In modern manufacturing industry, CNC machines have been widely popularized and applied because of their advantages of good machining flexibility, high machining efficiency and high machining precision. Among the performance indexes of CNC machines, machining accuracy is the most important index, which is not only an important embodiment of the development level of mechanical manufacturing industry, but also one of the important indexes to measure the technical level and industrial production level. Here is the research on error compensation for improving machining accuracy of CNC machine.
Generally speaking, the main factors affecting the machining accuracy of CNC machine tools are machining system error and random error. Specifically include:
① Machine tool equipment is the product of mechanical manufacturing, which will inevitably produce original manufacturing errors.
② CNC machine tools rely on CNC system to realize automatic machining operation, so the error of CNC system will also affect the final machining accuracy.
③ Cutting will produce heat, which will cause a certain degree of thermal deformation of the tool, resulting in error.
④ Mechanical cutting will produce cutting force. Cutting force will also deform the workpiece, tool, fixture and even the machine tool itself, which will naturally bring errors.
⑤ Modern CNC machine tools generally integrate detection system, but the detection system itself may also have errors.
⑥ When the machine tool vibrates, the influence of error is working
⑦ Errors caused by changes in processing environment and operating conditions; Finally, there are other errors.
After analyzing and determining the factors that may cause the machining error of the machine tool, the following two measures are mainly taken to improve the machining accuracy:
① By improving the design, eliminate the error source as much as possible, improve the manufacturing and assembly level of the machine tool and the processing environment, and effectively prevent the occurrence of errors by adopting high stiffness machine tool spindle, improving the manufacturing accuracy of machine tool ball screw, minimizing the error of machine tool guide rail and preheating the machine tool.
② The high stiffness, high stiffness, high stiffness, high stiffness, high stiffness and high stiffness of the machine tool spindle are analyzed. For the existing machining error forms, the error compensation model is established, and the effect of compensating the original error is achieved by manually adding new errors, so as to realize the soft improvement of the machining accuracy of the machine tool.
In the actual machining process, if the CNC machining accuracy is found to be reduced, it must be an error. At this time, the error compensation method can be used to compensate the existing error, so as to eliminate and adjust the error. Different from traditional machine tools, the machining process of CNC machine tools is realized through program control, that is, the machining process is automatic. Therefore, when making error compensation, we must also improve the CNC system and machining program. Firstly, the source and form of error should be determined, and then the error compensation method should be applied. The essence of reducing the original error is to artificially reduce or eliminate the new error. In this process, we need to master the characteristics and laws of the original error through analysis, statistics and induction, and further ensure that the constructed error compensation model is equal to the original error, so as to achieve the purpose of error compensation.
(1) Identification of cutting force error component. The cutting force is determined by the tool parts, and the parameters are calculated through the mathematical model. After the mathematical model is established, the problem can be identified and handled in time. In addition, in the machining process, too large amplitude will also affect the final machining accuracy. By observing the rated parameters of the model, the final adjustment scheme can be scientifically obtained to control the noise and vibration in the machining process within an acceptable range, so as to affect the CNC machining process to the greatest extent.
(2) Error identification. In CNC machining error compensation, the first thing to do is to identify the error. The accuracy of identification will directly affect the accuracy of error compensation. Error identification is a complex and time-consuming task. Many scholars at home and abroad have conducted relevant research and proposed many error identification methods, but generally speaking, these methods can be divided into the following three categories: single error direct measurement, comprehensive error measurement and indirect measurement.
(3) Error compensation technology. According to the process and principle of error compensation, machining error compensation technology can be further divided into three categories:
① Static compensation method. This method is to set the error compensation value in advance and then compensate according to the set value, which obviously has great defects.
② Real time error compensation method. The method is based on the detection and feedback of the hardware system. It can adjust the compensation value in real time according to the information fed back to the compensation system, and effectively improve the machining accuracy. The disadvantage is that all error elements cannot be compensated.
③ Comprehensive dynamic compensation method. This is developed on the basis of real-time error compensation method, which can dynamically adjust the compensation amount according to the changes of working conditions, environmental conditions and spatial position, so as to realize the comprehensive compensation of various errors.