数字制造环境下的加工过程仿真验证技术研究

生产线数字制造环境是数字化工厂的核心 ,而加工过程的仿真与验证技术构成生产线数字系统的底层结构与制造过程数字化分析的主要内容。分析了目前加工过程在几何仿真与物理仿真方面的研究情况、研究方法与存在问题 ,就该项技术向生产线数字制造环境融合的关键技术 ,即综合设备数字样机的完整数字加工环境的建立及加工过程仿真与上层制造环境的信息集成等进行分析与研究

串并联数控机床的作业空间分析

鉴于并联机床普遍存在有效作业空间小、运动控制复杂和实用刚度还不理想等不足．采用了串并联混合式机床运动结构．针对所研究的4—4构型串并联机床,分析了影响作业性能的几何约束条件,采用基于位置逆解模型的极限边界数值搜索法,确定了机床作业空间,并通过数值仿真研究获得了机床运动参数和结构参数对作业空间的影响规律，为优化机床结构尺寸以获得尽可能大的有效作业空间奠定了基础。

微机器人技术在超精密加工中的应用研究

文中阐述了超精密加工技术的发展现状及实现方法。通过介绍微机器人技术在超精密加工中的具体应用,论证了微机器人技术在超精密加工及精密工程中的应用价值。

基于三角网格曲面模型的刀位轨迹计算方法

离散三角网格模型在CAD/CAM中应用很广,但针对该模型的刀位轨迹自动生成算法并不多见。在正确重建网格模型的拓扑关系基础上,给出了新的曲面几何特性分析方法,并提出了具有特色的精确的刀位轨迹计算方法,克服了直接由网格模型求交计算刀位方式存在的精度问题。测试结果显示,该方法简捷、可靠,能够达到实用化要求,并显著提高了刀位计算精度和加工效果。

虚拟数控车削物理仿真系统的研究与开发

面向数控车削 ,开发了一套动态车削物理仿真系统 ,提出了仿真系统的总体框架 ,建立了动态物理仿真模型及相关子模型 ,分析了动态车削过程的影响因素 ,阐述了系统开发过程中有关模型构成及工件数据描述等技术性问题。

加工过程物理仿真技术研究

加工过程仿真是虚拟制造的底层关键技术 ,同时也是数字化制造系统的重要组成部分 ,而物理仿真是其中的研究重点和难点。建模难 ,通用性和实用性差是目前物理仿真中存在的主要问题。文章总结了物理仿真的研究内容和方法 ,分析了研究中存在的问题及加工过程建模的常用方法

“虚工件”法——提高柔性制造设备生产率和柔性的一种新方法

通常,在一台带有托板输送系统的柔性制造设备(如柔性制造单元)上一次在托板上只装夹一个零件进行加工。“虚工件”法是指在一个托板上装多个相同或不同的零件,将它们视为一个零件投入设备中,用对各零件的NC 程序进行相关处理后得到的 NC 新程序进行加工。应用这种方法可以提高生产率,提高柔性并有利于均衡生产。分析了应用“虚工件”法的一些限制条件及其技术实施中的苦干技术关键.

快速成型技术中分层算法的研究与进展

根据对零件制造精度和效率的关注程度的不同,开发出了多种分层算法。在同等加工时间的情况下,根据加工精度的不同,将这些分层算法分为等层厚分层算法和适应性分层算法两类。通过对STL模型、原始CAD模型和点云数据的分析,讨论了两类分层算法的研究和发展,然后介绍了斜边分层算法和曲面分层算法等先进分层算法的原理和成果,最后讨论了快速成型分层算法的研究方向和趋势。

