Numerical control machine tools will inevitably be affected by various factors in the processing process, which will cause certain deviations in processing accuracy and bring certain inconvenience to production and life.
1. The precision problem in CNC machine tool processing
(1) The influence of position error on machining accuracy in CNC machine tool processing
Position error refers to the degree of change or deviation of the actual surface, axis or plane of symmetry of the processed part relative to its ideal position, such as verticality, position, symmetry, etc. The position error of CNC machine tools usually refers to the dead zone error. The main reason for the position error is the machining error caused by the clearance and elastic deformation in the transmission process, and the position error caused by the friction of the cutter head. In an open-loop system, the position accuracy is greatly affected, while in a closed-loop servo system, it mainly depends on the accuracy of the displacement detection device and the speed amplification factor of the system, and the effect is generally small.
(2) Machining accuracy errors caused by geometric errors in CNC machine tool processing
In CNC machining, the geometric accuracy of fixtures is affected by external factors such as external forces and heat generated during machining. The geometric deformation of the machined parts on the machine tool will produce geometric errors. Research shows that the main reasons for the geometric errors of CNC machine tools are: internal factors and external factors. The internal factors of the machine tool geometric error refer to the geometric error caused by the machine tool itself, such as the levelness of the machine tool table, the levelness and straightness of the machine tool guide rail, and the geometric accuracy of the machine tool fixture. The external factors mainly include ly, which refers to geometric errors caused by factors such as external environment and thermal deformation during processing. For example, in the process of cutting tools or parts, geometric errors are generated due to thermal expansion and deformation, which affect the machining accuracy of machine tools and parts.
(3) Machining accuracy error caused by the position of the machine tool in CNC machine tool processing
Through long-term data analysis and actual operation of parts processing, it can be seen that machine tool positioning has a great influence on the machining accuracy of CNC machine tools. From the structural point of view, the machining errors of CNC machine tools are mainly caused by the positioning accuracy, and the machine tool feed system is the main link that affects the positioning accuracy. The CNC machine tool feed system usually consists of a mechanical transmission system and an electrical control system. In the structural design, the positioning accuracy is related to the mechanical transmission system. In a closed-loop system, CNC machine tools usually use a position detection device to prevent the position deviation of the main components of the feed system such as the ball screw. For the open-loop system, due to many factors that affect the accuracy of CNC machine tools, and the situation is more complex, it cannot be positioned and monitored, so it has a greater impact on the machining accuracy of CNC machine tools.
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