序列任务下的重构方案组合优化技术研究

针对单元制造系统的长期稳定运行和提高可实施性的问题，提出了一种采用遗传算法的解决方案。在将企业长期计划分解成多个阶段序列任务的基础上，考虑零件加工工艺、设备加工能力、任务交货期等约束，以最低生产成本、最快完工时间、最佳生产线利用率等优化目标为指导，采用遗传算法对不同时间节点下的制造单元重构方案进行组合优化，实现了制造系统的快速合理重构，导出了设备集合和瓶颈解决方案。最后，通过实例验证了算法的有效性。     

一种适应快速重构的可切换工作台及其自动传动系统设计

可重构模块化机床是可重构制造系统的主要组成部分,其设计方法是实现制造过程可重构的关键。为了及时响应不同加工工艺的变化需求,提出一种可重构机床的模块化工作台设计,工作台可快速切换。同时也为工作台设计了一个自动加工运转流程,解决了因工作台的单方向旋转造成的液压夹具输油管缠绕扯断的问题,使PLC控制与液压传动在自动化生产中能充分结合。该工作台系统采用PLC来控制液压元器件的传动,进而带动相关机械结构的运动,并能在没有故障及人工干预的情况下实现自动循环加工。     

A displacement measurement approach for machine geometric error assessment

It is complicated and time-consuming to evaluate the performance of a machine tool. In this research, a displacement method is proposed to shorten the measurement time and to simplify the measurement. By measuring the positioning errors along the 15 lines in the machine work zone, a total of 21 geometric error components can be determined. Among the 15 lines, seven of them are mandated by the ANSI/ASME standard for the performance evaluation of CNC machining centers. Therefore, only eight additional positioning error measurements are necessary to evaluate the machine's performance. The results from the experimental tests show that the method is feasible and accurate. This method shortens the calibration time and is beneficial, particularly to the reconfigurable machining system, which needs frequent calibration.     

Design Principles for Machining System Configurations

Until recently, mass producers have relied on long serial lines of dedicated machines in order to machine products at high volumes. Today, as the cost of CNC machining centers decreases, more and more high-volume manufacturers are examining the alternative of shorter lines with more machines configured in parallel. This paper presents the main principles for selecting the right machining system configurations. We propose a system classification and show that only symmetric configurations are of interest to industry. We compare four classes of systems: pure serial lines, pure parallel lines, short serial lines arranged in parallel, and short serial lines arranged in parallel with the ability to move products between the lines (i.e., with crossover). Specifically, we compare the different configurations in terms of throughput, line balancing, machine investment cost, and capacity scalability. Finally, we introduce an upgradable multi-spindle reconfigurable machine as a cost-effective alternative for system scalability.     

Development of a hybrid rapid prototyping system using low-cost fused deposition modeling and five-axis machining

Currently, two major processes are being used to produce prototypes, namely machining and rapid prototyping. Machining is generally more accurate and precise, but it is difficult to produce objects with certain complicated features. In contrast, rapid prototyping can produce objects with complicated features, which allows materials to be used more efficiently. However, due to the uneven shrinkage and residual stresses within rapid prototyping products, their accuracy is usually uncertain. This study attempts to integrate these two manufacturing processes and develop a hybrid rapid prototyping system in order to overcome the disadvantages associated with each process and to develop new applications. Fused deposition modeling (FDM) was used as the rapid prototyping process in this work. A spindle and a low-cost FDM extruder were designed to be placed on each end of a rotary axis in a five-axis machine tool. The proposed design allows the rotation of the axis on the five-axis machine to switch between machining and FDM, thus achieving the advantage of reducing costs for extra actuators without sacrificing working space. The case studies demonstrated that the proposed hybrid system can build FDM objects without using support materials and produce FDM parts with metal embedded to increase the stiffness. The system can also conduct five-axis machining on a completed FDM part or trim the freeform surface fabricated by FDM to achieve more accurate dimensions or better surface finish.     

