Generation of engineered surfaces by the surface-shaping system

Engineering surfaces are generated by a variety of manufacturing processes, each of which produces a surface with its own characteristic topography. A method for the prediction of the topography of engineering surfaces has been developed based on models of machine tool kinematics and cutting tool geometry. The model termed the surface-shaping system accounts for not only the nominal or global cutting motions but also takes into account errors during machining such as tool runout, machine deformation and vibration, as well as higher order motions.     

Development of monitoring system on the diamond tool wear

Recently, ultra-precision machining using a single crystal diamond tool has been developing very rapidly, especially in the fields of production processes for optical or magnetic parts such as magnetic discs, laser mirrors, polygon mirrors and copier drums. As a result, it has been successfully extended to machine various soft materials, generating mirror-like surfaces to sub-micron geometric accuracy with the ultra-precision CNC machine and the single crystal diamond tool. With the real cutting operation, the geometric accuracy and the surface finish attainable in machined surfaces are mainly determined by both of the sharpness of a cutting tool and stability of the machine vibration. In this study, for monitoring the progress of machining state for assuring the machining accuracy and the surface quality, a new monitoring method of machining states in face-cutting with diamond tool is proposed, using the frequency response of multi-sensors signal, which includes wear state of tool in terms of the energy within the specific frequency band. A magnetic disc is machined on the ultra-precision lathe.     

Development of new-concept desk top size machine tool

A desktop multiprocess machinery has been designed that has two concepts: miniaturizing of machine tool and multiprocessing with a same machine tool. The prototype of desktop multiprocess machinery is developed in this study. This is tabletop size machine tool that has five changeable machining heads. Outline of main body and machining head are presented.In order to know the basic accuracy of desktop multiprocess machinery, experimental evaluation is carried out. Machining head setting error, stiffness of multiprocess machinery and straightness of X, Y, Z stage is measured. To study the basic performance of desktop multiprocess machinery, a complex machining experiment is carried out with the developed machine tool. The complex machining consists of three steps: electrode machining by milling, hole shaping by EDM, and hole finishing by ECM. These steps are performed in sequence on the same machine tool. The complex machining is successfully carried out. In order to evaluate the desktop multiprocess machinery from environmental point of view, machining energy, volume of machining liquid, and installation space of desktop multiprocess machinery are measured. The measured values are compared with estimated values with conventional machine tools. The machining energy, the volume of machining liquid, and the installation space of desktop multiprocess machinery are smaller than those of conventional machine tool.     

Impact of the shape of electrode-tool on radical overcut of micro-hole in electrochemical micromachining

To make use of the full capability of electrochemical micro-machining (EMM), a meticulous research is needed to improve the material removal, surface quality and accuracy by optimizing various EMM process parameters. Keeping this in view, an indigenous development of an EMM machine set-up has been considered to carry out a systematic research for achieving a satisfactory control on the EMM process parameters to meet the micromachining requirements. In this study an EMM machine has been developed and experiments were conducted to study the influence of some of the major process parameters such as the machining voltage, electrolyte concentrations, the pulse-on-time and the machining current on the machining rate and accuracy. The effect of the shape of the tool electrode tips on EMM has been investigated experimentally with 304 stainless steel sheets. The machining rate and the overcut are significantly influenced by the shape of the tool electrode tip.     

A study on the machining of high-aspect ratio micro-structures using micro-EDM

Micro-electro-discharge machining (micro-EDM or μ-EDM) has been gaining popularity as a new alternative method to fabricate micro-structures. The main advantages of the micro-EDM method are its low set-up cost, high accuracy and large design freedom. Compared to etching or deposition techniques, micro-EDM has the advantage of being able to fabricate complex three-dimensional shapes with high-aspect ratio. However, there are many operating parameters that affect the micro-EDM process. The fabrication of micro-electrodes on the machine is also an important process to remove the clamping error to maintain high accuracy in the machined micro-structures.

