11 - Grinding Process Control

Abstract

While basic machine design is important, here we consider factors that limit process control and methods for improving process control. Process control is required to overcome process and machine system variability. Sources of variability and methods of control are described. Variability arises from sources such as wheel wear, dresser wear, temperature variations and machine errors. The level of control required depends on work tolerances. For close tolerances and ultra-precision parts, more attention must be paid to precision of the control system. One of the simplest levels of control that produces immediate benefit is the introduction of in-process gauging. Modern computer numerical control (CNC) systems make it possible to introduce intelligent control features. A framework for intelligent control and features that can be introduced such as adaptive control are described. Forms of adaptive control are introduced including dwell control, feed-rate control and multi-plunge grinding control. The importance of time constant is described including methods for automatic time constant identification. For grinding machine systems that operate overnight without human supervision, a controller is required that can take appropriate action to account for unexpected incidents. For systems that are only required to alert a human operator, a simpler control system is acceptable. Control systems vary between systems constrained by software provided by a proprietary CNC software system and more advanced CNC controllers that allow intervention from external control systems. Many modern CNC systems allow intervention from gauging systems, gap elimination and touch dressing sensors as well as balance sensors and power sensors. A number of references are given to other sources of information.