Application of multi-axis numerical control system in surface machining

The level of integration and automation of the manufacturing industry has become an important standard to measure a country's scientific and technological strength. China is a big manufacturing country, covering the vast majority of the world's machining categories [1], among which numerical control technology and numerical control system have played a very important role. For various complex types of machining tasks, only CNC machining technologies and methods with more axis number linkage can be completed more efficiently [2]. Therefore, the design of multi-axis CNC system and multi-axis CNC machining method have become the core content to judge the competitiveness of machining and manufacturing industry [3]. At present, China has a certain gap with the world's advanced level in the development of 5-axis and 5-axis CNC system and CNC machining methods, which has also become a bottleneck problem restricting the depth of development of China's machining industry. Therefore, this paper takes 5-axis CNC system as the research object, through mathematical model analysis and control process research, gives its specific application in surface machining.

1. Mathematical model of pose of multi-axis CNC system

The key to realize the control function and machining effect of multi-axis CNC system lies in the accurate characterization and reasonable dynamic connection of position and attitude. In this paper, the position and attitude of multi-axis CNC system are modeled in the form of homogeneous coordinates.

The completion of a series of actions of a multi-axis CNC machining system is manifested as the cumulative effect of rotation and displacement of each joint and each axis in three-dimensional space. Therefore, to describe the multi-axis CNC system mathematically, it depends on the characterization of the rotation matrix and the translation matrix.

Machining process control of multi-axis CNC system

After the numerical control system with multi-axis linkage can be described by mathematical model, how to set the numerical control program and let the system complete the machining task according to the established route is the difficulty of the whole numerical control process. In this paper, a real-time pulse control algorithm, RTPA (Real time pulse algorithm), is designed for the machining process of multi-axis CNC system.

The process of CNC machining is generally realized and completed by interpolation algorithm, and the control of each axis in CNC machining is realized according to the pulse of the stepper motor, which needs to form the corresponding relationship between the interpolation process and the pulse generation time series. However, the real-time performance of the traditional interpolation process based on pulse frequency is not ideal. Therefore, this paper designs a new pulse generation algorithm with better real-time performance from the perspective of V-F transform algorithm (voltage-frequency). The pulse train generated by this algorithm can realize more effective control of multi-axis CNC system.
Simulation test of surface machining for multi-axis numerical control system

In the previous work, the position and attitude modeling and RTPA control algorithm design were carried out respectively for the multi-axis linkage CNC system, and the effective control strategy of the multi-axis linkage CNC system was determined through the influence analysis of key parameters. Next, simulation experiments are carried out to verify the control performance of the RTPA algorithm proposed in this paper. The simulation test chooses surface machining as the machining object of multi-axis CNC system. The surface has certain complexity in various machining units, and the control algorithm has relatively fine requirements. The machining of the whole surface is completed by continuous curve machining trajectory.
In this paper, the numerical control system with multi-axis linkage is studied. Firstly, in the form of homogeneous coordinates, the position and attitude changes at any joint of the multi-axis linkage system are modeled, and the generation processes of translation matrix and rotation matrix are derived. Secondly, based on comparator, counter and generator components, a feedback RTPA algorithm is constructed, which is used for the actual control in the machining process of multi-axis CNC system. Finally, a validation test is carried out with surface simulation machining as an example. The test results show that the section data machining route method based on CC path combined with Z-shape cutting tool can be successfully completed. At the same time, the RTPA algorithm can effectively control the displacement and velocity in the three axis directions.