Cutter path generation for 2.5D milling by combining multiple different cutter path patterns

Different cutter path patterns have been shown to be efficient for different types of pocket geometries. However, for certain types of complex pockets, no single type of pattern produces efficient cutter paths throughout the pocket. In this paper, different cutter path patterns are systematically analysed, and several existing heuristics for selecting cutter path patterns are discussed. Based on observations, a new cutter path generation algorithm is described in this paper. This algorithm generates a cutter path by using different patterns in different regions of the geometry and seamlessly morphing them together. In case of complex pockets, it produces solutions superior to those generated by any single pattern.     

Tool path generation via the multi-criteria optimisation for flat-end milling of sculptured surfaces

A method of generating optimal tool paths for sculptured surface machining with flat-end cutters is presented in this paper. The inclination and tilt angles, as well as the feed directions of the cutter at each cutter contact point on a machining path are optimised as a whole so that the machining width of the tool path can be as large as possible, and concerns such as smooth cutter motion, gouging avoidance, scallop height and machining widths overlap are also considered when calculating a path. A multi-criteria tool path optimisation model is introduced, and it is converted into a single objective optimisation with the weighted sum method. The Differential Evolution (DE) algorithm is suitable for solving this highly non-linear problem. However, the searching process of the DE algorithm may be trapped in local minima due to large number of design variables. Therefore, an algorithm combining the DE algorithm and the sequence linear programming algorithm is developed to solve this optimisation model. The proposed method is applied to two freeform surfaces to illustrate its effectiveness.     

Efficient tool path planning for five-axis surface machining with a drum-taper cutter

This paper presents a new efficient approach to NC tool path generation for five-axis surface machining. First, an efficient cutter, named a drum-taper cutter, is proposed; its key dimension is determined to avoid gouging in surface machining according to the maximum curvature of the surface calculated with a genetic algorithm. Then, based on the drum-taper cutter, the tool paths are generated so that the scallop height formed by adjacent tool paths in machining is kept constant, and an improved algorithm for calculating the interval between tool paths is presented. Finally, an example of tool path generation with the above method for arbitrary surface impeller machining is conducted, and the results show that the presented method leads to a significant reduction in the total tool path length and is accompanied by a reduction in machining time.     

基于Zmap网格三轴加工无干涉刀具轨迹的加速算法

介绍和扩大了数控加工中的刀位面和保护面的概念,研究和实现了一种基于曲面离散生成三轴加工无干涉刀具轨迹的算法。通过Zmap网格节点的竖直线与三角片的刀位面和保护面求交并取z值最大的交点即为无干涉刀位点,采用双节点插值方法解决了生成刀具轨迹时因参考走刀步长不合适而产生的运动过切问题。该算法完全采用几何求交运算,过程简洁且精确度高,但需处理的数据点较多、运算量大,为此提出了几种生成轨迹的加速方法。     

Optimal cutter selection for complex three-axis NC mould machining

Proper cutter selection can reduce NC machining time greatly. Most researchers select cutters based on tool path generation, which is very time consuming, and only a very limited number of cutters can be selected. A new cutter selection methodology for complex mould machining based on an efficient interference detection algorithm is introduced. With this approach, the feasible regions for the candidate cutters are first identified without tool path generation. The machining times for different cutter combinations are then estimated based on the areas of the feasible regions and the cutter feed rates. The set of cutters that can machine the workpiece with minimum time is selected as the optimal candidate cutters. Since no tool path needs to be generated before cutter selection, the cutters can be selected efficiently, and the number of the cutters that can be used in NC machining can be quite large. The system has been tested with several industrial parts and it can select optimal cutters effectively and efficiently.     

基于曲率的曲面加工刀位轨迹生成算法

提出了一种自由曲面五轴数控加工无干涉刀位轨迹的生成算法。该方法利用曲面的曲率来确定环形刀的刀具姿态,使得刀具随被加工曲面的形状变化而倾斜,从而生成无干涉的刀位轨迹。     

A new cutter path construction technique for milling machines

This paper introduces a new method for generating cutter paths for milling machines. The generation of cutter paths is an important area for research, since it is critical to the validity of the path and efficiency of its production. In this paper, we show a mechanism by which paths may be de-constructed from initial paths, thus guaranteeing the validity of the path and lending itself to efficient generation.     