精密复杂曲面重构与多轴数控加工刀位规划策略

数控加工作为现代制造中的标志性加工技术，在航空航天、运载工具、动力装备等领域的精密复杂型面加工中占据着主导地位。随着国内高速数控加工中心及高档数控机床等硬件设备的日趋成熟和普及，围绕高速数控加工的一些深层次问题便逐步显现出来，这突出表现在数控机床的高速加工特性与传统加工方法之间的矛盾。本文将主要围绕复杂型面高速数控加工中的两大关键技术：曲面造型技术与刀位规划策略，展开论述，着重解决其中的一些关键科学问题，以期为复杂型面的高速数控加工提供新的技术支持。 1. 以罐车曲面重构为例，详细论述了从不完整散乱数据到曲面精确重构的整个过程，着重解决了自由曲面重构理论在实际应用中遇到的一些问题。针对不完整散乱数据，提出一种散乱数据的有序化处理方法，同时给出了面向NURBS的数据自动参数化策略，用于构造罐车的系列截面轮廓线。然后以曲面蒙皮操作为基础实现罐车曲面的快速重构。最后利用参数曲面的离散表达，完成罐车容积的快速检定并借以验证罐车曲面重建的精确性。 2. 以Bézier曲线/曲面为基础，运用多元Bernstein多项式算术运算，将点到复杂曲线/曲面最近点的计算转化为Bernstein多项式方程的求解，进而基于Bernstein基函数的线性精度性质，给出一种新的最近点计算模型。然后通过de Casteljau快速分割算法和二叉/四叉树递归分解的搜索策略寻找最近点。该方法可以有效避免繁琐的迭代计算和对初始值的选择，并从计算效率入手，对其加以改进，成功实现了分割算法与Newton-Raphson方法的融合。再利用B样条曲线/曲面与Bézier曲线/曲面之间成熟的转换算法，将所提出的方法进一步推广到应用更为广泛的B样条曲线/曲面。 3. 通过对刀具轨迹有效性的分析，将刀具轨迹规划分为曲面上曲线族的选择和有效合理排布方式的设计两个方面，为刀具轨迹规划提供了新的设计思路。并以此为基础，对最优刀具轨迹的定义进行了重新阐述，指出今后刀具轨迹规划的研究必须综合考虑轨迹的几何、刀具的运动以及机床的动力学特性。 4. 针对数控加工中心高速加工特性，提出一种等参数螺旋轨迹生成方法。该方法以减少抬刀和路径转接为目的，并综合考虑刀具轨迹几何与运动力学性能，特别适合自由曲面的高速数控加工。同时，在刀具路径的链接、误差分析等方面，也提出了一些颇具特色的方法，从而避免了传统偏置轨迹繁琐的自交干涉检测，能够有效抑制刀具负载的波动，减小刀具的磨损。 5. 在正确重建网格模型拓扑关系的基础上，从离散微分几何学这一新的角度入手，给出了一种新的三角网格曲面微分几何特性分析方法，进而以参数曲面上曲线偏置方法为基础，结合三角网格曲面的拓扑结构和局部区域的精确拟合，建立了网格曲面上的曲线偏置模型，并将计算最近点的方法进一步推广用来计算曲面上的偏置点，从而避免了繁琐的迭代计算。以此为基础，对网格模型的边界轮廓进行等残留偏置，给出了网格曲面上的等残留刀具轨迹生成方法。可进一步利用螺旋线连接各条轨迹，生成更为光滑刀具路径。

Uncertainty analysis to minimise risk in designing micro-electronics manufacturing processes

A design methodology based on numerical modelling, integrated with optimisation techniques and statistical methods, to aid the process control of micro and nano-electronics based manufacturing processes is presented in this paper. The design methodology is demonstrated for a micro-machining process called Focused Ion Beam (FIB). This process has been modelled to help understand how a pre-defined geometry of micro- and nano- structures can be achieved using this technology. The process performance is characterised on the basis of developed Reduced Order Models (ROM) and are generated using results from a mathematical model of the Focused Ion Beam and Design of Experiment (DoE) methods. Two ion beam sources, Argon and Gallium ions, have been used to compare and quantify the process variable uncertainties that can be observed during the milling process. The evaluations of the process performance takes into account the uncertainties and variations of the process variables and are used to identify their impact on the reliability and quality of the fabricated structure. An optimisation based design task is to identify the optimal process conditions, by varying the process variables, so that certain quality objectives and requirements are achieved and imposed constraints are satisfied. The software tools used and developed to demonstrate the design methodology are also presented.

