What is Quality Control?
Quality control is a process used by organizations to ensure that their products or services meet or exceed customer requirements and expectations. It involves monitoring the production process to detect and correct any defects or deviations from the desired quality standards.
Table of Contents
Quality Control Definition
From the above definition, it can be said that quality control is a process of examining the specific results of output against the desired standards.
“Quality control means setting standards for all activities, checking to see that the results actually achieved fall within these standards, and taking corrective action when they do not.” – Edward Deming
“Quality control is the process by which management seeks to ensure that the products and services produced meet or exceed customer expectations.” – Joseph Juran
According to Bethel, Atwater, and Stackman, “Quality control refers to the systematic control of those variables encountered in a manufacturing process which affect the excellence of the end product. Such variables result from the application of materials, machines, and manufacturing conditions.
Only when these variables are regulated to the extent that they do not detract unnecessarily from the excellence of the manufacturing process as reflected in the quality of the finished product, can the quality be said to exist.”
In other words, quality control focuses on monitoring and testing the final products, on the basis of which, a report is generated for the management of an organization. The management makes the final decision regarding the acceptance or denial of a product release.
Some of the most effective quality control techniques are used in the pharmaceutical industry. This is because, in pharmaceutical companies, special precautions and measures are followed to examine the purity of all chemicals, content, and biological ingredients used for manufacturing the drugs.
A wrong combination of chemicals can cause harm (including death) to the patients. Therefore, quality control is of prime concern for pharmaceutical organizations. In addition to medicines, there are many other products like soap, shampoo, cream, food items, etc. where the microscopic evaluation of the entire process is observed and controlled.
Objectives of Quality Control
Evaluation of quality-related feedback is very essential to improve quality continuously. However, it is not merely the responsibility of the quality control department to deliver quality products. However, all the units of an organization need to contribute their best to attain quality objectives.
This is because; the objectives of quality are not met only during the manufacturing of a product. Unless a product is well-accepted by customers in terms of quality, attributes, safety, etc. you cannot be assured that the desired standards of quality are obtained.
The following are the key objectives of quality control:
- To create value for customers by providing them with quality products and services
- To control overall costs by reducing the losses caused by defects or errors
- To maintain an optimum level of quality at a lower cost
- To identify and prevent errors during the operational process
- To take corrective measures for delivering zero-defect output
One separate department is required to perform all quality control activities in an organization. The quality control department of the organization is generally headed by a Quality Control Manager or Chief Inspector. In addition, the organizational management, design engineers, and manufacturing staff are also involved in quality control.
They all are responsible for:
- Developing quality-oriented policies
- Inspecting and controlling all the raw materials to ensure that they meet the desired standards of excellence
- Monitoring the performance of various equipment
- Monitoring and testing the product performances
Benefits of Quality Control
In a highly competitive and rapidly changing business environment, customers have become more quality-conscious. Customers are ready to pay extra prices in lieu of better quality goods and services. Therefore, in such emerging business practices, no manufacturer would think to eliminate the quality control function from their business process.
Today, when you buy a product from the market, you can easily identify the level of contributions made by an organization to sustain the quality of its products. One of the examples of such contribution includes the quality of plastics and other materials used in the packaging of a product.
Apart from delivering high-class outputs, quality control also ensures safe uses of the products. You may find that plastic containers are used in the packaging of products instead of containers made of hazardous materials like tin and iron.
In addition, user manuals or instructions are also provided to the customers for their convenience. The use of such materials also helps an organization attract the attention of customers.
Therefore, as you can see, in the absence of quality control a number of defective products would require re-work, which will increase the wastage of resources of an organization. Quality control practices not only improve standards of quality but also increase productivity.
Major Benefits of Quality Control:
- Produces quality products, thereby achieving a higher level of customer satisfaction
- Ensures that the raw materials are of the required standards of quality
- Mitigates defects in the final output
- Saves time and resources by minimizing reworking efforts
- Minimizes the cost of labor and material as defects are reduced
- Attains uniform quality and reliability of the product
- Reduces costs of inspection, production
- Controls customer complaints
- Increases quality consciousness among customers and clients
Quality Control Tools
In the years 2009 and 2010, Toyota recalled more than 14 million vehicles all over the world after they were sold to customers. The recall was due to a defect in the power window switches of the vehicles and unwanted acceleration.
- Check Sheets
- Pareto Chart
- Cause and Effect Diagram
- Scatter Diagram
- Control Charts
- Flow Charts
Similarly, Nokia recalled millions of its certain AC adapters for mobile phones in the year 2009. Therefore, as you can see, product defects have huge financial repercussions, which include the cost of liability, damages claimed by the customers, loss of goodwill, compensation paid by the company, and the cost of reverse logistics.
