Integration of Additive Manufacturing with CNC Sheet Metal Fabrication for Hybrid Fixtures: Design and Implementation of Precision Assembly Interfaces

Abstract

The objective of this project was to facilitate the integration of additive manufacturing and CNC sheet metal fabrication to create hybrid check fixtures. In this case the tool is a hybrid of a sheet metal base and an additive check surface. Using the Agile product development framework, the team conducted a series of sprints going from concept models to a final production tool in just over two months. Additive manufacturing investigations to converge on the best production solution included studies in dimensional process capability, additive process type, material tradeoffs, and business factors. Moreover, several sheet metal and tubing structures were tested to achieve a highly accurate base for the additively manufactured surface. The integration of these parts was enabled by elastic-averaging-based connector geometries that also evolved throughout the different sprints in conjunction with results from simple simulation models. The production hybrid fixture presented a range of benefits for automotive OEM and project sponsor, General Motors (GM). Compared to traditional fixtures, lead time was shortened by 92%, cost was reduced by 65%, and recyclability increased from 59% to 100%. These benefits were achieved while meeting all product owner requirements and technical specifications. Given the increasing demand for check fixtures owing to shortening product lifecycles, it is expected that the savings generated can scale up significantly. Moreover, many of the techniques developed can be applied to other types of fixtures such as those used for welding and subassembly. The project was also successful at fulfilling an internal company goal of generating sufficient traction to launch a series of collaborative initiatives between the sheet metal fabrication and additive manufacturing teams at GM.