Grinding, in comparison to turning or milling, is often considered somewhat of a “black art” where wheel life and cycle times cannot be determined from standard tables and charts. Certainly precision grinding, being a finishing process with chip formation at submicron dimensions occurring by extrusion created at cutting edges with extreme negative rake angles, is prone to process variability such as chatter, system instability, coolant inconsistency, etc. Nevertheless, with grinding equipment in a competent state of repair, performance can be controlled and predicted within an acceptable range. Importantly, rules and guidelines are readily available to the end user to modify a process to allow for system changes. It is also essential to ensure surface quality of the parts produced. These objectives are balanced through an analysis of costs as described in subsequent chapters on economics and on centerless grinding. The importance of the grinding parameters presented below is to provide an understanding of how process adjustments change wheel performance, cycle time, and part quality.
Probably the best way for an end user to ensure a reliable and predictable process is to develop it with the machine tool builder, wheel maker, and other tooling suppliers at the time of the machine purchase using actual production parts. This then combines the best of the benefits from controlled laboratory testing with real components without production pressures, resulting in a baseline against which all future development work or process deterioration can be monitored.
The number of grinding parameters that an end user needs to understand is actually quite limited. The key factors are generally associated with either wheel life, cycle time, or part quality. The purpose of this discussion is to define various parameters that relate to wheel life, cycle time, and part quality and to demonstrate how these parameters may be used to understand and improve the grinding process. In most cases, the author has avoided the derivations of the formulae, providing instead the final equation. Derivations and more detailed discussion can be found in publications such as Marinescu et al. [2004] or Malkin [1989].