In most industrial applications, wheel wear is assumed from workpiece profile deviations. In research settings, wheel wear is commonly determined by reproducing the rotating grinding wheel into a steel plate. The grinding wheel needs an unworn reference part such as a part of the abrasive layer that did not interact with the workpiece. Karpuschewski [KARP01, p. 126 ff] gives an overview about sensors for measuring the macroscopic profile of grinding tools.
6.3.2 Micro Effect—Sharpness Loss
High initial tool wear is observed after dressing or for a new tool; then a steady-state tool wear follows [JACK11, p. 50, 92, BUTT79]. Wheel collapse occurs as third wear phenomena presumably because of wheel dulling and high grinding forces [BADG09b]. The dressing process affects the initial wear dominantly, whereas the steady-state wear is dominated by the grinding process conditions. The reasons for sharpness loss are explained in Sect. 6.4 “Tool Wear Mechanisms”.
Loss of wheel sharpness, or dulling, leads to a change in surface roughness and higher process energy, which bears the risk of thermal workpiece damage. Excessive wear with large volume grit breakout reduces grinding forces and enlarges surface roughness, but dimensions are hard to keep and the shorter wheel life increases tool costs. A balance between self-sharpening and wheel costs is favored. For example, high performance processes need a grinding tool with high grit retention over a longer period [BAIL02]. Precision parts need high surface quality and high process stability, which is commonly accomplished through shorter dressing intervals.
Dressing restores tool sharpness and profile (see Sect. 6.5 “Tool Conditioning”). Multi-layered superabrasive tools enable longer intervals between dressing operations than conventional tools (Fig. 6.12). Single-layered tools show an initial wear
phase followed by quasi-stationary behavior until the tool’s end of life defined by thermal damage to the workpiece [KLOC09]. Single-layered tools are not profiled or sharpened in the common sense, although sometimes so-called touch-dressing is applied to level protruding edges.