| Abstract: | The paper is a report of an investigative study carried out to evaluate the quality of rings manufactured for rolling element bearings. The rings are manufactured from 36–75 mm diameter bars of high-carbon high-chromium bearing steel, grade SAE-52100 conforming to ASTM A295-1984 in a ring plant, which essentially consists of an induction furnace and a fast-acting hot forging machine consisting of a set of feed rolls, hot shear and four forming stations. The ring plant is capable of producing 17 million rings per annum. Thus the volume of rings produced is very large and the project was undertaken with the objective of process improvement to build in confidence during the manufacture of the product so that it can be sent out without final inspection. The project was carried out in three phases, namely use of variables charts together with the identification of the causal factors for the ovality of rings with the help of cause-and-effect diagrams, followed by process optimization using parameter design, and this, in turn, was followed by on-line control procedure instituted for the control of the variable which deteriorates with time. |
