Development and design of an active work piece holder driven by piezo actuators

The use of piezo actuators in machine tools is a current topic. There are many research works which show the advantages of this kind of actuators in various fields around machining. In this paper an active work piece holder is presented, which is designed for reducing the dynamic displacement between the tool and the work piece relatively. The paper shows the design process for the fixture, the finite element analysis of the mechanical parts and the actuators. Also a specially designed power amplifier is presented which fits best to the needs of voltage and frequency range of the active work piece holder. First experimental results are shown.     

A systematic optimization approach for the calibration of parallel kinematics machine tools by a laser tracker

Parallel kinematics machine has attracted attention as machine tools because of the outstanding features of high dynamics and high stiffness. Although various calibration methods for parallel kinematics machine have been studied, the influence of inaccurate motion of joints is rarely considered in these studies. This paper presents a high-accuracy and high-effective approach for calibration of parallel kinematics machine. In the approach, a differential error model, an optimized model and a statistical method are combined, and the errors of parallel kinematics machine due to inaccurate motion of joints can be reduced by this approach. Specifically, the workspace is symmetrically divided into four subspaces, and a measurement method is suggested by a laser tracker to require the actual pose of the platform in these subspaces. An optimized model is proposed to solve the kinematic parameters in symmetrical subspaces, and then arithmetical mean method is proposed to calculate the final kinematic parameter. In order to achieve the global optimum quickly and precisely, the initial value of the optimal parameter is directly solved based on the differential error model. The proposed approach has been realized on the developed 5-DOF hexapod machine tool, and the experiment result proves that the presented method is very effective and accurate for the calibration of the hexapod machine tool.     

球头碗球面加工组合机床设计

根据球面形成原理,利用铣刀和工件的两个圆运动,合成球头碗的不完整内球面。采用组合机床,结构简单,调整、维护方便,主轴弹性卡头便于工件装卸。对零件尺寸、形状和位置误差进行了分析。通过对铣刀和主轴电机的变频调速,找出最佳切削参数,实现了内球面的高效率高精度加工。     

Development of a warm cross wedge rolling process using FEA and downsized experimental trials

Cross wedge rolling is a forming technology that offers a lot of advantages: No flash occurs, cycle times are low, lubricants are not necessary and the machines are easy to automate. Currently, cross wedge rolling is applied at hot temperatures only. An adaption of this technology to warm temperatures (about 500?C950?°C) can increase the geometrical spectrum of warm forgings. The advantages of warm forged parts in comparison to hot forged parts are closer tolerances, reduced surface roughness, no scale and reduced decarburization. To apply cross wedge rolling at warm temperatures, the possibilities of defects e. g. internal voids and improper formed work pieces must be analysed. This paper describes the development of a warm cross wedge rolling process with one area reduction. The paper also includes results of finite element analysis (FEA), experimental trials with a downsized work piece and the adaption to the industrial work piece in original size. In the FEA simulations tools with serrations on the side have been used. The downsizing method is explained and the difference between FEA, downsized and originally sized work piece with the focus on forming forces, temperature distribution and defects are presented.     

汽车半轴多楔楔横轧成形应力变化规律分析

本文根据楔横轧多楔轧制特点,建立了楔横轧多楔轧制半轴细杆部的三维有限元模型,编制了半轴细杆部多楔轧制过程进行有限元模拟的命令流程序,详细的分析了轧制过程中楔入段、展宽段主楔在侧楔作用下轧件内部应力变化规律,为多楔轧制半轴的模具设计和工艺参数的确定提供理论依据.     

Modeling and simulation of adaptronic drilling tool axes as the basis of control design

Drilling bars with great overhang are used for the purpose of deep drilling. Vibrations of the drilling bar and changing cutting forces based on form and position errors of a pilot hole are interrupting influences within the manufacturing process. Therefore the Fraunhofer IPT is developing an intelligent adaptronic drilling tool which enables the use of different redundant adaptronic systems each consisting of piezoactuators, solid-state joints and sensors in order to improve the accuracy of the drilling process. This paper presents the physical state-space model of the static und dynamic behaviour of one adaptronic system as the basis for further control synthesis and describes a useful tool for the multidiscipline design of the system. The starting model parameters are calculated by FEM-simulation and are fitted to measured data by an optimisation-algorithm based on Newton’s method. By describing the piezoelectric hysteresis the linear model of the mechatronic transfer behaviour is extended to a nonlinear model, which is the starting point for complex control designs for adaptronic machine tools.     

