Research On The Testing Methods Of The Stiffness Of Machine Tool Based On S-shaped Specimen

The S-shaped test specimen is put forward for evaluating the dynamic performances of five-axis machine tools by Chengdu Aircraft Industry Group. It has played a good role in checking the performance of the machine tool before acceptance. But there is not so much theory about the new test specimen, so difficulties encountered in the promotion process. This paper takes “The precision measurement technology and standardization of five-axis NC machine tool” which is shared by Tsinghua University and UESTC and many other Schools and machine tool manufactures as the background. Set up a test method to the stiffness characteristics of machine tool using S-shaped test specimen based on the comprehensive study of elastic deformation, machine tool motion control strategy and the specimen curvature. The main contents of this thesis are as follows:(1) Taking the mechanical structure of the ball-screw driven servomechanism as the research object, a dynamic model of ball-screw driven servomechanisms including joint interfaces is built, and then the elastic deformation model of the machine tool consists of the direction of torsional, axial and vertical is got. A profile error model caused by machine tool’s elastic deformation is established.(2) Relationship between the profile error caused by machine tool’s elastic deformation and the curvature of the S-shaped specimen is studied. Strategy of the motion control is studied and realized in matlab. Obtained the velocity acceleration and jerk of the axis based on the G code of the specimen. Got the elastic deformation error by the union of the error model and the motion of the axis, and found that the deformation error is related to the curvature of the specimen. The conditions when testing machine tool’s stiffness using specimen is concluded after further study.(3) Taking Chinese S-shaped specimen, NAS979 specimen and German S-shaped specimen as the research object, combined with the profile error model and CNC motion control strategy model, the rule between the error caused by the elastic deformation of machine tool and tool path of the S-shaped test specimen are concluded based on the error model and the motion parameters. Verified the error modle theory by comparing the simulation data and the measurement data. Concluded the method of testing the stiffness of machine tool using S-shaped specimen through the study of the constraint conditions, feedrate and the curvature of specimen, and compared the testing ability between the three different specimens.