The influence of ball screw drive positioning errors on the accuracy of part manufacturing

The article considers the components of the total error of mechanical processing that occur when positioning the working units of the machine: ball screw drive elements. The reasons for the loss of positioning accuracy of the machine drives are described. The accuracy of the positioning of the machine spindle in determining the axes of the holes to be processed is analyzed. The numerical estimation of the values of the errors of the temperature deformations of the lead screw is carried out on the example of drilling holes in the workpiece. The causes of heating of the ball screw drive of the machine are identified. The dependence of the unit heating on the speed of movement of the operating elements of the machine is described. The optimal trajectory of the tool movement when processing holes in the workpiece is presented. The criterion of optimality of this trajectory is described. The values of the deviations of each hole in the workpiece from the specified accuracy of their location are obtained. The scheme of accumulation of errors of linear displacements resulting from the temperature deformation of the lead screw of the CNC machine drive is presented. The value of the accumulated total error of the temperature deformations of the ball screw pair is obtained. The error associated with the movement of the machine drive carriage is considered. The geometric characteristics of the carriage orientation are given. The schemes of occurrence of the error caused by the change of the roll angle and the carriage tilt angle are presented. The maximum axial load of the lead screw at translational acceleration is calculated. The scheme of possible carriage deflection under the action of the maximum translational force of a ball screw pair is presented. The numerical estimation of the maximum possible roll angle of the carriage, as well as the maximum deviation from the specified accuracy of the carriage, at the maximum load on the lead screw, is carried out. As a result, it is concluded that the total error of the machine drives positioning can go beyond the tolerances of the linear dimensions of the processed holes, which significantly affects the accuracy of the part manufacturing.