Conceptual design of a fixtureless reconfigurable automated assembly system

[摘要] ENGLISH ABSTRACT: The conceptual design of a fixtureless reconfigurable automated spot weldingsystem for manufacturing subassemblies for residential circuit breakers wasinvestigated. This research was aimed at developing a possible low cost automationalternative to a South African industrial manufacturer, which is presently heavilydependent on personnel for manual assembly of their core products.System reconfiguration allows for the assembly of a range of subassemblies withgeometric component variation on a given system configuration, as well as thepotential for the system to be reconfigured to assemble other ranges of circuitbreaker subassemblies.The subassembly selected as focus consists of six different components, which varygeometrically from one product variant to another. A fixtureless approach wasselected, to minimise reconfiguration down time and the need for reconfigurablefixtures since reconfigurable fixtures have not found significant acceptance inindustry. This varies from a fixture-based approach, which was considered in relatedresearch.The conceptual assembly system presented here consists of the following modules:a flexible vision based part feeder, twin 6 DOF robotic manipulators each with amultipurpose gripper, and a stationary spot welding station. Critical conceptualdesign elements were further investigated to refine their selection and confirmfeasibility with respect to the target industry application. This process ended with apreliminary cost estimate which served as a basis for comparison between thefixtureless, fixture-based and present manual assembly process. The fixturelessconcept was overall more expensive than the fixture-based concept, primarilybecause of the limits to production throughput. The fixtureless concept washowever cheaper than the present manual assembly approach but had a far longerpayback period than desired by the industry. The complexity and possibleuncertainties of the concept combined with the long payback period indicated thatthe fixtureless concept is not suitable for the target application.

[发布机构] Stellenbosch University