薄板激光切割气熔比数学建模及试验验证

为研究薄板激光切割气熔比规律,分析激光切割区域内材料气化和熔化去除的形式,研究熔化层能量和质量流动状态,建立薄板激光切割的气熔比数学模型,并得到气熔比值和残留熔融层厚度随激光功率和扫描速度的变化。借助激光切割半径的回归修正,模拟得到激光切割0.5 mm厚6063铝合金薄板时气熔比值及残留熔融层厚度。发现随激光功率增大和扫描速度的降低,气熔比增大,残留熔融层厚度减小。在JK701H型激光加工系统进行验证试验,得到并观察65 W、2.2 mm/s,85 W、2 mm/s和105 W、1.8 mm/s三种参数下的切口,计算试验气熔比值和残留熔融层厚度,表明模拟结果与试验基本吻合,验证模型的可行性,为基于气熔比控制的激光精密切割工艺提供重要依据。     

金刚石薄膜涂层刀具切削性能与磨损过程的研究

金刚石薄膜具有高硬度、低摩擦系数、高耐磨性和高导热性能。金刚石薄膜涂层刀具高速干切削硅铝合金可提高生产率。通过金刚石薄膜涂层刀具的切削试验和考察其磨损过程，表明了金刚石薄膜涂层刀具的使用寿命明显高于未涂层的硬质合金刀具，金刚石薄膜涂层刀具的磨损是由薄膜的显微断裂而逐渐脱落的过程。     

Strategies and Processes to Measure the Dimensional Geometry of Sheet Metal Parts for Exact Laser Cutting

This paper describes strategies and processes to measure the dimensional geometry and deformations of sheet metal parts, in order to improve accuracy in laser cutting. A robust circular triangulation laser probe was integrated into a CNC machining centre. For the development of the measuring system a non-contact laser sensor and a personal computer (PC) were integrated information-technically with the NC-controller of the machining centre, as introduced in this study. To meet the demands of the measuring tasks in laser machining, the meas-uring uncertainty of the selected laser probe with respect to different measuring procedures, such as the fixed height procedure, surface tracing procedure, and profile-orientated procedure for steel and plastic materials, was investigated in this study. When measuring uncertainty is considered, the profile-orientated procedure best meets the accuracy requirements. According to the experimental results, the uncertainty could be minimised to within ±20 μm in the middle measuring range. To shorten the measuring time, a twofold measuring strategy was developed. The first step checks for existing deviations quickly. If necessary, in the case of deviations of the actual machining path from the theoretical machining path, these can be quantified in the second step. A nine-point measuring strategy was proposed in this study in order to calculate the surface normal of the deformed sheet metal. An algorithm for calculating the path correction using these deviations and the calculated surface normal with respect to the coordinates and the surface normal of theoretical path position, was also presented. The algorithms were verified using the developed automatic measuring system on a 4-axis machining centre with satisfactory results. One specific characteristic of the strategy presented is that the machining path can be verified for the case of laser cutting for workpieces without edges or marks.     

Principle and Simulation of Fixture Configuration Design for Sheet Metal Assembly with Laser Welding, Part 2: Optimal Configuration Design with Genetic Algorithm

A fixture plays a key role in ensuring proper metal fit-up in sheet metal assembly with laser welding. In this paper, an optimal fixture configuration design model is proposed based on a new locating scheme which includes both total locating and direct locating on welds. In this model, both the number and the location of the concerned locators are taken as objectives. The proposed prediction and correction method is used for determining the number of direct locators, and a pattern sorting method is developed for determining the number of total locators. Considering the degree of metal fit-up (DMF) to be a fuzzy quantity, a feasible evaluation criterion of DMF is also developed using a fuzzy synthesis evaluation method. A powerful optimisation technique – genetic algorithm – is employed as the optimisation procedure. A case study is presented which demonstrates the effectiveness of the optimal model, and the degree of metal fit-up can be improved compared to the initial locating scheme.     

