基于尺度效应的介观尺度零件多工位制造误差建模与分析

针对介观尺度零件制造过程中的加工精度控制问题,提出包括尺寸误差传递模型、多元统计过程控制和误差源诊断的加工精度控制体系,为精密微小零件多工序数字化制造提供了技术基础。通过研究介观尺度零件的特点及其在切削加工中的特性,提出基于微细切削尺度效应的工件变形和刀具变形引起的加工误差模型,构建了介观尺度零件尺寸误差传递的状态空间模型;在此基础上提出集成尺寸误差模型和多元统计过程控制的质量监控策略以及基于协方差分析的误差源诊断方法,实现了对介观尺度零件加工误差的诊断与加工精度的控制。以不锈钢工件微细槽铣削加工为例,验证了模型的有效性和可行性。     

小型数控微细铣床的研制及铣削试验研究

总结了现有微小零件加工技术的局限性,阐述了微细铣削加工的优势,并自主构建了一台适于微小零件制造的小型三轴数控微细铣床,铣床本体尺寸为400mm×400mm×260mm,工作空间为50mm×50mm×50mm。介绍了组成微细铣床的六大子系统的性能,对微细铣床系统进行精度测试,该铣床的定位精度达到1μm,满足微细铣削加工的精度要求。使用硬铝LY12进行微直槽及薄壁、微同心圆槽的铣削加工试验。加工试验结果显示:该微细铣床已经具备加工介观尺度的高深宽比微小零件的能力。     

金属微结构的电解铣削加工技术研究

随着微机电系统的发展,微细加工技术成为了当今世界的研究热点。对微细电解铣削加工技术进行了深入研究,在难加工材料镍基高温合金上进行了一系列微细电解铣削加工工艺试验。首先,基于微细电解铣削加工原理,自行研制了一套高精度微细电解铣削加工系统。其次,分组试验并分析了各主要参数,如铣削层厚度、加工电压、脉冲宽度、电极直径,以及电解液浓度等对形状精度和加工精度的影响规律。最后,通过优化加工参数,成功加工出了数个典型三维平面及曲面微结构,形状精度高,加工稳定性好,充分展现了微细电解铣削工艺在加工复杂金属微结构方面的巨大潜力。     

基于MATLAB的微细铣削加工测试系统开发

由于微细铣削加工技术可以弥补微机电系统在微小零件加工中的不足,微细铣削加工机床的研制日益被重视.以正在研制的微细铣削机床为实验环境,开发了基于MATLAB软件平台的微细铣削加工测试系统(异于传统的测试系统),可以监测铣削加工中的切削力、切削温度和切削颤振等.介绍了美国仪器(National Instrument,NI)公司的数据采集设备(N19233)在MATLAB中的使用,以及应用MATLAB进行数据的分析和处理,最后通过监测机床振动的实验分析了微细铣削机床x轴的性能,为深入研究微细铣削加工机理奠定了基础.     

钛合金介观尺度铣削表面粗糙度特征分析及工艺优化EI北大核心CSCD

为提高钛合金介观尺度铣削加工表面质量,以主轴转速、每齿进给量、轴向切削深度为主要研究因素,对介观尺度铣削表面粗糙度特征进行了分析,优化了工艺参数。考虑到介观尺度铣削加工的间断性切屑形成和单齿切削现象,分析了刀具转角与切削厚度及累计弹塑性变形次数的对应关系。在此基础上,设计了正交实验,将铣削表面划分为逆铣区域、中间区域和顺铣区域,通过方差分析确认每齿进给量是介观尺度铣削表面粗糙度最重要的影响因素。采用田口方法分别对局部区域加工工艺参数进行优化。实验结果表明,相对于中间区域,逆铣区域和顺铣区域弹塑性变形更频繁,表面粗糙度更高,以逆铣区域或顺铣区域表面粗糙度为优化目标时的优化效果更好。     

