Inspection is important to maintain a certain quality during the manufacturing of a product. Quality control is a process by which customer ensures receive product free from defects.

Inspection is a specific activity within quality control. It’s a hands-on examination of products, materials, or processes to verify they conform to specifications. Inspectors look for defects, measure dimensions, test functionality, and check appearance.

Quality control is the systematic process of checking products and production processes to ensure they meet predetermined quality standards. Think of it as the overall strategy a company uses to maintain consistency and reliability in what they produce. It involves setting standards, measuring performance against those standards, and taking corrective action when things don’t meet expectations.

Let me explain both the term separately-

Definition of Inspection:

After manufacturing, the product is required to perform certain functions. The process of checking whether the product does so or not is called Inspection.

Inspection compares the qualities of the product with a standard product during manufacturing. In other words, Inspection is a process of checking the acceptability of a manufactured product.

 

Objectives of Inspection:

• Inspection separates defective components from the non-defective component so that adequate quality can be maintained.
• Inspection locates defects in process or raw material which otherwise causes problems at the final stage.
• It prevents further working on spoiled semifinished products. It helps the product to be more economical.
• Inspection detects the weak position and trouble in the weak position by checking the design.

Types of Inspection methods:

1. Revolving process, patrolling or floor inspection,
2. Fixed inspection,
3. Key-point inspection,
4. Final inspection.

1. Revolving Inspection:

In this type of inspection, the inspector walks around the workplace floor and checks machine to machine, samples of the work of various workers, and machines.

 

The revolving inspection helps to find errors during the process and before the final product is ready. It is more effective and not need to move the product to another department for checking.

 

2. Fixed Inspection:

Fixed Inspection finds defects after the job has been completed.

Fixed inspection is used when inspection equipment and tools can not be brought on the workplace. In this case, workers brought the sample to a centralized position of the workplace, at the interval to check the quality.

Advantages of fixed inspection are the number of inspectors needed is less and workers and inspectors do not come in contact with each other, thus it eliminates the chance of approving the doubtful products.

 

3. Key-point inspection:

A key point is a stage of production beyond which it requires an expensive operation or it may not rework. Every product has a key point in its process of manufacturing.

Inspection at key point separates faulty products and reject them from going to further processing. Thus avoid unnecessary further expenditure on those poor and substandard products. It reduces the cost of production.

 

4. Final Inspection:

In the final inspection, the inspector checks the performance and appearance of the product before delivery.

These types of checking include destructive and non-destructive testing such as tensile testing, impact testing, fatigue testing, etc. The final stage of inspection ensures that the product should pass the X-ray radiography, ultrasonic inspection, etc.

What is Quality control?

Quality control in manufacturing is a process through which a production system ensures that standard product quality is maintained or improved according to customers’ needs.

In other words, it incorporates the testing of units and determines if the product is within the specification for the final production. The role of testing is to determine there is any need for correction in the process, so that product can meet the customer’s desire.

 

If I explain “quality” and “control” separately, Quality is a relative term, and it is explained by comparing it with a standard product. For example, gear used in sugarcane juice extracting machine isn’t as correct, finished as gear used in an engine transmission system. So, a component is said to be good quality if the component works well for which it is meant.

On the other hand, control is a system for determining – what to inspect, how to inspect, how often to inspect. It also finds out the causes for producing a poor product, and suggest the corrective action.

An important aspect of quality control is the establishment of well defines controls. Limiting the chances of error and reduce the manufacturing cost will generate more profit.

 

Basic fundamentals of Statistical Quality Control

It called statistical quality control (S.Q.C.) if statistical techniques are applied to control the quality or to solve quality control problems. Statistical quality control makes inspection less costly and more reliable than other techniques. It controls the quality of outgoing products to conclude whether the quality of each product is as per laid quality standard or not.

The S.Q.C. technique collects, analyses the data, and permits more fundamental control over the product quality. It scientifically fixes the process tolerance.

The fundamental of statistical quality control is based on the probability theory.

The chance of the sample to represent the entire batch is developed from the theory of probability.

Statistical Quality Control uses 3 scientific techniques, namely,

1. Sampling Inspection,
2. Analysis of the data,
3. Control charting.

Inspecting all components is a very tiring and costly process. Instead of inspecting all components, some sample of the component can be inspected. This process is call sampling inspection. Chances of error in sampling inspection are high. On the other hand, if a random sample is selected from a lot and relying on the probability theory is assumed to represent the lot. So, there are much savings in the cost of the inspection.

In certain cases (example: tensile and fatigue testing, the chemical composition of an alloy, etc.) sampling inspection is the only method of inspection.

