Spindle Spatial Motion Test And Error Motion Analysis

In shafting system, the ideal movement of a rotating spindle is single-degree-of-freedom rotation, while the real movement is quite complex with six degrees of freedom, the deviation between them is the error motion. On basis of rigid body kinematics, the spatial motion of the rotating spindle was described, the inner link between the error motion test and the six-degrees-of-freedom position of spindle was revealed, and the error motion was evaluated and measured numerically. This paper can help describe the spindle’s rotary precision accurately, as well as provide the theoretical basis of developing test devices. It has a certain practical value and shows an application prospect.Firstly, the rotating spindle was modeled as a rigid body moving in six-DOF. Using the homogeneous coordinate transition method, the spatial pose of spindle was described, and the connection between an observation point’s locomotion in fixed X, Y and Z axis direction and the six-DOF motion of spindle was revealed. Then, the concept of spindle’s spatial error motion was put forward, and the relationship between the data get from the test devices and the spatial motion of a rotating spindle was analyzed.Secondly, the frequency components and periodical performance of the radial motion was analyzed. A four-point orthogonal difference method was proposed to realize the radial error motion test, and MATLAB calculation examples were used to prove it. On this basement, the author designed a test plan on two section and one end face of a rotating spindle. This scheme can help get the spatial five-DOF error motion results. After reconstructing the test-bed, the possible test system error caused by installation was simply analyzed.Three groups of spatial error motion test was conducted, the spindle’s direction error and position error was numerically evaluated. As a result, the diameter of minimum spherical envelope circle of angular error motion was 0.107281 μm, the corresponding rotation angle about the X and Y axis was 0°0’13.57" and 0°0’9.30". The diameter of minimum envelope circle of radial motion was 26.7563μm, while the difference between wave peak and trough of axial motion was 9.324μm These data met the criterion of simple shafting system assembled by rolling bearings of general precision.In the end, the repeatability was evaluated as uncertainty of dynamic measurement, the maximum range was 8.6675μm while the maximum standard deviation was 2.8896μm， which meant the radial error motion had repeatability of single rotary. The periodical performance of the test data was analyzed. In another two tests of 40-rotaries continuously, the testing data showed 5-rotaries as a cycle, which was in accordance with calculation.