Transparent window size study of the water beam assisted form error in-process optical measurement method

In precision machining, it is desirable to measure workpiece form profiles to provide feedback for control to maintain high machining quality. In many removal type machining processes, coolants are used to reduce the thermal effects to avoid thermal deformation. But the opaque optical property of coolant produces an inaccessibility problem for in-process optical form error measurement. To solve this problem, a new measurement approach in which an optically clean zone is generated by a water beam was proposed. In order to investigate input parameter effects on the transparent window generation process, an experimental testing rig was designed and developed. This testing rig can also be used to investigate the characteristics of the water beam assisted form error in-process optical measurement method. A new applicator was also designed and fabricated for implementation. It can also be used to investigate the transparent window generation process. Through an orthogonal factorial test, the ranking of four key input parameters is found. The water flow rate Qw and the height of medium hm are the most important parameters affecting the transparent window size At. Through a preliminary parameter test, parameter value selection in the experimental testing was finalized. Through a series of experimental studies, effects of five key input parameters on the transparent window size At and the transparent window stability est were found. The effects of five key input parameters on the transparent window size At and their ranking agree with the results of the factorial orthogonal test. Through a series of experimental studies, suitable ranges of the five key input parameters were found. The objective is to obtain suitable At and est values to permit stable and accurate form error in-process optical measurement. The results are ○ Qw ∈[0.45-0.75ml/s]; ○ hm ∈[0.3-0.5mm]; ○ cc ∈[0.05-0.15]; ○ vt ∈[60-150mm/s]; ○ ∅w ∈[1.0-1.5mm]. Within the above ranges, the transparent window size At is approximately 20-40mm2, and the transparent window stability est is typically less than 6%. This value is acceptable for the form error in-process optical measurement. The suitable ranges for At are almost the same as the ones for est. It means that, when the transparent window is formed in a size approximately 20-40mm2, it will be very stable. This finding is a very useful for accurate form error in-process optical measurement