Table of Contents:-
- Meaning of Quality Control
- Definition of Quality Control
- Objectives of Quality Control
- Functions of Quality Control
- Scope of Quality Control
- Tools and Techniques of Quality Control
- Role of Quality Control Department
- Responsibilities of the Quality Control Department
Meaning of Quality Control
The term “Quality Control” consists of two words: “Quality” and “Control.” Quality is a combination of a unique set of characteristics that differentiates one article from other goods of one manufacturer from that of competitors or one grade of product from another when both are the outcome of the same factory. The main characteristics that determine the quality of an article may include elements such as size, design, chemical composition, materials, electrical properties, artistry, mechanical functioning, finish, and appearance.
‘Control’ may refer to comparing the actual results (finished product) with the predetermined specifications and standards. It locates the deviations and attempts to remove them. Control is the correction in the quality of the produced goods when deviations in the quality are more than expected in the process.
Definition of Quality Control
According to Alford and Beatty, “Quality control may be defined as that industrial management technique or group of techniques by means of which products of uniform acceptable quality are manufactured”.
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, men, machines and manufacturing conditions”.
Thus, by the term ‘quality control,’ we mean the process of control where the management strives to conform the quality of the product to the predetermined standards and specifications. It is a systematic process of controlling those variables that affect the excellence of the ultimate product.
Objectives of Quality Control
The objectives of quality control are as follows:
1) To assess the quality of the raw materials, semi-finished goods, and finished products at various stages of the production process.
2) To determine whether the product conforms to the predetermined specifications and standards and whether it satisfies the expectations or needs of the customers.
3) If the quality of the products deviates from the specifications, locate the reason for deviations and take necessary remedial steps so that the deviation does not recur.
4) To suggest suitable improvements in the standard or quality of goods produced without a significant increase or no increase in the cost of production. New techniques in methods and machines may be applied for this purpose.
5) To cultivate quality consciousness in different areas of the manufacturing department.
6) To assess the different techniques, methods, and production processes of quality control and suggest improvements to make them more effective.
7) To reduce the wastage of raw materials, workforce, and machines during production.
Functions of Quality Control
Quality control is concerned with applying quality standards to products and rejecting units that do not meet standards within tolerance limits. This involves inspection, which is only one of its aspects.
Scope of Quality Control
It performs the following functions for achieving these objectives, which also define its scope:
1) Assists top management in making strategic decisions regarding product quality.
2) Coordinates with design engineers responsible for designing the product and specifying components, parts, and finished product tolerances.
3) Coordinates with industrial engineers who design tools and equipment, determining performance standards.
4) Coordinates with construction engineers involved in constructing plant and equipment.
5) Inspect and test materials, tools, parts, etc., purchased by the purchasing department.
6) Inspects and tests components, parts, sub-assemblies, and final assembly at various stages in the manufacturing process to prevent further processing of defective material and parts.
7) Identifies and analyzes the causes of deviations from standards at various stages of production and advises line management on preventive measures.
8) Inspects the final product before it is dispatched to inventory control for stocking or to customers.
Tools and Techniques of Quality Control
Specific simple tools and techniques can naturally be positioned within the TQM philosophy. Many of these tools can efficiently be utilized for everyday problem-solving or realizing opportunities. They can thus be effectively used to support the implementation of the quality management and improvement methodology.
Most of the tools are common sense tools, apparently simple and obvious. But the most valuable ideas are often the simple ones.
- Bar Chart/Histogram
- Block Diagram
- Cause and Effect Analysis
- Control Chart
- Flow Charts
- Pareto Analysis
- Scatter Diagrams
1) Bar Chart/Histogram
A histogram is a graphical representation of discrete groups or categories of data shown so that clear comparisons can easily be made. A histogram is frequently used to emphasize a point; this will dictate how the chart is drawn. The chart is typically used to highlight the variation and unevenness in data. Further investigation could follow using this information to determine why the variation occurred. The items are usually ranked from high to low, with the lengths of the bars indicating the value or frequency that a bar represents.
2) Block Diagram
If every activity, which is part of a process, is represented by a block (box), and all blocks are connected by lines representing the interfaces between activities, a macro-level view of the process is obtained; this is called a block diagram. The diagram traces the paths that any information, necessary actions, or materials can take between the original input and the final output of the process. For each activity in the process, there is a determination of the output it produces and what other activities it feeds into. Through the identification of special groups for particular work activities, there is also a determination of who performs the activity.
3) Cause and Effect Analysis
This technique identifies the most probable causes affecting a problem, condition, or project. It can aid in analysing cause-and-effect relationships and be used iteratively in conjunction with brainstorming. The tool being used, the cause and effect diagram, is a visually compelling way of recording the possible causes of a particular effect.
