After thousands of years of manual grinding with stones, the first synthetic grinding tools were known in the beginning of the 19th century. [COLL88, p. 894]
The grit material performs the main abrasive cutting action and has been discussed in the previous chapter. However, grits alone cannot maintain a sustainable process with sufficient workpiece quality. One method is to bond the grits together by a bonding system that has to fulfil several tasks as follows [KLOC05a, MARI04]:
• Provide sufficient grit retention without untimely grit pullout,
• Provide sufficient strength to transfer machining forces and centrifugal forces,
• Allow controlled bond erosion to expose new cutting edges,
• Offer enough pore space to transport chips and cooling lubricant,
• Provide adequate heat conductivity and thermo-shock resistance,
• Provide chemical resistance against cooling lubricant.
Bonded grits form either grinding wheels or grinding belts (see Sects. 4.1 “Grinding Wheels” and 4.2 “Coated Abrasive Tools”). As consequence of the complex requirement profile on the tools, maximum grit retention capability is not synonymous with high performance in the abrasive process [MARI04].
Several bonding systems have evolved for grinding tools and will be discussed in this chapter. As contrasting method, the abrasive grits can also be applied as loose abrasives, which will be described in Sects. 4.4 “Polishing Tools”,
4.5 “Lapping”, and 4.7 “Other Methods with Free Abrasives”.
The most important bonding systems for grinding wheels are resin bonds, vitrified bonds, and metallic bonds (multi-layer or single-layer) (Fig. 3.1). Besides the primary ingredients, there are fillers, separator agents, auxiliary components, or even secondary abrasives in the bonding composition to modify the abrasive tool. All ingredients need to be considered in their life cycle from raw material extraction to end of life.
© Springer International Publishing Switzerland 2016 B. Linke, Life Cycle and Sustainability of Abrasive Tools, RWTHedition, DOI 10.1007/978-3-319-28346-3_3
Grinding tools with resin, vitrified and multi-layer metallic bond systems pass through similar manufacturing steps, such as mixing, forming, pressing, heat treatment, and post-processing [TYRO03]. All tool manufacturing processes include additional auxiliary steps such as raw material quality control, weighing, intermediate control steps, sieving, stocking, etc.
The homogeneous distribution of abrasive grits, bonding material and pores inside the abrasive layer is crucial for a constant process performance. A non-uniform distribution of the abrasive material leads to an uneven material removal process and respectively to a change in average chip thickness. This results in varying loads affecting the generated workpiece surface as well as the wear behavior of the grinding wheel that decreases process sustainability [KLOC05c].
Variations in the manufacturing process of tools cannot be totally avoided. However, it is important to control the deviation of the quality parameters per single production step so that the final product stays within the acceptable quality ranges [KLOM86, p. 12].
In contrast to conventional grinding tools, superabrasive tools are commonly built from an abrasive layer applied to a carrier, so called body (see Sect. 4.1 “Grinding Wheels”). The abrasive layer is fixed to the body either as ring or as straight or curved segments for larger diameters (commonly above 200 mm wheel diameter). Like conventional grits, superabrasives can be held by resin and vitrified bonds. Resin and vitrified bonds, however, have to be adapted to the chemistry and performance of superabrasives. Metallic bonds have particular importance for superabrasive grits and are nearly exclusively used for this grit type.