Partial Fulfillment of the Requirements for the Degree of Master of Science in Mechanical Engineering

The new Profile Ring Mill (PRM) technology was developed to manufacture the initial preforms required for producing components of bearing assemblies. This continuous hot, single-step forming process was desired to replace the previous machining alternatives because of the increased throughput rate. The PRM technology was first incorporated into production in early 1998 at the new Tryon Peak facility. While there are several parameters that contribute to the successful operation of the PRM, like many other "hot" processes, the forming temperature is one of the most critical factors. It was initially assumed that the entire product formed from each shell was uniform. After preliminary testing revealed that there was significant dimensional variation along the length of the shell (DVAL), the Entry Temperature Profile (ETP) model was developed to explain this phenomenon. The ETP model predicts that there is a significant variation in the shell temperature as a result of radiant cooling during the forming process. Since the forming temperature directly affects many of the factors that determine the final product size: shrinkage, elastic recovery, and equipment swelling, a change in the forming temperature results in non-uniformity in the final product size. The results of continuously measuring the shell entry temperature and the PRM main drive current over the entire forming process confirmed that variation in the forming temperature is a root cause of the DVAL. The existence of significant DVAL will continue to result in increased scrap until an in-line temperature control system has been successfully implemented. Thesis Supervisor: Jung-Hoon Chun Title: Associate Professor of Mechanical Engineering