With the rapid development of science and technology, more and more industries use machinery production to increase productivity, and the requirements for machinery are further improved. In terms of mechanical parts, the precision requirements of machined parts have been improved, and the processing technology of CNC machine tools has been greatly improved. Numerical control processing technology is widely used in various fields and can complete the processing of parts and components in strict accordance with the requirements. However, in the actual operation process, there are still some factors that adversely affect the accuracy.
1 .The influence of CNC programming on the machining accuracy of machine tools and control measures
1.1 The influence of the choice of programming origin on machining accuracy and control measures
Before we use CNC machine tool processing, we need to determine the programming plan. The origin of programming must be analyzed first, and then the program can be written. Under normal circumstances, the determination of the programming coordinate system should be comprehensively analyzed by the operator according to the characteristics of the processed parts, drawings ,and other aspects. The determination of the origin will have a relatively large impact on the accuracy of the entire processed parts. In the specific processing link, some factors should be comprehensively considered in the programming coordinate system: such as programming benchmarks, design benchmarks, process benchmarks, etc., to achieve the unity of each benchmark-setting, so that the size error can be minimized. To ensure that all dimensional errors on the parts are within the scope of the design requirements, there is no over-tolerance problem, and normal use will not be affected. In specific operations, you can proceed according to the following points.
(1) The programming origin must coincide with the design benchmark in the drawing, and various processing operations must be completed in strict accordance with the process benchmark to promote the accuracy of the processed parts.
(2) In the calculation of each technical parameter, the standard of simplicity should be met, and at the same time, unnecessary dimensional chain calculations should be prevented, and processing errors should be avoided as much as possible.
(3) The determination of the programming coordinate system is also extremely important. It should be determined under the basic conditions of ensuring that the processing accuracy meets the standard to ensure that the overall processing size is qualified and the accuracy meets the specified requirements.
1.2 The impact of data processing on accuracy and control measures during programming
In the process of writing CNC machining programs, data analysis and processing should be carried out reasonably according to the requirements. At the same time, the external contours of the processed parts should be analyzed and understood. The most important task is to perform unknown programming nodes and dimensions. Tolerance calculation and analysis to better ensure that the accuracy of its dimensional data meets the standard.
(1) CNC machine tool equipment is the main form of processing equipment. It is necessary to select the best part contour form and size according to the requirements, and do the analysis and determination of the specific node coordinate system. In many cases, manual calculation is used. In fact, the error of manual and computer calculations can reach 0.01～0.03 mm. Therefore, accurate calculation and analysis can be carried out in some ways: if manual calculation is used, then when doing the calculation of each data, Intermediate data must be determined according to the method of retaining four digits after the decimal point; if it is a computer calculation, all data must be retained to ensure the accuracy of the final calculation result. Secondly, the size adjustment of the programming link should be carried out according to the pulse equivalent of the machine tool. This data is used to control the control of the system. After the pulse is emitted, the machine tool will automatically perform the necessary movement, which is generated during the operation and movement of the machine tool. For example, if the pulse equivalent of a machine tool is 0.001mm, then at least three digits should be retained after the decimal point when calculating.
(2) Under the condition that the dimensional tolerances at different positions of the parts are asymmetric or different, you can choose to use manual methods to calculate and determine the programmed dimensions. In the processing link, if you choose to use the same tool for processing, you should determine the programming plan based on the specific tolerance intermediate value, and reserve the necessary space for error processing, which can promote the improvement of processing accuracy. When the programming size tolerance meets the requirement of symmetry, the tolerance size programming process should usually be implemented as needed, so as to avoid excessive calculation amount and improve the accuracy of the data.
2 .The influence of CNC machine tool system error on machining accuracy and control measures
2.1 Pitch error and compensation
Error compensation is to record the movement of a specific axis according to the position in the CNC machine tool processing link, and carry out in-depth comparison and analysis in combination with the specific measurement and recorded parameters. In the actual operation link, select the measuring point that meets the requirements on the axis according to the needs, implement the necessary data measurement work according to the requirements, and transmit all the data to the system, through data processing, and then perform the error elimination work.
In order to meet the machining accuracy standards, the following points should be noted: (1) If the reset data accuracy of the CNC machine tool is poor, the technology cannot be effectively implemented; (2) The application of the technology is through the analysis of the CNC machine tool coordinate system (3) The reference point is an important factor affecting the machining accuracy of CNC machine tools. It should be reasonably determined to ensure that the error of the reference point is controlled within a reasonable range and does not exceed the specified requirements.
2.2 Backlash error and compensation
In the machining process of CNC machine tools, the transmission chain is prone to gaps during operation, which is unavoidable. If there is a backlash, it will cause the machine tool to move in the opposite direction. When the servo motor is running, the machine tool does not move, and there will be errors or oscillations in the machine tool processing. Therefore, in the design process of CNC machine tools, the influence of backlash should be comprehensively analyzed. No matter which improvement measure is selected, the existence of this gap should be prevented. If the CNC machine tool is a semi-closed loop structure, combined with the error compensation technology used above, and then record and analyze all aspects of the backlash, all the data can be included in the system, which can better Realizing reverse motion compensation can eliminate these errors. For fully closed-loop machine tools, backlash compensation can be implemented through the design of various parameters to improve the machining accuracy of CNC machine tools.
There are many reasons why CNC machine tools affect machining accuracy in actual operation. Some are unavoidable. Other factors, such as process design quality, tool quality, professional quality of operators, external environment, etc., will have a certain degree of accuracy. influences. Therefore, in the processing of CNC machine tools, a variety of influencing factors should be considered comprehensively, and then these factors should be avoided, while effective control measures should be taken to promote the improvement of CNC machine tool processing accuracy.