Development of an Optical Sensor for the Non-Destructive Testing of Grinding Burn

A simple yet an effective approach for the non-destructive testing of the occurrence of the grinding burn on the workpieces during and post grinding process using a stand-alone optical sensor is proposed. The fact of grinding burn deteriorating the surface morphology is exploited by an optical sensor set-up for the quantification and non-destructive detection of the grinding burn. Reference grinding burn with varying levels are ground in 42CrMo4 workpiece for the sensor development. The average roughness of the grinding burn is found to increase with increasing level of grinding burn, for e.g. it increased from 283 nm to 491 nm for the minimum and strongest degree of grinding burn, respectively. The light intensity (reflection mode) is found to decrease with increasing degree of grinding burn. A relative change of intensity within the investigated range of grinding burn is ca. 62%. Therefore, the degree of grinding burn can be categorized as the function of the sensor output. Correlation between optical properties and the average surface roughness of the grinding burn is also presented. The proposed optical sensor would be part of sensor fusion working complementary with a microfabricated eddy-current sensor to be integrated for real-time process monitoring of the grinding process using a special set-up (including dedicated compressed air output nozzles) which allows in situ optical inspection even under harsh environmental conditions along with the use of cooling lubricants.