Design For Quality – Concept, Benefits of Design for Quality (DFQ)
What is Quality :
According to Joseph Juran, the term quality of a part (or product or component) should refer to the product features that meet customers’ needs and satisfaction, and to avoidance from deficiencies that would minimize the chance of failure of the part.
Types of Design Quality
D.A. Garvin’s classic paper, “What Does Product Quality Really Mean?” lists “eight dimensions of quality.” These form a good starting point for a list of desirable attributes for a product design. Garvin’s list includes the following:
- Performance: How well the product functions
- Features: How many secondary characteristics the product has to enhance its basic function
- Reliability: Defined by some as quality in the time dimension; how well the product maintains its quality
- Conformance: How well the product conforms to the specifications or standards set for it
- Durability: How long the product lasts in use
- Serviceability: How easy the product is to maintain
- Aesthetics: How attractive the product is
- Perceived quality: How high the users believe the quality of the product is, that is, quality reputation of the product
To these desirable attributes, manufacturability, how easy and economical the product is to make, should certainly be added. Other desirable characteristics, not mentioned by Garvin, are safety, environmental friendliness, user friendliness or ergonomics, short time to market, and upgradability.
If customers are satisfied with the product after, for example, a year of ownership and at least moderate use and would recommend it to other potential buyers, then perhaps it can be said that the product is of high quality. Other measures, such as whether it conformed to some specifications, whether it had an acceptable reject rate, whether it was made under ISO 9000 conditions, or whether the company producing it got the Malcolm Baldrige award are less meaningful, in the author’s opinion, than the customer’s evaluation. Customer satisfaction is the prime measure of product quality.
Importance of Design for Quality
Design is more responsible for the quality than anything else. The designers determine the number of component in a specific part/product, decide which are to be procured externally, design the rest of the components and specify indirectly how they can be manufactured, determine how the parts must be assembled, and specify the overall function of the components in the final assembled part. In other words, the designers largely influence the entire procurement, manufacturing and assembly cycles of any small part or large component. Although manufacturing processes are often linked to the final quality of a part, both design and manufacturing are responsible for the final quality inherited by a part or component. If the quality is envisaged appropriately in the design procedure, the quality in manufacturing can also be ensured at lesser expenses and the cost of inspection reduces significantly. This leads to the concept of Design for Quality.
Benefits of Design for Quality (DFQ)
(1) The DFQ process allows the engineer to identify, plan for and manage factors that impact the robustness and reliability of the products in the design process.
(2) DFQ reduces or eliminates the cost of quality that can be envisaged as the cost incurred in the inspection and rework, in the procurement of replacement materials. Appropriate DFQ procedure can also avoid defects and errors, scrap, degradation of factory/machine capacity, re-qualifications/re-certifications expenses, and overhead demands
(3) Improved and consistent quality of parts provide better appeal to the customers that obviously lead to greater stability of the manufacturing shops and can create greater amount of opportunities.
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