Margins in design - review of related concepts and methods

Margins are defined as the difference between a design parameter's minimum required value to ensure functionality, and its actual capability. Margins allow engineers to mitigate uncertainties of various kinds. While some margins are intentionally allocated, some others may get included inadvertently in designs or arise from changes to requirements. Although common in use, the concept of margins has not been formalised systematically. This paper offers the first systematic literature review of margins. Concepts related to margins can be found in various interrelated domains with similar underlying principles. However, these concepts have developed in isolation, leading to a divergent and fragmented understanding. This paper brings these strands together by differentiating between margins which may be deliberately added or discovered during a typical product lifecycle and relates this to various domains such as safety, manufacturing etc. The paper discusses approaches to model, size and allocate margins. The thematic analysis presents insights into the importance of systematic use and management of margins and also raises currently observable gaps in the literature.