Optimized Tool Path Generation Research Articles

Optimal tool path generation and cutter geometry design for five-axis CNC flank milling of spiral bevel gears

Abstract Computer numerical control milling provides greater flexibility and universality for machining complex gears compared to dedicated gear manufacturing. A critical challenge in popularizing the use of five-axis flank milling to spiral bevel gears is to achieve acceptable machining accuracy that ensures the meshing performance of the finished gears. Previous studies, which used approaches such as gear design modification, using multiple tool paths, and end milling, failed to resolve this issue. Thus, this paper proposes a computational scheme to improve the machining accuracy of five-axis flank milling of spiral bevel gears by optimizing the tool path and cutter geometry. The scheme minimizes the geometric deviations between the machined surface and original design using heuristics and optimization algorithms. A simplified tooth contact analysis method was developed to quantitatively evaluate the contact path of the meshing gears. The simulation results of real gears show that the proposed scheme outperforms previous methods in reducing machining errors and further enhance the meshing performance by optimizing the design of form cutters. This work developed an effective approach for flexible and low-cost manufacturing of complex gears.

Toolpath planning for additive manufacturing using sliced model decomposition and metaheuristic algorithms

Fabrication efficiency has long been a challenge for additive manufacturing. Standard toolpath generation processes usually give rise to a significant number of non-productive motions that undermine production efficiency and degrade part quality due to frequent acceleration and deceleration in wasted motions. In this paper, we introduce an optimized toolpath generation process that comprises of decomposition of sliced model and optimization of fabrication sequences to minimize non-productive toolpaths. Unlike standard toolpaths, optimized toolpaths carry out fabrication of multiple objects in a staggered sequence to maximize manufacturing efficiency. To tackle the problem of interference between a printhead and objects due to changes in the fabrication sequence of layered depositions, an algorithm that adaptively determines collision-free heights is developed. Additionally, sliced model decomposition considerably reduces the number of entities for optimization. The computational cost involved in toolpath optimization is independent of slicing interval; therefore, the effectiveness and applicability of the proposed optimization approach are well maintained for small slicing intervals. Benchmarks are analyzed to demonstrate the effectiveness and robustness of the proposed toolpath planning approach, and two physical experiments are carried out using fused deposition modeling (FDM) and direct metal deposition (DMD) technologies. Non-productive toolpaths are reduced remarkably, and the desired fabrication quality is achieved for both non-metal and metal structures.

Study on Design and Diamond Turning of Optical Freeform Surface for Progressive Addition Lenses

Optical freeform surface components have attracted much attention due to their high degree of design freedom and small size. However, the design and processing difficulty of such components limit its wide application in optics industry. In recent years, diamond turning has been considered an efficient method for processing optical freeform surfaces, but the research on tool path generation of this processing method is not systematic. Progressive addition lens (PAL) is a typical optical freeform surface and is widely used to correct people’s vision problems. Firstly, this paper introduces a method of designing PAL. Then, an optimized tool path generation method for diamond turning of the optical freeform surface is proposed, the equal angle method is used to select the discrete points, and a tool nose radius compensation method suitable for both slow slide servo (SSS) and fast tool servo (FTS) is adopted. Finally, the turning experiment is carried out with a single point diamond lathe, and a PAL surface with a roughness of 0.087 μm was obtained. The power and astigmatism distributions were measured using a Rotlex freeform verifier to verify the rationality of the optical design.

One-step generation of hybrid micro-optics with high-frequency diffractive structures on infrared materials by ultra-precision side milling.

Hybrid micro-optics of infrared (IR) materials are of great advantage in realizing the function integration and minimization of advanced IR optical systems. However, due to the hard-and-brittle nature of IR materials, it is still challenging for both non-mechanical and mechanical technologies to achieve one-step generation of hybrid infrared micro-optics with high form accuracy. In the present study, a flexible method, namely ultra-precision side milling (UPSM), is first introduced to achieve one-step generation of infrared hybrid micro-optics in ductile mode, and the corresponding reflective diffraction characteristics are analyzed. In UPSM, the reflective/refractive primary surface of the hybrid micro-optics is formed via the removal of workpiece material, and the high-frequent secondary diffractive micro/nanostructures are simultaneously generated by the tool residual marks of cutting trajectories. With the consideration of the changing curvature of the primary surface, the optimal toolpath generation strategy is introduced to acquire the desired shapes of the secondary micro/nanostructures, and the selecting criteria of the machining parameters is discussed to avoid the brittle fractures of IR materials. In practice, two types of hybrid micro-optic components, namely hybrid micro-aspheric arrays and sinusoid grid surface with high-frequent secondary unidirectional phase gratings, are successfully fabricated on single-crystal silicon to validate the proposed method. The method adopted in this study is very promising for the deterministic fabrication of hybrid micro-optics on infrared materials.

