11.1 THE NEED FOR PROCESS MONITORING
11.1.1 Introduction
The behavior of any grinding process is very complex. There are a large number of input variables and the whole process is transient, that is, the mechanisms change with time. The general need for a monitoring system is expressed by Figure 11.1.
11.1.2 The Need for Sensors
An essential feature of any monitoring system is that there are sensors that can detect whether the process is running normally or abnormally. A monitoring system in an automatic grinding machine is incorporated into a control system. The system has to be able to correct the machine operational settings so that a near-optimal condition can be restored if the system is running abnormally or even in a suboptimal state.
Sensor systems for a grinding process should be capable of detecting any malfunctions in the process with high reliability so that the production of substandard parts can be minimized. Some major quality issues in the grinding process are the occurrence of chatter vibration, grinding burn, and surface roughness deterioration. Quality problems have to be identified in order to maintain the desired workpiece quality.
11.1.3 Process Optimization
In addition to quality detection, another important task of the monitoring system is to provide useful information for optimizing the grinding process in terms of total grinding time or total grinding cost. Optimization of the process can possibly be achieved if degradation of the process behavior can be tracked by the monitoring system. The information obtained with a sensor system can be used also to establish databases as part of an intelligent system [Rowe et al. 1994, Tonshoff, Friemuth, and Becker 2002].
11.1.4 Grinding Wheel Wear
An important aspect of a grinding process is grinding wheel performance. The grinding wheel should be properly selected and conditioned to meet the requirements of the parts. Grinding wheel performance may change significantly during the grinding process, which makes it difficult to predict process behavior in advance. Conditioning of the grinding wheel surface is necessary before grinding starts. It becomes necessary as well after the wheel has reached the end of its redress life to restore the wheel configuration and the surface topography to the initial state. Therefore, sufficient sensor systems are required to minimize the additional machining time, to assure the desired grinding wheel topography is maintained, and to minimize wasted abrasive material during conditioning.