Preparing a list of quality defects for QC inspectors

Preparing a list of quality defects for QC inspectors

This post discussed an Acceptable Quality Level and how it is used with product inspection. We also went over the three categories of defects found in a lot and gave an example of how they can be expressed. To understand the acceptable quality level table following parameters are to be kept in mind. A higher one may be acceptable for products used for personal use, while a lower one may be required for products used in a critical application. It provides the minimum sample sizes needed to detect specific percentages of defects at some confidence level. Acceptance sampling is a type of sampling where a certain number of units from each lot are selected and inspected.

Human hands involved in sewing and stitching, for example, raise variability in production. Whereas more automated production processes, like the use of injection molding in hardlines goods or robotics in electronic assembly, tend to lower variability. This typically results in more consistent product quality throughout a production run. And considering the quantity and severity of different types of defects found helps you make an informed shipping decision.


These cracks form after the weld is completed and the metal temperature has cooled. They can even be made after the steel has been welded, hours or days later. Slowing the operation and using a minor arc to allow the gases to pass. 5-axis CNC machining is offers extremely high manufacturing capabilities.

types of defects in quality control

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. 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. In a manufacturing plant, Inspection, and quality control are the most important process in order to make a high-quality product.

Why does correct defect classification matter?

It is more certain, and less expensive, as it aims to prevent defects rather than to discover and correct them later. From choosing the proper welding technique to ensuring adequate implementation of the process, welding can be a complex craft. Welding defects can affect your product’s quality and, ultimately, your business performance. Therefore, it is vital to understand the various types of welding defects, their causes, and how you can prevent them. This means when a product comes off an assembly line, like a car, it has all four tires. A car with only three tires would be a flawed product that a company would want to catch before it is shipped out.

  • Developers and programmers sometimes make mistakes which create bugs called defects.
  • Learn how to define what is quality control with Simplilearn’s Post Graduate Program in Lean Six Sigma, offered in partnership with the University of Massachusetts Amherst.
  • However, during the production employees do mistakes some time, machine and equipment have breakdowns.
  • You suspect that your supplier gave orders to several workshops to produce your goods, but he won’t tell you.
  • The process of electromagnetic particle inspection involves magnetizing the workpiece.

It is set by the relevant authority (e.g. the buyer’s quality manager). “The total number of samples to check visually is 317 pieces. The total number of samples to check visually is 317 pieces. Do not mix up “inspection levels” (I, II, III, S-1, S-2, S-3, S-4) and “inspection severity” .

Inspected units are marked according to the severity level of any characteristics which don’t meet accepted standards. The producer or supplier should provide checklists to inspectors to determine the acceptable quality tolerance level for defects or non-conformity. Quality control is a set of procedures that are used to ensure that a manufactured product adheres to the set standards of quality. The set standards of quality should meet the user’s requirements.


It also focuses on the small mistake made by developer while writing the code. Often the developers do the syntax defects as there might be some small symbols escaped. For example, while writing a code in C++ there is possibility that a semicolon(;) is escaped. 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.

Despite the relative meaning of “value,” quality control is the process by which products/services are tested and measured to ensure they meet a standard. Through this process, a business can evaluate, maintain, and improve product quality. This defect couldaffect the function, performance, or appearanceof a product.

Sampling process Acceptable Quality Limit tables provide the minimum sample sizes needed to detect specific percentages of defects at some confidence level. It works by taking a sample set from each lot and determining whether it meets requirements based on its characteristics. For example, let’s say you have 1000 widgets in your warehouse. It can also refer to the acceptable quality limit, a method used for sampling inspection that determines whether a sample of some product meets specific requirements. In quality control, AQL refers to the maximum allowable number of defects per unit that a lot can have and still be considered acceptable for delivery to the customer.

Using ISO standard sampling procedures for a PSI, inspectors systematically inspect a portion of randomly selected units in all batches when production is at least 80% complete. This is the last chance to spot any defects and take corrective action before production is complete, and before the products are packed for shipping. Quality control is a significant element in producing high-quality products that meet consumers’ expectations. Good quality requires employees that embody hard work, are attentive to details, and have a sound system that monitors and assesses the standards of the product.

types of defects in quality control

Common critical defects with hardline products include sharp points and protrusions on the surface of the items. Like with E&E products, surface imperfections such as welding protrusions that don’t affect the functionality of the product are usually considered minor defects. Many buyers have a zero-tolerance policy for critical defects. A single fault of this type will usually cause the item to fail the inspection and get recalled.

Defect – Definition and Causes

During the inspection process, they focus on appearance, construction, and working of the product. Inspection is one of the operational parts of quality control. Most importers set a lower limit for major defects than minor defects in their inspected sample size.

Types of Product Quality Defects

Depending on the severity of the defect and the level of risk involved, the buyer may even cancel the whole order. Once production has started at a supplier’s site, then a first article inspection can be conducted. With an FAI inspection, your quality control inspector will inspect the first mass production run of your product from both the factory floor and the design documents. Performance defects are the defects when the system or the software application is unable to meet the desired and the expected results. When the system or the software application doesn’t fulfill the users’s requirements then that is the performance defects. It also includes the response of the system with the varying load on the system.

It often occurs due to improper filling of the crater before breaking the arc. This leads to faster cooling of the outer edges than the crater. Insufficient volume of the weld may prevent it from types of defects in quality control overcoming metal shrinkage. As a result, there is the formation of a crater crack welding defect. These are “delayed” cracking defects that develop after the solidification of weld metal.

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