TABLE OF CONTENTS The unit event is made up of the various generating mechanisms within a manufacturing process. Consideration of the unit event generating mechanisms will allow an understanding of how and why the surface is as it is. It will also permit surfaces to be designed or engineered for particular requirements or performance. Unit event generating mechanisms can be simplistically divided into three basic types: mechanical, thermal and chemical. These unit event mechanisms will always be present to a greater or lesser degree in all manufacturing processes and there is often no clear distinction between them.
Figure 2.2 shows the three mechanisms in the form of a triangle. Five archetypal processes (electro-chemical machining (ECM), abrasive jet machining (AJM), turning (T), grinding (G) and electro-discharge machining (EDM)) have been added to the diagram at positions appropriate to the balance of the inherent generating mechanisms. The CHM and AJM processes will tend towards chemical and mechanical mechanisms respectively. EDM is obviously a thermal process but, since the surface is reactive, there will also be a chemical aspect hence, it is on the chemical side of thermal . The other processes are a combination of the three generating mechanisms. Note that gentle, conventional and abusive grinding are spread across the diagram because the mechanical and thermal balance changes. Gentle grinding tends towards mechanical, and abusive towards thermal changes. Because there is such a range, it is more appropriate to split manufacturing processes into five classes and not just...
