5.1 Principles of Cooling Lubricants in the Grinding Process
The shearing, cutting and rubbing processes involved in grinding generate large heat flow, which can only be removed to a small extent with the chips and thus can lead to considerable thermal stress on the workpiece and the tool [GROF77, LOWI80].
In grinding, the cooling lubricant must fulfil primary and secondary tasks. The two primary functions are
1. reduction of friction between the abrasive grain and the workpiece and between the bond and the workpiece by forming a stable lubrication film and
2. cooling the contact zone and the workpiece surface by absorbing and transporting heat.
Specific secondary functions include:
• purifying the grinding wheel and the workpiece,
• chip transport from the machining location and
• building up corrosion resistance for both the machine and the workpiece material
Since the physical, chemical and biological properties of the cooling lubricant influence the machining process to a decisive extent, not only tool selection, but also the selection of the right cooling lubricant is of the greatest importance. Which of the cooling lubricant’s tasks is in the foreground depends on the machining task at hand.