The grinding wheel state is of substantial importance for the quality of the grinding results. The wheel condition can be described by the characteristics of the grains. Wear can lead to flattening, breakage, and even pullout of whole grains. Moreover, the number of cutting edges and the ratio of active/passive grains are of importance. Also, the bond of the grinding wheel is subject to wear. Due to its hardness and composition, the bond significantly influences the wear and variation of the grain distribution. Wheel loading, when it occurs, generates negative effects due to insufficient chip removal and coolant supply.
All these effects can be summarized as aspects of wheel topography, which changes during the wheel life between two dressing cycles. As a result, the diameter of the grinding wheel reduces with wear. In most cases, dressing cycles have to be carried out without any information about the actual wheel wear. Commonly, grinding wheels are dressed without reaching the end of acceptable wheel life in order to prevent workpiece damages, for example, workpiece burn. Figure 11.13 gives an overview about different geometrical quality features concerning the redress life of grinding wheels. As a rule, the different types of wheel wear are divided into macroscopic and microscopic features. Many attempts have been made to describe the surface topography of a grinding wheel and to correlate the quantities to the result on the workpiece.
In Figure 11.14, methods are introduced that are suitable for dynamic measurement of the grinding wheel. Most of the systems are not able to detect all micro — and macrogeometrical quantities, but can only be used for special purposes.
Macrogeometry
FIGURE 11.14 Sensors for grinding wheel topography measurement.