钛合金介观尺度铣削表面粗糙度特征分析及工艺优化

为提高钛合金介观尺度铣削加工表面质量,以主轴转速、每齿进给量、轴向切削深度为主要研究因素,对介观尺度铣削表面粗糙度特征进行了分析,优化了工艺参数。考虑到介观尺度铣削加工的间断性切屑形成和单齿切削现象,分析了刀具转角与切削厚度及累计弹塑性变形次数的对应关系。在此基础上,设计了正交实验,将铣削表面划分为逆铣区域、中间区域和顺铣区域,通过方差分析确认每齿进给量是介观尺度铣削表面粗糙度最重要的影响因素。采用田口方法分别对局部区域加工工艺参数进行优化。实验结果表明,相对于中间区域,逆铣区域和顺铣区域弹塑性变形更频繁,表面粗糙度更高,以逆铣区域或顺铣区域表面粗糙度为优化目标时的优化效果更好。     

异种材料微尺度铣削力试验与对比分析

在传统切削研究中,工件材料通常是均匀和各向同性的,但当切削过程从宏观尺度变化到介、微观尺度时,微铣削加工中起主要作用的因素与宏观铣削加工相比有很大不同。因此,微细铣削的研究必须考虑工件材料的影响。本文从理论上对螺旋微立铣刀受到的铣削力机理进行了分析,采用试验方法对微铣削不同工件材料时的微铣削力进行对比研究。在微铣削加工中,切削力随着微刀刃切入角度的变化而变化,其中微切削力的计算采用平均力。试验考虑主轴转速n、进给速度Vf、轴向切深ap以及不同工件材料对微切削力的影响,工件材料选择铝合金5083-O和6082-T6、钛合金Ti6Al4V、45钢、不锈钢304、工具钢SKH-9。试验结果表明:微铣削加工过程中的微切削力受铣削参数和加工材料影响,其中硬度、塑性越大的材料,切削力越大,材料的导热率越小,其微切削力越小。     

基于多误差源耦合的五轴数控铣床加工误差综合预测及评判

在综合考虑机床动静态多种误差源的基础上,建立了各运动轴伺服运动模型和多体联动模型,给出了刀具的实际运动位置和姿态,基于包络理论求解了曲面加工实际成形面,对比理想数学模型,对加工误差进行了综合预测和评判。以复杂非可展曲面--S试件为例,给出了S试件的铣削精度构建方法,分析了机床动态因素(位置环、速度环等)对零件铣削精度的影响,并通过切削实验后的数据回归分析予以验证。建立了基于神经网络的机床铣削误差辨识模型,用于评估机床加工后的状态。该平台的搭建为实现大型、关键零件的加工精度预测和保障提供了技术支撑。      

微细铣削加工表面位置误差的分析与预测

微细铣削系统的动态不稳定性会导致零件表面几何精度的偏差,以微细铣削加工表面位置误差为分析对象,在不考虑可再生颤振效应的加工条件下,建立了微细铣削系统动态切削力模型,确定了表面位置误差的分析方法。采用数值分析并结合前期的铣削试验,得到了微细铣削加工的稳定域叶瓣图和表面位置误差的解析解。对比了顺铣、逆铣加工的表面位置误差,详细分析了主轴转速和轴向切削位置对表面位置误差的影响。最后,通过把稳定域叶瓣图和表面位置误差数据组合在同一个图里面进行综合分析,预测表面位置误差并优化选择加工条件。     

微细铣削切削力正交实验研究

在自行研制的三轴联动微细铣床上,选取典型微三维零件特征进行铣槽和侧铣两种工况正交铣削实验,对微细切削力进行测量和分析。深入研究了主轴转速、轴向切深、每齿进给量等工艺参数对微细切削力的影响规律,以优化加工参数,提高微铣削的加工效率和加工精度。     

Development of meso-scale milling machine tool and its performance analysis

To overcome the shortcomings of current technologies for meso-scale manufacturing such as MEMS and ultra precision machining, this paper focuses on the investigations on the meso milling process with a miniaturized machine tool. First, the related technologies for the process mechanism studies are investigated based on the analysis of the characteristics of the meso milling process. An overview of the key issues is presented and research approaches are also proposed. Then, a meso-scale milling machine tool system is developed. The subsystems and their specifications are described in detail. Finally, some tests are conducted to evaluate the performance of the system. These tests consist of precision measurement of the positioning subsystem, the test for machining precision evaluation, and the experiments for machining mechanical parts with complex features. Through test analysis, the meso milling process with a miniaturized machine tool is proved to be feasible and applicable for meso manufacturing.     