五轴数控旋风铣削机床加工螺纹的误差补偿研究

基于小误差运动假设,分析了五轴旋风铣削机床误差运动和补偿运动间的相互关系,建立了考虑工件热胀冷缩时进行其空间5个误差量计算的数学模型,为五轴旋风铣床用于螺纹精加工时的误差实时插补提供了理论基础,也是建立考虑工件热变时通用五轴旋风铣床误差实时插补数学模型及以旋风铣削精加工质量为目标函数、约束于多变量的数学模型的第一步.     

PLC和触摸屏在多工位冷锻成形机中的应用

五工位冷锻成形机是一种能将成卷线材从矫直、送料、剪料、五工位加工成形,并由输送机输出成品的自动化加工设备。通过对冷锻成形机工作流程的分析,介绍用工业级PLC和触摸屏实现多工位冷锻成形机的自动控制,满足机器高效要求。控制系统采用PLC,大大提高了系统的可靠性、柔性,运行更加稳定;操作系统采用触摸屏,显示直观,操作简易,为设备的调整及维护提供了便利条件。     

盘型件碾压成形载荷的理论分析

在某些简化假设条件下,对盘型件局部辗压成形的载荷及其影响因素进行了理论分析.分析发现,碾压载荷随压下量和碾压头的几何尺寸增加而增加,其中碾压头所承受的最大的载荷分量是轴向力和弯矩.这些分析结果对于盘型件辗压成型设备的设计和辗压成型工艺参数的确定具有重要参考价值.     

“Hardware in the Loop” Simulation of Machine Tools

This paper describes a time-deterministic model for the real-time simulation of machine tools using a real CNC. The realized virtual machine tool was validated by comparing the simulated milled work piece with a machined one. The results demonstrate that despite the real-time demands an accurate representation of the machine tool's behavior can be achieved.     

平地机前机梁焊接工艺改进与专机的研制

根据平地机前机架的特点和要求，研制了一台平地机前机梁焊接专机，采用接触式光电跟踪，焊接起点和终点识别，焊接过程自动控制，工件变位焊接；保证了前机梁焊接过程持续、稳定，提高了前机梁的焊接质量。     

专用硬质合金凸、凹模数控磨削加工的建模

提出了一种用于硬质合金凸、凹模加工的专用CNC工具磨床加工建模设计原理 ,分析了建模误差 ,确定了工件夹紧定位后的位置测定和刀位计算方法。     

厚铝板张力拉伸机压缩柱机加工工艺分析

压缩柱是厚铝板张力拉伸机重要受力构件,两根平行压缩柱组成了拉伸机承压梁装置。压缩柱采用锻焊结构,每根压缩柱由前部和尾部组成,两部分通过连接板进行连接,单件长度约21m,整体全长达41.5m。压缩柱全长平行度要求高,每根压缩柱上的多个长圆销孔不仅位置度要求高,而且要保证两根平行压缩柱相对应的销孔位置一致。否则在使用时会受力不均匀,影响设备的使用功能。因此,压缩柱在加工过程中如何控制工件的变形是能否达到设计要求的关键,本文从机加工工艺方面进行分析,提出合理的工艺措施,保证工件的精度符合设计要求。     

方盒件拉深摩擦状况的分析与控制

摩擦状况是评定拉深成形难易甚至成功与否的重要指标之一，而法兰部分又是拉深时的主要变形区域。鉴于上述原因，本文通过探针法来获取各种情况下不同部位的摩擦系数，进而分析出方盒件的成形特点，并分析出各种工艺参数与材料参数对成形时摩擦的影响规律，以便在实际生产中能对摩擦状况进行控制。     

A hexapod-based machine tool with hybrid structure: Kinematic analysis and trajectory planning

This paper shows kinematic analysis and trajectory planning for a novel machine tool structure consisting of a six degree-of-freedom hexapod machine and a two-degree-of-freedom rotary table. Accordingly, to operate the proposed machine tool, eight coordinates should be defined. Since a conventional part programming can define at the most five axes, the three remaining coordinates should be defined by using appropriate trajectory planning. An analytical model is developed that defines the relationships among the parameters in the proposed structure. A rule-based model is also developed to select the redundant coordinates without going through any complex and time-consuming calculations.     

