Development Of Three-Component Piezoelectric Dynamometer On Turning

The cutting force generated during metal cutting have a direct influence on the generation of cutting heat, tool wear, and quality of machined surface, and accuracy of the workpiece. Duo to the complex cutting conditions of metal cutting operation and some unknown factors, theoretical cutting force calculations fail to produce accurate results. Therefore, experimental measurements of cutting force become unavoidable. For this purpose, many dynamometers have be developed, most of which concentrated on static cutting force. Now there is need to put great emphasis on the dynamic component of cutting force to satisfy high machining accuracy.In this paper, two piezoelectric dynamometers which can measure both the static cutting force and the dynamic cutting force have been designed and manufactured. One dynamometer with two elastic rings consists of two three-component force sensors fitted under high preload in the elastic slot while the other contains one three-component force sensor fitted under high preload between bit tool and toolbar by screws. Each sensor contains three pairs of quartz plates, one sensitive to pressure in the Z direction and the other two responding to shear in the X and Y direction respectively.The distributed dynamometer is made up of bit tool, force sensor, toolbar and screws. The middle screw which goes through quartz plates is used to constrain thermal deformation and compensate the decreasing preload caused by cutting heat based on ANSYS simulation and theoretical analysis. It is proved that this structure can reduce the influence of cutting heat in some degree by cutting test, but can not meet the demand.The unitary dynamometer has a "push-pull" structure, which can improve the sensitivity and compensate the errors caused by cutting heat automatically. This structure essentially contains an important elastic ring element, which must produce deformation proportional to external load and has high rigidity. By the finite element analysis of ANSYS and orthogonal test, it is proved that the elastic ring meet the demand.In order to determine accuracy, the unitary dynamometer is calibrated statically and dynamically. The percentage linearity errors of three directions were calculated as 0.2%, 0.1% and 0.1% respectively and the values of cross-interference errors were calculated in the range of 5%. In turning operation, appropriate results of machining tests performed at different parameters are obtained and shows that the dynamometer reached designed standard and can be used reliably to measure cutting force.