Quality Control Explained: Definition, Purpose And Processes

Quality Control

In modern manufacturing and production, quality control plays a pivotal role. Product quality not only shapes the initial impression consumers have but also wields a substantial influence on a company’s brand reputation, customer satisfaction, and financial results.

What is Quality Control?

Quality Control (QC) involves systematic procedures and activities within the manufacturing or production process to ensure that products meet defined quality standards.

Its primary aim is to detect and address defects or variations in manufacturing, resulting in products that consistently meet or surpass customer expectations and quality standards.

Purpose of Quality Control

Amidst intense market competition, consumers now prioritize not only a product’s function and efficiency but also its appearance and quality. Consequently, product quality inspection becomes an essential component of product quality management.

So, What is Quality Control important?

(1) Enhancing consumer confidence

A product that looks flawless often leads to a positive first impression, giving the impression of high quality. When a product’s appearance is perfect, it’s more likely to build trust and goodwill among consumers, increasing their desire to buy it.

(2) Avoid returns and customer complaints

A product with a perfect appearance leaves a positive first impression, indicating high quality. Such products tend to foster trust and goodwill among consumers, leading to a greater willingness to purchase.

(3) Strengthen the brand image

A brand’s image isn’t just about product functionality; it’s also closely linked to product design and quality. Upholding high product quality through regular inspection standards plays a crucial role in building and maintaining a positive brand image.

(4) Maintain production standards

Frequent quality inspections assist the production department in evaluating if its production standards align with the enterprise’s requirements. When necessary, adjustments to the production process can be made to maintain consistent product quality.

(5) Improve economic efficiency

Although quality inspections may involve extra expenses, they are a worthwhile long-term investment. They help reduce costs related to returns and remanufacturing and boost consumer confidence in making purchases, resulting in significant economic benefits.

Quality Control Process

Quality Control

Examining products is a vital step in maintaining product quality and satisfying consumer expectations. Every stage, from raw materials to the finished product, can impact product quality. Therefore, having a thorough inspection process doesn’t just improve product quality; it also fosters consumer trust.

The following section will provide a detailed overview of the product inspection process.

(1) Inspection of raw materials

It is very important to check the quality of raw materials before production. This ensures that the materials used meet the standards and can achieve the desired effect.

(2) Inspection in production

In the product manufacturing process, it is essential for the staff to conduct periodic spot checks on the products to ensure that each step adheres to the necessary standards.

(3) Preliminary inspection of finished products

Upon completion of the product, a preliminary inspection should be conducted to verify its compliance with standards in terms of appearance, function, and performance.

(4) Functional testing of products

For products with specific functions or performance requirements, manufacturers need to conduct more in-depth testing. For example, electronic products need to be tested for electrical performance, while mechanical products may need durability and strength testing.

(5) Appearance and packaging inspection

Before products are officially launched, their appearance and packaging need to be carefully inspected to ensure that they are free of defects or damage and that they will appeal to consumers.

(6) Storage and transportation inspection

During storage and transportation, products may be affected by environmental factors or handling processes. Regular inspections ensure that the product remains in good condition until it reaches the end consumer.

(7) Terminal inspection and market feedback

The performance of the product in the market is also a test. By collecting feedback from consumers, companies can understand how a product actually works and make improvements as needed.

Methods for handling nonconforming products

In any industry, subpar products are an unavoidable issue. They can stem from raw materials, production processes, inspection procedures, or various other factors. When dealing with these nonconforming products, every manufacturer and distributor must consider effective management and solutions.

The following outlines several approaches for handling such products.

(1) Isolation and marking

To begin, when encountering a nonconforming product, it should be promptly separated from the compliant products to prevent any mixing. Furthermore, clearly labeling non-conforming products is essential for their subsequent handling.

(2) Record in detail

For every nonconforming product, it’s important to maintain detailed records that include the cause of the nonconformity, the discovery time, location, and relevant circumstances. This documentation aids in pinpointing the root cause of the issue and devising suitable corrective actions.

(3) Evaluate the possibility of reprocessing

In certain situations, nonconforming products can be reworked or repaired to bring them up to standard. For instance, some appearance defects can be resolved through polishing or painting.

(4) Recovery or destruction

When nonconforming products cannot be reprocessed or repaired, the options of recycling or destruction should be considered. During this process, it’s crucial to adhere to all applicable laws and environmental regulations.

