航空发动机壳体2.5轴铣削加工刀具优选方法

为提高2.5轴零件数控加工过程中的加工效率和加工精度,合理选择刀具直径组合是非常必要的.然而,目前刀具的选择主要依靠工艺人员的实际生产经验或结合大量的试验确定,代价昂贵.为解决上述问题,文章提出一种基于2.5轴零件数控加工刀具直径优选方法.首先分析了2.5轴零件的结构特点,将图形区域按照加工精度要求转换为二值图像,并利用相关方法获取图像骨架;然后采用拓扑细化法获取图像的初始骨架,并结合动态骨架法进行初始骨架的修正,获得图像的准确骨架,继而得到沿骨架加工时刀具的直径分布.针对型腔类零件数控加工的算例分析表明,采用本文方法能够快速获取给定刀具数量下的最优刀具组合和相应的加工轨迹,提高了加工效率.     

飞机结构件数字化设计与制造技术

飞机结构件逐步向大型化、整体化和复杂化发展,且制造精度要求较高.对设计和制造技术提出了更高的要求.因此,开展飞机结构件设计技术和制造技术的研究,在飞机结构件设计和制造过程中应用数字化技术和智能技术,构建飞机结构件设计制造协同化平台,实现飞机结构件高效、高质、低成本和环保的柔性化设计和制造,对提高企业核心竞争力具有重要意义.     

飞机结构件数控加工工序计算技术

近年来,智能制造已引起国内制造业广泛关注,成为学术界的研究热点.零件自动加工是智能制造的重要组成,也是智能制造的一项具体体现,数控加工自动编程是实现零件自动加工的关键.首先,立足于加工工程实际和本质重新梳理数控加工编程流程,提出自动编程技术思路并确立技术实施的核心和关键;然后,简述了当前数控加工自动编程相关关键技术的发展现状以及存在的问题;最后,基于当前的研究基础,指出自动编程技术的核心并预测了未来的发展趋势.     

发动机叶片椭圆进排气边智能磨削加工检测一体化技术

本文论述了航空发动机叶片进排气边的先进制造技术。首先介绍了椭圆叶片进排气边的重要性,然后描述了叶片进排气边加工的特点和制造技术现状,进而讨论了叶片进排气边智能加工检测一体化技术,最后对其中的关键技术和解决方案进行了分析。     

Convex shaping process simulation during counter-rotating electrochemical machining by using the finite element method

In counter-rotating electrochemical machining(CRECM), a revolving cathode tool with hollow windows of various shapes is used to fabricate convex structures on a revolving part. During this process, the anode workpiece and the cathode tool rotate relative to each other at the same rotation speed. In contrast to the conventional schemes of ECM machining with linear motion of a block tool electrode, this scheme of ECM is unique, and has not been adequately studied yet. In this paper, the finite element method(FEM) is used to simulate the anode shaping process during CRECM, and the simulation process which involves a meshing model, a moving boundary,and a simulation algorithm is described. The simulated anode profiles of the convex structure at different processing times show that the CRECM process can be used to fabricate convex structures of various shapes with different heights. Besides, the variation of the inter-electrode gap indicates that this process can also reach a relative equilibrium state like that in conventional ECM. A rectangular convex and a circular convex are successfully fabricated on revolving parts. The experimental results indicate relatively good agreement with the simulation results. The proposed simulation process is valid for convex shaping prediction and feasibility studies as well.     

Influence mechanism of machining angles on force induced error and their selection in five axis bullnose end milling

In the machining of complicated surfaces, the cutters with large length/diameter ratios are used widely and the deformation of the machining system is one of the principal error sources. During the process planning stage, the cutting direction angle, the cutter lead and tilt angles are usually optimized to minimize the force induced error. It may lead to a low machining efficiency for bullnose end mills, as the material removal rates are different largely for different machining angles. In this paper, the influence mechanism of the machining angles on the force induced error is studied based on the models of the instantaneous cutting force when the cutter flute traveling through the cutting contact point and the stiffness of the machining system. In order to evaluate the machining angles, the force induced error/efficiency indicator (FEI) is defined as the division of the force induced error and the equal volume sphere of the removed material. FEI is dimensionless, with the lower FEI, the lower force induced error and the higher machining efficiency. For optimal selection of the machining angles, the critical FEI is calculated with the constraint of force induced error and the desired material removal rate, and the critical FEI separate the set of the machining angles into two subsets. After the feed rate scheduling process, the machining angles in the optimal subset would have higher machining accuracy and efficiency, while the machining angles in the other subset have lower machining accuracy and efficiency. Through the machining experiment of five axis machining and freeform surface machining, the effectiveness and superiority of the proposed FEI method is verified with a bullnose end mill, which can improve the machining efficiency with the constraint of force induced error.     

Surface-improvement mechanism of hybrid electrochemical discharge process using variable-amplitude pulses

Superalloys are commonly used in aircraft manufacturing; however, the requirements for high surface quality and machining accuracy make them difficult to machine. In this study, a hybrid electrochemical discharge process using variable-amplitude pulses is proposed to achieve this target. In this method, electrochemical machining (ECM) and electrical discharge machining (EDM) are unified into a single process using a sequence of variable-amplitude pulses such that the machining process realizes both good surface finish and high machining accuracy. Furthermore, the machining mechanism of the hybrid electrochemical discharge process using variable-amplitude pulses is studied. The mechanism is investigated by observations of machining waveforms and machined surface. It is found that, with a high-frequency transformation between high- and low-voltage waveforms within a voltage cycle, the machining mechanism is frequently transformed from EDM to pure ECM. The critical discharge voltage is 40 V. When pulse voltages greater than 40 V are applied, the machining accuracy is good; however, the surface has defects such as numerous discharge craters. High machining accuracy is maintained when high-voltage pulses are replaced by low-voltage pulses to enhance electrochemical dissolution. The results indicate that the proposed hybrid electrochemical discharge process using variable-amplitude pulses can yield high-quality surfaces with high machining accuracy.     

数控机床校准周期的合理确定

从具体实际出发，充分分析影响机床最终加工精度的诸多因素，应用田口方法科学合理地确定数控机床的最佳校准周期，保障机床加工过程的质量控制。     

利用电化学方法制备有序多孔硅阵列

采用电化学刻蚀的方法，在自制的电解槽中制备n型〈100〉晶向多孔硅条状阵列。通过扫描电子显微镜对生成的多孔硅进行形貌观察，并对多孔硅条状阵列的生长速率与形貌进行了初步的理论分析和实验研究。实验结果表明，多孔硅的生长速率主要由临界电流密度决定，多孔硅生成初始阶段产生锥形刻痕的原因是初始电流密度比较小，加大电流密度可以消除刻痕。多孔硅分又是由孔间距远远大于自由电荷区而产生的，而深槽中出现分立小孔的原因是反应产生的氢气阻碍了阳极氧化的进行。本实验结果对开展多孔硅进一步的研究工作具有指导意义。     

大面积回转复杂凹凸型面高效电解加工工艺探索

论述了采用电解加工大面积复杂凹凸型面的加工工艺可行性,通过优化加工参数,得到了具有代表性的加工时间与电流之间的关系曲线。研究结果表明:电解加工方法加工大面积复杂形状的结构有着较大优势,加工时间相比传统的机械加工大幅缩短,提高了加工效率,具有重要的应用价值。