4) Control Chart
A control chart is a graphical representation of the collected information. The information may pertain to measured or judged quality characteristics of samples. It detects the variation in processing and alerts if any departure is from the specified tolerance limits.
5) Flow Charts
A flow chart is a pictorial representation of the stages in a process. A series of symbols, connected logically, portrays activities, decisions, and databases, determining how the process works. This allows complex procedures to be broken down into manageable parts for examination, better understanding, and, if necessary, redesigning. Potential sources of trouble and wastage can be uncovered, making flow-charting a cost-saver in diverse fields such as processing orders, faulting procedures, corporate planning, product realization, operations methodology, etc.
6) Pareto Analysis
Pareto analysis is a technique for ordering causes or problems from the most to the least significant. This way, the most critical aspects are identified, and efforts can be concentrated on those, thus achieving the maximum benefit with the least effort. The analysis makes use of the Pareto diagram, which is a particular case of the bar chart. It is used for brainstorming, cause and effect analysis, and cumulative line charts. In decreasing order, the diagram displays the relative contribution of each cause (or problem) to the total. The relative contribution can be based on the number of occurrences, the quality of damage, or the cost associated with each cause (or problem).
7) Scatter Diagrams
The scatter diagram is one of the tools of quality. It is a graphical technique used to analyze the relationship between two variables, and the analysis produced by the scatter diagram is known as Regression Analysis. It shows whether or not there is a correlation between two variables. Correlation refers to measuring the relationship between two sets of numbers or variables. Two data sets are plotted on a graph, with the y-axis being used for the variable to be predicted and the x-axis for the variable to make the prediction. The graph will represent possible relationships (although two variables might appear related, they might not be; those who know most about the variables must make that evaluation). However, correlation does not necessarily imply a direct cause-and-effect relationship. If values for one of the variables can be predicted based on the value of the other variable, then there is a correlation.
Role of Quality Control Department
Each holder of a manufacturing authorisation should have a quality control department. This department should be independent of other departments and under the authority of a person with appropriate qualifications and experience who has one or several control laboratories at their disposal. Sufficient resources must be available to ensure that all the quality control arrangements are reliably and effectively carried out.
The quality control department, as a whole, has many duties, such as establishing, validating, and implementing all quality control procedures, overseeing the control of the reference and retention samples of materials and products when applicable, ensuring the correct labelling of containers of materials and products, ensuring the monitoring of the stability of the products, participating in the investigation of complaints related to the quality of the product, etc. All these operations should be carried out by written procedures and, where necessary, recorded.
Quality Control Department commitment starts at the top and cascades through the whole line management. Quality processes are designed to add value to external and internal customers and continuous improvement opportunities. Processes align with our customer requirements and continuously improve as the process evolves.
Quality Departments deliver comprehensive services, including inspection, testing, auditing, certification, training, generating method statements, customer complaints, Non-Conformance Reports (NCRs), corrective and preventive actions, and related technical assistance. It also provides advisory services in closing out projects, snagging, de-snagging, and handing over. It protects the organisation’s assets and business and is crucial in failure mode effects analysis, risk management, and performance improvement.
Responsibilities of the Quality Control Department
Although the term “Quality control” is very familiar, what it means and the process it entails are not apparent to most people. The Quality Control Department has many responsibilities, with the quality of the end product being the main objective. However, this task is complex, as it entails several checks before we can sell the product.
The following are some significant activities undertaken by the Quality Control Department:
Quality control personnel sample the company’s products to ensure the integrity and quality of the manufactured items. Tests and hands-on inspections are performed before, during, and after production to ascertain that products are flawless and of the utmost quality. Quality managers instruct workers on addressing the issues or recommend different production techniques to senior management when standards still need to be met.
Quality control managers build and manage teams of workers who ensure that quality production and performance standards are met. A quality control manager’s responsibilities include keeping workers motivated and providing clear performance standards for the team. Senior management looks to the quality control department for recommendations to improve procedures and processes to maintain quality standards. An adequate quality control department or team will troubleshoot and investigate reasons for poor-quality products.
Compliance with legal requirements and industry standards is the responsibility of the quality control department. Monitoring compliance and maintaining accurate documentation is essential to the quality control team. Reports and paperwork about inspections must be kept on all tools, equipment, and machinery, as well as records and results of product sampling and testing.
The quality control manager handles government quality audits and inspections. Regular reporting to senior and executive management is essential for strategic planning and budgeting considerations for improved performance and quality production. Supervision, enforcing, and updating the company’s quality control manual is another vital function for quality control managers.