Performance-based control of variability and tolerance in off-site manufacture and assembly: optimization of penalty on poor production quality

Defects and quality problems in off-site manufacturing of building parts are caused by different variables. Subsequently, rework is required during on-site subassembly aggregation. Rework and tampering with prefabricated parts has implications including suboptimal structural/non-structural performance, delays and increased costs. Currently there is a gap in the off-site construction literature in developing effective interventions to reflect on variability in operations of subassembly manufacturers. On this basis, and in the first step of the current research, point clouds of the as-built status of parts are generated by laser scanners and compared with the as-designed status represented by Building Information models (BIM). Then, optimization modelling is used for development of a balanced penalty and incentive (PI) scheme to minimize variability. For this purpose, total expenditure on variability reduction is offset by revenues generated from penalties on poor quality. This optimization-based research contributes to the off-site construction literature by providing cost-effective solutions to quality problems. Furthermore, models and findings are of practical importance to off-site manufacturers by encouraging precision and discouraging discrepancy.