Development Of Piezoelectric Dynamometer Applying In Small-Deep-Holes

As a special technology, the small-deep-hole drilling has some disadvantages, for instance, the low rigidity of drill pipe, the difficulties of the chip removal and heat dissipation and so on. All above the weakness affects the quality and efficiency of the drilling seriously and also restricts development of the correlative fields including precision engineering and aerospace industry.More research has been put into the turning, planning and milling, but the drilling study is far less. With the objective of the monitoring of forces caused by the small-deep-hole drilling, this paper developed piezoelectric force-testing equipment. The achievement that the drilling forces can be detected accurately and in real-time will raise the degree of automation in small-deep-hole drilling, reduce rejection rate during the drilling process, and the efficiency will be improved obviously. As one of the important parameters, the drilling forces detection contributes to understanding the drilling mechanism, optimizing the tool parameters, and providing the information for the machine components design.The piezoelectric drilling dynamometer is based on the piezoelectric effect of quartz crystal. And its manufacture contains two parts:the core component-sensor and the whole structure design of the dynamometer. The force from the small-deep-hole drilling is dynamic and its magnitude is small. Manufacture of the inside sensor consults the design requirements of the micro-force sensor, the process referring to choosing transfer mechanism, the sensitivity design, optimizing the chips dimensions, arranging the wafer class and so on. At last, the structure with two sensors combination is confirmed and the measurement range is: Fz=0-600N, Mz=±100N·m.The structure optimization of the dynamometer's shell is realized through the stress analysis by aid of the Inventor software. And the main optimization parameters are the spanΦ2R and the cover thickness h. With the optimization of the two parameters, the objective to get the dynamometer's deformation and the natural frequency optimal can be done.In order to calibrate the static and dynamic parameters, the static and dynamic calibration system has been developed for the dynamometer. The experiments prove the dynamometer both has the high sensitivity and natural frequency; also the linearity and interphone interferences meet the CIRP-STCC standards which defined for the cutting dynamometer. The experiments verifying the axial sensitivity consistency demonstrate this dynamometer can make the no-centering measurement. And the dynamic small-force measurement can come true with this dynamometer proved by the experiments for the small-deep-hole drilling and also has low dynamic drift.