Objective: construction of a cause-and-effect diagram by Kaoru Ishikawa for a specific product or service.

Theoretical part

Cause and effect diagram is used, as a rule, in the analysis of defects that lead to the greatest losses.

It allows you to identify the causes of such defects and focus on eliminating these causes. In this case, four main causal factors are analyzed: man, machine (equipment), material and method of work.

When analyzing the factors, secondary, and maybe tertiary causes are identified that lead to defects and must be eliminated. Therefore, in order to analyze defects and build a diagram, it is necessary to determine the maximum number of causes that may be related to the admitted defects.

It consists of a quality indicator that characterizes the result and factor indicators (Fig. 1).

Fig.1. Cause and Effect Diagram Structure

Such a diagram in the form of a "fish skeleton" was proposed by the Japanese scientist K. Ishikawa. It is also called the “branching scheme of characteristic factors”, and sometimes the “four M” diagram - according to the composition of the four main factors: Man, Method, Material, Machine. The diagram reveals the relationship between the indicators and the factors that affect them. First, a quality problem or defect is formulated. This is the head of the fish. The four main factors of analysis are the "large bones of the skeleton". For each factor, the probable causes of defects are plotted on the diagram - these are “ribs”, i.e. "medium" and "small bones of the fish skeleton" (Fig. 2).

Fig.2. Ishikawa diagram.

The construction of diagrams includes the following steps:

Stage 1. The quality indicator is determined, i.e. the result to be achieved.

Stage 2. The selected quality score is placed in the middle of the right margin clean slate paper. A straight line (“ridge”) is drawn from left to right, and the indicator is enclosed in a rectangle. The following are the main reasons that affect the quality score. They are enclosed in rectangles and connected to the "ridge" by arrows in the form of "large bones of the ridge" (main causes).

Stage 3.(Secondary) causes are written that affect the main causes (“big bones”). They are arranged in the form of "medium bones" adjacent to the "large". The causes of the tertiary order that affect the secondary causes are recorded. They are arranged in the form of "small bones" adjacent to the "medium".

Stage 4. Causes (factors) are ranked by their importance using the Pareto chart. Particularly important reasons are highlighted, which presumably have the greatest impact on the quality score.

Stage 5. All the necessary information is applied to the diagram: name; name of the product, process or group of processes; names of process participants; date, etc.

The principle of constructing a diagram is shown in fig. 3.

Rice. 3. The principle of constructing the Ishikawa diagram.

When structuring the scheme at the level of primary arrows of factors in many real situations, one can use the “five M” rule proposed by Ishikawa himself. It consists in the fact that general case there are the following five possible causes of certain results: materials, machines, technology (methods), measurements, people. All these words in English begin with the letter "M": Material, Machine, Method, Measurement, Man, from where the name of this rule came from. On fig. Figure 4 shows the result of a group of 5 people determining the relative importance of the factors that cause the loudspeaker driver to fail the quality standard.

Fig.5. Cause and effect diagram to identify the causes of consumer dissatisfaction.

As examples in Fig. Figures 6 and 7 show Ishikawa diagrams for quality control of products and quality of training.

Rice. 6. Factors affecting product quality.

The Ishikawa diagram is one of seven simple ones. By using this method, you can find bottlenecks in the production process, determine their causes and effects.

From the history

K. Ishikawa was a Japanese quality researcher. In the middle of the twentieth century, he took up quality management methods and their active implementation in Japanese enterprises.

He proposed a new graphical quality management method called the cause-and-effect diagram or Ishikawa diagram, which is also called the "fish bone" or "fish skeleton".

This method, which belongs to the simple tools quality assurance, everyone in Japan knows - from a schoolboy to the president of a company.

Initially, Ishikawa introduced the "six M" rule for his diagram (all words in English language, which determine the production reasons leading to different results, start with the letter "M"): people (man), material (material), equipment (machine), method (method), management (management), measurement (measurement).

Today, the Ishikawa cause-and-effect diagram is used not only for quality analysis, but also in other areas, and therefore the first-order causes may already be different.