Integration of reconfigurable inspection with stream of variations methodology

This paper describes an advanced closed loop quality control methodology for reconfigurable manufacturing systems. The methodology enables rapid root-cause diagnostics for faster ramp-up of reconfigurable systems through integration of the Reconfigurable Inspection Machine (RIM) and the Stream of Variations (SoV) methodology. The RIM enables reconfigurable, rapid, and accurate inspection using non-contact sensors while the SoV methodology is used to quickly analyze the measurements and identify the root-cause of the errors produced during machining.The feasibility of the industrial concept was experimentally validated. A machining error was introduced during machining of an engine head. Measurement information collected by the RIM was processed and used to locate the root-cause of the error using the SoV methodology.     

Active integration of tool deflection effects in end milling. Part 2. Compensation of tool deflection

This study presents a compensation method in milling machining in order to take into account tool deflection during tool-path generation. Tool deflection that occurs during machining, and especially when flexible tools such as end mills are used, can result in dimensional errors on workpieces. The study presented here is part two of a two-part paper. In part one the cutting force models and the surface prediction method have been presented.Here the focus is on tool deflection effects' integration during the generation of the tool path. A strategy is proposed that modifies the nominal tool trajectory, compensates for the machining errors due to tool deflection, without degrading the production performance and the machined accuracy. The methodology allows optimization of the tool path trajectory in order to achieved a specified tolerance. Some experimental results are presented.     

立式加工中心主轴箱静动态特性分析及拓扑优化

主轴箱是立式加工中心的重要部件，其静动态特性对加工中心的加工精度以及平稳性有重要影响。以某型号立式加工中心主轴箱为研究对象，应用SolidWorks建立主轴箱的三维模型，利用ANSYS Workbench软件对其在典型工况下进行静动态特性分析。根据主轴箱静动态特性分析结果可对主轴箱结构进行优化设计。利用ANSYS Workbench中拓扑优化模块对主轴箱结构进行拓扑优化，根据拓扑优化结果以及实际工作情况，对主轴箱结构进行合理的改进。对比改进前后的分析结果可知:改进后主轴箱质量减少2.3%、最大等效应力减小3.34%，静刚度得到提高,达到优化目的。该研究结果为其他类型机床主轴箱优化设计提供参考     

TiNi形状记忆合金的电火花加工性能

TiNi形状记忆合金由于具有优异的超弹性和形状记忆效应等性能而被大量地应用于工业生产中。然而,形状记忆合金的传统加工相当复杂。因此,研究TiNi形状记忆合金的电火花线切割加工（WEDM）性能。采用L27正交阵列以尽量减少实验。在不同的脉冲持续时间、脉冲关断时间、伺服电压、冲洗压力和线速度条件下进行实验。为同步优化提出一种利用Taguchi设计与实用理念的多响应优化方法。通过对信噪比（S/N）的均值分析和方差分析,确定最佳参数水平。Taguchi分析表明：1μs脉冲持续时间、3.8μs脉冲关断时间、40 V伺服电压、1.8×105Pa冲洗压强和8 m/min线速度,有利于同时使材料去除率最大化和表面粗糙度最小化。TiNi形状记忆合金电火花线切割加工的优化结果表明：脉冲持续时间显著影响材料去除率和表面粗糙度。在较长的脉冲持续时间时,在加工表面可观察到放电坑、微裂纹和重铸层。     

基于软测量的可重构模块机器人分散力/位置控制

在受限空间内,可重构模块机器人末端腕力传感器造价昂贵且易受环境影响,它的使用还提高了机器人在软硬件设计上的复杂程度,针对这一问题,提出了基于软测量的可重构模块机器人分散力/位置控制方法。将可重构模块机器人系统在各个方向上进行模型分解,各方向的模型看作一个子系统,利用自适应RBF神经网络去估计各子系统间的不确定项和耦合关联项。在末端未安装腕力传感器的情况下,利用自适应RBF神经网络去估计末端接触力,并推导出了RBF神经网络的权值、径向基函数中心和宽度的自适应律。2类不同自由度可重构模块机器人的仿真结果验证了所提方法的有效性。     

