The design parameter of a bonded tool implies that an initial tool profile needs to be defined and then maintained as well as an initial tool sharpness needs to be defined and maintained (Fig. 7.13). Design parameters to define profile and sharpness are profiling and sharpening respectively. Profiling and sharpening can be combined to one dressing process, but then the design parameters are coupled (Fig. 7.15).
Loosing the tool profile can be overcome by a sufficient bond strength, low grit friability, and high grit hardness (Fig. 7.13). Loosing the tool sharpness is partially conquered by low grit wear and partially by tool self-sharpening (Fig. 7.14). In the case of a single-layered grinding tool, only low grit wear counts, whereas the multi-layered tools need self-sharpening largely.
Low grit wear is achieved by avoiding abrasive, thermal, and chemical grit wear. The according design parameters are high grit hardness, grit heat resistance, and chemical resistance of the grit material respectively (Fig. 7.14). Tool self-sharpening leads to the functional requirements of having grit splintering and providing new grits. The design parameters high grit friability and adjusted bond strength or a continuous dressing process respectively serve these requirements.
If only one dressing process is conducted instead of separate profiling and sharpening, the initial tool profile and initial sharpness are coupled (Fig. 7.15). The functional requirements of a dressing process are defining the dressing tool, the engagement of the dressing grits into the tool and the dressing intervals. Here, a diamond form roller is chosen as dressing tool, so the axial dressing feed rate vfad, dressing speed ratio qd, and depth of dressing cut aed are the parameters defining the
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Fig. 7.13 Bonded tool (diagram follows Fig. 7.12) |
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Fig. 7.15 Profiling and sharpening (diagram follows Fig. 7.13) |
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Fig. 7.16 Chip removal (diagram follows Fig. 7.12) |
interaction between dressing tool and grinding tool. The machined workpiece volume between the dressing cycles defines the dressing intervals.
The grinding tool transports the generated chips (Fig. 7.16). On the one hand, pore space needs to be available, i. e. the design parameter is high wheel porosity. On the other hand, the pore space needs to be cleaned, which is done by a cleaning nozzle, the sharpening process, and/or self-sharpening of the tool.