Method Of Feed Rate Planning In Five-axis Machining Of Complex Surface

Five-axis CNC machine tools are constituted by three-axis machine tools and two rotational degrees of freedom. Using the two rotary axes, five-axis CNC machine tools can improve the accessibility and become an important means of machining complex surface parts. However, due to the introduction of rotation, the relationship between machine tool NC code feed rate and the tool tip speed is nonlinear. Feed rate in NC code can not reflect the actual feed rate of the tool. Aimming at high efficient five-axis CNC machining of complex surface parts, we studies a feed rate planning method to solve the velocity fluctuation problem in both machine tool coordinate system and the workpiece coordinate system. The main research topics are:1. Based on the structural characteristics of three different five-axis CNC machine tool structures, the basic concepts of post-processing the reasons for the error of rotation center are introduced. Then we study the algorithm to compensate the rotary center error in post-processing. The algorithm are validated on the head-head five-axis CNC machine tools.2. A feedrate scheduling method is proposed to solve the tool tip point's velocity fluctuation problem considering kinematic properties of both machine tool coordinate system and the workpiece coordinate system. According to the study of the transformation relationship between machine coordinate and workpiece coordinate and considering the constraints of speed and acceleration of machine tool axis and relative velocity and acceleration between the tool tip and workpiece, we give a federate to every block in the NC code. A smooth velocities of both machine tool and the tool tip point are achieved. A scheduled NC code is validated in a head-table CNC machine tool and the machining time is shortened by 32.9%. Using the Optipath module of Vericut, we study about a feedrate scheduling method based on the material removal rate of speed programming method.3. Based on Visual Studio 2008, a dedicated five-axis CNC machine tool post-processing program for three structures is developed. During the post-processing, NC code is generated and the rotary center error is compensated. The five-axis machining process of wooden ship model and engine impeller are planned. Using the dedicated five-axis CNC machine tool post-processing software we generate NC codes and schedule the federate. Experimental verification is finished at last.