Development of meso-scale milling machine tool and its performance analysis

To overcome the shortcomings of current technologies for meso-scale manufacturing such as MEMS and ultra precision machining, this paper focuses on the investigations on the meso milling process with a miniaturized machine tool. First, the related technologies for the process mechanism studies are investigated based on the analysis of the characteristics of the meso milling process. An overview of the key issues is presented and research approaches are also proposed. Then, a mesoscale milling machine tool system is developed. The subsystems and their specifications are described in detail. Finally, some tests are conducted to evaluate the performance of the system. These tests consist of precision measurement of the positioning subsystem, the test for machining precision evaluation, and the experiments for machining mechanical parts with complex features. Through test analysis, the meso milling process with a miniaturized machine tool is proved to be feasible and applicable for meso manufacturing. __________ Translated from Chinese Journal of Mechanical Engineering, 2006, 42(11): 162–167 [译自: 机械工程学报]     

Integration of thermo-dynamic spindle and machining simulation models for a digital machining system

A digital machining system is a core subsystem of a virtual machining system at the lowest level, and it provides physical attributes of both the machining process and machine tool to the upper application level. A digital machining system based on mechanistic models is developed. An expandable general base model is built in the system and the interfaces for extending to upper level models are provided for easy integration. The system consists of many integrative dynamic machining process simulation models including milling, turning, boring and grinding. The development of the digital machining system is completed by integrating a spindle analysis model through a modular interface using modal superposition methods. The digital machining system is evaluated in aspects of determining spindle related machining process constraints, predicting spindle condition-dependent chatter boundaries and selecting cutting tools.     

Experiment research on green machining of clay prototype for plasma spray tooling

For plasma spray molding technology, it is a key issue that the process of high-temperature prototype manufacturing is long, which lead to the loss of prototype precision. Clay prototype is milled directly by CNC machine, which can reduce the loss of precision for repeated reproduction. However, there are some difficulties for the direct processing of the clay prototype, such as holding and clamping of clay blank and chip removal. The sintering clay is too hard and brittle, which would result in tool wear and prototype destruction. The common process is to add some binders in ceramic powder; blank strength would increase after being dried, but the binders have neurotoxicity. In this paper, the prototype blank was directly dried without the use of adhesive, avoiding the side effects of binders. After the repeated drying experiment, the drying process of the blank without cracking was obtained. The experiment proved that the blank was suitable for machining after drying, while the measurement test of milling force was also designed for pre-drying the clay to study the relationship between cutting parameters and milling force. Through analysis of milling test, the change curve of cutting force was obtained with the cutting parameters. The empirical formula of the milling force was established by linear regression method; it was verified through the experiment. The results of the research provide a theoretical and practical foundation for further studies of surface quality and machining efficiency of clay prototype.     

专用旋风铣床的振动测试分析及其加工工艺改进

针对某旋风铣床加工大型锚具外螺纹时,振动较大,出现刀具早期崩刃现象,致使不能进行正常加工的情况,对该机床进行振动测试分析,结果表明:旋风铣头刚度不足、工艺参数中切深、进给量、刀盘齿数和转速是影响振动的主要因素,原工艺参数使机床加工发生共振。根据分析结果对机床加工工艺提出改进措施。通过增厚铣头基座以提高刚度,工艺上粗、精加工分别切削,减小铣刀齿数,采用变频器控制电动机改变切削速度,以避开共振区,解决了机床刀具早期崩刃问题,使加工能顺利进行。     

Feedrate optimisation/scheduling on sculptured surface machining: a comprehensive review, applications and future directions

