Development of a rotary two-colour pyrometer for thermal measurements in face grinding operations

Abstract

Grinding burn is one of the main problems in grinding and it is nowadays a matter of concern both for Academia and Industry. Research works along the last 50 years have shown that as much as 60-85% of the total consumed power is conducted to the workpiece in the form of heat. As a consequence, surface and subsurface temperature of the component rises, leading to phase transformations, loss of previous heat treatments, development of harmful tensile residual stresses, etc. Temperature measurement becomes thus a critical point to predict thermal problems and for optimization of process parameters. However, temperature measurement in grinding is a very difficult task: values over 800ºC, thermal gradients over 4000ºC/s, the presence of large amounts of cutting fluid and high pressure, and the difficulty to access the contact point have led researchers to study very different approaches. For instance, the use of thermocouples has been presented in numerous research works. However, thermal inertia of thermocouples and the problems related to efficient location limit their actual application field. Other instruments such as one colour pyrometers and infrared cameras have also been used in research, but effective calibration is very difficult. Also, the presence of cutting fluid has limited their use to dry grinding operations. The problem is even more evident in cylindrical grinding, where specific wireless instrumentation must be developed. In this work, with the aim of avoiding grinding burns in the face grinding operations in automotive-part manufacturing, a new efficient pyrometer together with the electronics has been developed.