Method usage

This method can be used to identify the causes of any problems, in order to analyze the business processes in the enterprise, if necessary, to assess the relationship of "cause and effect" relationships. As a rule, the Ishikawa diagram is born during a team discussion of a problem, carried out by the "brainstorming" method.

Classification of the causes that form the "skeleton" of the diagram

The Ishikawa diagram consists of a central vertical arrow, which actually represents the effect, and large "edges" suitable for it, which are called first-order causes. Smaller arrows, called second-order reasons, approach these "ribs", and even smaller ones - third-order reasons - approach them. Such "branching" can be carried out for a very long time, up to the causes of the nth order.

Applying brainstorming to diagramming

In order to build an Ishikawa diagram, you must first discuss with the team the existing problem and what are the most important factors affecting it.

The method of brainstorming or brainstorming assumes that not only employees of a certain enterprise participate in the discussion, but other persons can also take part, since they have an "open eye" and approach solving the problem from an unexpected angle.

If during the first stage of the discussion it is not possible to reach a consensus on the causes that cause a certain effect, then as many stages as necessary to identify the main factors are carried out.

During the discussion, no ideas are discarded, all of them are carefully recorded and processed.

Construction order

The construction of the Ishikawa diagram includes several stages. The first is the correct formulation of the problem:

• It is written in the vertical center of the sheet and right-aligned horizontally. As a rule, the inscription is enclosed in a rectangle.
• First-order causes are brought to the problem-consequence, which are also mainly placed in rectangles.
• Arrows point to first-order reasons for second-order reasons, which in turn lead to third-order reasons, and so on up to the order that was determined during the brainstorming session.

As a rule, the chart should have a title, date of compilation, object of study. In order to determine which reasons belong to the first order, and which ones belong to the second, etc., it is necessary to rank them, which can be carried out during a brain attack or using a mathematical apparatus.

Analysis of the causes of product defects

Consider the Ishikawa diagram using the example of analyzing the causes of product defects.

In this case, a manufacturing defect acts as a consequence (problem).

During the brainstorming, various reasons were identified that affect the rejection of the product. As a result of reaching a consensus by the participants in the brainstorming, all the reasons were ranked, insignificant ones were discarded and the most important factors were left.

The first order reasons were materials, equipment, components, labour, working conditions and technology.

They are directly affected by second-order causes: impurities, moisture, delivery, accuracy, control, storage, air, workplace, production culture, age of the machine, maintenance, discipline, qualifications, experience, tools, measuring instruments, technological discipline, documentation, equipment (its availability).

Second-order causes are influenced by third-order causes, which include temperature, storage humidity, inspection acceptance, illumination and noise in the workplace, and tooling quality.

All these reasons are placed in the appropriate places and the Ishikawa diagram is constructed. An example is shown in the figure. At the same time, it must be understood that the reasons for another group may be different.

The main question when building a chart

Any Ishikawa diagram, when analyzed, must be accompanied by the question "Why?". First we ask this question in relation to the problem: "Why did this problem arise?" Answering this question, it is possible to identify the causes of the first order. Next, ask the question "Why?" in relation to each of the causes of the first order and, thus, we identify the causes of the second order, etc. Also, they usually do not distinguish, but in relation to the causes of the third order and further, it is more correct to ask the question not “Why?”, but “What? " or "What exactly?"

By learning to answer these questions using the given examples of the Ishikawa diagram, you will learn how to build it yourself.

Considering the problem of "Dispersion in details"

Consider Ishikawa diagrams using the example of an enterprise.

An industrial enterprise engaged in the production of any parts often faces the problem of part size variation.

To solve this problem, it is necessary to gather technologists, workers, suppliers, managers, engineers, you can invite other people who will help find approaches that are not provided for by specialists in their field.

With a well-conducted analysis, it is not enough to identify only the factors that cause the problem to arise, they must be correctly ranked. This can be done during the brainstorming process, after the process of identifying the causes is completed. Each member of the group must put down estimates of the significance of individual causes from their point of view, after which the overall significance of the causes will be determined.

