The pores of vitrified grinding wheels may be filled with lubricants such as sulfur, wax, or resin after sintering [MARI07, p. 113, KING86, p. 79]. Sulphur is in use as high-temperature extreme pressure lubricant in internal grinding operations in the bearing industry; yet, the use is declining because of environmental considerations [MARI07, p. 113].
Other concepts for internal tool cooling involve coolant supply through the tool body. Aurich et al. [AURI11] present a channel design similar to centrifugal pump impellers in a steel body. Nguyen and Zhang [NGUY08] invented a tool body with a coolant chamber for grinding operations on aerospace alloys.
9.2.2.3 Sensor Integrated Grinding Wheels
Many grinding machinists still rely on their sense of hearing for monitoring, for example, to define the contact position between dressing tool and grinding wheel or find out if the dressing tool is in continuous contact with the grinding wheel. In the case of superabrasives and small depths of dressing cut, it is very hard to hear the contact between dressing and grinding tool, so automatic sensors become necessary [STUC88, p. 107 f.].
Besides acoustic emission, grinding wheel spindle power is the main control parameter in grinding [BRIN07]. The spindle power relates to the tangential grinding forces (Eq. 7.2). Direct force measurement gives higher resolution, but sensors might be hard to apply to the workpiece, e. g. in external grinding. Brinksmeier et al. [BRIN07] successfully integrated force sensors and temperature sensors into a grinding wheel.
Miniaturized sensors can be integrated in grinding tools to form an “intelligent grinding tool”. Superabrasive tools with a reusable body are a special case, and can hold temperature, acoustic emission or force sensors. Challenges lie in the wireless data and energy transfer to the rotating tool [KARP01, p. 190 ff.].