Abstract
To better understand the impact of early versus late design decisions, a study was undertaken on the root causes of missed requirements in new product development and their impact on development cost through rework activities. The context is the industrial development of unmanned aerial vehicles. The aim is to understand the occurrence rate of missed requirements, their root causes, and their relative impact. A quantitative approach of counting requirements changes and using engineering documentation enabled traceability from observation back to root cause origin. The development process was partitioned into sequential program segments, to categorize activities to before and after concept and design freeze. We found that there was a significant difference in the rate of design defects arising before and after concept freeze; and found there was a significantly higher number of corrective activities required for design defects arising earlier before concept freeze. The revision rate of concept phase decisions was over 50%, and the rework multiplier if detected late was over 10X. In combination, design decisions made before design freeze accounted for 86% of the total expected program cost, and 34% was determined before concept freeze. These results quantify and support the anecdotal 80–20 impact rule for design decisions.
Highlights
Out of 211 total system-level requirements, a total of 58 system-level design defect missed requirements occurred from the two major product development programs
Our results would suggest that by assessing requirement change impact early, a design team could develop a forward perspective and plan strategies to mitigate or correct their impact. This indicates research is needed to establish formalized systems that can incorporate and manage not just design requirements and their margins and mitigation strategies early and throughout development. This should be complemented with current product development processes to aid in the enhancement of design practitioners
Our work showed that design defects occur before and after the conceptual design freeze
Summary
The design of complex systems involves activities such as sizing subsystems and components, selecting configurations, and determining possible design solutions and implementations. Throughout, the process requires decisions (Hazelrigg 1998) that determine what needs to be analyzed, considered and determined. Create concepts, form specifications from requirements, shape the final configuration and physical form, and define production and testing (Saad et al 2013) and lifecycle/operating principles. A design research question of interest is the relative importance of design decisions made early versus late in the design process (Ulrich & Scott 1998; Ullman 2015)
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