Methods of Measuring Design Quality

There are several methods by which companies measure the design quality of products, services and processes. The companies select the methods in accordance to their goals. Accordingly the methods for measuring design quality may be generic like the reusability of design or specific like the size dimensions of motion system. Whatever be the metrics used, there is a trend towards using a combination of weights and rating scales for objectively measuring design quality.

One approach to measuring design quality is examining the extent to which the different parts or the subsystems of the design depend on one another. From this stand point those designs that are inflexible, and have a high degree of interdependence cannot easily be changed.  When a change is introduced it has a surging effect and it becomes impossible to guess the cost of such a change. These designs create a situation where the managers very rarely allow changes.

Another way of assessing design quality is to test its reusability. If the needed parts of the design are highly dependent on other details, design is highly interdependent. In such a situation is important to see if the design can be used in a different situation or a combination. For example, if there is an embossing unit designed as a part of a plastic stretching line. Can the embossing unit be separated from the line and used in a different plastic stretching line? Continuing with the example, can the plastic extruder be separated from the line and used as a part of another plastic strapping line?

Finally, is there a tendency of the system to break in several places when a one change is made to the system? If the design is brittle then there are problems in areas that have no direct connection with the changed area (Akao, Yoji 2004). In the plastic stretching line if the embossing unit is removed there is a problem in the cooling unit. Such brittleness reduces the reliability of the design and creates maintenance problems. The production personnel cannot rely on the production specifications.

Another approach to measuring the quality of design is to examine the specifications of the designs in terms of the realization of its objectives. The cost of implementing the design and the ease with which the device can be produced are evaluated. A strong correlation is usually present between the design and the specifications and the ratio can be used as a reliable measure of design quality (Park, Sung H1996).

Another measure of design quality is to measure design performance(Belavendram, N 1995). In this case the design quality evaluates a number of factors like the craftsmanship, the cost of design, the cost of production, and even the return on investment of the design process. In case the design is made by an internal team there is even a comparison of the performance of the design with the expected performance from external designers.

Measuring the design quality has assumed new importance with how designs are being managed to increase value of the organization to its customers. Instead of tangible end products, there are companies that evaluate the designs of business models and improve its designs to ensure that every interaction with a customer is dependable and persuasive.

Design quality is also measured from the point of view of the user. The design is expected to make the process clear to the user. Moreover, the design should make the behavior of the organization, system or the process dependable to the user, Further; the design should be such that the process or the system should provide feedback. In case of interaction with the customer, the feedback should be both visual and audio. The message however, should be clear.

The design of a process or a system should be such that the user should effectively be able to trace the path of action (Hoyle, David 2005). There should be a close correspondence between the specifications that have been given to the user and the manner in which the system works. Finally, the design should allow for measures of control.

Measuring design quality is often a task of applying general principles of designing. The general principles of designing include questions like is the design trouble-free? An uncomplicated and simple design is preferred. Also is the design is long lasting? An adaptable design is desirable and so is a timeless design. The design should appeal to the future generation.

A good design solves the moot problem (Hayes, Bob1998). A good design gives a few elements to the users that can be combined by the users themselves. A lot of work goes into a high quality design and this is reflected in the design itself. One of the metrics widely used in measuring design quality is the use of symmetry. Further, the fine tuning that has been done to the design to improve its quality and performance. Quality design can be replicated and is different from the norm. Finally, good design is done in large pieces.

From the perspective of production management it is important to remember that the design quality is important in motion control system. In this context the quality of design embraces the selection of the motor drive electronics, positioning mechanism and motion controller.. Design quality emerges from the planning that goes into the development of the system. Designing quality entails full description and understanding of the process. Meticulous details go into this designing stage like the precision of the motion, the travel length of every axis and the number of axis.

A good quality design specifies if the positioning is rotary, linear or a combination of stages (Card, David N & Glass. R 1990). The quality of design is also evaluated by the manner in which it incorporates the stage as an integral part of the larger system. The ability of the stage to meet its specifications is also an important consideration in measuring design quality. The design also encompasses the way in which the system is mounted on a flat surface to avoid distortions. The quality of design is also judged from the way in which the lifetime requirements of the system are incorporated into the stage specifications.

If the requirements change then the system may have to be removed to a different position during its lifetime. Good quality design takes into consideration the size and the environmental consequences of the system. Both horizontal and vertical size constraints need to be considered. Factors like the choice of drive type, selection of motor and the mechanical and electrical aspects of the system motions are important factors in appraising the design quality.

In the context of customer service, measuring design quality means evaluating parameters that go into a better provision of service to the customers. To deliver consistently superior service requires a high level of design quality. The design must include processes, people and the technology. Only if the design is of high quality will the company get increased sales from customers that have experienced superior service.  The design often extends to aspects of information technology.

The designing of products and service responses based on data often are critical in attracting and retaining customers. The quality of design reflects on the services provided like tracking the choices of individual customers, payment methods, patterns of buying, support websites and live chats with technical staff. To be successful the design must consider factors like support technology, culture of the organization, incentive system, training and recruitment of customer support staff.

In most situations like a production setting or a customer service system, there are some metrics that are selected for measuring the design quality. Usually, these metrics are based on the objective of the organization and are discussed with the designer before the design commences (Wood, Jane & Silver, Denise 1989). For example, the company that wants to design a motion control system will discuss with its production engineers specifications that are required for the motion control system and agree on a few metrics that will be used to measure the design quality.

For example it may be the positioning of the linear rotary, the adaptability of the system, the size of the system, the stopping ability of the drive and precision of the description of the system. Each of these metrics for measuring design quality should be given a weight so that the sum of the weighs adds up to 1. For example, the stopping ability of the drive may be given a weight of 0.3 and the precision of the description of the system may be given a weigh of 0.1 and so on. In practice these weights are decided jointly by the management and the designer.

A document for measuring design quality typically has a rating scale of five attached to each metric. After the design is completed a rating is given to each metric. The rating may range from 1 to 5, where 1 is the lowest rating and 5 is the highest rating. Each rating is multiplied with the respective rating. For example the stopping ability of the drive may get a rating of 3, this figure is multiplied by its weight of 0.3 and we get a score of 0.9. The scores for each metric is added and a composite score is calculated. As the weights add up to 1, the composite score ranges from 1 to 5, with 1 being the lowest design quality and 5 the highest possible quality measure. The actual composite measure for design quality will range between 1 and 5.

To sum, there is a wide range of metrics used for measuring design quality. Some are generic metrics like the flexibility of the design, the adaptability or its brittleness. Others are metrics related to specific situations like the metrics for measuring the design quality of a motion system. Design quality of customer support systems or HRM recruitments systems are also measured with respect to the goals of the design. These metrics are then rated according a previously decided standard, weighted and a composite score is calculated to give a comprehensive measure of design quality.

References:

Akao, Yoji (2004), Quality Function Deployment: Integrating Customer Requirements into Product Design, Productivity Press

Belavendram, N (1995) Quality by Design, Prentice Hall

Card, David N & Glass. R (1990) Measuring Software Design Quality. Prentice Hall

Hayes, Bob (1998) Measuring Customer Satisfaction: Survey Design, Use, and Statistical Analysis Methods, ASQ Quality Press

Hoyle, David (2005) ISO 9000 Quality Systems Handbook, Elsevier

Park, Sung H (1996) Robust Design and Analysis for Quality Engineering,

Springer

Wood, Jane & Silver, Denise (1989), Joint Application Design: How to Design Quality Systems in 40% less Time, John Wiley & Sons Inc