General tool correction for five-axis milling

In this paper a method is presented by which cutter location data can be determined for any type of milling tools defined according to DIN 66215 whereby any point of the tool can be defined as the contact point. In addition, the cutter location point for 5-axis milling can be determined using a single formula for any type of milling tool.     

A study on the five-axis end milling for sculptured surfaces

The direction vector of milling cutter for CL-data of five-axis milling is obtained by the fact that the bottom part of the milling cutter rides on free-form surfaces using the z-map method. Since the direction vector is known, CL-data can be transformed to the NC-code with regard to the geometry of the five-axis machine and post-processing. For uniform surfaces, the tool path is created from the prediction of cusp heights. After generating the NC-code, a sculptured surface was machined by five-axis end milling and cusp heights on the machined surface were measured by a three-dimensional CMM with laser scanner. From this machining test, it was found that this machining method is effective.     

Specialized numerical control system for five-axis planing and milling center

The architecture and design features of the numerical control system for an E7106MF4 machining center are considered. This system permits five-axis machining by three-dimensional planing. Organization of the automatic electrical automation subsystem is discussed. Practical aspects of the control system are presented.     

Near net-shape five-axis face milling of marine propellers

We present an optimal cutter location (CL) data computation for face-milling of large marine propellers composed of CL point optimization and CL path optimization on a given tool path. The CL point optimization at a single cutter contact (CC) point is conducted by maximizing the effective radius of the face milling cutter, while the CL path optimization on a series of CC points is performed by conforming deviation of the tool-swept surface from the design surface between consecutive CL data to a given machining tolerance. The proposed algorithm was implemented and applied to the machining of a large marine propeller which proved effective from a quantitative point of view, and is used on the shop floor in a Korean ship building company.     

Optimisation of workpiece setup for continuous five-axis milling: application to a five-axis BC type machining centre

When machining complex geometries on five-axis machining centres, the orientation and positioning of the workpiece in the machine workspace are generally chosen arbitrarily by the operator from the Computer-Aided Manufacturing software. Nevertheless, these two factors have considerable influence on the machining time. The present article firstly studies the choice of workpiece orientation. Relying on analysis of the machine’s kinematic behaviour, orientations of the workpiece in the machine workspace are proposed minimising the overall distance travelled by the rotary axes. Secondly, choice of workpiece positioning in translation is studied. To this purpose, the work volume in five-axis machining is identified so as to avoid overshooting the machine travels when the program is executed. The optimum positioning is chosen to minimise the overall distance covered by the machine’s axes of translation. Finally, the proposed method provides for a workpiece setup to be adopted that minimises the distances covered by the machine axes. This leads to reduced machining time with concomitant gains in productivity and greater respect for the cutter/workpiece relative feed rate for enhanced quality.     

Tool path planning for five-axis flank milling with developable surface approximation

This paper presents a novel approach that automatically generates an interference-free tool path for five-axis flank milling of a ruled surface. A boundary curve of the machined surface is subdivided into curve segments. Each segment works as a guide curve in the design method for developable Bézier surface that controls a developable patch for approximating the surface with available degrees of freedom. Geometric algorithms are proposed for calculating consecutive patches with G¹ continuity across the patch boundary. A tapered tool can move along the rulings of these patches without inducing local tool interference as a result of their developability. The machining deviation is controlled by the surface approximation error. A machining test is conducted with the generated CL data and the result verifies the feasibility of the proposed approach. This work successfully transforms avoidance of tool interference into a geometric modeling problem and provides a simple solution. It thus demonstrates a good potential for the developable surface theory of five-axis flank machining .     

