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Gary Kilpatrick, PE, NSPE

Quality control starts at the point of product conception and is carried all the way through to the final design and manufacture of a product. Product defects and failures can be attributed to poorly designed product, a poorly designed manufacturing process and/or a poorly designed quality system. Separate engineering groups within a company are assigned to (1) design and develop products referred to as product design engineers, (2) design and develop the manufacturing processes referred to as industrial-manufacturing-process engineers and (3) design and develop the quality system referred to as quality control or quality assurance engineers. Some companies require their manufacturing and process engineers to function as quality control engineers as well which is usually the practice of smaller companies.

Product Design

When a company designs a product for sale in the open marketplace, the engineers should use the engineering design sciences to design each component of the product. During the initial design phase, a prototype is made. The prototype should then be tested in the lab and in the field. These tests should determine functionality, safety, product durability and life span. If design problems become apparent during testing, a product redesign should be performed to eliminate the issue. Then product testing should resume. If the product is improperly designed and not thoroughly tested, design flaws could be the result, and the product could be unsafe and could fail. Failure may be catastrophic or may fail from use over time. The failure may or may not injure a customer depending on the type of product. The bottom line is that if a product has one or more design flaws and has not been properly tested before it is released for mass production, it will fail in some way at some point. The failure could be either from lack of performance, safety or durability.

In the world of engineering, good engineers use the engineering sciences to design products. In this endeavor, design problems must be worked out and solved if the engineering science is available. A product must be designed to operate safely and must be designed and manufactured with a reliability that will ensure a long and trouble free life. But whether the science is available or not, performance, durability and safety issues must be solved, and whatever form the design solution takes under these conditions is called "Engineering".

Product Manufacturing

Most products are made up of one or more components. Depending on a component and its material, the product is manufactured using a specific process. This process could be made up of tooling and dies, material handling and holding fixtures, high precision high volume multi-axis machining and turning centers, high pressure injection molding machines, punch or forming presses, roll formers, finely detailed electronic manufacturing etc. These components must then be transported from one operation to the other either by conveying, by robots or by forklift utilizing palletizes containers. Once each component part of the product has been manufactured, the components must then be assembled into a complete and functional unit. This can be performed manually by hand or using automated processes via robots and other automatic assembly machines. The final assembly must then be inspected for proper function. And finally it must be packaged and shipped to the end user. In any one of these operations, the product or its components can be made incorrectly or damaged in some way. If a defect is mistakenly manufactured into the product and is not discovered through inspection, then performance or safety issues could surface at some point. For example, if a jagged edge is machined onto a component by mistake, it could cut the end user. If a shaft that is designed to experience torsional stresses is mistakenly manufactured in a machining operation leaving an undesirable tool mark on the circumference of the shaft, this tool mark could become a stress riser and cause the shaft to fail catastrophically in service due to fatigue. It is important for a company to inspect components and assemblies for manufacturing defects before the product reaches the end user to avoid a catastrophic failure that could lead to a personal injury.

Quality Control

Some companies design a product, manufacture and inspect it all in-house. These companies have direct control of their product's quality. Other companies design a product and then have it manufactured by a contract manufacturer (contractor). Contractors may be located in the United States or in other countries. Today, more and more contractors are being chosen in Mexico, Asia, Central and South America and the Middle East. Companies that have their products made by contractors' loose direct control of quality assurance.

A company that wished to contract out the manufacturing of it products must establish a professional relationship with a contractor and audit the contractor to assure themselves that the contractor has the employees, talent, capability and capacity to produce their products. These contractors must have experience manufacturing similar products. The contractor will be instructed by the customer company on how they wish the product to be manufactured. They will also instruct the contractor on inspection procedures to make sure that a quality system is in place so that the product quality will meet their requirements. If a customer company has no prior relationship with a contractor in a foreign country, a customer company may retain a broker firm that has expertise in establishing relationships with companies in other countries. The broker communicates with and establishes the relationships and bring the customer company and contractor together. The brokers also assist the customer company in establishing the manufacturing and quality control processes.

When products first arrived from the contractor, the customer company will usually inspect 100% of the products to make sure that the product is manufactured correctly, meets appearance criteria and inspect for proper function. As this relationship grows, 100% inspection is reduced to a random sample inspection of products. If the contractor fails to always control the quality of the product, defects can start showing up in products. Defects may be difficult to find with random sampling inspections. If these defects are not discovered, these products will make their way to the consumers. It is not until a consumer files a warranty claim that the customer company learns of the defect. If the number of warranty claims increase, the customer company then goes into crisis mode in an attempt to discover what the contractor has done wrong. If this defect affects the safety of the product, customers may contact the Consumer Product Safety Commission and post this information. The manufacturer may then be required to submit a recall notice to repair or replace the defective product.

Manufactures' Quality Systems

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Gary E. Kilpatrick and Associates, PA, is a Forensics Engineering Firm dedicated to the application of the art, science and methodology of engineering and the scientific method to answer questions of fact in the jurisprudence system pertaining to personal injury and wrongful death.

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