errors that are prone to mechanical machining
The manufacturing error of the machine tool. The manufacturing errors of machine tools mainly include spindle rotation error, guide rail error and transmission chain error.
1. The manufacturing error of the machine tool. The manufacturing errors of machine tools mainly include spindle rotation error, guide rail error and transmission chain error.
Spindle rotation error refers to the variation of the actual rotation axis of the spindle relative to its average rotation axis at each moment, which will directly affect the accuracy of the processed workpiece.
The main reasons for the spindle rotation error are the spindle coaxiality error, the bearing itself error, the coaxiality error between the bearings, the spindle winding degree and so on.
The guide rail is the benchmark for determining the relative positional relationship of various machine tool components on the machine tool, and it is also the benchmark for machine tool movement. The manufacturing error of the guide rail itself, the uneven wear of the guide rail and the installation quality are important factors that cause the guide rail error.
Transmission chain error refers to the error of the relative movement between the transmission elements at both ends of the transmission chain. It is caused by the manufacturing and assembly errors of each component of the transmission chain, as well as the wear during use.
2, the geometric error of the tool. Any tool will inevitably wear out during the cutting process, which will cause the size and shape of the workpiece to change. The influence of tool geometry error on machining error varies with the type of tool: when using fixed-size tools for machining, the tool manufacturing error will directly affect the machining accuracy of the workpiece; and for general tools (such as turning tools, etc.), the manufacturing error There is no direct influence on machining errors.
3, the geometric error of the fixture. The function of the fixture is to make the workpiece equivalent to the tool and the machine tool have the correct position, so the geometric error of the fixture has a great influence on the machining error (especially the position error).
4. Positioning error. Positioning errors mainly include fiducial misalignment errors and positioning pair manufacturing inaccuracy errors. When machining the workpiece on the machine tool, several geometric elements on the workpiece must be selected as the positioning datum during machining. If the positioning datum and design datum are selected (the datum used to determine a certain surface size and position on the part drawing) ) Does not coincide, it will produce benchmark misalignment error.
The positioning surface of the workpiece and the positioning components of the fixture together form the positioning pair. The maximum position change of the workpiece caused by the inaccurate manufacturing of the positioning pair and the fit gap between the positioning pairs is called the inaccurate manufacturing error of the positioning pair. The inaccurate manufacturing error of the positioning pair will only occur when the adjustment method is used, and will not occur in the trial cutting method.
5. The error caused by the force and deformation of the process system. Workpiece stiffness: In the process system, if the stiffness of the workpiece is relatively low compared to the machine tool, tool, and fixture, the deformation of the workpiece due to insufficient stiffness will have a greater impact on machining errors under the action of cutting force.