The concept of reliability refers to the probability of the product fulfilling its functions under given service conditions for a predetermined period of time without becoming defective. Not only for environmental reasons is it important to attain a high reliability of the products and to use them as long as possible. Product design providing for protective devices (e.g. fuses against overload) are also closely related to this issue. The "Failure Mode and Effect Analysis" (FMEA) is a tool permitting to evaluate and improve the reliability of products.
Functional quality refers to the interaction of the various parts and components. High functional quality ensures that the product fulfills its functions even if service conditions are not optimal. If the user perceives the product as functioning well this not only contributes to a high appreciation but is also a prerequisite for prolonged use of the product; this need not necessarily be identical with the actual lifetime of the product. Products intended for daily use often become waste before their end of life on account of their poor functional quality.
An important measure to ensure prolonged use of the product consists in a design providing for possible upgrading. This is particularly important in areas where technological progress is fast and the product would become outdated soon. Usually, not the whole product becomes outdated but only certain parts or components; therefore it makes sense to design these as modules that can be exchanged thus ensuring that the product may be equipped with upgraded parts and used for a longer time. This often requires designers to take into account a larger context. The graphics card shown as an example here makes possible to continue to use technologically outdated (fixed frequency) monitors in spite of new software requirements.
Combining several functions in a product may considerably reduce the overall consumption of resources involved in meeting the demand for given functions. The concept of offering multiple-use products must, however, not lead to an impairment of the functional quality. It is also conceivable to design particularly resource-intensive components, such as drive units for different appliances (e.g. garden or kitchen appliances) for multiple purpose application. The beneficial effect as compared to a variant providing for individual drive units for each of the appliances seems obvious.
Basically, the concept of simple principle of functioning aims at reducing material input by integration of functions. Consumption of resources is to be reduced by realizing the principle of functioning with fewer structural parts. Minimizing the number of connecting parts is equally important with a view to materials savings as well as to a reduction of assembly and disassembly times.
In the context of high functional quality products or components exposed to wear and tear should be designed in such a way that wear and tear can be easily compensated for. If a design providing for self-adjustment should prove too complicated or too expensive readjustment to compensate for wear and tear should be possible in order to ensure maximum service life.
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