Identification of Defects Causes: Ishikawa Diagram and 5 Whys in Theoretical and Practical Terms

*Barbara Ciecińska*

### **Abstract**

The chapter briefly presents the issue of quality and its management in production. In the relevant part of the chapter, the Ishikawa diagram, its variations, and the possibility of extending its application to new areas will be discussed. Similarly, the 5 Whys method is presented. The application of the Ishikawa diagram and how to use the 5 WHYS method are presented with practical examples, enabling them to be transferred to the operation of real enterprises. These examples concern machining, laser processing, and gluing in the context of defective products and processes. The discussion includes case studies of what defects may appear in this type of (or similar, in the field of mechanical engineering) processes, a discussion of their importance in production. Ways to improve machining and assembly operations in the presented context are shown.

**Keywords:** Ishikawa diagram, 5 Whys, machining, laser processing, bonding

#### **1. Introduction**

Production management is currently a difficult but also interesting and dynamically developing field. In production plants, with a constantly changing range of manufactured products, the challenge is to maintain a certain acceptable level of production, especially in relation to product quality. In production, the method of carrying out the production process may change; modern technologies and different devices and materials are implemented. The range of produced products can be very different at different times of the year. An example of a particular challenge may be the concept of Industry 4.0, which talks about mass-scale production of individualized, unitary products. In addition, the manufacturing process is significantly affected by the environment in which legal and normative guidelines change; various concepts of production management appear, such as Total Productive Maintenance regarding the maintenance of the machine park in efficiency, Cleaner Production expressing the need to reduce the negative impact of production on the natural environment, and implementation of a systemic approach based on ISO 9001 (quality management), 14001 (environmental management) or 45001 (occupational safety management) standards. The classic production model draws attention to the input elements, such as materials, energy, and knowledge, and to the output

elements—products, services, and profit, which are processed in a specific way conditioned by technology. All these elements are somehow "fastened together" by the clamp of the management philosophy. In addition to the abovementioned concepts, decisions are also influenced by social and cultural conditions, customs, financial resources, and many other factors [1, 2].

For these reasons, quality can be perceived in different ways. In one case, it will be identified with the characteristics of the product, in another—with a specific manufacturer. In still other situations, quality may be defined as specific operating conditions, functional features, and features of the work environment, in relation to the natural environment, esthetic values, and others [3].

Despite the constant changes in the reasons for production decisions, the tools and methods of quality management known for a long time remain constant and effective. An example is the Ishikawa diagram and the 5 Whys method, which make it possible to identify the causes, places, and problems with insufficient quality, not only of products but also of defects in the broader sense. The identification process can be supported by other techniques, for instance, a kinship diagram or teamwork (like brainstorming), which trigger creativity and some freedom in defining problems and organize corrective or improvement actions [4].

### **2. Quality and quality management**

Crosby defined quality as the fulfillment of requirements and Juran defined it as usability or applicability. Tse Li used to say that quality is "excellence, perfection of workmanship". The EN ISO 9001:2015 standard says that quality is the extent to which a set of inherent properties meet requirements [5, 6].

Quality and the concepts related to it have evolved from antiquity to the present. Groundbreaking changes in the attitude to the quality of products and services took place thanks to the American scientists William Deming and Joseph Juran. Their work was used in Japan in 1950–1955, which, combined with Japanese culture and lifestyle, led to the concept of Total Quality Management (TQM). The concept of TQM refers to all the goals of the enterprise and is often called a management philosophy that is applied in activities related to all undertakings and processes of the organization. The main role in these processes is played by people: management, which has a leadership role, and employees who make up a team that creates quality. In this philosophical approach, quality is seen as a process of continuous improvement that applies to the entire organization, customers, and suppliers. Feedback is maintained with the client in mutual communication, and the client's expectations and needs are taken into account in the work on quality. Suppliers are also an important element in the company's value creation chain, as their inappropriate products or services may be the beginning of the company's problems. The ISO 9001 standard is the basis for a systemic approach in which customer needs are defined by contract and quality management focuses on [7–9]:


*Identification of Defects Causes: Ishikawa Diagram and 5 Whys in Theoretical and Practical… DOI: http://dx.doi.org/10.5772/intechopen.113990*


With regard to the concept of quality, kaizen talks about the need to improve in small steps. Kaizen is synonymous with rational and skillful time management, communication, creative teamwork, as well as cost reduction by avoiding defects. Kaizen is based on foundations such as [10]:


Kaizen postulates are closely related to other concepts of production management, such as Lean Manufacturing, by striving to achieve maximum productivity, efficiency, and products without errors. This goal can be achieved, among others, by the use of a variety of quality management techniques and tools, both older and newly developed, combined with modern production management [11, 12]. **Table 1** shows the quality management tools. The first column lists the so-called old ones, and the second column lists the new ones.