A comprehensive approach to determining minimum cutter lengths for five-axis milling

Interference detection and avoidance by the shortest cutter for the five-axis milling machining is a critical task. Short tool length increases the rigidity and chatter stability of the cutter. In this research, a new and efficient method of interference detection and avoidance by the shortest cutter is developed. For the specific five-axis machine configuration, first possible candidate parts for the collision are found, which are complete cutting system (spindle, tool holder, and cutter), the work in process model, and the fixture. Spindle, tool holder, and tool are represented by the solid geometry identity of the cylinder, truncated cone, and cylinder, respectively, with the length and diameter as parameters. The surfaces of the work in process model and the fixture model are represented as the point cloud data of the suitable density. The Kd-tree data structure is employed on point cloud data which gives an efficient searching of the potential candidate points for the interference detection with the complete cutting system. All existing methods are able to detect the collision, but they are not capable to remove it with the optimum cutter length. The proposed algorithm has not only the capability of collision detection; it can also remove the collision with the optimum tool length. Other scope of the proposed algorithm is the selection of the tool holder to minimize the overhang tool length.     

Cut geometry calculation for the semifinish five-axis milling of nonstraight staircase workpieces

Journal of Mechanical Science and Technology - The cut geometry prediction, especially the issue regarding computational time, of a complex part surface in five-axis milling remains as a challenge....     

Design and manufacturing of parts for functional prototypes on five-axis milling machines

This paper presents the manufacturing process for complex parts in the aim of building functional prototype mechanisms. Functional prototypes are used during testing in order to validate new product design. Their layouts are very similar to the final product, wherein lies the interest of testing many modifications. The mechanism must respect the functional geometrical requirements and be capable of withstanding forces or, for example, ensuring a tight seal. The principle being proposed consists of decomposing the complex parts into several simple ones that can then be manufactured on a five-axis, high-speed milling machine from thick (approximately 40 mm) sheets made of resistant materials, notably aluminum. The problem at hand is threefold: the choice of slicing in order to avoid cutting functional areas; the choice of both positioning mode and sheet fastening mode; and lastly, the choice of machining process. This paper also presents a detailed application with a machining simulation, using CATIA (Dassault Systèmes) for a five-axis MIKRON UCP 710 milling machine.     

Geometric error compensation for five-axis ball-end milling by considering machined surface textures

Arbitrarily adjusting tool poses during error compensation may affect the quality of surface textures. This paper presents one tool center limitation-based geometric error compensation for five-axis ball-end milling to avoid the unexpected machined textures. Firstly, the mechanism of cutter location generation with cuter contact (CC) trajectory is analyzed. Due to zero bottom radius of ball-end cutter, CC points of the surface are only related to the tool center of the cutter. Realizing that, tool center limitation method of ball-end milling is established based on the generation of movements of all axes in order to ensure the machined textures. Then, geometric error compensation of ball-end milling is expressed as optimizing rotation angles of rotary axes by limiting tool centers of cutter locations. Next, particle swarm optimization (PSO) is intergraded into the geometric error compensation to obtain the compensated numerical control (NC) code. The limited region for particles of rotation angles is established, and moving criterion with a mutation operation is presented. With the help of the tool center limitation method, fitnesses of all particles are calculated with the integrated geometric error model. In this way, surface textures are considered and geometric errors of the machine tool are reduced. At last, cutting experiments on five-axis ball-end milling are carried out to testify the effectiveness of the proposed geometric error compensation.     

Tool deflection error compensation in five-axis ball-end milling of sculptured surface

Manufacturing of aircraft structural parts have the characteristics of complex process, large variety, small batch, and frequent change of production status. In order to shorten lead time and reduce cost, high-efficiency communication and collaboration among manufacturing departments are required. However, in the existing research literature, tool/fixture design, manufacturing simulation, and online machining process monitoring are not fully taken into account for collaboration. In order to address these challenging issues, this paper proposes a collaborative manufacturing framework based on machining features and intelligent software agents. The components of the proposed framework include a machining process planning agent, a numerical control (NC) programming agent, a simulation and verification agent, a tool/fixture design agent, a cost estimation agent, a production management agent, and an online machining process monitoring agent. Machining features are used as information carrier for communication and collaboration among these agents. This paper particularly focuses on the collaboration between tool/fixture design and NC programming, as well as the collaboration between online machining processes and related departments. The proposed approach has been implemented through a prototype system and tested in a large aircraft manufacturing enterprise with some very promising results.     