In addition, product defects also spoil the image of a brand. Therefore, it is an utmost priority for organizations to monitor defects and control quality. There are seven basic quality control tools that help organizations in controlling quality and minimize defects.
TQM tools have changed the sphere of quality management for the past six decades. Corporations across the world have found these TQM tools helpful in quality management processes. The tools and techniques have provided dynamic infrastructure in monitoring and managing TQM processes.
The seven basic tools of quality control: check sheets, Pareto charts, cause and effect diagrams, scatter diagrams, control charts, flow charts, and histograms came into practice in the 1960s.
Kaoru Ishikawa, the then head of the Japanese Union of Scientists and Engineers (JUSE) expanded the use of these tools in Japanese manufacturing industries.
In order to identify quality issues, an organization needs to collect a lot of data. For example, if automobile manufacturer wants to find out the reasons for technical problems in the phones, it would require collecting data related to the material used, production processes, etc.
Next, the data is analyzed for finding out the reasons for the technical problems. Therefore, as you can see data collection and analysis is an important part of quality control.
The check sheet is a very effective quality control tool used for data collection in the organization. In other words, check sheets are easy to understand and customized tools that facilitate data collection to resolve quality issues. Generally, check sheets are prepared in tabular forms in which the frequency of various phenomena under observation is recorded.
The check sheet shows different types of defects in a product on different days of production. As you can see, check sheets use tally marks to count the frequency of a phenomenon. In tally marks, four marks or horizontal lines are drawn to count to four and then a mark is drawn across four marks to denote five occurrences of a phenomenon.
Therefore, in the figure, there are 3 instances of missing paperwork on day-1 and 5 instances on day-5. Check sheets are best suited for manual data collection in an organization. Data collected is either quantitative or qualitative. In addition, Data are interpreted by observing the number of marks against the instances of defects on the sheet.
Organizations select a sample of products and use check sheets to record the possible defects in the products. The data collected through check sheets are further analyzed to find useful patterns. Further enhancement and decisions are made to the product and organization based on the analysis.
A Pareto chart refers to a tool that helps in prioritizing quality issues. A Pareto chart is very often used to analyze the data collected through check sheets. This chart is named after an Italian Economist named Vilfredo Pareto. A Pareto chart consists of bars and line graphs.
The bars represent individual values in descending order. The line graphs are used to show cumulative frequency. Therefore, bars are used in descending order in the chart from left to right. This means that the values represented on the left are relatively more significant as compared to those on right.
The above chart is drawn on the basis of the figures shown in Table:
|Reported damages in Cars||Percentage of occurrence||Cumulative Percentage|
|Burning out of bulbs||41||41%|
|Damage in brake pads||11||86%|
|Flattening of tires||9||95%|
|Flattening of tires||5||100%|
A Pareto chart is based on the Pareto principle (80/20) according to which 80% of problems come from 20% of causes. In simpler words, the Pareto principle suggests that 80% of product defects or other quality issues arise because of 20% of reasons. This is to say that instances of defects are measured against the issues.
Therefore, it is useful in identifying those factors that have the greatest effect on the system. Pareto charts can be generated by simple spreadsheet programs. Basically, this chart breaks a big problem into smaller pieces, recognizes the most significant factors, and highlights the areas to be focused on more based on the defect issues.
In addition, the chart helps in utilizing the limited resources of the organizations in the most effective manner. For example, without the help of the Pareto chart organizations would require to investigate each and every reason for product defects with equal effort.
This would involve a high level of cost and effort. However, Pareto charts help in identifying the most significant reasons for a product’s defects. Therefore, organizations can put more effort into resolving the most significant reasons first.
In addition to the product defects, Pareto principles recognize that:
- 80% of the customer complaints are related to 20% of the products or services.
- 80% of the production delays take place because of 20% of the possible reasons for delays.
- 80% of the system glitches happen because of 20% of the causes. Therefore, as you can see Pareto charts can be used to analyze different types of quality issues, starting from product defects to glitches in the systems ranging from production to quality.
In addition, service quality and profitability of services, such as banking, telecommunications, and travel are done on the basis of Pareto analysis.
Cause and Effect Diagram
In an organization, quality issues are nothing but a set of causes and effects like any other real-life problem. Therefore, as you can see finding the causes of the effects like product defects are essential to quality control.