In the presented Ishikawa diagram, the following first-order causes were identified using the example of an enterprise: workers, materials, technology, machine, measurements, environment and management.

The figure shows second and third order causes. Asking questions "Why?" and what?" you can get to the root cause that created the problem.

The members of the group determined that the most significant indicators that affect the spread of details are the measurement period and the accuracy of the instruments.

Thus, the significance does not depend on what order the given reason belongs to.

Advantages and disadvantages of the method: continuation of research

The main advantages of the applied method:

• disclosure of creative potential;
• finding interdependencies between causes and effects, determining the significance of causes.

The main disadvantages when using this tool:

• there is no possibility to check the chart in reverse order;
• the diagram can be greatly complicated, which makes it difficult to perceive and the possibility of drawing conclusions logically.

In this regard, the analysis of causes and effects must be continued using other methods, first of all, such as A. Maslow's pyramid, Pareto diagram, stratification method, control charts and others. For a simple solution, it may be sufficient to carry out an analysis using a cause-and-effect diagram.

Finally

The Ishikawa diagram can be used primarily in product quality management. In addition, it can be used in the design of new products, modernization production processes and in other cases. It can be built by one person or by a group of people after a preliminary discussion. As a result of using this tool in its activities, the enterprise gets the opportunity in a fairly simple form to systematize the causes of the problem-consequence under consideration, while selecting the most important ones and highlighting the priority ones among them by ranking.

Statistical methods of analysis and quality control

2 Graphical statistical methods or “Seven quality control tools”

2.3 Causal Diagram (Ishikawa Diagram)

Serves for a graphical representation of the relationship of a product quality indicator with all possible causes.

A cause-and-effect diagram or Ishikawa diagram is a graphic representation that distributes causes in a concise manner and in a logical sequence.

The main purpose of the diagram is to reveal the influence of causes at all levels technological process. Its main advantage is that it gives a visual representation not only of the factors that affect the object under study, but also of the cause-and-effect relationships of these factors (which is especially important).

This diagram is often referred to as a "fish bone" or "fish skeleton" because of its shape. The scheme is a graphical ordering of factors that affect the object of analysis.

When drawing the Ishikawa diagram, you should select one quality indicator or one of the consequences that you want to control and place it on the right at the end of the horizontal line. The main groups of causes are then distributed like a fishbone, individual causes with arrows indicate the main cause (large primary arrows are summed up, indicating the main factors affecting the object of analysis).

Further, it is necessary to bring arrows of the second order to each primary arrow, to which, in turn, arrows of the third order are brought, etc. until all the arrows are plotted on the diagram, indicating factors that have a noticeable effect on the object of analysis in a particular situations. Each of the arrows plotted on the diagram should represent, depending on its position, either a cause or an effect: the previous arrow in relation to the next one always acts as a cause, and the next as a consequence. Each factor boundary includes specific causes that can be controlled and actions taken to eliminate them. The principle of constructing the Ishikawa circuit is shown in the figure.

When considering the scheme at the level of primary arrows of factors in many real situations, one can use the “six M” rule proposed by Ishikawa himself (the rule is extended). It consists in the fact that in the general case there are the following six possible causes of certain results: material (material), equipment (machine), measurement (measurement), method (method), people (man), management (management). All these words in English begin with the letter "M", hence the name of this rule. Of course, there may be other factors that more accurately characterize the object of analysis. The main thing is to ensure the correct subordination and interdependence of factors, as well as a clear design of the scheme so that it looks good and is easy to read. Therefore, regardless of the slope of each factor, its name is always placed in a horizontal position, parallel to the central axis.

When constructing a cause-and-effect diagram, it is best to combine the causes by considering them in sequence: from “small bones” to “medium” and from “medium” to “large”. Using the Ishikawa scheme, one can not only determine the composition and interdependence of factors affecting the object of analysis, but also reveal the relative importance of these factors. After the diagram is completed, the next step is the distribution of factors according to their degree of importance. Not all of the factors included in the chart will necessarily have a strong impact on Quality Score.