一种激光切割柔性生产线板材上料定位系统的设计及控制

为了实现在激光切割加工应用中使板材上料定位位置准确,设计出一种特别适合应用在激光切割柔性生产线上的定位系统,该系统采用B eckhoff控制器实现定位的各个动作以及整个生产线上下料的控制,不仅切割机自身加工定位精度高、各类动作连贯,而且也为激光切割柔性生产线上后续的废料分离及分批释放进行精确分选提供了保证。     

典型车削零件数控工艺分析与加工

分析了数控车削零件编程加工中可能出现的一些问题,通过对典型数控车削轴类零件的工艺分析,制订出详细的加工工艺,最终完成典型数控车削轴类零件的编程与加工.以典型零件为例,较全面地剖析了数控车削轴类零件的整个工艺过程,为初学者指明了较为明确的道路,有助于增强其对数控车削的掌握能力,减少出错几率,提高生产效率.     

冲压成形模拟过程中的工艺切口算法及应用

针对板料成形模拟过程中的工艺切口问题,提出了网格自适应加密与减密技术的工艺切口算法。算法采用向前推进方式对切边线经过的单元进行网格调整,通过网格映射方法完成新旧单元体系下物理量信息传递。将算法集成到基于动力显式算法的FASTAMP软件中,模拟实际生产的汽车覆盖件成形过程,优化工艺切口时的模具行程、切口的大小、位置和形状等。将工艺切口方案应用于实际拉深成形中,其成形结果不仅验证了数值模拟结果的准确性,同时也证明了工艺切口算法的实用性。     

Principle and Simulation of Fixture Configuration Design for Sheet Metal Assembly with Laser Welding, Part 1: Finite-Element Modelling and a Prediction and Correction Method

The quality of the stamping process has a direct effect on laser welded sheet metal assembly. The fixture plays an important role in the satisfactory metal fit-up that laser welding requires. The traditional "3-2-1" locating scheme will no longer suffice for the deformable laser sheet metal assembly process. Because of the often poor stamping quality, a complex die fixture has to be employed to meet the metal fit-up requirements. The die fixture corresponds to an "infinite-2-1" locating scheme where the tooling cost is very high and yet lacks flexibility. This limits the application of laser welding. In this paper, a new locating scheme with both total locating and direct locating for welds is proposed. A total locating scheme is used to locate the overall assembly, and a direct locating scheme is used to locate the weld location, which is critical for ensuring correct metal fit-up. A finite-element model and a prediction and correction method for the direct locator configuration are developed in this paper. A case study is used to show that the proposed method is effective for sheet metal assembly for laser welding.     

An Experimental Study and Statistical Analysis of the Effect of Laser Pulse Energy on the Geometric Quality During Laser Precision Machining

In laser precision machining, process parameters have critical effects on the geometric quality of the machined parts. Due to the nature of the interrelated process parameters involved, an operator has to make a host of complex decisions, based on trial‐and‐error methods, to set the process control parameters related to the laser, workpiece material, and motion system. The objective of this work is to investigate experimentally the effect of laser pulse energy on the geometric quality of the machined parts in terms of accuracy, precision, and surface quality. Experimental study of formation of machined craters on thin copper foil with variation in laser pulse energy, the geometry and the surface topology of craters is presented. The geometrical parameters were measured and statistically analyzed with respect to incident pulse energy. Statistical analysis including pattern recognition was employed to analyze the experimental data systematically and to serve proper selection of the process parameters to achieve the desired geometric quality of the machined parts. Plausible trends in the crater geometry with respect to the laser pulse energy are discussed. The technique has been verified experimentally on simple geometrical features such as circles and grooves, and the geometric quality is evaluated.     

An Experimental Study and Statistical Analysis of the Effect of Laser Pulse Energy on the Geometric Quality During Laser Precision Machining

In laser precision machining, process parameters have critical effects on the geometric quality of the machined parts. Due to the nature of the interrelated process parameters involved, an operator has to make a host of complex decisions, based on trial-and-error methods, to set the process control parameters related to the laser, workpiece material, and motion system. The objective of this work is to investigate experimentally the effect of laser pulse energy on the geometric quality of the machined parts in terms of accuracy, precision, and surface quality. Experimental study of formation of machined craters on thin copper foil with variation in laser pulse energy, the geometry and the surface topology of craters is presented. The geometrical parameters were measured and statistically analyzed with respect to incident pulse energy. Statistical analysis including pattern recognition was employed to analyze the experimental data systematically and to serve proper selection of the process parameters to achieve the desired geometric quality of the machined parts. Plausible trends in the crater geometry with respect to the laser pulse energy are discussed. The technique has been verified experimentally on simple geometrical features such as circles and grooves, and the geometric quality is evaluated.     