假肢接受腔阳模数控加工刀具的运动轨迹规划

应用表面建模方法，建立了假肢接受腔的三维数学模型。针对假肢接受腔的独特外形特征，研制了加工假肢接受腔阳模的三轴联动数控机床，该机床控制系统采用开环系统，可以运行CAD／CAM软件。对加工假肢接受腔阳模的刀具进行了运动轨迹规划，推导出了切削点的计算公式。根据三维刀具半径补偿原理，确定了刀具的刀位点运动轨迹。经过临床实例加工表明：该数控机床和刀具运动轨迹规划算法完全满足实际应用要求。     

New algorithm to minimise kinematic tool path errors around 5-axis machining singular points

The singular points of a given 5-axis CNC machine could be found in the domain of the joint variables of the machine. In the neighbourhood of a singular point, even for a small change of the tooltip position, an enormous change of axis displacements of the machine is often required. This causes a large deviation between the real cutting path and the desired tool path, and the machining surface could be destroyed. This paper provides with an analytical scheme for identifying singular configuration of 5-axis CNC machines. In particular, an efficient and robust algorithm is proposed to compute the cutter path across the neighbourhood of the singular points identified such that the computed cutter path tracks the desired tool path within a controllable error. Numerical examples and real cutting parts are carried out and discussed to show the effectiveness and the efficiency of the presented method.     

Integrated method for tool path generation in five-axis sculptured surface machining

Five-axis machining allows continuous adjustment of cutter orientation along a tool pass. Unfortunately, the flexibility has not been fully exploited due to the separate consideration of tool path generation and cutter orientation in current machining methods. This paper presents an integrated method (IM) for tool path generation, which is tightly integrated with the orientation strategy, to minimise tool path length under the constraint of smooth cutter orientation. Distinctively, cutter orientation along a tool pass is optimised by balancing considerations of maximum material removal and smoothness of cutter movement. Further, the intervals between successive tool passes are maximised according to the optimised orientation. In the paper, the IM is combined with the quadric method, a recently developed cutter orientation strategy, for iso-parametric machining with a flat-end cutter. However, the method could be applied to other orientation strategies with different machining mechanisms and cutter types. Simulated examples illustrate that the IM is more efficient in machining than established methods.     

基于UG NX6.0的整体叶轮的多轴加工技术

叶轮加工是当今多轴联动数控加工最常见的实例,也是数控加工的难点之一.本文从实际出发,使用UG/CAM五坐标编程系统对整体式叶轮进行数控编程,采用插值方式对刀轴矢量进行匀化处理,采用SWARF方法对叶片进行精加工,同时合理控制进退刀,实现了整体叶轮叶片高质量无干涉的五坐标螺旋铣削加工刀位点轨迹生成.为复杂产品的造型和数控加工提供了设计思路和方法,也给其他类型叶轮的设计与加工提供了参考方案.     

Tool path generation for triangular meshes using least-squares conformal map

Tool path generation is an interesting and challenging task in free-form surface machining. Iso-planar tool path generation is one of the common approaches to dealing with this task. However, it suffers from an inherent drawback that intersecting intervals of the iso-planar method are limited to surface geometric features. This results in poor machining efficiency in flat regions due to redundant machining paths. For this problem, a new tool path generation method for triangular meshes is proposed based on the least-squares conformal map (LSCM). After LSCM parameterisation with minimal stretching energy, the triangular meshes are unfolded on a plane, where the principal component analysis (PCA) technique is employed to determine a suitable drive line for calculating cutter contact paths by the iso-planar strategy. Therefore, the tool paths are generated in a plane and the unevenness of the traditional iso-planar method is improved. The feasibility and effectiveness of the developed method is demonstrated through a test experiment.     

Cutting path generation of the Stewart-Platform-Based Milling Machine using an end-mill

This paper investigates an algorithm for generating the cutting path of a Stewart-Platform-Based Milling Machine (SPBMM) using an end-mill. While using the iso-scallop method in the process of generating the cutting path, we use the Genetic Algorithm (GA) to find the configurations of the tool without a singular position. After choosing the objective function, using GA to find the optimum value is an extremely effective method for both quickly converging to a reasonable value and avoiding a futile blind search. In our results, when the curvature of the workpiece is equal to the curvature of the cutter at the contact point, one equation in terms of curvature and two degrees of freedom of the end-mill are formed. Keeping the six axial forces of the SPBMM as small as possible is our objective function. We can find an optimal set of solutions in this equation at every contact point. Finally, we find a planned cutting path without a singular position.     

Interference-free tool path generation for 5-axis sculptured surface machining using rational Bézier motions of a flat-end cutter

This paper presents a new approach that uses rational Bézier motions to generate 5-axis tool path for sculptured surface machining (finish cut) with a flat-end cutter. By using dual quaternion to represent a spatial displacement, the representation of kinematic motions for the cutter bottom circle of the flat-end cutter is formulated. Based on that, a new approach for tool path generation using rational Bézier cutter motions is described, in which key issues such as interference avoidance and surface accuracy requirement are addressed. First, a set of cutter contact points on an iso-parametric curve of the designed surface is obtained based on a given fitting tolerance. The associated cutter locations (CLs) are then obtained by finding the suitable cutter orientations that avoid any gouging. The conversion from the CLs to dual quaternion representation is carried out and the rational Bézier dual quaternion curve for cutter motion is generated. The entire tool path is therefore established based on the cutter undergoing the rational Bézier motion. Next, the whole tool path is checked to find (1) if there is any interference between the cutter and the designed surface, and (2) whether the deviation between the surface generated by the cutter motion and the designed surface is larger than the given tolerance. The problematic CLs, which cause either gouging or accuracy problem, are then modified. The process of tool path checking?→?CLs modification?→?tool path regeneration continues until the whole tool path is interference-free and satisfies the accuracy requirement. Furthermore, a more accurate representation of the effective cutting shape is proposed, which is used to evaluate the scallop height between adjacent tool paths. A method for constructing the adjacent tool path has been developed by considering the allowable scallop height. Finally, computer implementation and an illustrative example are presented to demonstrate the efficacy of the approach.     