Modelling and prototyping the conceptual design of 3D CMM micro-probe

This paper details the prototyping of a novel three axial micro probe based on utilisation of piezoelectric sensors and actuators for true three dimensional metrology and measurements at micro- and nanometre scale. Computational mechanics is used first to model and simulate the performance of the conceptual design of the micro-probe. Piezoelectric analysis is conducted to understand performance of three different materials - silicon, glassy carbon, and nickel - and the effect of load parameters (amplitude, frequency, phase angle) on the magnitude of vibrations. Simulations are also used to compare several design options for layout of the lead zirconium titanate (PZT) sensors and to identify the most feasible from fabrication point of view design. The material options for the realisation of the device have been also tested. Direct laser machining was selected as the primary means of production. It is found that a Yb MOPA based fiber laser was capable of providing the necessary precision on glassy carbon (GC), although machining trials on Si and Ni were less successful due to residual thermal effects.To provide the active and sensing elements on the flexures of the probe, PZT thick films are developed and deposited at low temperatures (Lt720 degC) allowing a high quality functional ceramic to be directly integrated with selected materials. Characterisation of the materials has shown that the film has a homogenous and small pore microstructure.

Optimisation methodology for risk mitigation in advanced micro-system electronics manufacturing

This paper presents a design methodology based on numerical modelling, integrated with optimisation techniques and statistical methods, to aid the development of new advanced technologies in the area of micro and nano systems. The design methodology is demonstrated for a micro-machining process called Focused Ion Beam (FIB). This process has been modelled to provide knowledge of how a pre-defined geometry can be achieved through this direct milling. The geometry characterisation is obtained using a Reduced Order Models (ROM), generated from the results of a mathematical model of the Focused Ion Beam, and Design of Experiment (DoE) methods. In this work, the focus is on the design flow methodology which includes an approach on how to include process parameter uncertainties into the process optimisation modelling framework. A discussion on the impact of the process parameters, and their variations, on the quality and performance of the fabricated structure is also presented. The design task is to identify the optimal process conditions, by altering the process parameters, so that certain reliability and confidence of the application is achieved and the imposed constraints are satisfied. The software tools used and developed to demonstrate the design methodology are also presented.

Manufacturing knowledge verification in design support systems

This paper identifies the need for a verification methodology for manufacturing knowledge in design support systems; and proposes a suitable methodology based on the concept of ontological commitment and the PSL ontology (ISO/CD18629). The use of the verification procedures within an overall system development methodology is examined, and an understanding of how various categories of manufacturing knowledge (typical to design support systems) map onto the PSL ontology is developed. This work is also supported by case study material from industrial situations, including the casting and machining of metallic components. The PSL ontology was found to support the verification of most categories of manufacturing knowledge, and was shown to be particularly suited to process planning representations. Additional concepts and verification procedures were however needed to verify relationships between products and manufacturing processes. Suitable representational concepts and verification procedures were therefore developed, and integrated into the proposed knowledge verification methodology.

Experimental validation of the performance of a microreactor for the high-throughput screening of catalytic coatings

In this paper, the results of computational fluid dynamics simulations of flow, temperature, and concentration distributions used in the design of a microreactor for the high-throughput screening of catalytic coatings (Mies et al., Chem. Eng. J. 2004, 101, 225) are compared with experimental data, and good agreement is obtained in all cases. The experimental results on flow distribution were obtained from laser Doppler anemometry measurements in the range of Reynolds numbers from 6 to 113. The measured flow nonuniformity in the separate reactor compartments was below 2%. The temperature distribution was obtained from thermocouple measurements. The temperature nonuniformity between the reactor compartments was below 3 K at a maximum heat production rate of 1.3 W in ethylene oxidation at 425 degrees C over CuO/Al2O3/Al coatings. With respect to concentration gradients, a deviation from the average rate of reaction of only 2.3% was obtained at realistic process conditions in the ethylene ammoxidation process over identical Co-ZSM-5 coatings in all reactor compartments. The cross talking noise between separate compartments does not exceed 0.1% when the reactor parts have a smooth surface finish. This illustrates the importance of ultraprecision machining of surfaces in microtechnology, when interfaces cannot be avoided.