基于VERICUT二次开发的粗加工数控代码优化

针对航空钛合金结构件数控粗加工效率低、刀具磨损快、加工过程中切削功率变化较大的问题,基于VERICUT软件二次开发技术进行了粗加工数控代码优化的研究,阐明了常规数控代码编制方法存在问题的原因,给出了识别优化位置的算法和不同情况下数控代码优化的计算方法。测试结果表明：优化后的数控代码加工效率明显提高,刀具磨损程度减小,切削功率变化平稳。提出的优化方法为实现大型航空钛合金结构件安全、高效的数控粗加工技术提供了一种新思路。     

Tolerancing for manufacturing via cost minimization

The purpose of dimensioning and tolerancing for process planning is to determine the dimensions and tolerances that are to be produced at each stage in the manufacture of a component in order that the design dimensions and tolerances specified on the engineering drawing of the component are satisfied. Three proposed objective functions for cost minimization are developed in this paper according to various situations. When cost information is available average cost per acceptable unit produced in minimized, otherwise ratio of number of components to be machined to output is minimized. If residual tolerances exist sum of manufactured tolerances are maximized by assigning weights according to their process capabilities. Combining these objective functions a computerized optimization program has been developed which determines the optimum set of dimensions and tolerances which satisfies the specified design dimensions and tolerances and the permissible machining allowances, with the cost of producing all dimensions to the respective tolerances to be minimal.

This system takes into account machining cost, scrap and where in the production process it occurs, manufactured dimensions and their distributions, allocated tolerances and process capabilities.     

Real-time surface interpolator for 3-D parametric surface machining on 3-axis machine tools

The conventional approaches for surface machining use a sequence of straight lines to approximate the part surface. These straight lines are subsequently translated into linear g-codes by a post processor, and then sent to the CNC system. This process limits the surface machining capability of CNC systems. For example, the CNC machine tool can be controlled only to follow these approximated straight lines since the machine loses the surface information. In contrast, this research utilised a real-time approach for 3-D parametric surface machining on 3-axis CNC machine tools. This real-time approach, called CNC surface interpolator, can read surface g-codes and perform surface machining interpolation. The input to the CNC surface interpolator is the surface g-code, which contains geometric information, such as the coefficients of the parametric surface, as well as cutting conditions. This results in better machining feedrate controls, interpolates more precise machining commands, and requires less machining time compared to that produced by off-line approaches.     

基于遗传算法的现场修复机床可重构设计方法的研究

现场修复机床是再制造工程的重要组成部分,其设计是一个多目标优化问题。从机床可重构性角度出发,阐述了现场修复机床设计的基本原理,提出了一种基于遗传算法的现场修复机床设计方法。在此基础上,依据多级模糊综合评价的方法对重构方案的适应性进行评价,以生成最优的机床配置,实现机床在整个生命周期内的可重构。     

Optimization of multiple tuned mass dampers to suppress machine tool chatter

Chatter is more detrimental to machining due to its instability than forced vibrations. This paper presents design and optimal tuning of multiple tuned mass dampers (TMDs) to increase chatter resistance of machine tool structures. Chatter free critical depth of cut of a machine is inversely proportional to the negative real part of frequency response function (FRF) at the tool–workpiece interface. Instead of targeting reduction of magnitude, the negative real part of FRF of the machine is reduced by designing single and multiple TMD systems. The TMDs are designed to have equal masses, and their damping and stiffness values are optimized to improve chatter resistance using minimax numerical optimization algorithm. It is shown that multiple TMDs need more accurate tuning of stiffness and natural frequency of each TMD, but are more robust to uncertainties in damping and input dynamic parameters in comparison with single TMD applications. The proposed tuned damper design and optimization strategy is experimentally illustrated to increase chatter free depth of cuts.     

