A closed-loop machining system for assembly interfaces of large-scale component based on extended STEP-NC

Machining process is usually needed to fettle the assembly interfaces of large-scale component before the final assembly. There are several issues that make the process time and effort consuming, such as hard-to-machine material, difficulties in positioning and alignment, errors between as-built component, and as-designed model. Shop floor optimization is essential for machining this kind of large and complex workpiece but is limited by information loss from CAD/CAM to CNC (Computer Numerical Control) using traditional G&M codes. STEP-NC has been proven to perform excellently in data exchange between CAD/CAM and CNC but it does not support some special processes in machining the assembly interfaces. To solve these matters, this paper proposes a closed-loop machining system based on extended STEP-NC data models which cover aligning and laser tracker measuring process. The system consists of: (1) a STEP-NC compliant CAD/CAM system which exports STEP-NC programs, (2) a STEP-NC high-level process controller which translates STEP-NC programs and makes closed-loop optimization, and (3) CNCs and mechanical systems which perform machining and measuring tasks. In the end, a vertical tail of a large passenger plane is used as a study case to demonstrate the advantages of the proposed data models and systems. This paper contributes to machining the assembly interfaces of large-scale components, and the future development of STEP-NC in large-scale manufacturing.