三角Bézier曲面数控加工刀轨生成算法研究

针对目前三角Bézier曲面数控加工刀轨生成效率与精度较低且难以有效解决刀轨干涉等问题,提出了一种基于三角Bézier曲面的数控加工刀轨快速生成算法,该算法依据三角Bézier曲面模型的型面特征规划刀位驱动点,基于三角Bézier曲面的动态索引获取瞬时加工区域,迭代求解瞬时加工区域中各三角Bézier曲面片对应刀位点,...     

后置处理中平面轮廓拐角加工程序自动生成技术

为解决早期数控程序中没有考虑拐角加工问题,本文提出了围绕NC代码识别拐角并自动生成拐角加工数控程序算法,以满足产品升级与加工高要求之需,进一步确保数控加工安全与零件表面质量。为实现拐角识别,首先总结归纳常见数控代码结构;其次还原NC代码的几何形态并采用线链表示,计算线链走向、线链边之切矢;将拐角分为点式拐角与圆弧式拐角两大类型,综合拐角的离散结构与线链的封闭性,给出了拐角的识别原理与相应准则。拐角加工按分层铣削加工,从刀具轴向上减少刀具在拐角位置处加工瞬时的切削量;各层拐角加工刀轨由进刀、切入、拐角加工、切出与退刀五段组成;层间刀轨采用进退刀连接线衔接。最后用实例验证了该算法的正确性。     

基于STL数据的数控加工刀轨快速生成算法

磨牙具有复杂的尖、嵴、窝等特征,采用手工制作,修复精度低、试戴周期长,若用计算机辅助制作方法可以弥补其不足.磨牙修复体CAD模型通常为STL格式,三角片的遍历与高效等距是数控加工刀轨快速、正确计算的关键.基于STL格式,给出了新的拓扑结构、提出了基于顶点的实体等距算法,实现了磨牙修复体粗、精加工刀轨快速、正确计算.该算法已应用于DentalCAM中,经仿真加工结果表明,所提出的算法稳定性好,计算速度快,加工精度高.对于加速国产口腔修复体CAD/CAM软件的临床应用,起到了积极的推动作用.     

并联机床后置处理器的开发及实验研究

以六自由度6-TPS型并联机床为模型，阐述了机床控制数据的生成原理和流程；以此为基础，规划了后置处理器的功能和整体结构。对若干关键技术进行了研究和探讨，包括基于参数化二进制格式的内部数据传输，基于刀轴矢量的笛卡儿空间粗插补算法，三维和二维刀具半径补偿，刀位文件的预处理以及加工代码的词法和语法检查等。最后介绍了利用本系统进行的切削实验，验证了系统的工程实用性。     

六自由度坦克模拟驾驶仪时间和冲击综合轨迹规划

为确保坦克模拟驾驶仪运动平稳性和动作实时性,提出了一种在笛卡儿空间基于Stewart机构的时间和冲击综合优化轨迹规划方法.建立了六自由度运动平台运动学模型,利用分段三次样条曲线对坦克姿态点进行插补,以六自由度运动平台速度、加速度为约束条件,以时间和冲击为优化目标,对样条曲线进行控制,规划出满足模拟驾驶仪运动要求的轨迹曲...     

一种新的平面曲线圆弧插补节点获取方法

数控加工中，平面曲线的圆弧插补前，先要在曲线上取节点，在分析了传统的等弦长江和等误差法取点的不足后，提出了一种基于曲率分析的平面曲线获取点的方法，对一条三次B样条平面面线的处理结果表明，本方法所产生的节点数比等弦长法和等误差法所8产生的节点数量减少。     

TH6916型落地镗床介绍及故障分析

TH6916是齐齐哈尔二机床有限责任公司生产的数控落地镗床,它可在一台机床上完成铣槽、镗削、圆槽切削、方孔铣削、矩形凹槽切削、三维(3D)线性插补、螺旋性插补、极坐标编程等多种加工。数控机床是高度机、电、液一体的技术装备,在生产中会不可避免地出现各种故障,此时应细致检查、综合分析,便可及时排除故障。     

汽车覆盖件模具数控加工中刀轨规划优化设计

系统研究模具实施数控加工的关键技术一刀具轨迹优化,介绍数控加工中刀轨规划原则,提出刀轴控制方式及加工模式,建立模具数控加工刀轨规划系统。     

汽车覆盖件模具数控加工中刀轨规划优化设计

系统研究模具实施数控加工的关键技术一刀具轨迹优化,介绍数控加工中刀轨规划原则,提出刀轴控制方式及加工模式,建立模具数控加工刀轨规划系统。     

三次B样条曲线插补算法的VC实现

本文结合三次B样条曲线的数学性质,理论分析了三次B样条曲线的插补过程,推导出了三次B样条曲线的插补运算公式。在对三次B样条曲线进行研究的基础上,介绍三次B样条曲线插补算法实现方法,并在VC环境中对B样条曲线的插补过程进行了实现数控插补的动态运算。     

Computer-aided design,manufacturing and inspection system integration for optical lens production

The main objectives of this research are the development of an integrated manufacturing strategy and the construction of a database management system for the design, machining and inspection of sculptured surfaces. Specifically, the optical lens for colour display tube/colour picture tube is selected as an application example to show the effectiveness and efficiency of the developed manufacturing strategy and database construction methods. In the machining strategy, the total machining time reduction method is proposed for the rough cutting operation based on the optimum tool path planning. In the finish cutting operation, a modified cutter contact variable step method is employed, and optimal tool paths are generated by selecting the proper tool radius within the given tolerance of a designed model. In the inspection strategy, the shortest measuring path is calculated to reduce the inspection time in CMM. In addition, an efficient database management system, which conducts the process from the surface design stage to the inspection result analysis stage, is constructed for the optimization of the sculptured surface manufacturing process. Finally, the required simulation and experimental works are carried out to verify the proposed strategy.     

