Tool Path Generation For Machining Research Articles

A region-based 3 + 2-axis machining toolpath generation method for freeform surface

Due to the geometric complexity, tool orientations usually change dynamically during freeform surface machining with 5-axis machine tool. As the kinematic performance of the rotary axes is usually weaker than that of the linear axes, the real cutting speed is difficult or even impossible to reach the desired level, which further leads to low machining efficiency. This paper presents a region-based 3 + 2-axis machining toolpath generation method with 5-axis machine tool. The surface is first divided into several preliminary sub-surfaces using K-means clustering algorithm. A post processing procedure is then carried out to optimise the preliminary sub-surfaces to ensure the machinability. For each sub-surface, gouging-/collision-free tool orientations are first calculated and then the optimal combination of the fixed tool orientation and the feed direction is determined by maximising the average machining strip width for toolpath generation. The proposed method is tested by a case surface and the comparisons to some other traditional methods are also provided.

A Study of Tool Path Generation for Machining of Precision Roller with Wavy Patterned Microstructures by Slow Tool Servo

Embossing by patterned rollers is one of the most efficient machining approaches for manufacturing plastic films with patterned microstructures, and the precision roller with patterned microstructures is the key tooling component in the roll-to-roll process. Single-point diamond turning with a slow or fast tool servo is an enabling and efficient ultra-precision machining process to fabricate microstructures through a simple process to achieve optical surface finish directly. Most of the current studies on slow or fast tool servo machining processes either focus on face machining of patterned microstructures, or on tool servo machining of microstructures in the radial direction of precision rollers. Relatively little research work is found in relation to machining patterned microstructures on a precision roller by using the tool servo in the axial direction. This paper presents a pilot study on the development of a tool path generator for machining precision rollers with wavy patterned microstructures by using slow tool servo machining in the axial direction on a precision roller. The machining mechanism is firstly explained, based on which the tool path generator is developed for machining wavy patterned microstructures on a precision roller surface. Preliminary experimental work was conducted to study the generation of wavy patterned microstructures on a precision roller using a four-axis ultra-precision machine. The machined wavy microstructures on the roller surface are measured and analyzed to successfully validate the performance of the proposed tool path generator.

Smooth Cutting Operation Strategy for High Finishing Machining

High finishing machining tool path generation methods are usually adopted for five-axis computer numerically controlled machining of sculptured surface parts. The quality of the high finishing machining has an important effect on that of the surface. In this paper, a high finishing machining tool path generation method is introduced to generate an optimal tool path. The initial tool path is firstly created based on the constant scallop height, then the derived tool paths are generated as a kind of the diagonal curve by the initial tool path, and at last, the tool path smoothing algorithm is applied to the generated tool path. This path algorithm can ensure higher level of smooth of the surface been machined. Finally, the results of simulation and experiment of the machining process are given to verify the smooth and applicability of the proposed method.

High speed machining tool path generation for pockets using level sets

With the increasing application of high speed machining for pockets, the conventional methods of tool path generation show their limitations, such as the existence of a high curvature region along the tool path. This paper presents a level set approach of tool path generation for high speed machining of pockets. Pocket boundary is first embedded into a higher dimensional function, namely, the level set function. Then the tool paths are realised by the propagation of the pocket boundary. The topological changes of tool path can be naturally handled during the evolution of moving fronts. In order to avoid the appearance of high curvature corners along tool paths, a curvature-dependent term is adopted to regulate the velocity function of the level set equation. At the same time, the curvature flow motion is used to identify the machinable region of pockets. The vector level-set functions are utilised to handle complex pockets with multiple islands. The simulation of material removal rate based on the implicit description is also discussed. Numerical examples are presented to demonstrate the robustness of the proposed approach on different kinds of pockets with islands.

1302 自由曲面加工に適した工具パスの生成方法(OS1-3 生産加工システム)

Freeform surfaces are machined in many different methods. In this research, Z-level finishing machining tool path generation method is studied. The machining strategy by separating the freeform surface into horizontal area and vertical area by the maximum slope angle of the surface inclination create best possible surface finishing. Four different tool motion patterns: zigzag, offset, spiral, and morphing are compared in terms of machining time, rapid machining length, and feed machining time. Tool path generation pattern setting can machine the complex surface in an efficient way with good quality.

Tool path generation for machining of optical freeform surfaces by an ultra-precision multiaxis machine tool

Optical freeform surfaces are crucial to the development of complex and optical-electromechanical devices used in many photonics products. The fabrication of high-quality freeform lens is based on ultra-precision freeform machining technology which allows direct machining of freeform surfaces with submicrometric form accuracy and nanometric surface finish. In this paper, the application of ultra-precision freeform machining to the fabrication of an optical freeform surface is addressed. The methodology for the development of the tool path generator for a progressive lens is discussed. According to the model of the freeform surface, which is represented by a double cubic B-spline surface, the method of changing parameters is used to calculate the numerically controlled (NC) machining tool path. The formula for calculating cutter location data, which considers the compensation of both the tool nose radius and tool swing radius of the fly cutter, is deduced. The cutting experiment of machining a freeform progressive optics lens by a multiaxis ultra-precision machine tool shows that the developed tool path generator can perform its function successfully.

Integrated machining tool path planning using feature free spaces

We describe an automatic machining tool path generation method that integrates local and global tool path planning for machining features. From the solid model and the tolerance specifications of the part, we automatically recognize machining features, and obtain the geometry-based precedence relations between these features. A separate process planning module uses this information to determine the machining sequence, tool selections, and machining conditions. From the resulting process plan, we then generate machining tool paths for each set-up, combining local and global tool paths. Machining features are expanded through their fictitious faces to obtain feature free spaces. These comprise the cells of a free space decomposition, which enables the use of established robot motion planning techniques. Global tool paths between features are generated incrementally by searching the adjacency graph of feature free spaces, which represents the free space of the part at each step of the process plan. Local tool paths for each machining feature are generated by successive offsetting operations. The start and end positions for each feature's local tool paths are selected using a heuristic method to minimize the cost of each segment of the global tool path. This feature recognition method and the automatic tool path generation method are being developed as modules of a comprehensive machining process planning system.

Three dimensional biarc approximation of freeform surfaces for machining tool path generation

In typical methods for machining freeform surfaces, the machining tool paths are generated by approximating the surface curves using line segments. While the approximated shape of the surface can be produced using cutters traversing along the line segments, the final surface produced may lack smoothness and continuity due to the zigzag patterns of the line segments. To reduce the difference and increase smoothness and continuity, the arc splines can be used to approximate the freeform curves and surfaces. A biarc is composed of two consecutive circular arcs with an identical tangent at the connecting point. Since the tangents at the connecting node are the same, the C1 continuity property can be preserved. In addition, if the difference between the curvatures at the connecting node is minimized, then the C2 smoothness property can be enhanced. In this research, the biarc segments are used to approximate the 2D and 3D freeform curves and surfaces using the largest deviation distance between the curves and the biarcs as the approximation criterion. The tool contact points generated and biarcs can be used to generate NC tool paths for machining 2D curves and 3D curves and surfaces. The methodology presented is implemented on a personal computer. Example parts modelled with B-spline curves and surfaces are tested and discussed. The test results show that the number of tool contact points and the number of segments are fewer than the typical linear approximation methods.

4907164 Automatically optimized NC tool path generation for machining : Margaret Guyder assigned to General Electric Company

4907164 Automatically optimized NC tool path generation for machining : Margaret Guyder assigned to General Electric Company