CNC machining is to use the automatic control system to install digital program flow commands to control the automatic start stop, direction change and speed change of CNC machine tool bearings. NC blade can be selected, the drilling amount and moving track of NC blade can be changed, and all kinds of auxiliary posture needed for lifetime machining can be carried out. CNC machining can greatly reduce the number of work clothes, and produce parts with complex processing methods, only need to change the process flow. CNC machining is relatively stable and will not cause machining error. What are the reasons that affect the accuracy of CNC machining? Let’s take a look at it
From the long-term data analysis and practical operation of parts processing, we can see the machining accuracy error caused by CNC machine tool positioning. The positioning of machine tools has a great influence on the machining accuracy of CNC machine tools. From the perspective of structure, the machining error of CNC machine tools is mainly caused by the accuracy grade, and the feed system of machine tool is the key stage affecting the accuracy level. The feed system of CNC machine tool is generally composed of mechanical transmission system and electrical control system. In the overall design, the accuracy level is related to the mechanical transmission system. In the closed-loop control system, CNC machine tools can generally avoid the position error of key components (such as ball screw and other components) according to the positioning inspection equipment. However, for the open-loop system, because of many factors and complex conditions, it is impossible to carry out positioning detection, so the machining accuracy of CNC machine tools is greatly affected.
The influence of CNC machining position error on machining accuracy. Position error refers to the transformation or offset level of the specific surface layer, center line or symmetry face of the machined part relative to its ideal position, such as flatness, symmetry, symmetry, etc. Position error in NC machining generally refers to over-current protection error. The key reason for the position error is the machining error caused by the gap and elastic deformation caused by the transmission system in the whole machining process of machine tool parts, and the position error caused by the sliding friction force that the special tool head needs to get rid of in the production process. In the open-loop system, the position precision is greatly affected, while in the closed-loop control system, the key to the position precision is the offset test.
The machining accuracy error caused by geometric figure error of CNC machining. In the processing of CNC machine tools, because of the influence of external factors such as external force, heat generated during processing, the geometric precision of the machine tool is affected, and the geometric shape deformation of parts processed on the machine tool will cause geometric error. According to scientific research, there are two reasons for the geometric error of CNC machine tools: internal factors and external factors. The internal factors causing geometric errors of machine tools refer to the geometric errors caused by the machine itself, such as the flatness of the machine tool table, the flatness and parallelism of the guide rail of the machine tool, and the geometric precision of the special tools and fixtures of the machine tool. The key of external factors refers to the geometric error caused by environmental factors and thermal deformation in the production process. For example, the geometric error caused by thermal deformation and deformation of NC blade or parts in the whole drilling process will affect the machining accuracy of machine tools and parts.
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