In this paper, the machining of micro-structures is divided into two basic processes. One is the on-machine fabrication of the micro-electrodes with high-aspect ratio, and the other is the EDM of the workpiece in micrometer range. An optical sensor has been developed to measure and control the dimension of the thin electrode during the tool fabrication process. Different methods have been investigated to fabricate a thin electrode into the desired dimension without deflection. The performance of the micro-EDM process is evaluated in terms of the material removal rate (MRR), tool wear ratio (TWR), and the stability of the machining. Influences of the various operating parameters of the micro-EDM process, such as the operating voltage, gap control algorithm, and resistance and capacitance values in the R–C spark control circuit, are discussed.     

A multiprocess machine tool for compound micromachining

Compound micromachining is the most promising technology for the production of miniaturized parts and this technology is becoming increasingly more important and popular because of a growing demand for industrial products, with an increased number not only of functions but also of reduced dimensions, higher dimensional accuracy and better surface finish. Compound micromachining processes that combine multiple conventional and non-conventional micromachining processes have the capability to fabricate high aspect ratio microstructures with paramount dimensional accuracy. Such machining should be carried out on the same machine with minimum change of setups. At the same time, on-machine tool fabrication along with on-machine tool and workpiece measurement facilities should also be available for further enhancement of the functionality of the machine and higher productivity. In order to achieve effective implementation of compound micromachining techniques, this research seeks to address four important areas, namely (a) development of a machine tool capable of both conventional micromachining including microturning, micromilling, etc., and non-conventional micromachining including microelectrical discharge machining (micro-EDM), wire-cut electrical discharge machining (WEDM), etc.; (b) process control; (c) process development to achieve the necessary accuracy and quality and (d) on-machine measurement and inspection. An integrated effort into these areas has resulted in successful fabrication of microstructures that are able to meet the miniaturization demands of the industry. This paper presents a few tool-based approaches that integrate micro-EDM, micro-EDG, microturning and microgrinding to produce miniature components on the same machine tool platform in order to demonstrate the capabilities of compound micromachining.     

微细超声加工机床运动控制系统设计

微细超声加工机床设计包括硬件设计与运动控制系统设计,运动控制系统是机床的核心组成部分,直接或者间接地影响到加工质量与加工效率。采用宏微复合的硬件设计结构能有效地保证运动控制精度,针对精密微三维运动平台,基于LabVIEW开发了微细超声加工中的运动控制系统,该系统包括初始化模块、粗对刀模块、精确对刀模块、绝对坐标实时显示模块、数据采集模块与加工模块。将微细工具所受的实时力与微三维运动平台的运动结合形成闭环控制,能有效地实现精确对刀以及恒压力进给加工。最后,对控制系统进行了测试,研究了恒力控制范围与增量位移、进给速度、回退速度之间的关系。     

基于PC的全软件雕铣机数控系统设计及实现

为简化雕铣机数控系统的硬件结构、降低硬件成本、增强可拓展性,基于PC平台提出一种全软件数控系统的设计方案。搭建雕铣机数控平台,构建以Linux+Xenomai双内核实时系统为基础的EtherCAT主站。在Linux域中基于Qt开发数控系统软件,设计UI界面、逻辑处理、运动控制、功能接口等模块;在Xenomai域中基于实时函数库开发硬件驱动程序,设计进程通信模块和定时驱动模块,重点说明采用有限状态机开发的定时驱动模块程序。阐述数控加工工作流程,进行系统性能测试和加工实验。结果表明：该系统实时性强、运行稳定,可满足雕铣机的数控加工要求。     

Design and development of a precision machine tool using counter motion mechanisms

In order to meet the increasing demand for high-quality miniature parts made of a wide variety of materials, the electronics, biomedical and optical industries are moving towards micro/nano-machining. Currently, mechanical micromachining can only be performed under very low feed rates and small depth of cut, which makes it very difficult to reach reasonable productivity. To cope with the low-productivity problem for micro/nano-machining of high-precision molds or miniature parts, a highly accurate and productive machining center has been designed and developed in this paper. The developed machine tool is equipped with counter balance axes, and each axis is driven at its center of gravity to achieve high acceleration/deceleration without causing any vibration. This paper describes the theoretical and practical background of the design of the machine tool and its control and measurement system. Then, experiments are carried out to evaluate the machining performance of this designed machine tool.     