Decoupled chip thickness calculation model for cutting force prediction in five-axis ball-end milling

Cutting force prediction plays very critical roles for machining parameters selection in milling process. Chip thickness calculation supplies the basis for cutting force prediction. However, the chip thickness calculation in five-axis ball-end milling is difficult due to complex geometrical engagements between parts and cutters. In this paper, we present a method to calculate the chip thickness in five-axis ball-end milling. The contributions of lead and tilt angles in five-axis ball-end milling on the chip thickness are studied separately in detail. We prove that the actual chip thickness can be decoupled as the sum of the ones derived from the two individual cutting conditions, i.e., lead and tilt angles. In this model, the calculation of engagement boundaries of tool–workpiece engagement is easy; thus, time consumption is low. In order to verify the proposed chip thickness model, the chip volume predicted based on the proposed chip thickness calculation model is compared with the theoretical results. The comparison results show that the desired accuracy is obtained with the proposed chip thickness calculation model. The validation cutting tests, which are in a constant material removal rate and with only ball part engaged in cutting, are carried out. The optimized lead and tilt angles are analyzed with regard to cutting forces. The geometrical as well as the kinematics meaning of the proposed method is obvious comparing with the existing models.     

整体叶轮五轴侧铣刀位优化新算法与误差分析

为提高整体叶轮数控侧铣加工的精度和效率,分析厂锥形球头铣刀包络面与刀轴轨迹面之间的关系,提出了一种不可展直纹曲面五轴数控侧铣刀位优化的新算法.该算法首先利用两点偏置法确定圆柱刀初始刀位,然后通过刀轴旋转半锥角得到锥刀初始刀位,最后以刀具包络面与设计曲面间的极差最小为优化目标.采用刀轴上三点优化初始刀位.针对锥刀侧铣加工编程误差计算复杂问题,建立了一种编程误差计算新方法,并成功应用于整体叶轮的锥刀编程误差计算.通过数控加工仿真实例、实际加工试验和编程误差综合对比分析证明,所建立的刀位计算优化新算法正确有效,可显著减小编程误差.     

Implementation of analytical boundary simulation method for cutting force prediction model in five-axis milling

A simulation system was developed that deals with cut geometry and machining forces when a toroidal cutter is used during semifinishing in five-axis milling. The cut geometry was calculated using an analytical method called analytical boundary simulation (ABS). ABS was implemented to calculate the cut geometry when the machining used an inclination angle and a screw angle. The effect of tool orientation on the cut geometry was analyzed. The accuracy of the proposed method was verified by comparing the cut lengths calculated using ABS with cuts obtained experimentally. The result indicated that the method was accurate. ABS was subsequently applied to support a cutting force prediction model. A validation test showed that there was a good agreement with the cutting force generated experimentally.     

整体叶轮五轴数控插铣加工刀位轨迹生成算法研究

为了提高整体叶轮粗加工效率和质量,提出了一种整体叶轮五轴插铣加工刀位轨迹的计算方法。根据整体叶轮的几何特征和插铣特点,定义与叶轮轴线垂直的截平面族,构造截平面与叶片型面交线的单侧包络直线族,作为边界面加工刀位,在边界面刀位之间插值,得到整个流道的插铣加工刀位轨迹。运用UG/Open API开发了整体叶轮插铣加工软件模块,最后通过实例验证了所提出的方法是有效的。     

Feedrate optimization based on hybrid forward-reverse mappings of artificial neural networks for five-axis milling

With recent advances in five-axis milling technology, feedrate optimization methods have shown significant effects in regard to enhancing milling productivity, especially when machining complex surface parts. The existing study is aimed at calculating the optimal feedrate values through modeling milling processes. However, due to the complexity of five-axis milling processes, optimization efficiency is the bottleneck of applying them in practice. This paper proposes a novel milling process optimization method based on hybrid forward-reverse mappings (HFRM) of artificial neural networks. The feedrate values are directly used as the outputs of network mappings. Three kinds of artificial neural networks are compared to determine the one with the highest accuracy and the best training efficiency. The study shows that with the collected datasets, the trained Levenberg-Marquardt back-propagation network (LMBPN) could predict feedrate values more precisely than other alternatives. Compared with previous methods, this HFRM-based optimization method is more adept in the area of parameter adjustment because as it has the advantages of high precision and much less calculation time. Combining other multiple milling constraints, an optimization system is developed for five-axis milling processes. The optimized results could be directly used to modify a cutter location (CL) file. A typical milling case was provided to verify the optimization performance of this method, which was found to be effective and reliable.     