Development of Optimized Tool Path Generation Method for to Reduce Energy Consumption of 5-Axis Machine Tool

Development of Optimized Tool Path Generation Method for to Reduce Energy Consumption of 5-Axis Machine Tool

Optimal five-axis tool path generation algorithm based on double scalar fields for freeform surfaces

In order to generate efficient tool path with given precision requirements, scallop height should be kept under a given limit, while the tool path should be as short as possible to reduce machining time. Traditional methods generate CC curves one by one, which makes the final tool path far from being globally optimal. This paper presents an optimal tool path generation model for a ball-end tool which strives to globally optimize a tool path with various objectives and constraints. Two scalar functions are constructed over the part surface to represent the path intervals and the feedrate (with directions). Using the finite element method (FEM), the tool path length minimization model and the machining time minimization model are solved numerically. The proposed method is also suitable for tool path generation on mesh surfaces. Simulation results show that the generated tool path can be direction parallel or contour parallel with different boundary conditions. Compared to most of the conventional tool path generation methods, the proposed method is able to generate more effective tool paths due to the global optimization strategy.

Large-scale fabrication of micro-lens array by novel end-fly-cutting-servo diamond machining.

Fast/slow tool servo (FTS/STS) diamond turning is a very promising technique for the generation of micro-lens array (MLA). However, it is still a challenge to process MLA in large scale due to certain inherent limitations of this technique. In the present study, a novel ultra-precision diamond cutting method, as the end-fly-cutting-servo (EFCS) system, is adopted and investigated for large-scale generation of MLA. After a detailed discussion of the characteristic advantages for processing MLA, the optimal toolpath generation strategy for the EFCS is developed with consideration of the geometry and installation pose of the diamond tool. A typical aspheric MLA over a large area is experimentally fabricated, and the resulting form accuracy, surface micro-topography and machining efficiency are critically investigated. The result indicates that the MLA with homogeneous quality over the whole area is obtained. Besides, high machining efficiency, extremely small volume of control points for the toolpath, and optimal usage of system dynamics of the machine tool during the whole cutting can be simultaneously achieved.

Tool path generation for single point incremental forming using intelligent sequencing and multi-step mesh morphing techniques

A new methodology of generating optimized tool paths for incremental sheet forming is proposed in this work. The objective is to make parts with improved accuracy. To enable this, a systematic, automated technique of creating intermediate shapes using a morph mapping strategy is developed. This strategy is based on starting with a shape different from the final shape, available as a triangulated STL model, and using step-wise incremental deformation to the original mesh to arrive at the final part shape. Further, optimized tool path generation requires intelligent sequencing of partial tool paths that may be applied specifically to certain features on the part. The sequencing procedure is discussed next and case studies showing the application of the integrated technique are illustrated. The accuracy of the formed parts significantly improves using this integrated technique. The maximum deviations are brought down to less than 1 mm, while average absolute deviations of less than 0.5 mm are recorded.

Optimal CNC plunge cutter selection and tool path generation for multi-axis roughing free-form surface impeller channel

Plunge milling is the most effective way for rough machining of impeller parts, but previous research had not considered the optimization of plunge cutter selection and tool path. In this paper, a new method for optimizing the plunge cutter selection and tool path generation in multi-axis plunge milling of free-form surface impeller channel is proposed in order to improve the efficiency in rough machining. Firstly, in the case of fixing a rotation axis at a certain angle in five-axis machine, a mathematical representation is formulated for the geometric model of the cutter interfering the impeller, and an optimization model of the cutter size is established at a cutter contact point on the impeller channel surface, so the largest tool could be determined. Secondly, by analyzing the machine tool movement characteristics, the geometric constraint model of the plunge tool path which relative to the largest tool, step distance, and row space is established, and a tool orientation calculation method of impeller channel machining is given, and then, the plunge tool path and tool orientation could be obtained. Finally, the generated tool path and tool orientation are simulated and verified in practical processing. Simulation and experimental result shows that the rough machining efficiency of the impeller part is improved up to 40 % with this method.

