Grit size and grit size distribution affects tool manufacturing and tool use (see Sect. 2.8.1 “Grit Size”). Therefore, these grit characteristics provide a good case study on sustainability [LINK12c]. Grit size can be controlled by different standardized methods, such as sieving and sedimentation (Sect. 2.9.1 “Grit Size Selection”). The user might want to consider the three conventional pillars of sustainability plus the technological pillar. The costs of tool making is not included.
Figure 7.39 suggests looking into productivity and process stability for economic sustainability, which is affected by the functional requirements “Make chip formation effective” and “Be cost-effective”. Figure 7.36 shows that grit size has a positive effect on the effective chip removal and on high material removal rate, but grit size has a bipolar effect on cost-efficiency. The undeformed chip thickness increases with grit size (Eq. 7.8), leading to a more effective chip formation with an earlier cutting phase and shorter phases of rubbing and plowing (Fig. 7.20). The grit forces however increase with chip thickness leading to higher mechanical load, a less stable process, and higher scrap rate and costs (Fig. 7.32). These mechanisms are contrasting, but the more effective chip formation is mostly dominating so that economic sustainability is basically improved with bigger grits.
Environmental sustainability can be evaluated through energy intensity for example (Fig. 7.39). Bigger grits at constant grit concentration make chip formation more effective, i. e. less plowing and rubbing happens and chip formation consumes less processing energy per material volume removed.
Social sustainability is connected to labor intensity and therefore processing time (Fig. 7.39). A high material removal and effective chip formation coming from bigger grits as discussed both reduce processing time, hence improving social sustainability.
Technological sustainability includes surface integrity and roughness, which are affected by heat, chemical reactions, and grinding grooves. Bigger grit sizes have a mainly reducing effect on heat generated, although the inner material shearing at large chip thicknesses increases heat generated. Low process heat has a positive
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Indicators |
Acquainted functional requirements |
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Technological sustainability |
• Product quality, e. g. surface structure, surface integrity, and • Product performance and lifetime |
Suppress chemical reactions Reduce mechanical impact on workpiece Control workpiece surface grooves Control workpiece surface pattern Take away heat Reduce heat generation Do not loose tool sharpness |
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Economic sustainability |
• Grinding costs, • Productivity, • Process stability and capability. |
Make chip formation effective Be cost-effective |
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Environmental sustainability |
• Energy intensity, • Residuals intensity, • Intensity of pollutant releases to air. |
Suppress chemical reactions Do not lose tool profile Reduce heat generation Make chip formation effective |
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Social sustainability |
• Labor intensity, • Worker noise level, • Hours of training and education per operator. |
Reduce processing time |
Fig. 7.39 Useful sustainability indicators for grinding technology and acquainted functional requirements [after LINK13] influence on surface integrity. However, big grits lower the surface quality due to the larger undeformed chip thickness. A high distribution of grit sizes might result in a surface profile with large variation of depth and low predictability due to outlier grits [LINK12c]. The technological sustainability is therefore affected controversially by grit size. The negative effect on surface roughness is often dominating over the positive impacts on the other three pillars of sustainability, leading the user to choose small grit sizes after all.
This case study showed how the axiomatic matrixes on grinding tool user highlight qualitative knowledge on grinding process functions and help to compare sustainability of different scenarios [LINK12c]. Quantitative equations would allow to calculate the benefits and impacts of the grinding system components.