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Session 1526

MACHINABILITY VERSUS TOLERANCE CONTROL OF CERAMICS THAT HAVE BEEN PRE-FIRED K.A. Forland IMSE Department, GMI Engineering & Management Institute

Experience with ceramic machining is vital not only for evaluating the production cost of ceramic parts requiring close tolerances and/or fine surface finishes, but also for determining the manufacturability of designs using ceramic components. Therefore, students who are pursuing degrees in manufacturing engineering should have exposure to the machining of ceramics. In addition, machining ceramics teaches students about the mechanical properties of the hard, brittle materials. They learn that ceramics require specialized machining equipment and longer machining times than required for ductile materials. Furthermore, they see that cracking and chipping sometimes cannot be avoided and may significantly reduce the structural integrity of the ceramic.

In the course, Properties and Processing of Ceramics, taught at GMI Engineering & Management Institute, undergraduates use an ultrasonic drill to machine alumina after different levels of sintering and after final firing. All parts are then fired to maximum density. The three parameters, machining time, dimensional control and level of pre-firing, as well as their interdependency are examined. Machining rate is approximated by the relationship between flexural strength and the porosity of the alumina. Dimensions and warpage of the drilled holes are evaluated using a coordinate measuring machine.

I. Introduction

Ceramic materials are hard and brittle, displaying very little or no plastic behavior. These mechanical properties set ceramics apart from other classes of materials, such as metals and polymers, that are generally more ductile. The fundamental differences become very apparent when working with the materials, or more specifically, when trying to machine them. Machining ceramics will teach students about the mechanical properties of the material through comparison with their prior machining experience with metals (Manufacturing Processes, a required freshman course at GMI Engineering & Management Institute). Ceramics require specialized machining equipment and longer machining times than typically required for metals. Cracking and chipping sometimes cannot be avoided and may significantly reduce the structural integrity of the part.

An informal study conducted by Iowa State University revealed that new graduates in materials-related fields had problems relating fundamental engineering principles to manufacturing1. In order to address this deficiency, several experiments are being developed at GMI to explore the mechanical properties of ceramics and the differences between various ceramic materials by machining them. The addition of these experiments to the course, Properties and Processing of Ceramics (IMSE 408), will make the course more appropriate to the

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Forland, K. (1997, June), Machinability Versus Tolerance Control Of Ceramics That Have Been Pre Fired Paper presented at 1997 Annual Conference, Milwaukee, Wisconsin. 10.18260/1-2--6671