Free-form or sculptured surface milling is one of the continually used manufacturing processes for die/mould, aerospace (especially turbine blades), precision machine design, bio-medical devices and automotive industries. Developments of machining technologies for quality enhancement of machining results have become a very important fact in current real industry. Therefore, reducing milling time, tool wear, cutter deflection and improving surface texture quality and machining operations through adaptation and optimisation of tool feedrates based on changing surface geometry in sculptured surface machining is a great step in this direction. Various feedrate optimisation strategies have different feedrate rescheduling control parameters such as chip thickness, material removal rate (MRR), min(mrr,chip,force), max(expo.Acc/dec) and resultant forces. Some commercial CAM softwares come with MRR-based feedrate optimisation algorithms which have a very short calculation time. However, commercial feedrate scheduling systems have some limitations in generating the scheduled feedrates because they use the MRR or the cutting force model which is dependent on milling conditions. However, for the processes in which machining precision/accuracy is very important, it is inevitable that mechanistic force-based feedrate optimisation approaches, for which the calculation time is improved, will be integrated into commercial CAM software packages. Here, developing only the mechanistic cutting force-based algorithm is not enough. In this paper, improvement and optimisation of machining feedrate value, which is one of the cutting parameters which has a tremendous effect on the precise machining of free-form surfaces, was discussed by using the virtual machining framework. For this purpose, the boundary representation solid modelling technique-based free-form milling simulation and feedrate optimisation system integrated with commercial CAD/CAM software is developed for three-axis ball-end milling. This review study includes the information regarding the following topics: The algorithms developed for the feedrate value optimisation, MRR calculation approaches, cutting force computation methods, details of algorithms, the effects on the surface accuracy, the effects on the machining time, the capabilities of the present commercial CAM software packages, the encountered difficulties and overcoming those difficulties, recent developments and future research directions.     

New tool-workpiece setting up technology for micro-milling

A major issue in micromilling is the setting up with the necessary accuracy the work coordinate system on the machine. The spindle thermal stability during the setting up procedure make this a very difficult task. Thus, it is essential to develop new tool setting up technology to increase the process productivity, reduce machine setting up times and errors, and at the same time improve the precision and quality of machined components. The paper presents a cost-effective and reliable method for setting up the work coordinate system for micro-milling operations employing an on-line tool–workpiece voltage monitoring system. The viability of the proposed method was verified in a series of experiments conducted on an ultra-precision micromilling machine centre. The experimental trials involved the machining of test parts in brass with cutters 100 and 200 µm in diameter. The results of these experiments were analysed and compared with the capabilities of currently available methods and technologies on micro milling machine tools for condition monitoring and setting up the working coordinate systems. Finally, conclusions are made about the effectiveness of the proposed new tool-workpiece setting up technology for micro milling.     

先进切削加工技术综述

从机床、刀具、工艺参数等方面综合介绍了几种先进切削加工技术 (包括高速切削、干切削、硬切削、精密切削和虚拟切削 )的主要研究内容及关键技术     

Optimization of machining parameters using genetic algorithm and experimental validation for end-milling operations

Optimization of cutting parameters is valuable in terms of providing high precision and efficient machining. Optimization of machining parameters for milling is an important step to minimize the machining time and cutting force, increase productivity and tool life and obtain better surface finish. In this work a mathematical model has been developed based on both the material behavior and the machine dynamics to determine cutting force for milling operations. The system used for optimization is based on powerful artificial intelligence called genetic algorithms (GA). The machining time is considered as the objective function and constraints are tool life, limits of feed rate, depth of cut, cutting speed, surface roughness, cutting force and amplitude of vibrations while maintaining a constant material removal rate. The result of the work shows how a complex optimization problem is handled by a genetic algorithm and converges very quickly. Experimental end milling tests have been performed on mild steel to measure surface roughness, cutting force using milling tool dynamometer and vibration using a FFT (fast Fourier transform) analyzer for the optimized cutting parameters in a Universal milling machine using an HSS cutter. From the estimated surface roughness value of 0.71 μm, the optimal cutting parameters that have given a maximum material removal rate of 6.0×10³ mm³/min with less amplitude of vibration at the work piece support 1.66 μm maximum displacement. The good agreement between the GA cutting forces and measured cutting forces clearly demonstrates the accuracy and effectiveness of the model presented and program developed. The obtained results indicate that the optimized parameters are capable of machining the work piece more efficiently with better surface finish.     

三维有限元分析在高速铣削温度研究中应用

高速切削过程中切削温度对刀具磨损、工件加工表面完整性及加工精度有极大的影响。应用有限元法对高速铣削铝合金薄壁件过程中工件与刀具接触面温度、工件内部的温度分布进行了仿真研究,仿真过程中考虑了切削速度、进给量对切削温度的影响。通过红外热像仪对不同主轴转速下工件表面温度的测量,验证了仿真结果与试验结果比较接近。得出在高速切削铝合金过程中,随着切削速度的增加,刀具与工件接触区的温度变化存在二次效应。该结论对铝合金薄壁件加工具有重要的实用价值。