In the case of simpler processes, it is easy to identify the causes of the quality issues. However, in the case of organizations manufacturing highly complex and sophisticated products, such as commercial aircraft, it is relatively very difficult to identify the quality issues.
In such cases, sophisticated tools and techniques are required to identify the causes. The cause-and-effect diagram was introduced in 1968 by Kaoru Ishikawa, a Japanese professor, and proponent of quality management practices.
Because of this, the cause-and-effect diagram is also called as Ishikawa diagram. He introduced quality management practices in the Kawasaki shipyards and went on to become of the founding fathers of modern quality management. A cause-and-effect diagram is one such technique that helps in identifying the quality issues in an organization.
The cause and effect diagram was published in his book named, ‘Introduction to Quality Control’. This diagram, as the name suggests, explores all potential or real causes of quality issues and arranges them in a hierarchical diagram according to the relative importance of the causes. The diagram is of the structure of the fishbone and it is also known as the fishbone diagram.
In the previous section, you studied that quality issues are main the effects of various factors or causes. However, it is not always easy to identify the direct causes of quality issues. In all such cases, the scatter diagram helps in identifying the relationship between two variables.
Even though scatter diagrams cannot establish the cause-and-effect relationships between two variables, the diagram can indicate whether there is any relationship between two variables or not. For example, if we study two variables (let’s say, the number of product defects and the price of materials), the scatter diagram would show if there is any relationship between the two variables or not.
In other words, a scatter diagram indicates correlations between variables. For example, production and cost of a shoe manufacturer, production would be on the x-axis and cost would be on the y-axis. Correlations may be positive (rising), negative (falling), or null (uncorrelated). A scatter diagram consists of a horizontal axis containing the values of one variable and a horizontal axis containing the values of the other variable.
After plotting the different values of variables, a general trend of points going up and to the right indicates that an increase in one variable corresponds to an increase in the other. In case, the trend is down and to the right, an increase in one variable corresponds to a decrease in the other. If no trend can be seen, it means the variables are not related. The scatter diagram provides clues on how to improve the process.
So far we discussed quality control tools that help in finding out the reasons of very quality issues. In TQM quality improvisation is a continuous process. Let us move forward and study about control chart that helps in monitoring quality on a continuous basis.
In control charts, data points are plotted on a line over time to provide a picture of data movement. These charts were proposed by Walter Shewhart in 1924. They demonstrate the consistency of data or when there are high or low outliers in the occurrences of data or variation of data over a point in time.
It focuses on monitoring performance over time by looking at variations in data. Control charts distinguish between common cause and special cause variations. These charts are the backbone of statistical process control for organizations.
There are two broad categories of control charts: control charts for attributes and control charts for variables. Control charts for attributes measure the presence or absence of attributes or qualities, for example, the number of products not conforming to specifications.
Control charts for variables measure the variations in variables, such as height, weight, temperature, pressure, etc. On the basis of the number of characteristics of the variable to be observed, there are mainly two types of control charts for variables: univariate control chart and multivariate control chart.
In univariate control charts, only a single characteristic of a variable is considered, whereas, in the case of a multivariate control chart, more than one characteristic of a variable is considered.
A flow chart refers to a graphical representation of processes that is complementary to other process-related diagrams. Processes with various steps are represented by this diagram with boxes and arrows.
In quality control flowchart depicts the necessary steps to be taken to ensure the high quality of products and services. For example, the graphical representation of various steps involved in the process of manufacturing shirts or pants from yarns.
Similar to control charts, Flow charts help in controlling and improving qualities in an organization by establishing quality checks and standardizing the reporting system. For example, Da Ming International Holdings Limited (“Da Ming International”), a Chinese large-scale stainless steel manufacturer uses flow charts to control and improve the quality of the steel manufactured by the company.
When the warehouse department of the company finds quality issues in the raw materials, it forwards the quality problem to the quality control department. The quality problem is then forwarded to the material supplier. After the settlement with the supplier(s), notices are sent to the sales department, warehouse department, and production department regarding the settlement.
This is the seventh and the last basic quality control tool. Histogram is basically used to graphically present data like the other tools of TQM. This tool was introduced by Karl Pearson Histogram can be defined as a bar graph depicting the distribution of data. The bars in a histogram represent the frequency of occurrence of the different classes of data.
Histograms Are Used in Quality Control:
- When numerical data regarding quality issues (such as the number of defects) are available
- While analyzing whether the output of the process can meet the customers’ requirements or not
- While analyzing whether a process change occurred at different points in time
- While presenting and communicating the distribution of quality data to others