微小齿轮模具的微细电火花线切割加工研究

介绍了微细电火花线切割加工微小齿轮模具的方法，其关键技术包括：晶体管可控微能量RC脉冲电源、间隙放电状态检测系统、基于压电陶瓷电机驱动的精密伺服机构和偏开路加工控制策略。使用微细电火花线切割加工机可一次切割出厚度为1mm、模数为0．04和厚度为3、5mm、模数为0．1的微小齿轮模具，表明由微细电火花线切割加工出的微小齿轮模具能满足微成形加工的技术要求。     

直线电机高速进给系统性能优化研究

高速切削技术越来越引起人们的关注。实现高速切削的关键技术之一,是开发具有高速能力的高性能数控机床。机床主轴的转速近年来有很大的提高,而机床进给系统大我仍采用滚珠丝杆传动的方式,使机床的最大进给速度受到限制,阻碍了机床高速性能的进一步发挥。本文介绍了一种采用直线电机直接驱动的机床高速进给系统。采用非线性系统稳定性分析的方法确定系统的参数,并对伺服系统性能进行实验研究。实验证明,用这种方法优化该类系统     

A new approach to contour error control in high speed machining

High speed machining technology attempts to maximize productivity through the use of high spindle speeds and axis traverse rates. The technology is dependent upon the development of suitable mechanical hardware, electrical drives and associated control software to ensure that all components are used to maximum advantage. The role of the control software is particularly demanding since one needs to maximize traverse rates while providing the necessary accuracy, and indeed providing a margin of safety to deal with unexpected changes in process, or system parameters. There have been relatively few improvements in commercial CAD or CAM systems that would help machine tool users to take maximum advantage of high speed machining; rather the majority of the approaches have been undertaken at the machine tool controller level. This paper uses circular interpolation and corner tracking to compare several such control techniques, (Cross Coupled Control (CCC), Zero Phase Error Tracking Control (ZPETC), and Realtime Frequency Modulated Interpolation (FMI)), each of which have been proposed in the literature order to improve machining accuracy. None of these approaches are found to be universally successful when used alone and the authors, in this paper, examine the use of these systems in combination. Particular attention is focused upon an extension of a simplified version of cross coupled control together with Frequency Modulated Interpolation. It is shown that the combined system performs extremely well, and is easily actuated at high frequencies with conventional hardware. A custom built high speed x-y table is used to confirm system performance with multiple constraints present.     

Simulation of turning operations

One of the most important factors affecting the quality and productivity of turning operations is the dynamics of the system. In this study a computer program is developed to simulate turning operations. The program represents turning operations with a tool geometry simulation module, and the discrete transfer functions of machining process and machine tool structure. The discrete transfer functions of the turning operation are determined by dynamic experiments. The developed program is run at different depth of cuts to study the development and finite amplitude vibrations of chatter. The characteristics of the simulated data agree with the results of previous experimental studies. The simulation program is very convenient to study the chatter susceptibility of machine tool, workpiece and tool geometries.     

Analysis–synthesis of dimensional deviation of the machining feature for discrete-part manufacturing processes

Dimensional deviation analysis has been an active and important research topic in mechanical design, manufacturing processes, and manufacturing systems. This paper proposes a comprehensive dimensional deviation evaluation framework for discrete-part manufacturing processes (DMP). A generic, explicit, and transmission model is developed to describe the dimensional deviation accumulation of machining processes by means of kinematic analysis of relationships between fixture error, datum error, machine tool geometric error, fixturing force inducing error and the dimensional quality of the product. The developed modeling technology can deal with general fixture configurations. In addition, the local contact deformations of the workpiece–fixture system are determined by solving a nonlinear programming problem of minimizing the total complementary energy of the frictional workpiece–fixture subsystem in machining system. Moreover, the deviation of an arbitrary point on machining feature can be also evaluated based on a point deviation model with prediction dimension deviation from the transmission model. The dimensional error transmission within the machining process is quantitatively described in this model. A systematic procedure to construct the model is presented and validated. This model can be also applied to process design evaluation for complicated machining processes.     

