Research On Feature-based CNC Machining Key Technologies For Complex Workpiece

With the rapid development of numerical control technology, the enterprise canprocess various kinds of workpiece of different shapes. The structure of workpiecetends to become complicated and the integrated, difficult in technology and complex inprocessing, so it brings a new challenge to the CNC processing technology. How toprocess large workpiece of CNC with high-quality, high efficiency and low-cost hasbecome a more and more important theme. Feature-based machining is one of thedeveloping tendency of CNC machining technology, and it is benefitial to thedigitization, integration and automation of CNC machining for complex workpiece. Toidentify the typical characteristics of the complex workpiece of products is the basis ofthe Feature CNC machining. The characteristics of processing always plays animportant role for technology planning, CNC code generation, as well as the analysisof the clamping for the CNC machining.We need five-axis CNC machine tools to produce some complex workpiece. Thefive-axis CNC machining not only improves the quality of processing, but also brings atough challenge for the tool path planning and CNC machining geometric simulation.Therefore, the more complex the shape of the workpiece becomes, the morecomplicated the NC code will be. During the producing process of five-axis CNCmachining, as the tool rotates and moves continuously, it can lead to collision. CNCMachining Process Simulation System Verification System can create a virtualprocessing environment, so the five-axis CNC machining simulation process can berealized in order to detect the correctness of the CNC program effectively.While analyzing the present situation of CNC processing of complex workpiecehome and abroad, and focusing on the problems and limitations existing in the researchwork, combined with my commitment to the major national projects and thedevelopment needs of the high-grade digital system, I studies the CNC machining ofthe complex workpiece based on the characteristics and simulation verification keytechnologies. The specific content includes several parts as follows:1. The design of the CNC machining system of the complex workpiece based onthe features. The paper presents CNC machining system of the complex workpiecebased on the features, and identifies the characteristics automatically. The entire systemuses the features of workpiece as driven, and this paper presents the automaticplanning process based on the characteristics, processes a stock model based oncharacteristics of simplified and recover technical, describes the programming systemof NC machining based on the features, and establishes NC machining simulation system.2.Research on key technologies for feature recognition of complex workpiece.The paper presents the recognition algorithms for the blend, chamfer and hole features,and the algorithms control feature size by setting threshold value. Based on therequirement of the machining of complex workpiece, the paper presents featuresimplification and recovery algorithms, develops overall simplification and simplifiestwo scenarios after achieving recognition features to simplify and streamline aselective restore. Feature recognition, simplification, and recovery of process planningfor complex workpiece and tool path generation has played a very important role.3.Research on NC machining method of solid modeling of complex workpiece.The paper presents quadrilateral mesh generation algorithm and mesh qualityoptimization algorithm which is used in keeping key features and is based on physicalnetwork mesh node adjustment, and making models for machine workpiece that doesnot have shape change, such as fixture, and table. The effect of entity model complexdegree on the method is small and the algorithm of implementation complex degree islow. The paper presents grid Voxel entity model on stock for modeling. In processing,shape change of stock entity makes model occurs and the conversion algorithm ofboundary model to entity model has implemented on the real surface of drawn fordiscrete-time model. The paper establishes a five-axis CNC machine kinematics model,describes the process of change of coordinates and movement, and takes AC machineas an example, and establishes a geometric model and kinematic modeling of machinetools.4. Establishment of simulation system of NC machining of complex workpiece. Thepaper makes research on the tool in movement process and in the formed tool swept ofcalculation method because the accurate solution method is complex and cannot meetreal-time sexual of requirements. The paper presents decomposition method toapproximate solution calculation; the method of material based on the grid Voxel entityis implementated to remove dynamic simulation, and the precision of displayed can berealized by adjusting the size of mesh; the paper establishes NC machine workpiece oflevel direction surrounded box OBB tree by using separation axis collision detectionmethod for rough sentence, and proposed a hierarchical collision detection algorithmbased on quadrangle grid through outsourcing so it can not only detect collisions in realtime of the simulation system, and can give specific workpiece where machine collisionoccurs.