Evaluation of Grit Analysis and Sorting Techniques

The sorting method affects the variance of grit characteristics in a batch. This has a direct correlation to tool manufacturing and tool performance. One has to be aware that variances in the process chain add up. A narrow distribution band of grit characteristics defines the tool performance more precisely. This potentially leads to highly efficient and well balanced abrasive processes. Low scrap rates and high product quality are important for sustainable manufacturing technologies. However, the sorting method to obtain the narrow band might be more expensive. Additionally, a broad grit size distribution can facilitate tool manufacturing by lower mold pressure and higher packing density. Both, selection method and tool manufacturing affect the tool price.

Uniformity of the grit batch is a useful characteristic for the quality of grit selection; however, the overall quality of the batch has to be judged according to the application. Novikov et al. [NOVI08] describe a calculation method for uniformity, which allows assessing powder uniformity from diverse characteristics. Uniformity can be improved during the abrasive grit production, at the stage of grit selection, and by grit sizing [NOVI10].

In Table 2.6 the most important analysis and selection methods are compared. Criteria are the applicability for superabrasives or conventional grits, use as selection method, or non-destructive method. Some methods are only applied for macrogrits or for powders. In addition, measurement methods can be characterized by the following criteria [BENE10]:

• Accuracy = closeness of the measured value to the true value,

• Precision = variation in repeated measurements,

• Reproducibility = variation between different instruments, operators and sample preparation,

• Resolution = minimum detectable differences between features,

• Upper and lower limits.

These criteria were not evaluated in Table 2.6 because they differ for the equipment and are in constant development. Future research should focus on the effort per sorting method and the achievable tool performance and productivity. This could be connected to the sustainability analysis in Chap. 7 “Sustainability of Grinding”.