Static rigid force model for 3-axis ball-end milling of sculptured surfaces

Static rigid force model is used to estimate cutting forces of sculptured surface in a straightforward way, without considering tool deflection, machine tool dynamic behavior and any vibration effects. Two programs were used for calculations, “ACIS” the 3-D geometric modeler and “VISUAL BASIC”. Two programs were edited and used to perform the calculations, the scheme program to model the work piece, tool and cutting edge and to obtain the geometric data and the VISUAL BASIC program design to use ACIS geometric data to calculate the cutting forces. The engaged part of the cutting edge and work piece is divided into small differential oblique cutting edge segments. Friction, shear angles and shear stresses are identified from orthogonal cutting database available in literature. The cutting force components, for each tool rotational position, are calculated by summing up the differential cutting forces. Laboratory tests were conducted to verify the predictions of the model. The work pieces were prepared from CK45 steel using an insert-type ball-end cutter. No coolant was used in any of the experimental works. The cutting forces predicted have shown good agreement with experimental results.     

数控机床位置伺服系统的无模型自适应迭代学习控制

数控机床位置伺服系统在加工过程中受负载、摩擦和电路系统响应特性等因素影响,很难精确建立其加工过程动力学模型。针对批量零件加工过程中的重复执行过程,设计了一种数据驱动的无模型自适应迭代学习控制方案。该方案借助沿迭代轴的动态线性化方法,将数控机床位置伺服系统加工动力学过程等价转化成一个虚拟的迭代数据模型,并根据设计的迭代学习控制律和参数估计律构建数控机床位置伺服系统的无模型自适应迭代学习控制方案。仿真结果表明:该迭代学习控制方案基于数控机床重复运行的特点,仅利用位置和电机电流信息,完成了对零件加工过程的改善,提高了加工精度。     

Manufacturing linear and circular contours using CNC EDM and frame type tools

In traditional electro discharge machining (EDM) the usual practice is to form a 3D female cavity in the work piece by making a corresponding male shaped tool and plunging this into the work piece. Recently, however, computer numerical control (CNC) EDM machines have become available which have the potential to generate a detailed shape without using complex electrodes. This paper describes a novel method of electro discharge machining which makes the generation of linear, circular and curved contours possible without any special electrodes. The experimental work employs CNC EDM, mild steel work pieces and inexpensive “frame type” copper tools. The results indicate, relative to the cavities produced, an improved effective material removal rate (MRR), a better surface finish and a lower powered machine. The paper also introduces the effect of EDM parameters on the process performance by modelling and analysing the experimental results using statistical techniques. Finally, a few applications are discussed.     

A virtual machine concept for real-time simulation of machine tool dynamics

When designing CNC machine tools it is important to consider the dynamics of the control, the electrical components and the mechanical structure of the machine simultaneously. This paper describes the structure and implementation of a concept for real-time simulation of such machine tools using a water jet cutting machine as an application. The concept includes a real control system, simulation models of the dynamics of the machine and a virtual reality model for visualisation. The real-time capability of the concept, including the simulation of electrical and rather detailed mechanical component models is proofed. The validation process indicates good agreement between simulation and measurement, but suggests further studies on servo motor, connection and flexibility modelling. However, already from the initial simulation results presented in this paper it can be concluded that the influence of structural flexibility on manufacturing accuracy is of importance at desired feeding rates and accelerations. The fully automated implementation developed in this work is a promising base for dealing with this trade-off between productivity and accuracy of the manufacturing process through multidisciplinary optimisation.     

门体手把成形模设计

通过对门体手把的工艺分析 ,确定了成形工艺中的两大难点是工件毛坯尺寸计算和工件在最后的成形工序中必须对中合缝 ,并介绍了解决两大难点的切实可行的方法