Tools & Techniques for Measuring Quality

Quality control is an important issue in manufacturing, and using expert tools and techniques to measure quality can ensure that your product is well received by your customers and undergoes any necessary government oversight. Technology may vary depending on your type of business, but the goal of all tools is to produce high quality products.

Inspection

Inspection is an important part of measuring quality, and for small operations, random product testing can be an effective technique. Statistical sampling, a method of using mathematics and the science of probability, is best for producing large quantities, where you have enough samples compared to the whole. Several software programs and other tools are available to perform this type of inspection. The product can also be evaluated to see if it conforms to predetermined criteria, perhaps by visiting a checklist of essential functions and physical characteristics.

Testing

One type of product testing is failure testing, where the product is tested to its limits and beyond evaluating where it will stop working. These usually include emphasizing the mechanical properties of the product such as the strength, elasticity and impact resistance of the material. Vibration and temperature tests can also be done. Which tests to use are determined by the product, its usage, and the time and financial constraints of the business.

Process Control and Ownership

Everyone involved in manufacturing the product or providing the service should be encouraged to take ownership of a part of the process. Businesses can take this concept even further and bring the entire company on board with the concept of quality control. Given the responsibility, employees will take more pride in their work and strive for a successful outcome for the job for which they are responsible. Managers, employees and vendors need to provide a firm commitment to meet deliveries and milestones. Process flow can be monitored by a project manager who will coordinate the parties involved and ensure that the deadline is met, or that the process is running smoothly. 

Control Charts

Charts can be an effective tool for evaluating the quality of your product. The use of two basic types of statistical charts - inseparable and multivariate - will depend on the number of attributes you measure. A unilateral chart represents a feature, and multivariate charts are used to evaluate several features. The next types of charts that may be useful include trend charting, Pareto bar charts that allow you to improve quality and create a scatter diagram that can show the relationship between the actual product and the standard.

How to Determine Product Sample Size to Determine Quality

There is a method called "Acceptable Quality Level" (AQL) that can be easily applied to determine the size of a product sample to determine quality. This method defines the number of samples that must be taken from a large population to determine quality. The American Society for Quality (ASQ) publishes a book defining and explaining this sampling method. This is called the "Zero Approval Number Sampling Scheme" by Nicholas . This book states that the C = 0 sampling method is an upgrade over the MIL-STD-105E (military standard) that has been used by some government contractors and the military. The C = 0 sampling planning method can lead to higher levels of productivity in your inspection and quality assurance departments, by reducing sample volume. The c = 0 designation is important because you want zero defects to be found in a sample of products that are randomly selected from a large population. There is an easy-to-use C = 0 chart that defines the number of samples that must be statistically determined to determine whether a specific population size meets a predefined quality level. In this case the number of defects for the population should be zero or accepted as a lot of quality.

Determine or calculate the total number of products in a certain lot or population.

Use the c = 0 chart to determine the number of samples to be taken from the overall population.

Choose the correct number of samples from the whole population at random. If there are multiple boxes of the same product, you must open several boxes to get the correct random sample of the correct quantity.

Inspect samples according to accepted predefined specifications or criteria.

If all the criteria are considered acceptable then size up the entire population.

Reject the entire population lot size if one or more defects are found in a random sample.

Quality Control Problem Solving Methods

Quality control is an essential function of business operations. Companies can choose from a variety of quality control methods to solve any problem or potential problem. Most quality control problem resolution methods are designed to prevent quality control problems or to minimize the negative effects of quality control problems. Other quality control problems may be largely reactionary. Elements of different methods may overlap with other methods.

Quality Assurance

The quality assurance method prevents quality problems and isolates problems quickly. Each stage of the production process, from design to market, must undergo inspection before proceeding to the next stage. An independent or in-house quality control inspector can review the end of each step to ensure that it meets specifications. The quality assurance process also involves inspection of all raw material inputs before production. If a problem occurs, the company can quickly review its quality assurance process to identify the misstatement.

Failure Testing

Consumer products require a failure test to uncover weaknesses before sending the product to market. Failure testing is an active quality control problem resolution method. Manufacturers make every effort to find weakness in their product. For manufactured goods, the products undergo repeated pressure tests, drops, spills and many other everyday possibilities until the product breaks down. Failure testing demonstrates product strengths and weaknesses that may reflect design, raw material, or manufacturing quality problems.

Company Quality

Some quality control problems require a complete overhaul in the company's quality. Unsuccessful products can be the result of a disinterested or untrained workforce, poor management, lack of documentation of the production process and weakness of the internal quality control process. Company management will redefine every aspect of the company, address the mission and purpose of the firm, provide on-site training to workers and change the company's culture concerned with quality at every level.

Statistical Control

Companies understand that completeness is impossible, but those implementing statistical control as a quality control method try to accomplish completeness anyway. Statistical control is a problem-solving method that employs the use of statistics to reduce the incidence rate of some known problems. Mean calculations, control charts and range charts monitor customer complaints and make consistent returns to ensure that a product stays within an acceptable statistical margin, such as 8 defects sold per million. Random testing is done on the percentage of manufactured goods to ensure that the statistical margin meets the specifications. The company will redesign the product to ensure that its statistical goal is met