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.     

Efficient five-axis machining of free-form surfaces with constant scallop height tool paths

Generation of efficient tool paths is essential for the cost-effective machining of parts with complex free-form surfaces. A new method to generate constant scallop height tool paths for the efficient five-axis machining of free-form surfaces using flat-end mills is presented. The tool orientations along the tool paths are optimized to maximize material removal and avoid local gouging. The distances between adjacent tool paths are further optimized according to the specified scallop height constraint to maximize machining efficiency. The constant scallop height tool paths are generated successively across the design surface from the immediate previous tool path and its corresponding scallop curve. The scallop surface, an offset surface of the three-dimensional design surface based on the specified scallop height, is used to establish accurately the scallop curve with the constant scallop height. The present method was implemented and validated through the five-axis machining of a typical free-form surface. The results showed that the conventional isoparametric tool paths were over 36% longer in the total tool path length and less efficient than the constant scallop height tool paths generated by the present method.     

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.     

Angular feedrate interpolation for three-dimensional implicit curves

The paper presents an approach for angular feedrate interpolations for three-dimensional (3D) tool paths in multi-axis machining. The tool path is identified by a position curve assumed to be 3D implicit curve, and a tool orientation curve is obtained based on the position curve. The angular feedrate interpolations calculate the tool position and orientation at each sampling cycle based on specified angular feedrates and given tool paths. The paper relates analytically geometric properties of the prescribed path to rigid body motions along the path by angular feedrates and angular feed acceleration. The results are then used to develop the angular feedrate interpolation. The angular feedrate is further related to the linear feedrate, the contour error and the orientation error. Illustrations for complex implicit curve interpolation are provided with contour error and orientation error analysis. Further simulations are carried out to illustrate the effectiveness of the interpolation scheme for complex curves.     

An interpolation scheme for tool-radius compensated parabolic paths for CNC

In general, NC systems provide only linear and circular interpolations. Complex shapes to be machined are first approximated with linear and circular segments to some predetermined tolerance. Parabolic curves are more suitable for piecewise approximation of higher-order curves because less segments than lines or circular arcs are required. In machining operations, the tool motion controlled by the interpolator does not move along the profile of the job. The tool path is offset from the profile by the tool radius. Tool-radius compensations for linear and circular tool paths involve simple offsets of the initial and final points. The tool paths remain linear or circular. For parabolic profiles, the offset tool paths are not parabolic; hence, parabolic interpolations cannot be used to generate the offset paths. This paper presents an algorithm to perform interpolations for the tool to follow parabolic curves as well as the offset paths passing through two user-defined end points. The parabolic interpolation is based on the principle of operation of the Digital Differential Analyzer (DDA) integrator and is capable of constant tangential velocity.     

Experimental Investigation to Optimize Tool Life and Surface Roughness in Inconel 718 Machining

In addition to the cutting conditions, the surface quality is also affected significantly by a worn tool in machining processes. Identification of the desirable tool life so that the surface quality is maintained within a desirable level is an essential task, especially in the machining of hard materials. In this paper, an optimal tool life and surface quality were identified in the turning operation of Inconel 718 Superalloy by means of experimental investigations and intelligent methods. First, the effect of machining time (MT) at the different cutting parameters was widely investigated on the surface roughness using the neural network model. Then, the modified Non-dominated Sorting Genetic Algorithm (NSGA) was implemented to optimize tool life and surface roughness. For this purpose, a new approach was implemented and the MT was taken into account as the input and output parameters during the optimization. Finally, the results of optimization were classified and the suitable states of the machining outputs were found. The results indicate that the implemented strategy in this paper provides an efficient approach to determine a desirable criterion for tool life estimation in machining processes.     

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.     

非圆回转曲面CNC 磨削加工轨迹直接插补技术研究

针对非圆回转曲面数控磨削加工轨迹插补特点,动用曲面直接插补（ＳＤＩ）思想,提出一种适合于非圆回转曲面类零件轨迹处理的集成式ＣＮＣ轨迹插补模式,并系统研究了实时插补中加工工艺余量智能决策方法和轨迹自生成原理等,成功地解决了非圆回转曲面磨削加工的轨迹实时插补控制问题。     

Real-time cutting simulation system of a milling operation for autonomous and intelligent machine tools

The conceptual architecture of autonomous and intelligent machine tools has been proposed not only to generate flexibly the process and operation plan but also to utilize the machine tools and cutting tools' performance while satisfying the requirements of the products and avoiding unexpected machining trouble. In order to realize the autonomous milling, machining strategy such as tool paths and cutting conditions must be decided, not in advance like current NC machining, but in a real-time manner. The objective of this research is to develop a real time machining optimization with machining simulation. Consequently, a cutting simulation system called a virtual machining simulator has been developed for this purpose. This simulator can calculate the changing geometry of the workpiece and estimate the instantaneous cutting force, torque, etc using the physical model. This estimated information enables the system to decide the suitable cutting conditions according to the machinability evaluated. In this paper, the machining status is evaluated and the cutting conditions are modified in real time so that the requirement of the machining operation is satisfied by referring to the physical model. The reliable and safe machining operation is carried out by maintaining the cutting force and torque desired value.