The Ishikawa diagram is compiled by a group or by brainstorming. Using the Ishikawa scheme, it is necessary to identify the relative importance of the factors that affect the object of analysis: each member of the group, regardless of other members, needs to select from the full list of factors indicated in the scheme those that, in his opinion, have the greatest impact on the object of analysis in this specific situation. Evaluation can be done by distributing points. Such factors should not include primary arrow factors and those second order arrow factors to which several third order arrow factors are attached.

This should be followed by a joint discussion of the views of the participants in the analysis. In case of divergence of opinions regarding the factors, a second round of determining the significance of the factors is held, during which each member of the quality group again, independently of the others, establishes the most significant factors on a personal copy of the scheme. Attention should be focused on those factor arrows that ultimately received the most marks.

To investigate the causes of the phenomenon, it is permissible to use third parties who are not directly related to the work, as they may have an unexpected approach to identifying and analyzing the causes, which may not be noticed by those involved in this working environment.

When drawing up a cause-and-effect diagram, the last arrow among the reasons should definitely indicate “others”, since unaccounted factors can always remain.

Usually acceptable accuracy of the results is achieved after the third round of analysis.

The work on determining the significance of factors can be organized as follows. The developed scheme is drawn. All members of the analysis group, independently of each other, note on the copies of this scheme that they have the three most significant factors, in their opinion. Then each member of the group approaches the general scheme and marks “their” factors on it by putting points on the Ishikawa diagram. In the end, after all members of the group mark their options, the diagram will reveal - by the highest number of points on the arrows - the three most significant factors, from the point of view of all members of the group. Figure 6.3 shows the result of a group of five members determining the relative importance of the factors causing non-compliance with the product size variation standard. It follows from the diagram that the most significant (in accordance with the number of points on the arrows-factors) are: the accuracy of the device (5 points), the period of measurements (4 points) and the preparation of the worker (3 points).

It is necessary to put all the information on the diagram: its name, the name of the product, process or group of processes, the names of the participants in the process, etc. An example of the design of the Ishikawa diagram is shown in Figure 6.3.

It is necessary to build a cause-and-effect diagram for each quality indicator. Trying to include everything in one diagram will end up being large and complex, almost useless, which only makes it harder to make decisions.

The wording of the quality indicator should be concise and clear, otherwise if the indicator is not specifically formulated, then a diagram based on general considerations will be built. Such a diagram will not give results in solving specific problems.

The cause-and-effect diagram must be constantly improved as you work with it.

When analyzing causes, one often has to use other statistical methods and, above all, by the method of stratification. It is useful to use a Pareto chart in combination with a cause-and-effect diagram to solve problems.

The Ishikawa scheme should serve as the basis for drawing up a plan of interrelated measures that provide a comprehensive solution to the problem posed in the analysis.

product name		Names of participants in the process
Material
Technological process
Lot size
Order number
Product cost
Date of analysis

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In almost every area of ​​life, a person from time to time faces the fact that certain obstacles and problems arise on his way. But it is far from always possible to determine the true cause of the appearance of a particular problem, and it itself can only be a visible consequence of what is hidden from our attention somewhere inside ourselves or the activity that we are engaged in. And in order to understand the main causes of problems and eliminate them, it is very convenient to resort to using a technique developed specifically for this purpose - the diagram of Kaoru Ishikawa, a professor at the University of Tokyo and a leading specialist in quality management. This diagram is also known as Root Cause Analysis Diagram, Cause and Effect Diagram, and Fishbone Diagram. The presented lesson is devoted to the description of this method as a useful tool in any work and daily life.

What is the Ishikawa diagram for?

The Ishikawa chart is one of the main tools that are used to measure, evaluate, control and improve the quality of manufacturing processes and together with the scatterplot, stratification, control sheet, histogram, Pareto chart and control chart, it is included in the list of "seven quality control tools".

The diagram itself is a graph, on the basis of which it becomes possible to investigate and determine the main cause-and-effect relationships of factors and consequences in a problem or situation of interest, as well as to prevent the occurrence of undesirable factors and causes. Like other quality tools, the Ishikawa diagram is considered an excellent tool for visualizing and organizing knowledge, making it easier to understand and diagnose problems and processes. In most cases, the fishbone diagram is used in development new products, identifying the factors that have the greatest effect on its quality, and the main causes that give rise to specific consequences and are manageable. However, if you figure it out, then anyone can apply this diagram to identify the causes of problem situations in life and work.