自由曲面五坐标环形刀铣削加工刀位轨迹优化

将圆环面刀等效为变直径平底刀,推导切削行距与进给方向和刀具姿态之间的函数关系式,分析进给方向、刀具前倾角和侧偏角对切削行距大小的影响,给出一种新的检查和消除环形刀瓶颈干涉的方法.在无干涉的前提下,选取较小的前倾角,沿最小主曲率方向进给,切削区域宽度最大,加工效率最高.     

基于MATLAB铣削动力头中蜗杆传动的优化设计

基于MATLAB的优化理论,将优化原理运用到铣削动力头中单级蜗杆传动的优化设计,在满足使用要求条件下,蜗杆蜗轮啮合中心距为最小,以达到结构紧凑、传动效率高的目的,铣削动力头外形结构尺寸、重量随之减小.建立了4个设计变量,16个约束条件的单目标优化设计数学模型.利用MATLAB的优化工具箱中的fmincon函数处理含有连续和离散变量的单目标多变量优化设计问题,不需编写大量算法程序,提高了设计效率,算法可靠.运算结果表明,优化设计方案与常规设计方案相比,中心距减少了23％,充分显示了优化设计的效益和应用价值.     

Process modeling and toolpath optimization for five-axis ball-end milling based on tool motion analysis

In free-form surface machining, the prediction of five-axis ball-end milling forces is quite a challenge due to difficulties of determining the underformed chip thickness and engaged cutting edge. Part and tool deflections under high cutting forces may result in poor part quality. To solve these concerns, this paper presents process modeling and optimization method for five-axis milling based on tool motion analysis. The method selected for geometric stock modeling is the dexel approach, and the extracted cutter workpiece engagements are used as input to a force prediction. The cutter entry?Cexit angles and depth of cuts are found and used to calculate the instantaneous cutting forces. The process is optimized by varying the feed as the tool?Cworkpiece engagements vary along the toolpath, and the unified model provides a powerful tool for analyzing five-axis milling. The new feedrate profiles are shown to considerably reduce the machining time while avoiding process faults.     

Extracting cutter/workpiece engagements in five-axis milling using solid modeler

Predicting cutting forces in milling process simulation requires finding cutter/workpiece engagements (CWEs). The calculation of these engagements is challenging due to the complicated and changing intersection geometry between the cutter and the in-process workpiece. In this paper, a solid modeling based methodology for finding CWEs generated in five-axis milling of free form surfaces is presented. The proposed methodology is an extension of the solid modeler based three-axis CWE extraction method given in [21]. At any given instant of the five-axis tool motion, the velocity vectors along the cutter axis may move in directions that do not lie in the same plane, and therefore the cutter envelopes need to be approximated by spline surfaces. Considering the spline surface approximations, the CWE methodology described in [21] does not work properly for the five-axis milling. Therefore in the proposed method, the in-process workpiece is used instead of the removal volume for extracting the CWEs. A terminology the feasible contact surfaces (FCS), defined by the envelope boundaries, is introduced. To extract the CWEs at a given cutter location, first the BODY entity, obtained by offsetting the FCS with an infinitesimal amount, is intersected with the in-process workpiece. Then, the resultant removal volume is decomposed into faces. Finally, the surface/surface intersections are performed between those faces and the FCS to obtain the CWE boundaries. To be used in the force model, the CWE boundaries are mapped from Euclidean 3D space to a parametric space defined by the engagement angle and the depth-of-cut for a given tool geometry.