Tool Path Generation for Single Point Incremental Forming Using Intelligent Sequencing and Multi-Step Mesh Morphing Techniques

A new methodology of generating optimized tool paths for incremental sheet forming is proposed in this work. The objective is to make parts with improved accuracy. To enable this, a systematic technique of creating features using a morph mapping strategy is developed. This strategy is based on starting with a shape different from the final shape, available as a triangulated STL model, and using step-wise incremental deformation to the original mesh to arrive at the final part shape. Further, optimal tool path generation requires intelligent sequencing of partial tool paths that may be applied specifically to certain features on the part. The sequencing procedure is discussed next and a case study showing the application of the integrated technique is illustrated.

Optimized tool path generation for fast tool servo diamond turning of micro-structured surfaces

Fast tool servo (FTS) diamond turning is a promising machining process for fabricating ultra-precision micro-structured surfaces which have already gained wide application especially in the optics industry. However, most research focused on designing different types of FTSs for better performance, including bandwidth, stroke, stiffness, acceleration, accuracy, etc. There is a lack of systematical tool path generation (TPG) for FTS diamond turning, especially from the influence of TPG on surface quality point of view. This paper presents an optimized tool path generation for FTS diamond turning of micro-structured surfaces with either analytical description or non-uniform rational B-spline description. The tool path is optimized from three aspects to ensure high precision form and nanometric surface finish. Firstly, the tool path is optimized by a stable tool nose radius compensation method, which is different from the conventional one, to reduce the form error caused by the tool nose radius. Secondly, the ideal machined surface profiles are simulated to predict the ideal surface quality, with which the cutting conditions and tool geometry can be optimized to ensure nanometric surface finish and avoid tool interference. Thirdly, the influence of the control dynamics of the machine axes on machined surface quality, which is ignored in conventional machining, was considered. As the FTS dynamics dominate the influence, it is controlled to be a desired dynamics which was then used to modify the tool path to minimize the form error in machined surface. Experiments were carried out to prove the effect of TPG on surface quality and the effectiveness of the optimized TPG method.

565 マグネシウム合金管端末部スピニング加工におけるファジィモデルを用いた最適工具経路生成法(OS8-4 軽量化,機能化のための界面・表面創製技術,OS8 軽量化,機能化のための界面・表面創製ならびに塑性加工技術)

565 マグネシウム合金管端末部スピニング加工におけるファジィモデルを用いた最適工具経路生成法(OS8-4 軽量化,機能化のための界面・表面創製技術,OS8 軽量化,機能化のための界面・表面創製ならびに塑性加工技術)

Optimized tool path generation based on dynamic programming for five-axis flank milling of rule surface

This paper presents a computation scheme that generates optimized tool path for five-axis flank milling of ruled surface. Tool path planning is transformed into a matching problem between two point sets in 3D space, sampled from the boundary curves of the machined surface. Each connection in the matching corresponds to a possible tool position. Dynamic programming techniques are applied to obtain the optimal combination of tool positions with the objective function as machining error. The error estimation considers both the deviation induced by the cutter at discrete positions and the one between them. The path planning problem is thus solved in a systematic manner by formulizing it as a mathematical programming task. In addition, the scheme incorporates several optimization parameters that allow generating new patterns of tool motion. Implementation results obtained from simulation and experiment indicate that our method produces better machining quality. This work provides a concise but effective approach for machining error control in five-axis flank milling.

Effective machining region planning method of tool path generation for five-axis NC machining

A new effective machining region planning method is represented for optimal tool path generation in five-axis sculp-tured surface machining.Based on the analysis of work-piece surface geometrical feature and the cutter shape,the developed method determines the optimal effective machining region width and the optimal cutting direction in special position of the part surface.By interpolating the adjacent sampling effective machining regions,the optimal initial tool path is generated based on the optimal machining region set,and an itera-tive-searching algorithm is constructed in this proceeding to resolve the machining region select-planning problem.Follow-ing tool paths are generated from the initial tool path until the whole part surface was covered with effective machining re-gions.Compute implementation and illustrative example con-firm that the method reduces the total tool paths length and the machining time,generates better tool paths and finish of work-piece surface comparing with other conventional tool path generation methods.Thus,the effective machining region plan-ning method can improve the quality of products and reduce the cost of five-axis machining.

