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Grinding is a bonded abrasive machining process where material is removed in the form of tiny chips by means of a high speed rotating disc shaped wheel in which large number of hard abrasives particles having irregular and random geometry are held together with the help of bonding agent. Grinding is mainly used for high quality surface finish and tight tolerances.
Grinding can be classified in terms of applied depth of cut as: shallow cut grinding and deep cut grinding. In shallow cut grinding, depth of cut is kept from 0.001 to 0.05 mm and workpiece speed is kept from 1 to 30 m/min. Shallow cut grinding can be further classified as: low speed shallow cut grinding (30 m/s) and high speed shallow cut grinding (180 m/s). In deep cut grinding, depth of cut is kept from 0.1 to 30 mm. Deep cut grinding can be further classified as: high speed deep grinding (wheel speed up to 200 m/s) and creep- feed grinding (workpiece speed ranges from 0.05 to 0.5 m/min). In high speed deep grinding, workpiece speed can go up to 10 m/min whereas in creep-feed deep grinding, speed of the grinding wheel is kept relatively low from 20 to 60 m/s (Tawakoli, 1993).
From the configuration point of view, the grinding process can be used in surface grinding mode, cut off grinding mode and face grinding mode. Therefore, high speed deep grinding (HSDG) can also be further classified as: high speed deep surface grinding (HSDSG), high speed deep cut off grinding (HSDCG) and high speed deep face grinding (HSDFG). In the present work, high speed deep surface grinding (HSDSG) has been considered for the investigation.
Figure 1 shows the basic scheme of HSDSG in down grinding mode. The main characteristics of the high speed deep surface grinding (HSDSG) is the large depth of cut, high workpiece speed, high wheel speed and long arc of contact. It can achieve very high material removal rate and good surface integrity of the ground component. Specific grinding energy in HSDSG can be very low due to high material removal rate (Stephenson et al., 2002). Tawakoli (1993) compared the specific grinding energy requirement among the high speed deep grinding, creep feed grinding and shallow-cut grinding as illustrated in Figure 2. Heat transfer conditions in HSDSG are very different from those in conventional shallow-cut and creep-feed grinding due to large work-wheel contact length and high workpiece speed. In HSDSG, a significant amount of grinding heat can be taken away by the grinding chips, and only a small percentage is convected into the grinding fluid and grinding wheel. Due to very high wheel speed the grinding forces are reduced and rate of wheel wear is also reduced (Stephenson et al., 2002; Tawakoli, 1993).
Figure 1. Schematic diagram of HSDSG in down grinding mode
Figure 2. Effect of workpiece speed and specific removal rate on surface-zone (Tawakoli, 1993)
A sufficient number of research papers are available related to the development of thermal models relating process parameters to temperatures generated during grinding process. But most of them are basically suitable for shallow cut (where depth of cut is less than 1mm) conventional finish grinding. The detailed literature reviews can be found in Rowe (2001a) and Brinksmeier et al. (2006). Limited papers related to thermal modeling of deep grinding processes are available. Therefore, some relevant papers of thermal modeling and few related to temperature measurement in deep grinding processes are reviewed here.