(5) Notify customer service or related personne

If a nonconforming product has already been shipped or sold, it’s essential to promptly inform the customer, distributor or other pertinent individuals. Appropriate steps, such as recovery, replacement, or refund, should be implemented as necessary.

(6) Conduct root cause analysis

In the case of any nonconformance, it’s important to conduct a root cause analysis to pinpoint the actual source of the issue. This aids companies in devising effective corrective and preventive actions to avoid a recurrence of the same problem.

(7) Continuous monitoring and improvement

The corrective and preventive measures put in place must undergo ongoing monitoring and assessment to verify their effectiveness. Furthermore, manufacturers and distributors should continuously strive to enhance production and inspection processes to minimize the occurrence of nonconforming products.

Common Defects Of CNC Machining Parts

CNC Machining Parts

Surface Roughness: Uneven or rough surfaces can result from improper tool selection, feeds, speeds, or machining strategies.

Tolerances and Dimensional Inaccuracies: Parts may not meet specified dimensions due to issues like tool wear, temperature fluctuations, or errors in programming.

Burrs: Excess material may be left on edges or surfaces of the part, typically due to tool wear or improper machining parameters.

Chatter Marks: These are caused by vibrations during machining and can result in irregular patterns on the part’s surface.

Porosity: Air or gas pockets within the material can create voids or holes in the part, often due to inadequate cutting fluids or poor material quality.

Cracking: Cracks can appear in the material, often caused by excessive heat during machining or from residual stress.

Warping: Distortion of the part’s shape can result from uneven heat distribution during machining or residual stresses in the material.

Inadequate Thread Fit: Threads may not properly align or fit, often due to errors in threading tool selection or machining parameters.

Incomplete Machining: Some features or details of the part may be missed during machining, resulting in incomplete or nonfunctional components.

Surface Pitting: Small pits or depressions on the part’s surface can occur due to contamination or issues with the cutting tools.

Common Defects Of Injection Molding Parts

injection molded parts

Sink Marks: These are depressions on the surface of the molded part, often caused by variations in material cooling rates.

Weld Lines: Weld lines, also known as knit lines, are lines or marks where molten material has recombined during the injection process, resulting in a weaker area.

Flash: Excess material that escapes from the mold cavity, typically along the parting line, leading to thin, unwanted protrusions on the part.

Short Shots: These occur when the mold cavity is not completely filled, resulting in incomplete or underfilled parts.

Warping: Distortion or deformation of the part’s shape, often caused by uneven cooling, internal stresses, or material issues.

Burn Marks: Dark or discolored areas on the part’s surface, usually caused by excessive heat or overheating of the material.

Voids or Air Traps: Trapped air bubbles or voids within the part, typically due to inadequate venting or improper material flow.

Mismatched Colors: Inconsistent color distribution or blending, resulting in color variations in the part.

Flow Lines: These are lines or streaks on the part’s surface, resulting from non-uniform material flow during injection.

Surface Delamination: Layer separation or peeling on the part’s surface, often related to material or temperature issues.

Crazing or Cracking: Fine cracks or fissures in the part’s surface, often resulting from rapid cooling or incompatibility between the material and mold.

Ejector Pin Marks: Marks or depressions on the part’s surface due to the action of ejector pins during part removal.

What is Quality Assurance?

Quality Assurance is a part of quality management that strives to provide confidence that quality requirements will be met. It involves the establishment of standards, process control, and continuous improvement to meet or exceed quality expectations.

Quality Control Vs Quality Assurance, What is difference?


QA begins at the project’s inception, introducing important guidelines to keep products within the intended scope and make them ready for testing. Its aim is to set up a structure that minimizes bugs from the start and even shapes how programmers carry out their work. QA guides how quality is integrated and assured in a product, while QC responds to the final product by identifying and addressing any remaining defects.

Working Time:

QA spans the entire software development life cycle (SDLC). QA isn’t a standalone development phase; it’s an ongoing process focused on implementing, enforcing, and ensuring digital quality. In contrast, QC can only occur when a developed product is ready for testing and can take place both before and after the initial product release.

Focus on key points:

QA is primarily focused on improving quality by optimizing manufacturing processes and quality control processes, which involve activities like training, documentation, monitoring, and audits. On the other hand, QC concentrates on the product itself to detect defects that persist post-development. QC experts uncover these issues through methods like software testing, beta testing, or canary testing.