Concave edge-based part decomposition for hybrid rapid prototyping

As one of the solutions to the limitations of the current layered manufacturing, hybrid rapid prototyping systems that perform both machining and deposition are being introduced. In the hybrid rapid prototyping, a part of a complicated shape is realized by adding layers of a simpler shape, each of which is obtained by machining a sheet of constant thickness from its top and bottom surfaces. Thus it is desired to decompose a given part into the minimum number of layers while guaranteeing each layer to be fabricated from the given sheets using a 3-axis milling machine. To satisfy these requirements, a concave edge-based approach is proposed to decompose a part into layers by considering the tool accessibility, the total number of layers, and the allowable sheet thickness. In this approach, for a given build-up direction, the undercut edges, which cause a part to be inaccessible by a tool, are extracted and classified into two types and eliminated in two decomposition steps.     

电火花加工工艺参数的优化及其应用

论述了在电火花加工中工艺参数对工艺效果的影响关系和目前常用的工艺参数优化的方法。介绍了KBE技术及其在电火花加工工艺参数优化中的应用前景，提出应用KBE技术将为电火花加工的工艺参数优化提供比较完美的解决方案。     

Feedrate scheduling strategies for free-form surfaces

Free-form machining is one of the commonly used manufacturing processes for several industries such as automobile, aerospace, die and mold industries. In 3D complicated free-form surfaces, it is critical, but often difficult, to select applicable cutting conditions to achieve high productivity while maintaining high quality of parts. It is essential to optimize the feedrate in order to improve the machining efficiency of the ball-end milling. Conservative constant feedrate values have been mostly used up to now since there was a lock of physical models and optimization tools for the machining processes.The common approach used in feedrate scheduling is material removal rate (MRR) model. In the MRR based approach, feedrate is inversely proportional to either average or instantaneous volumetric removal rate. Commonly used CAM programs and NC code generators based on only the geometric and volumetric analysis, but they do not concern the physics of the free-form machining process yet. The new approach that is also introduced in this paper is based on the mechanics of the process. In other words, the force-based models in which feedrate is set to values which keep either average or instantaneous machining forces to prescribed values. In this study, both feedrate scheduling strategies are compared theoretically and experimentally for 3D ball-end milling of free-form surfaces. It is shown that MRR based feedrate strategy outputs higher feedrate values compared to force based feedrate strategy. High feedrate values of the MRR strategy increase the cutting forces extensively which can be damaging to the part quality and to the CNC Machine.When the new force based feedrate-scheduling strategy introduced in this paper is used, it is shown that the machining time can be decreased significantly along the tool path. The force-based feedrate scheduling strategy is tested under various cutting conditions and some of the results are presented in the paper.     

面向大规模定制的可重构生产线及其关键技术

分析了大规模定制及可重构制造模式的特点,提出了面向大规模定制的可重构生产线.在阐述了面向大规模定制可重构生产线特性的基础上,构建了面向大规模定制可重构生产线的系统集成框架,研究了面向大规模定制可重构生产线设计中的建模及仿真技术、生产线布局与规划技术、生产线物流自动化技术、生产线的可评价体系、可重构机床设计技术、可重构控制器设计技术、生产控制及管理技术、系统诊断技术等关键技术.     

粗加工过程中进给速度的优化

粗加工进给速度优化是指以最高生产率为目标函数,以最大主功率等为约束条件,按照用户设定的优化参数自动调整不同加工段的进给速度来保持恒定最大主功率状态,从而使单位时间内的材料切除量最大.使用仿真、验证与优化软件VERICUT,可以自动编制带有最佳进给速度的加工程序,减少或避免人工调整进给速度产生的种种问题,大量缩短加工时间.以粗加工为例,对其优化原理进行了探索,初步建立了优化数学模型,并通过典型实例实现了优化.