Tool Path Planning for Five-Axis U-Pass Milling of an Impeller

U-pass milling is a roughing method that combines the characteristics of flank milling with conventional trochoidal milling. The tool cuts in and out steadily, and the tool–workpiece wrap angle is maintained within a small range. This method can smooth the cutting force and reduce the peak cutting force while avoiding cutting heat accumulation, which can significantly improve the processing efficiency and reduce tool wear. In this study, a tool path model is established for U-pass milling, and the characteristic parameters of the path are defined. Through a comparative test of three-axis groove milling, it is demonstrated that the peak value and average value of the cutting force are reduced by 25% and 60%, respectively. An impeller runner is considered as the processing object, and the milling boundary parameters are pretreated. A tiling micro-arc mapping algorithm is proposed, which maps the three-dimensional boundary to the two-dimensional parameter domain plane with the arc length as the coordinate axis, and the dimensionally reduced tool contact point distribution form is obtained. The geometric domain tool position point and the interference-free tool axis vector are obtained by calculating the bidirectional proportional domain of the runner and the inverse mapping of any vector in the parameter domain. Finally, the calculation results are nested into the automatically programmed tool (APT) encoding form, and the feasibility of the five-axis U-pass milling tool path planning method is verified through a numerical example.

Five-axis Tri-NURBS Spline Interpolation Method Considering Nonlinear Error Compensation and Correction of CC Paths

In order to improve the accuracy of tool axis vector position and direction in traditional five-axis NURBS interpolation methods and the controlling accuracy of cutter contacting(CC) paths between cutter and work-piece, a five-axis Tri-NURBS spline interpolation method is presented in this article. Firstly, the spline interpolation instruction format is proposed, which includes three spline curves, such as CC point spline, tool center point spline and tool axis point spline. The next interpolation parameter is calculated based on the tool center point spline combined with the conventional parametric interpolation idea. Different from the traditional spline interpolation using the same interpolation parameter for all spline curves, the idea of equal ratio configuration of parameters is proposed in this paper to obtain the next interpolation parameter of each spline curve. The next interpolation tool center point, tool axis point and CC point on the above three spline curves can be obtained by using different interpolation parameters, so as to improve the accuracy of tool axis vector position and direction. Secondly, the producing mechanism of CC paths’ nonlinear error of the traditional spline interpolation is analyzed and the mathematical calculation model of the nonlinear error is established. And then, the nonlinear error compensation and correction method is also put forward to improve the controlling accuracy of CC paths. In this method, the next CC point on the cutter can be firstly obtained according to the next interpolation tool center point, tool axis point and CC point on the three spline curves. And then, the error compensation vector is determined with the two next CC points. To correct the nonlinear error between the next CC point on the cutter and the CC point spline curve, the cutter is translated so that the two next CC points can be coincided. In the end, the new tool center point and tool axis point after translation can be calculated to obtain the motion control coordinates of each axis of machine tool. The MATLAB software is used as simulation of the real machining data. The results show that the proposed method can effectively reduce the CC paths’ nonlinear error. It has high practical value for five-axis machining in effectively controlling the accuracy of CC paths and im-proving the machining accuracy of complex surfaces.

Analysis and Compensation Strategy of Non-Linear Error in Five-Axis CNC Machining

This paper presents a new strategy of analysis and compensation of non-linear error. Non-linear error is an important source of machining error in multi-axis numerical controlled machining and it is unavoidable. In view of tool positions optimization in five-axis CNC machining of complex surface, this paper presents a strategy for non-linear error compensation in five-axis machining: Firstly, non-linear error caused by the change of tool axis vector is analyzed and the non-linear error model is established, in order to get the maximum non-linear error of interpolation segment; Then, the tool position that meets the machining accuracy is obtained; Finally, Simulation and analysis of the model show that the proposed method is effective and greatly improves the geometric accuracy.

Research on Cutter Location Optimization of Tapered Ball End Mill Finish Flank Milling Ruled Surface Blade

For the low efficiency and poor surface quality problem of finishing ruled surface blade in the traditional method, tapered ball end mill cutter location optimization methods had been proposed to ensure that the envelope surface of tapered ball end mill is close to intractable ruled surface blade as much as possible. First, the tapered ball end mill initial cutter location was obtained based on the improved two point offset algorithm. Then to realize the cutter location optimization calculation, selected three point in tool axis to slide for the target of the minimum range between cutter envelope surface and blade surface. Finally, the blades instance was calculated according to the obtained tool center point and optimized tool axis vector. Simulation and experiments verified the effectiveness of cutter location optimization method proposed in this paper.

Research of the Tool Orientation Optimization with Kinematical Constraints

Drastic change of the tool axis vector for five-axis CNC machining due to avoid global interference, proposed gentle forward, over-backward correction method to optimize the tool axis vector. Established a machine tool axis of rotation angular velocity constraints, and feed coordinate system, through the feed coordinate system adjust the inclination angle and swing angle of the existing tool axis vector to make the tool axis vector change between each adjacent cutter contact points satisfy the machine axis of rotation kinematics constraints and to ensure the continuity of feed rate during processing. Algorithm simulation examples show that the proposed method is reasonably practicable, make the tool axis vector changes fairing to ensure the smooth and efficient processing.