events of multidimensional problems, arrange them into a matrix diagram, and then analyze the problems according to the matrix diagram to determine the key points. It is a good method to explore the problem through comprehensive thinking of various factors.
6. Matrix data analysis chart.
If the relationship between elements on the matrix diagram can be expressed quantitatively by data, the results can be sorted and analyzed more accurately. This matrix diagram method which can be represented by data is called matrix data analysis. Among the seven new QC tools, data matrix analysis is the only method to use data to analyze problems, but the results still need to be graphically represented.
7. Indication chart
The arrow bar diagram method is a method to represent the steps and operations needed in project implementation with network diagram according to the affiliation.
Extended data
Of course, there are more than seven useful quality statistics management tools. In addition to the old and new seven tools, the commonly used tools include experimental design, distribution diagram, transition diagram, trend diagram and so on.
In fact, the methods of quality management can be divided into two categories: one is organizational quality management based on the idea of total quality management; The second is quality control based on mathematical statistics.
Organizational quality management method refers to the method of quality management from the perspective of organizational structure, business process and personnel working methods. It is based on the idea of total quality management, and its main contents include formulating quality policy, establishing quality assurance system, carrying out QC group activities, sharing quality responsibilities of various departments, and making quality diagnosis.
Baidu Encyclopedia-Seven Skills of Quality Control