Elliptical vibration cutting of large-size thin-walled curved surface parts of pure iron by using diamond tool with active cutting edge shift

Large-size thin-walled curved surface parts of pure iron are crucial in aerospace, national defense, energy and precision physical experiments. However, the high machining accuracy and surface quality are difficult to achieve due to the serious tool wear and deformation when machining the parts with conventional cutting tools. In this paper, an elliptical vibration cutting (EVC) with active cutting edge shift (ACES) based on a long arbor vibration device is proposed for ultra-precision machining the pure iron parts by using diamond tool. Compared with cutting at a fixed cutting edge, the influence of ACES on the EVC was analyzed. Experiments in EVC of pure iron with ACES were conducted. The evolutions of the surface roughness, surface topography, and chip morphology with tool wear in EVC with ACES are revealed. The reasonable parameters of ultra-precision machining the pure iron parts by EVC with ACES were determined. It shows that the ACES has a slight influence on the machined surface roughness and surface topography. The diamond tool life can be significantly prolonged in EVC of pure iron with ACES than that with a fixed cutting edge, so that high profile accuracy and surface quality could be obtained even at higher nominal cutting speed. A typical thin-walled curved surface pure iron part with diameter ∅240 mm, height 122 mm, and wall thickness 2 mm was fabricated by the presented method, and its profile error and surface roughness achieved PV 2.2 μm and Ra less than 50 nm, respectively.     

Path,feedrate and trajectory planning for free-form surface machining: A state-of-the-art review

Nowadays, free-form surfaces have been widely used in various industrial fields. They are usually machined by CNC machine tools, but recently have also begun to be manufactured by industrial robotic arm manipulators, thanks to low cost, large operation reaching space and high machining flexibility of robot. So far, various methodologies have been proposed to improve efficiency and quality of free-form surface machining, thus this paper aims at providing a state-of-the-art review on research advances in free-form surface machining. In this review, tool path generation, feedrate scheduling in Cartesian space and trajectory planning in joint space are focused for both CNC machining and robot machining, and their research statues, existing difficulties and key issues are discussed in detail. Finally, the feasible routes, breakthrough points and future development trend are also expounded.     

光学元件数控单轴加工中的边缘效应控制建模方法

边缘效应严重制约了计算机控制光学表面成型技术（CCOS）的加工精度和加工效率，是亟待解决的技术难点之一。基于Preston方程，建立工具盘在加工工件边缘时的定量去除模型，是解决该问题的重要途径。将加工工件、工具盘尺寸，磨削压力、速度、时间，磨削点位等加工参量进行数学建模，建立边缘去除函数模型，精确计算边缘压力分布和磨削累计时间。随着工具盘在工件边缘露边量增加，工具盘压力呈指数级增长。工件磨削累计时间随工具盘中心点位不同呈现分段变化规律。研发单轴机数控设备，利用工具盘沿工件边缘母线点位移动方式，进行边缘效应控制研究。通过实验精确求出Preston方程比例系数k，验证模型仿真与实际加工结果吻合性，准确度达到91.9%。数控单轴机修边方法和建立的数学模型可以很好地指导实际研磨抛光过程。     

微织构刀具对钛合金切屑形成影响的仿真研究

针对微织构刀具对钛合金Ti6Al4V切屑形成以及微槽二次切削机理分析的不足，通过建立热-力耦合仿真模型对比研究不同微织构刀具、微织构几何尺寸以及切削速度对切屑形成的影响规律。数值仿真结果表明：微织构刀具更有利于断屑，二次切削作用使切屑的弯曲半径变大，微织构可以减小刀屑之间实际接触面积，降低切削温度。增大微织构宽度可以增强微槽的二次切削作用，利于断屑，但应注意其对刀具强度的削弱作用，而增大相邻微槽间距则会出现相反的二次切削作用机制。提高切削速度对各刀具均有利于断屑，弧形微织构刀具的降温效果最好，V形微织构刀具次之，矩形微织构刀具降温效果最差。研究结果对进一步理解微织构刀具对钛合金切屑的二次切削作用机理提供一定参考。     

超声振动辅助切削对碳纤维增强树脂复合材料面下损伤影响的仿真研究

碳纤维增强树脂基复合材料（CFRP）在传统加工（OC）过程中存在着切削力过大、表面质量不佳、面下损伤较为严重等问题。为了改善上述问题，本文提出使用超声振动辅助切削（UVC）工艺加工CFRP，通过仿真分析对切削力与面下损伤深度进行研究。结果表明：使用UVC加工CFRP可降低13%~80%的切削力，且纤维方向角对切削力影响较小。与OC相比，UVC切削0°、45°纤维方向角的CFRP时可以减少约50%的面下损伤深度；在切削90°、135°纤维方向角的CFRP时虽然没有改善面下损伤深度，但取得了较为平整的已加工表面以及较小的损伤区域。