An Analytical Approach to Optimize NC Tool Path Planning for Face Milling Flat Convex Polygonal Surfaces

CAD/CAM systems currently generate the tool cutter path for many NC operations. However no mathematical model is available for computing an optimal tool cutter path for face milling. By utilizing such a model, the minimum length of cut can be identified for face milling flat surfaces. In this paper, the authors present an analytical procedure from which the optimal cutting path may be derived.     

Tool path generation for five-axis machining of blisks with barrel cutters

A barrel cutter has a cutting segment with a large radius on its profile, and this arc segment allows the cutter to tilt away from the part surface, avoiding the collisions of the tool with the part. Therefore, barrel cutters are suitable for five-axis blisk machining. However, the barrel cutters are more challenging for CAM software to generate paths. A method of generating collision-free and large-machining width flank milling paths with smooth axes movements for blisk machining with barrel cutters is proposed. Local gouge between the tool flute surface and the blade to be machined is considered, and the collisions of the blisk with the non-cutting parts of the tool, i.e. tool shank and holder, are also detected. The machined part geometry is the complement of the cutter’s swept envelope from the stock. Accordingly, the swept profile of the cutter at each cutter contact point is employed to evaluate the machining width naturally. Thereafter, a multi-criteria tool path generation model is established, and it is converted into a single-objective optimization with the weighted sum method. An algorithm based on the Differential Evolution algorithm is developed to solve this model. The numerical example illustrates the effectiveness of the proposed method.     

数控加工中的刀位干涉检查

干涉检查是数控加工的关键问题之一,本文提供了一套可靠的干涉检查算法。介绍了研制CAX系统的基本原则;说明刀位计算方法;详细讨论曲面间、曲面自身及边界部位的干涉检查算法,其方法均是首先将曲面离散为三角小平面,然后计算球头刀球心至有界三角小平面的距离。该距离即作为判断干涉与否的依据。运行表明,算法可靠,效率较高。附有若干实例。     

A survey of cutter path construction techniques for milling machines

Cutter path generation is a surprisingly active research and development area. Together with cutter path topology, it is critical to the validity and efficiency of cutter path generation. Here we survey the main generation techniques used and discuss the performance of each method.     

Optimal cutter size determination for 2½-axis finish machining of NURBS profile parts

A curve model of non-uniform rational B-spline (NURBS) has been widely adopted in mainstream CAD/CAM software systems to design complicated geometries of mechanical parts, for example, the curved profiles of pockets, sides, and islands. NURBS profile parts (the profiles include NURBS curves for pockets and islands) are produced in 2½-axis rough and finish machining. In rough machining of the parts, several end-mills with different sizes are employed for high cutting efficiency, and in finish machining, a single end-mill is usually used to cut along the profiles for high surface quality. To accurately produce the geometries with NURBS curves in finish machining, the cutter size should be optimised in order to eliminate gouging and save machining time. Although this topic has been a research focus for a decade, optimal cutter size determination still remains as a technical challenge. To rise to this challenge, our work proposes a new approach to determining the largest allowable size for the cutter to move along all the profiles (including NURBS curves) in 2½-axis finish machining without global and local gouging. The salient feature of this approach is that an original model of the cutter size is formulated and an effective solver–the particle swarm optimisation method–is employed to compute the largest allowable cutter size. This intelligent approach is more efficient and accurate than the conventional computational method based on the test examples in this work. It can also be applied to global and local gouging detection for NURBS profile machining. Our research work has great potential to advance CNC machining techniques.     

Five-axis NC milling of ruled surfaces: Optimal geometry of a conical tool

The Side milling of ruled surfaces using a conical milling cutter was studied. This is a field that has largely been ignored by research scientists, but it is much used in industry, especially to machine turbine blades. In this study, we first suggest an improved positioning with respect to the directrices of the ruled surface. As compared with the methods already developed for the cylindrical cutter, this positioning enables the error between the cutter and the work-piece to be reduced. An algorithm is then introduced to calculate error so one can determine the cutter dimensions (cone radius and angle) in order to respect the tolerance interval imposed by the design office. This study provides an opportunity to determine cutters with greater dimensions, thus alleviating bending problems during milling.