#### **3. Ishikawa diagram and 5 Whys**

The method of analyzing the causes of various defects and irregularities, called the fishbone diagram or Ishikawa diagram, was developed by Kaoru Ishikawa in 1943. This diagram makes it possible to link the causes and effects of various technological, organizational, and economic problems in a universal way. In Ishikawa quality problems, the diagram is often used where the chain of cause and effect can be extended. The fishbone diagram makes it possible to see previously invisible or unconscious relationships and dependencies. The diagram comes in different versions, which


**Table 1.** *Quality management tools [11, 13].*

differ in the type of analyzed areas or their number. Typical lists of areas for analysis are given in **Tables 2–6**; however, each time, the team can establish its own set [5, 14, 15].


#### **Table 2.**

*5M Ishikawa diagram—basic.*


#### **Table 3.**

*5M+E Ishikawa diagram.*


#### **Table 4.**

*5M+3 M Ishikawa diagram.*


#### **Table 5.** *8P Ishikawa diagram—for marketing.*

*Identification of Defects Causes: Ishikawa Diagram and 5 Whys in Theoretical and Practical… DOI: http://dx.doi.org/10.5772/intechopen.113990*


#### **Table 6.**

*4S Ishikawa diagram for services.*

**Table 2** shows the simplest, basic version of the five areas of analysis in the Ishikawa diagram. For each of the areas listed in the first column, a question was proposed to facilitate the general formulation of the problem (shown in the second column).

**Table 3** lists the basic areas as 5M and an additional frequently used area, Environment.

Yet another version of the areas in the diagram is shown in **Table 4**. It is called 5M+3M because other areas, occurring in production conditions such as measurement and maintenance of machines in working order, as well as the impact of changing natural conditions, are added to the basic five areas.

A different set of areas for analysis are shown in **Table 5**. This is a variation of the Ishikawa diagram for situations where the product is already produced and we are not looking for reasons for the lack of quality of this product. It is intended for departments such as sales, promotion and, customer relations.

The last example shown in **Table 6**, on the other hand, is a suggestion for service providers who may be struggling to maintain delivery quality, logistics, and other non-production processes.

However, the principle of creating a fishbone diagram is one. In its basic form, the diagram resembles the skeleton of a fish, where the bones converge at the spine. Principal bones correspond to the causes in a given area of analysis (1 principal axis = 1 area). Major bones can have many minor bones that illustrate the possible causes of a problem with a given effect. The line of the spine is the line of the formulated problem (effect of causes) (**Figure 1**) [4, 16].

The construction of the diagram corresponds to the original assumption of its creator. According to Ishikawa, effects, or problems, always have a cause, and in most cases, there are a number of active factors that caused them. The purpose of using the diagram is to discover, collect, and classify the causes of the problem in terms of the importance of the impact exerted.

**Figure 1.** *Ishikawa diagram: (a) general concept, and (b) main and auxiliary bones.*

Initially, the diagram as a tool for managing the production process was used to manage quality. It has now evolved and is used in other fields such as safety management to identify the causes of accidents or hazards, or in environmental management to identify the causes of negative environmental impact (e.g., waste generation, occurrence of industrial failures).

The cause and effect analysis should be carried out in an orderly manner: Step 1—Creating a detailed description of the problem: What is wrong? When and where does the problem occur? How is it going?

Step 2—Creating an analysis group, that is, a team of employees who will use the "brainstorming" technique to generate as many potential causes of problems as possible. A leader should be chosen in the group, for instance, a department manager, who will coordinate the work of the team. The team should also include other competent people who come into contact with the problem due to their daily duties. Team work should take place in a calm, friendly, and creativity-enhancing atmosphere, assuming that there are no bad ideas at this stage, and you do not immediately look for a solution to the problem.

Step 3—Selecting and entering the main categories of causes into the diagram and matching the emerging proposals of their sources to them.

Step 4—Selecting the most probable causes of the analyzed problems and discussing the possibilities of remedying the situation.

The basic technique for determining the root causes of defects and process disruptions is the 5 Whys. It is a preventative technique, as opposed to the philosophy of taking action based on actual defects found. 5 Whys, originally written by Sakichi Toyoda and then developed by Taiichi Ohno, was based on the perception of a child's curiosity about the world. It is the child who, reaching the information, repeatedly asks "Why is it the way it is?" Hence, in quality management, 5 Whys is called "a child's play method for solving adult problems". 5 Whys is most effective in situations concerning work organization, employee relations, cooperation between departments, disputes, and where human error may be the cause [17, 18].

The 5 Whys technique requires the following [19]:


The diagram of the analysis is shown in **Figure 2**.

A variation of 5 Whys, called 5W2H, can be used to define the problem. Then, the questions are answered [20]:

1.What?—What exactly is the problem?

2.Who?—Who reported the problem?

*Identification of Defects Causes: Ishikawa Diagram and 5 Whys in Theoretical and Practical… DOI: http://dx.doi.org/10.5772/intechopen.113990*


Then, you get full information about the nature and effects of the problem. The spreadsheet shown in **Table 7** can be used to define the problem.


**Table 7.** *Problem identification and solution—5W2H sheet.*
