Analysis of the factors influencing the machining accuracy of CNC lathe

As an advanced processing equipment, CNC lathe can bring huge economic and social benefits in practical application. In the process of CNC lathe machining, the accuracy control of product quality is very important, especially the application of automation technology. Compared with the traditional machining technology, the advantages are more prominent, which puts forward new requirements for the machining accuracy of CNC lathe in the new era. In NC lathe machining, the programming accuracy, servo accuracy and interpolation accuracy are directly related to the machining accuracy. In addition, the CNC lathe in the production and processing, but also by the environment, manufacturing and materials and other factors, if the lathe construction deviation can not be effectively controlled, will directly affect the quality and accuracy of parts processing, there is still to be further improved.

1. Working principle of CNC lathe

As a kind of mechanical and electrical integration product, CNC lathe integrates many modern technologies in practical application, which is helpful to improve the processing efficiency and accuracy. In the process of parts processing of general lathe, the operator needs to change the moving track of the workpiece in combination with the construction drawings, which puts forward higher requirements for the processing of the workpiece in the new era. In the process of machining parts with CNC lathe, it is necessary to fully grasp the process parameters and process flow, compile the process flow through CNC language, issue instructions to the servo system, and realize the automatic processing and manufacturing of parts.

2. Influence factors of machining accuracy of CNC lathe

In the process of NC lathe machining, there are many factors, and the servo control method and accuracy will affect the machining accuracy of NC lathe to a great extent, which will lay a hidden danger for the subsequent parts processing. In terms of machining accuracy of CNC lathe, the influencing factors mainly include: ① lathe geometric error; ② lathe tool geometric parameter error; ③ lathe thermal deformation error; ④ servo feed system error; ⑤ tool wear error.

In terms of the influencing factors of lathe machining accuracy, the error of servo feed system and the error of turning tool geometric parameters are common factors, which affect the machining quality of parts to a certain extent. At present, in the processing of CNC lathe in our country, the ball screw is driven by servo motor to control the processing position, and the transmission error of ball screw is one of the main factors affecting the positioning accuracy of CNC lathe. Throughout the current situation of CNC lathes in China, mainly closed-loop control system. In the actual operation, if the servo motor lead screw moves in the opposite direction, it will not only affect the machining accuracy of the parts, but also lead to the idling of the CNC lathe due to the emergence of the gap, which is difficult to avoid [3]. Under the influence of external forces, the moving parts may have elastic deformation, which aggravates the severity of CNC lathe error, and cannot effectively control the machining accuracy of CNC lathe.

In the process of machining parts, the turning tool cuts the parts in the preset motion track. Due to the deflection angle and arc radius of turning tool, there will be a certain size deviation when machining parts, and the axial size change will increase with the increase of arc radius. Therefore, the change of axial displacement length depends on the adjustment of axial dimension. In the process of machining parts of CNC lathe, it is necessary to comprehensively analyze the axial dimension and displacement length, and optimize the processing flow. It should be noted that the parameters of tip distance, arc radius and part center will directly affect the accuracy of part processing, and the service life of CNC lathe also depends on the grasp of these parameters, whose importance is self-evident.

3. Effective measures to improve the machining accuracy of CNC lathe

(1) Optimizing the overall design of CNC lathe

In the overall design of CNC lathe, we should choose a reasonable production strategy according to the actual situation to improve the manufacturing efficiency and accuracy of CNC lathe. From the current development status of CNC lathe manufacturing enterprises in China, it is mainly through self-designed host structure, outsourcing key functional components, which can not only improve the processing quality, but also effectively reduce the processing cost. At the same time, in the overall design of CNC lathe, it is necessary to ensure that the deformation stress is evenly distributed to each part, so as to avoid the weak parts of rigidity and improve the deformation of lathe.

