Incorporating design effort complexity measures in product architectural design and assessment
Section snippets
Modularity
A module, as it is used in this paper, is a structurally independent building block of a larger system with well-defined interfaces. A module has fairly loose connections to the rest of the system allowing an independent development of the module as long as the interconnections at the interfaces are carefully considered.
One feature of good product modularity is the ease with which modules can be changed within a product i.e. their degree of isolation. Yet, there are few methods to quantify
Approach
We introduce here a six-step procedure to modularize a product and to identify and evaluate module boundaries (Figure 1). This procedure will help in designing products that are flexible to change. The core of the method is in the steps 4 and 5, where we construct a measure of the design effort complexity of the module boundaries in terms of design effort to change the boundaries i.e. module interfaces.
The method starts by customer need identification. The needs can then be used either to build
Methodology
We conducted multiple interviews in two case studies in order to evaluate the design effort complexity of different interface types. On these case studies, we examined dozens of modules and asked experienced practicing design engineers how long it would take them to both redesign this module at larger or smaller capacity and incorporate that as a redesign into the original product as compared to the original effort. We did this with a total of 11 engineers from three different companies
Results
Figure 3 shows an example of how the relative redesign effort changes as the redesign change percentage increases. The data points support a linear model. Another observation can be made from Figure 3; the data points seem to fan out as the percentage increases. This is an indication of the fact that it becomes harder for the engineer to estimate the required redesign effort as the change increases, since more options become available and the change becomes impossible to isolate to only a
Use
To test our approach, we applied the procedure introduced above with the design effort complexity metrics to a gas sensor.
The gas sensor measures the gas content of an environment with a capacitor and a resistor. These values are transmitted to a circuit board where the actual gas content calculation is done. This information is used to control the sensing, the outside process, and to provide user with appropriate information.
Conclusions
We introduced a method design module interfaces so that in case of a change the product is quick to adapt as well as to relatively compare proposed product architectures based on design effort complexity. Our method is an effort to help the definition of module boundaries after the module‘cores’ have been identified with a modularization method. We used the design structure matrix approach as an example and showed the use of our method through a real industrial case study. The design effort
Acknowledgements
The authors would like to thank the MIT Center for Innovation in Product Development and Helsinki University of Technology, Department of Machine Design for supporting this research. We finally thank the interviewees at all case study companies, Hannu Valo for help with case study 2, and Product Genesis, Inc.
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Visiting from: Helsinki University of Technology, Department of Machine Design