成形铣齿切削载荷与加工精度的分析

错齿盘铣刀可用于齿轮的成形铣齿加工,具有多刃断续切削和变切屑厚度等特点,属于非自由强力铣削。切削载荷、加工精度逐渐成为切削机制的主要内容。通过试验方法,测量获得铣齿加工的典型载荷,可知切入、切中、切出三个阶段具有不同的特征。通过三坐标测量加工精度,分析得出齿向呈现了倒锥形的结果。其中切中阶段,加工精度为正并逐渐提高;而切出阶段,加工精度为负。基于对三向切削载荷及机床主轴箱体的悬伸对加工精度的直接影响分析,解释了"收口"现象的主要原因。该类实时的切削数据可用于现场分析与控制,进而实现精度补偿。     

一种用于大型套筒类零件加工的自定心专用夹具

套筒类零件一般由孔、外圆、端面和沟槽组成,其主要工作表面为内圆表面和外圆表面,形状精度和位置精度要求较高,表面粗糙度值较小,孔壁较薄且在加工过程中因受夹紧力、切削力、切削热等作用后易变形。因此,保证主要表面的相互位置精度和防止变形,是加工套筒类零件的关键。针对大直径的套筒类零件加工,设计制造了一种自定心专用夹具,解决了套筒类零件的装夹、定位问题,保证了零件的加工精度,提高了生产效率。     

国外高档加工中心的可靠性分析与评价

以故障总时间法对国外高档加工中心的故障数据进行了数据处理,并应用Matlab软件对故障数据进行了包括模型选择、参数估计和校验等可靠性统计分析,得到了加工中心的故障数据服从二参数威布尔分布。并基于所得到的各种可靠性指标对此加工中心进行了可靠性评价。     

工艺参数对微小方孔的微细电解加工精度的影响

微小方孔结构是航空航天、兵工、仪器仪表等领域中常用的结构且加工困难。为了提高金属材料微小方孔结构的加工精度,在分析微细电解铣削加工原理和实验系统基础上,进行了一系列镀镍不锈钢微小方孔(50μm×50μm)的微细电解铣削加工正交实验,探讨了加工电压、电解液浓度、进给速度、脉冲宽度等参数对微细电解铣削加工精度的影响。结果表明:在合理参数范围内采用较低的工作电压、较低浓度电解液、较高进给速度和较小脉宽电源有利于提高镀镍不锈钢材料微小方孔的微细电解加工精度。     

Effects of microstructure and strength on wear performance in rough milling of austempered ductile iron

The machinability of various grades of austempered ductile iron (ADI) has been investigated for rough milling operations. ADI 900, ADI 1050 and ADI 1200 grades were commercially produced, commercially heat treated and machined under controlled conditions using coated carbide inserts with coolant in the laboratory. The milling performance of the various grades was compared to that of AISI/SAE 4340 with similar hardness. In this study, machinability characteristics relative to wear rate (ISO 8688-2) and machining forces were measured and related to initial microstructure and properties. These preliminary results have been used to establish initial rough milling machining guidelines for machining ADI with coated carbide milling inserts.     

模具自由曲面球头刀高速铣削点速度研究

球头铣刀高速铣削是加工模具自由曲面的重要工艺方法。在分析自由曲面铣削中球头刀铣削点和零件加工曲线几何位置关系的基础上,探讨球头刀铣削点的运动规律,得到加工模具自由曲面过程中球头刀铣削点的线速度和角速度方程。铣削点的速度方程将为研究球头刀的均匀磨损提供必要的理论依据,为曲面零件的超精密加工打下提供参考。     

加工中心故障分析及其可靠性增长的措施

从加工中心的故障诊断分析着手,根据加工中心工作和功能特点,研究其故障模式和原因,提出排除故障的方法,最终提高机床的可靠性,为实施可靠性增长技术提供相应的支撑,有助于提升数控机床行业的核心竞争力。     

On the influence of gamma prime upon machining of advanced nickel based superalloy

Whilst gamma prime (γ′) phase is the strengthening phase in Ni-based superalloys its influence on machining has been seldom investigated. This paper reports for the first time on the effect of γ′ upon machining of Ni-based superalloys when cutting with parameters yielding different cutting temperature intervals which lead to strengthening/softening effects on the workpiece (sub)surface. In-depth XRD, SEM/FIB, EBSD analysis and unique micro-pillar testing in the workpiece superficial layers indicated that with the increase of γ′ fraction the grain plastic deformation significantly decreased, while specific cutting energy can switch from low to high values influenced by the real cutting temperature.     

Virtual process systems for part machining operations

This paper presents an overview of recent developments in simulating machining and grinding processes along the NC tool path in virtual environments. The evaluations of cutter–part-geometry intersection algorithms are reviewed, and are used to predict cutting forces, torque, power, and the possibility of having chatter and other machining process states along the tool path. The trajectory generation of CNC systems is included in predicting the effective feeds. The NC program is automatically optimized by respecting the physical limits of the machine tool and cutting operation. Samples of industrial turning, milling and grinding applications are presented. The paper concludes with the present and future challenges to achieving a more accurate and efficient virtual machining process simulation and optimization system.     

A novel approach to fixture layout optimization on maximizing dynamic machinability

In the aerospace industry, the reasonable layout of fixture can efficiently suppresses machining vibration of thin-walled aerospace structure during machining. Based on the analysis of typical structural components encountered in the aerospace industry, a general frame-structure workpiece with fixture constraints can be equivalent as Mindlin plates with simultaneous elastic edges and internal supports. On basis of the equivalent models, the powerful pb-2 Ritz method defined by the product of a two-dimensional polynomial and basic functions can be introduced to be taken as trial functions. Substituting displacement functions into energy functional and minimizing total energy by differentiation leads to eigenfrequency equations of the workpiece–fixture system. Consequently, a novel nonlinear programming problem based on the frequency sensitivity can be built to optimize the layout of fixture supports to maximize the fundamental nature frequency of the workpiece–fixture system. The feasibility of the proposed approach is validated by a machining case.