The guide rail is the datum to determine the relative position relationship of each machine tool component on the machine tool, and it is also the datum of the machine tool movement. The accuracy requirements of lathe guide rail mainly include the following three aspects: straightness in horizontal plane; straightness in vertical plane; parallelism (distortion) of front and rear guide rails.
Straightness error of horizontal lathe guide rail
Influence of straightness error in vertical plane of horizontal lathe guide rail on machining accuracy
In addition to the manufacturing error of the guide rail itself, the uneven wear and installation quality of the guide rail are also important factors causing the error of the guide rail. The wear of guide rail is one of the main reasons for the decline of machine tool precision.
Drive chain error
The relative error between the two ends of the transmission chain refers to the error between the two ends of the transmission chain. It is generally measured by the angle error of the end components of the transmission chain.
The spindle rotation error refers to the variation of the actual rotation axis relative to its average rotation axis at each moment. It can be divided into three basic forms: radial circular run out, axial movement and angle swing.
The main reasons for the radial rotation error of the main shaft are: the coaxiality error of several sections of the spindle journal, various errors of the bearing itself, the coaxiality error between the bearings, and the winding degree of the main shaft. However, their influence on the radial rotation accuracy of the spindle varies with different machining methods.
The main reason for the axial movement is the Perpendicularity Error of the spindle shoulder end face and bearing bearing end face to the spindle rotation axis.
Different machining methods lead to different machining errors caused by spindle rotation error. When machining outer circle and inner hole on lathe, the radial rotation error of spindle can cause roundness and cylindricity error of workpiece, but it has no direct effect on the end face of workpiece. The axial rotation error of the spindle has little effect on the machining of outer circle and inner hole, but has great influence on the perpendicularity and flatness of the machined end face. In the process of thread turning, the rotation error of the main axis can make the lead of the processed thread produce periodic error.
The rotation accuracy of machine tool spindle can be improved by properly improving the manufacturing accuracy of spindle and box, selecting high-precision bearings, improving the assembly accuracy of spindle components, balancing high-speed spindle components, and preloading rolling bearings.