大型板材离散多点成形工艺及装备研究

针对大型板材的冲压成形问题,提出了一种离散多点成形工艺。介绍了此工艺中模具及柔性杆的结构。与已有的多点成形工艺——杆系柔性成形和活络方形压头非对压技术相比,离散多点成形工艺在大型板材成形过程中有其自身的优势。     

钛合金板料激光冲击变形的数值模拟和实验

实验研究了激光能量和不同的冲击路径、冲击次数对TA2钛合金板料变形的影响，并用ABAQUS软件进行了有限元模拟。结果表明：随着激光能量的增加，板料的变形量增大；板料几何尺寸和厚度越大，板料越难变形；冲击次序不同，板的变形量也不同，板的变形以沿板的长度方向且对称冲击为最大。通过数值模拟可优化激光冲击的相关参数，预测板料变形。     

板材冲孔FMS生产管理系统的信息流分析及实现

结合国产板材冲孔 FMS的开发 ,分析了板材 FMS生产管理系统的信息流。将生产管理系统分为 :系统设置、数据管理、计划与调度、通信接口以及 CAD/ CAM管理等五个模块 ,研究了计划及调度模块的功能及其实现 ,基于关系型数据库 SQL Server及 Client/ Server结构开发了相应的生产管理软件     

Optimisation of the Plated Through Hole (PTH) Process Using Experimental Design and Response Surface Methodology

The process of producing side-to-side and innerlayer connections for printed circuit boards by metallising with copper is called the plated through hole (PTH) process. The copper deposition rate of the PTH process is one of the major quality characteristics. In this project, experimental design and response surface methodology were employed to investigate the PTH process behaviour and perform the process optimisation. First, a 2_v ⁵⁻¹ fractional factorial design was used to screen out the significant factors as well as their interactions on the response of the copper deposition rate of a PTH process. The location factors were identified to be operation time, temperature, concentration of copper additive and the interaction of operation time and temperature. A normal probability plot of the residuals was used to determine the factors which give the minimum thickness variability of deposited copper in the PTH process. The interaction of operation time and temperature was found to be a dispersion factor. Model adequacy checking was conducted to check the normality, independence, and constant variance assumptions of the model. It is then followed by employing response surface methodology to locate the optimal operating point within the process window for the minimum thickness variability of deposited copper. First, a first-order model was regressed on the standard deviation of copper thickness of the four corners of the process window. The path of steepest descent was found and a new first-order model was then regressed at the point. The lack of fit of the new first-order model indicates that a second-order model is required. A central composite design (CCD) method was used to fit the second-order model. The stationary point obtained by the partial differentiation of the second-order model is 10.623 min in operation time and 24°C in temperature which was characterised by canonical analysis to be a minimum point. The predicted minimum variation of copper deposition rate calculated, based on the second-order model, is 1.02μin. A confirmation experiment was conducted based on the recommended optimal setting. The minimum variation of deposited copper was found to be 1.08 μin. ID="A1"Correspondance and offprint requests to: Dr C. K. Kwong, Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong. Email: mfckkong@inet.polyu.edu.hk     

测力刀柄结构设计与分析

介绍了适用于加工过程中切削力测量的测力刀柄的设计，测力刀柄的弹性元件采用薄壁圆筒的结构形式，成功地解决了灵敏度和刚度之间存在的矛盾。利用有限元分析软件ANSYS进行仿真计算，结果表明所设计的测力刀柄具有良好的静、动态性能。     

An Improved Method for the Determination of 3D Cutting Force Coefficients and Runout Parameters in End Milling

A simple improved method is suggested for determining constant cutting force coefficients, irrespective of the cutting condition and cutter rotation angle. This can be achieved through the combination of experimentally deternimed cutting forces with those from simulation, performed by a mechanistic cutting force model and a geometric uncut chip thickness model. Additionally, this study presents an approach that estimates runout-related parameters, and the runout offset and its location angle, using only one measurement of cutting force. This method of estimating 3D end milling force coefficients was experimentally verified for a wide range of cutting conditions, and gave significantly better predictions of cutting forces than any other methods. The estimated value of the runout offset also agreed well with the measured value.