Development of a tool failure detection system using multi-sensors

Tool monitoring and machine diagnosis in real machining have been crucial to the realization of fully automated machining. Also, the on-line detection technique of the tool breakage in machining should be supported. The effect of tool breakage is usually revealed from an abrupt change in the processed measurements, which is in excess of a threshold value. Although these techniques are generally effective for a specific cutting condition, they are often not sufficiently reliable for use in production due to the inability of single measurement to reflect tool breakage under various cutting conditions. In order to enhance the reliability of tool breakage signatures obtained from a single sensor, an integrated approach based on measurements from several sensors has been put forward. In this study, the tool breakage detection method using multi-sensors is proposed and the sensor fusion algorithm is developed to integrate and make decisions from data measured through the multisensors. Also, the performances of this scheme are compared and evaluated with real cutting process.     

基于开放式系统的曲面加工误差动态补偿控制

将基于传感器信息的智能型开放加工系统应用于曲面的高精度加工,提出了曲面加工误差的动态补偿方法。为预测加工误差的补偿量,建立了刀具弯曲模型,分析了刀具弯曲对加工误差的影响。实验结果表明,本系统可有效地提高加工精度,使加工误差降低1／3－1／4。     

八轴五联动加工中心几何仿真环境构建方法研究

通过分析几何仿真环境的功能需求,设计了几何仿真环境的结构。以某公司生产的1台八轴五联动镗铣加工中心为原型,分析机床的几何约束关系和运动关系,构建机床模型、控制模型与测量分析模型,建立了具备现实机床系统全部功能、特征和行为的几何仿真加工环境。实际应用表明：构建的仿真环境能真实反映机床的静态特征和动态特征,在该仿真环境中进行仿真测量分析,能有效保证产品加工质量和机床安全性。所提的几何仿真环境构建方法为构建其他类型多轴加工几何仿真环境提供技术支持和参考。     

基于AutoCADR14和VB5开发的数控自动编程系统

利用ＡｕｔｏＣＡＤ Ｒ１４的ＡｃｔｉｖｅＸ Ａｕｔｏｍａｔｉｏｎ编程接口,提出了一种基于Ｒ１４和ＶＢ５的数控自动编程系统。该系统可以Ｒ１４环境中直接进行加工零件的工艺设计和数控编程,并且具备了刀具半径补偿的动态模拟和加工程序的检验功能,生成的加工程序可以通过磁盘或ＲＳ２３２通讯接口输送给数摧机床。     

In-process control of surface roughness due to tool wear using a new ultrasonic system

This paper presents in-process monitoring and control of surface roughness during machining processes via ultrasonic sensing. A newly developed system is utilized to measure the reflected intensity of ultrasonic beams from the surface and in-process measurement capability is evaluated under machine vibration and tool wear. The experimental results show that the system is able to detect the changes in surface roughness caused by tool wear and can possibly be used to monitor tool wear. Finally, in-process control of surface roughness using the ultrasonic system is demonstrated by adapting the system to a CNC machining center and performing geometric adaptive control. The results show it is possible to maintain surface roughness within 10% of the target value for tool wear up to 0.3 mm.     

三轴数控机床加工精度可靠性分析

机床作为机械制造业的基础,几何误差、热误差、装配误差等都会影响数控机床的加工精度,数控机床加工精度的高低直接决定产品的生产质量。为保证数控机床对产品的加工质量,需要对数控机床的加工误差数据处理,求得数控机床加工精度可靠性,而一次二阶矩法和蒙特卡罗法是常用的可靠性分析方法。以三轴数控机床为研究对象,针对给定的误差数据,运用一次二阶矩法和蒙特卡罗法分析出数控机床加工精度可靠性。此分析对提高数控机床加工精度及保证使用寿命具有重要指导意义和参考价值。