Stages of working with the Ishikawa diagram

Working with the Ishikawa diagram can be divided into several main stages:

• Determination of all causes and factors that influence the result of interest
• Systematization of these factors and causes according to cause-and-effect and semantic sections
• Evaluation and prioritization of factors and causes within sections
• Analysis of the resulting structure
• Identification and cutting off factors and causes that cannot be influenced
• Omitting insignificant causes and factors

In order to more accurately determine the factors and causes that have the greatest impact on the result under study, it is recommended to use, based on the stimulation of creative activity and suggesting the offer of as many options as possible. Usually a diagram is drawn on a board or piece of paper, and then the main causes and their features are determined. The graph should be filled in until the entire diagram is filled with cause-and-effect relationships. Once this stage is over, you should move on to identifying the root or root cause.

The construction of the Ishikawa diagram, as you can see, is a rather complicated process and has a number of features that need to be mentioned separately.

Features of constructing an Ishikawa diagram

First: before starting to build a graph, it is necessary to clearly define the formulation of the problem under consideration. If, for example, there are several participants in the discussion of the issue, then all of them should come to the same opinion, and only after that begin to build a diagram.

Second: for ease of perception, the problem under consideration is best placed (written down) on the right side of the board or sheet of paper, and to the left of it, horizontally draw the “ridge of the fish”.

Third: The main causes influencing the problem are the "big bones of the fish skeleton". They need to be framed and connected to the "ridge" with slanted arrows.

fourth: then the secondary causes are plotted on the diagram, which affect the main ones, which are their consequences. These are already “medium bones”, which are adjacent to the “large bones”.

Fifth: “small bones” are applied adjacent to the “middle” ones - these are third-rate causes that affect secondary ones. If any of the reasons are not identified, then the “bone” remains empty, i.e. the cause is not fixed, but a place for it should be left.

sixth: when analyzing a diagram, absolutely everything, even seemingly insignificant, causes and factors should be taken into account. This is done in order to find the root cause and find the most effective method solutions to the problem under study.

seventh: causes and factors should be judged by their significance, i.e. it is necessary to find and highlight the most important of them - those that have the greatest impact on the problem under consideration.

eighth: it is desirable to enter into the diagram all the information related to the problem: the names of the causes and factors, dates, days of the week, the names of the participants in the process, the names of the products (if this is a production issue), etc. etc.

ninth: it is important to remember that the process of searching, analyzing and interpreting the causes and factors is fundamental in creating a holistic structure of the problem and moving to concrete actions.

tenth: when identifying each new cause or factor, you should ask yourself the question “why”, because. this way you can find the root cause that affects the problem as a whole.

Following these principles, you will be able to consider the problem most objectively and gradually uncover the whole chain of cause and effect relationships and find those factors that need to be adjusted in order to achieve a solution to the problem and get the desired result.

Based on the foregoing, one can identify the obvious advantages of the Ishikawa diagram. They, in turn, are, firstly, the opportunity to reveal one's (and other participants') creative potential, which will allow one to find extraordinary ways to solve the problem. And, secondly, the ability to find the relationship between all the causes and factors influencing the problem, and to assess their impact on it.

However, the Ishikawa method also has its drawbacks, which must also be taken into account in your work. The first disadvantage is that there are no rules for checking the diagram backwards from the root cause to the results, i.e. it is not possible to consider the logical chain of causes and factors leading to the root cause. The second disadvantage lies in the fact that, in the end, the diagram drawn up can be expressed in a very complex scheme and not have a clear structure, which greatly complicates objective analysis and excludes the possibility of drawing the most correct conclusions.

Therefore, when approaching the issue of finding the causes of emerging problems and their solutions, it is important to use not only the Ishikawa diagram, but to supplement it with other tools, among which are checklists and maps, as well as others. effective methods verification, analysis and improvement of the effectiveness of actions. But all this concerns the most complex problems and issues, the solution of which must be approached most comprehensively.

