Development of Rapid In-process Measurement of Surface Roughness for In-line Total Check of Surface Quality

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The surface finish is generally measured by the surface roughness tester with lower tracing stylus speed of zero point several millimeters per second. Therefore, the surface finish of all parts manufactured in the lot is judged based on the measured results of only few parts by the acceptance sampling. We propose the novel on machine measurement technique of surface finish with the thermoelectric effect for rotating ground workpiece and the rapid on machine measurement system of surface finish is developed. In a grinding process, the temperature-rise of workpiece surface affects the output of developed sensor, which has a pair of parallel separate thermocouple wires with a certain tension. In order to cancel the signal component by a temperature-rise of workpiece surface for an extraction of component estimating surface roughness, we developed two kinds of cancellation methods and experimentally investigated their availability As a result, we have successfully measured a variation of surface roughness in a cylindrical plunge grinding process. Other conclusions are follows. 1. The output from the developed contact sensor with thermocouple wires approximately has the liner relationship with surface finish 2. The sensitivity improves with an increase of measuring speed, peripheral speed of workpiece, and the system can obtain the surface finish at the measuring speed which is about two thousands times as large as that of surface roughness tester. 3. The sensitivity improves by use of thicker thermocouple wires of sensor. 4. It is necessary for this measurement system to apply the measuring load so large that thermocouple wires keep steady contact with workpiece surface. In addition, the sensitivity at 0.98 N in measuring load is higher than that at 0.29N.