FAQs

What are the 4 types of quality inspection?

The 4 Types of Quality Inspection are:

1. Pre-Production Inspection

This happens before manufacturing begins. Inspectors check raw materials, components, and machinery to ensure everything is ready and meets specifications. This prevents problems from starting in the first place.

2. During Production Inspection (In-Process Inspection)

Conducted while products are being manufactured, typically when 10-30% of the order is complete. This catches defects early in the production run, allowing for immediate corrections before too many defective items are made.

3. Pre-Shipment Inspection (Final Inspection)

Performed when production is complete, and products are ready for shipping, usually when at least 80% of the order is finished and packed. This is the final check to ensure products meet all quality standards before they leave the factory.

4. Container Loading Inspection

Takes place during or after the loading of products into shipping containers. Inspectors verify that the correct products and quantities are being shipped, check packaging integrity, and ensure proper loading to prevent damage during transit.

Each inspection type serves a specific purpose in the quality control timeline, working together to minimise defects, reduce costs, and ensure customer satisfaction. The key is catching problems as early as possible in the manufacturing and shipping process.

Is inspection QA or QC?

Inspection is part of QC (Quality Control), not QA (Quality Assurance).

Here’s the quick difference:

QA (Quality Assurance) is proactive and process-focused. It’s about preventing defects by designing good processes, training people properly, and creating systems that build quality in from the start.

QC (Quality Control) is reactive and product-focused. It’s about detecting defects through inspection, testing, and measurement of actual products.

Inspection is a QC activity because it involves examining finished or in-process products to find defects that have already occurred.

Think of it this way: QA asks, “Are we doing things right?” while QC asks, “Did we make it right?” Inspection answers that second question by physically checking the product.

The 7 QC Tools

The 7 Basic Quality Control Tools are simple statistical and graphical methods used to identify, analyse, and solve quality problems in manufacturing:

1. Check Sheet (Tally Sheet)
   • A simple form for collecting and organizing data
   • Uses tick marks or checkmarks to record how often something occurs
   • Makes data collection easy and systematic
2. Histogram
   • A bar chart showing the frequency distribution of data
   • Displays how often different values occur
   • Helps visualise patterns and variation in measurements
3. Pareto Chart
   • A bar graph that ranks issues from most to least frequent
   • Based on the 80/20 rule (80% of problems come from 20% of causes)
   • Helps prioritise which problems to solve first
4. Cause and Effect Diagram (Fishbone/Ishikawa Diagram)
   • Shows all possible causes of a problem
   • Organised into categories like materials, methods, machines, and people
   • Helps teams brainstorm root causes
5. Scatter Diagram
   • Plots two variables to see if they’re related
   • Shows correlation between factors (like temperature and defects)
   • Helps identify cause-and-effect relationships
6. Control Chart
   • Tracks process data over time with upper and lower control limits
   • Shows whether a process is stable or out of control
   • Detects trends and unusual variations
7. Stratification (Flowchart)
   • Separates data into groups or layers for analysis
   • Sometimes replaced by flowcharts that map process steps
   • Helps understand where problems occur

Quality expert Kaoru Ishikawa popularised these tools, and they remain widely used because they’re simple, practical, and effective.

What are the 8d and 7 QC tools?

8D Problem Solving

8D (Eight Disciplines) is a structured method for solving problems and preventing recurrence. The 8 steps are:

1. Form a Team – Gather people with relevant knowledge
2. Define the Problem – Describe what’s wrong specifically
3. Implement Containment – Stop the problem from reaching customers
4. Find Root Cause – Identify why the problem happened
5. Choose Solutions – Select permanent corrective actions
6. Implement Solutions – Put fixes in place
7. Prevent Recurrence – Update procedures and systems
8. Congratulate the Team – Recognize the team’s work

It’s widely used in automotive and manufacturing when serious defects occur.

7 QC Tools

The Seven QC Tools are basic visual techniques for analyzing quality data:

1. Check Sheet – Simple form for collecting data with tick marks
2. Histogram – Bar chart showing frequency distribution of data
3. Pareto Chart – Bar chart identifying the vital few problems (80/20 rule)
4. Cause-and-Effect Diagram (Fishbone/Ishikawa) – Shows potential causes branching into categories
5. Scatter Diagram – Plots two variables to see if they’re related
6. Control Chart – Line graph tracking process stability over time
7. Stratification (Flow Chart) – Separating data into categories for analysis

These tools help teams visualize problems, identify patterns, and make data-driven decisions without complex statistics.