Intelligent Programming of CNC Turning Operations using Genetic Algorithm

CAD/CAM systems are nowadays tightly connected to ensure that CAD data can be used for optimal tool path determination and generation of CNC programs for machine tools. The aim of our research is the design of a computer-aided, intelligent and genetic algorithm(GA) based programming system for CNC cutting tools selection, tool sequences planning and optimisation of cutting conditions. The first step is geometrical feature recognition and classification. On the basis of recognised features the module for GA-based determination of technological data determine cutting tools, cutting parameters (according to work piece material and cutting tool material) and detailed tool sequence planning. Material, which will be removed, is split into several cuts, each consisting of a number of basic tool movements. In the next step, GA operations such as reproduction, crossover and mutation are applied. The process of GA-based optimisation runs in cycles in which new generations of individuals are created with increased average fitness of a population. During the evaluation of calculated results (generated NC programmes) several rules and constraints like rapid and cutting tool movement, collision, clamping and minimum machining time, which represent the fitness function, were taken into account.

A closed-form solution to the problem of optimal tool-path generation for sculptured surface machining on multi-axis NC machine

The topic of the paper is in the field of sculptured surface machining ( SSM) on multi-axis NC machines. It presents novel results of investigation of tool-path generation for sculptured surface machining on multi-axis NC machines. The purpose of the paper is to develop an integral form of solution to the problem of optimal tool-path generation. The concept of time-minimal tool-paths is introduced, as well as the optimization problem being formulated analytically. The problem of optimization is subdivided into the following three partial sub-problems: (a) the problem of local tool-path generation; (b) the problem of regional tool-path generation, and finally, (c) the problem of global tool-path generation. The paper presents a closed-form solution to the first two sub-problems. A solution to the problem of optimal tool-path generation is given in the form of an integral equation. The obtained solution enables one to retain the optimal cutter configuration (i.e., the cutter position, and the cutter orientation), as well as the optimal instant direction of feed-rate at every cutter location-point (further, CC-point).

Integrated steepest-directed and iso-cusped toolpath generation for three-axis CNC machining of sculptured parts

Today, sculptured parts are widely used in aeronautical, automotive, and many other industries. To make high-quality sculptured surfaces through efficient toolpaths in three-axis CNC machining is a major technical challenge. In this work, a new toolpath generation method for three-axis CNC milling, the Steepest-Directed and Iso-Cusped (SDIC) toolpath generation scheme, is introduced. The method integrates the steepest-directed and iso-cusped toolpaths in three-axis CNC programming. The steepest-directed toolpaths ensure the best geometry matching between cutter and surface for high cutting efficiency, and form a frame to control the trend in direction of the iso-cusped toolpaths. The iso-cusped toolpaths eliminate overmachining on the surface. Their combination ensures high sculptured part productivity, less redundant milling, and good surface quality. Machining examples of a half-cylinder part and a sculptured part are used to illustrate and to compare a range of SDIC toolpath patterns. The proposed SDIC toolpath scheme produces shorter toolpaths with higher machining efficiency. With the help of global optimization algorithms, this method of optimal toolpath generation can be applied to three-axis CNC machining of sculptured surfaces.

Manufacturing of Dies and Molds

The design and manufacturing of dies and molds represent a significant link in the entire production chain because nearly all mass produced discrete parts are formed using production processes that employ dies and molds. Thus, the quality, cost and lead times of dies and molds affect the economics of producing a very large number of components, subassemblies and assemblies, especially in the automotive industry. Therefore, die and mold makers are forced to develop and implement the latest technology in: part and process design including process modeling, rapid prototyping, rapid tooling, optimized tool path generation for high speed cutting and hard machining, machinery and cutting tools, surface coating and repair as well as in EDM and ECM. This paper, prepared with input from many CIRP colleagues, attempts to review the significant advances and practical applications in this field.