For the adjustment of the center of gravity of the CNC lathe structure, the height of the center of gravity can be properly reduced according to the actual requirements, and the swing mode frequency can be increased while the manufacturing quality of the CNC lathe is not affected. On the basis of ensuring the structural rigidity, reduce the consumption of structural materials as much as possible, and effectively control the center of gravity of the machine tool. In order to effectively improve the machining accuracy of CNC lathe, through the optimization design of the thermal characteristics of the spindle system, it is helpful to improve the defects and deficiencies in the traditional technology, improve the rationality of the spindle system design, improve the spindle drift as much as possible, and control the error within a reasonable range.

(2) Improve the geometric accuracy of lathe guide rail

In the manufacturing of CNC machine tools, the geometric accuracy of the lathe bed guide rail should be further optimized, the development goal of high accuracy should be defined, and the structural design of the lathe body base and guide rail should be optimized. For the full function CNC lathe, the inclined bed can be selected for design, and the closed cylinder structure can reduce the self weight and optimize the manufacturing process. Through the cylindrical structure, the CNC machine tool can improve the bending strength and rigidity of the bed under the cutting load, and obtain considerable geometric accuracy. Generally, it is necessary to consider the moving speed comprehensively, choose the guide rail with strong load capacity as much as possible, and optimize the machining process of CNC lathe. In addition, under the condition of high load cutting, to improve the accuracy of CNC lathe, the steel inlaid sliding guide pair structure can be selected according to the actual situation. The installation of injection materials on the steel guide rail with bolts is helpful to improve the gap between the steel guide rail and the base guide rail, optimize the defects and deficiencies in the process, improve the processing accuracy of the guide rail, and provide a solid guarantee for the subsequent processing quality.

(3) Error compensation method error compensation method

As an effective system compensation method, the machining error of CNC lathe parts can be controlled within a reasonable range, and the machining accuracy can be improved by error compensation. Through modern technology, high quality and precision parts can be obtained while reducing the machining deviation of CNC lathe. Using the semi closed loop servo system CNC lathe, affected by the reverse deviation, it is difficult to effectively control the error of repeated positioning accuracy of lathe, which affects the accuracy and quality of machining parts. Based on this, through the error compensation method, the machining error of parts can be controlled within a reasonable range, and the effective compensation for the machining error of parts can be realized. In terms of the current positioning error of CNC lathe, most of them are kept at about 0.02 mm, without compensation function. With the help of corresponding hardware and software, accurate positioning of tools can be realized, and the gap existing in them can be eliminated as much as possible.

At the same time, it does not affect the low-speed unidirectional positioning of the CNC lathe, and effectively interpolates the CNC lathe. In this process, the reverse problem can be interpolated on the basis of determining the gap value, so as to meet the needs of parts processing. For other CNC lathes, multiple addresses can be built in for data storage to realize the storage and compensation of shaft reverse clearance. By changing the movement direction of the lathe axis, the reverse clearance value can be obtained, the coordinate displacement can be effectively compensated, the deviation can be controlled within a reasonable range, the machining accuracy of the workpiece can be improved, and a solid foundation can be laid for the subsequent processing activities.

(4) Error prevention method

The error prevention method is an effective prevention method, which is not to control the error, but to avoid or control the error within a reasonable range through prevention. Through the optimization design of the machine tool, the possible error problems are analyzed comprehensively, and the error is controlled in a reasonable range as far as possible. For example, according to the machining needs to improve the machining accuracy of lathe parts, further optimize the existing lathe structure, and provide support for the subsequent machining accuracy and rigidity of parts. In addition, it can effectively control the processing environment and optimize the processing technology. However, it should be noted that the error prevention method also has certain defects and deficiencies. Excessive improvement of CNC lathe precision will not only affect product quality, but also increase processing costs, which is not conducive to the long-term survival and development of enterprises.

4. Conclusion

To sum up, CNC lathe in the production and processing, but also by the environment, manufacturing and materials and other factors, if not effectively control the lathe construction deviation, will affect the quality of parts processing. Therefore, it is necessary to select a reasonable range, further optimize the existing process, improve the existing defects and deficiencies, and improve the machining accuracy of CNC lathe.