Role of Tolerances and Process Capability Data in Product and Process Design Integration

A case from the authors' experience reveals that dimensional tolerance, in terms of physical dimensions of components and their position within the system; interact to compound the process variability and uncertainty within a project. Variability adds to the costs of a process with long cycle times, high work in progress levels; wasted capacity due to low utilization of resources; lost throughput, and a general increase in waste (poor quality and increased scrap). Early constructability research supports this observation: as it identified dimensional tolerances as a major factor in ease of construction and subsequently cost and schedule. Though constructability research has developed many tools for application to design, none appear to have focused on how to identify appropriate tolerances. In addition, other industries outside AEC have made significant improvements by carefully measuring and understanding the effects of tolerances within their systems. Quantifying dimensional tolerances for construction operations and materials, and developing strategies to mitigate their effects is therefore an important objective in research and design practice. Based on a case study, a strategy is recommended in which product designers are challenged to design systems that accommodate most process variability without compromising project goals.