If the problem implies a simpler way to find its solution, then the Ishikawa diagram will be quite enough, because it allows you to structure all the possible causes of this problem in an extremely understandable and accessible form, identify the most significant of them, find the root cause, and then correct or eliminate it . For many people, the Ishikawa Cause and Effect Diagram is the "golden key" to overcoming the huge number of obstacles that arise on the way to achieving success.

Understanding the Ishikawa Causal Diagram

The diagram is a means of graphical ordering of the factors influencing the object of analysis. The main advantage of the Ishikawa diagram is that it gives a visual representation not only of the factors that affect the object under study, but also of the cause-and-effect relationships of these factors. The diagram is based on the definition (statement) of the problem to be solved.

When drawing the Ishikawa cause-and-effect diagram, the most significant parameters and factors are located (see Fig.) closest to the head of the "fish skeleton". The construction begins with the fact that large primary arrows are brought to the central horizontal arrow depicting the object of analysis, indicating the main factors (groups of factors) that affect the object of analysis. Next, second-order arrows are brought to each primary arrow, to which, in turn, arrows of the third order are brought, etc., until all arrows are plotted on the diagram, indicating factors that have a noticeable effect on the object of analysis in a particular situations. Each of the arrows plotted on the diagram represents, depending on its position, either a cause or an effect: the previous arrow always acts as a cause in relation to the next one, and the next one - as a consequence.

Tilt and size don't matter. The main thing when building a diagram is to ensure the correct subordination and interdependence of factors, as well as to clearly design the diagram so that it looks good and is easy to read. Therefore, regardless of the inclination of the arrow of each factor, its name is always placed in a horizontal position, parallel to the central axis.

1. Determine the list of quality indicators (types of failures, defects, defects) that should be analyzed.

2. Choose one quality score and write it in the middle of the right edge of a blank piece of paper. From left to right, draw a straight line that will represent the "backbone" of the future Ishikawa diagram.

3. Write down the main reasons that affect the quality score;

Mnemonic reception 4M... 6M

Product quality management specialists very often use English in their work. Therefore, in foreign literature, when stratifying (stratifying) statistical data, it is recommended to use the 4M ... 6M mnemonic technique, which makes it easy to remember the typical reasons (factors) for which grouping (stratification, stratification) of statistical data can be made. This mnemonic device is based on the fact that in English words were chosen that begin with the letter M and determine the main groups of reasons (factors) by which statistical data are most often stratified.

Below are these English words defining the main reasons (factors) for data stratification.

1. Personnel - stratification by performers (according to their qualifications, work experience, gender, etc.).

2. Machine - stratification by machines, machine tools, equipment (by new and old equipment, brand, design, manufacturing company, etc.).

3. Material - grouping by type of material, raw materials, components (by place of extraction or production, manufacturer, batch of raw materials, grade of material, etc.)

4. Method, technology - stratification by production method (by technological method, workshop number, team)

5. Measurement - according to the measurement method, type of measuring instruments, accuracy class of the device, etc.

6. Environment - by temperature, air humidity in the workshop, magnetic and electric fields, solar radiation, etc.

Most often, statistical data are grouped according to the first four reasons (mnemonic device 4M). If it is necessary to add a fifth or sixth to these four reasons (factors), then the mnemonic devices 5M and 6M are obtained, respectively.

4. Connect with lines (“big bones”) the main causes with the “backbone”, placing the main of these main causes closer to the head of the “fish skeleton”.

5. Identify and record secondary causes for the primary causes already recorded.

Note. Use brainstorming to identify secondary possible causes of the selected quality problem.

6. Connect lines ("medium bones") secondary causes with "big bones".

7. Check the logical connection of each causal chain.

8. Apply all the necessary information (inscriptions) and check the completeness of the Ishikawa cause-and-effect diagram.

Despite its relative simplicity, the construction of the Ishikawa diagram requires its performers good knowledge object of analysis and understanding of the interdependence and mutual influence of factors.