An innovative strategy for open loop control of hot deformation processes

A new strategy for systematically calculating near optimal control parameters for hot deformation processes is presented in this article. This approach is based on modern control theory and involves deriving state-space models directly from available material behavior and hot deformation process models. Two basic stages of analysis and optimization are established in this strategy for nonlinear, open loop control system design for producing required microstructural characteristics, uniformity of deformation and temperature distribution, and other important physical requirements of hot worked products.     

等离子弧金属快速成型设备控制系统设计

等离子电弧的弧柱温度高于普通电弧焊的两倍,且电弧发散非常小,等离子弧焊接时热影响区非常小,所以利用其进行零件制造时的成型精度高于其他电弧快速成型方法,并且不存在激光、电子束设备造价和使用费用高的缺陷,因此利用等离子弧作为热源进行快速成型制造成为研究热点。根据金属快速成型的主要特点和工艺流程,设计了等离子弧金属快速成型设备控制系统,该控制系统的控制核心为CP1H-PLC,配备了MT8-070i H3触摸屏、OMRON MY2N-J中间继电器单元。采用该设备进行实验,在合适的工艺条件下,成型件达到设计要求,证明该控制系统工作可靠、性能稳定。分析试验结果,初步掌握等离子弧金属快速成型工艺参数。     

Virtual high performance grinding with CBN wheels

The development of future products requires designing, manufacturing, and testing components in a virtual environment before hardware parts are actually made. This paper presents a generalized process simulation and multi-constraint optimization strategy for five-axis grinding with cubic boron nitride (CBN) wheels to increase material removal rates while avoiding process problems such as damage to the machined surfaces and premature wheel failure. The wheel-workpiece engagement conditions under five-axis grinding are extracted from a CAM system by geometrically processing the NC program, the wheel geometry and the part geometry. The interpreted geometric contact data are used in combination with empirical grinding models to predict physical process parameters such as forces, power, heat flux, and temperature. These parameters are then used as the decision variables in a multi-constraint optimization to optimize process parameters such as workspeed to reduce cycle time.     

Parametric process optimization to improve the accuracy of rapid prototyped stereolithography parts

The functional requirements of a rapid prototyping system are speed and accuracy, and they are both functions of vendor defaulted and user selected manufacturing parameters. Accuracy is evaluated by dimensional errors, form errors and surface roughness of manufactured parts. A specially designed specimen with 20 dimensional, geometrical, and surface roughness features has been used in the inspection of RP manufacturing processes. In terms of Taguchi experimental design techniques, an orthogonal array of experiments has been developed which has the least number of experimental runs and desired process parameter settings. Using a 3-D coordinate measuring machine and surface profilometer, a series of measurements in evaluating the SLA parts quality has been conducted to find the functional relationships between the output part quality and input manufacturing process parameters. Two analysis tools, response surface methodology and Analysis of Variance (ANOVA), have been used to evaluate the SLA RP process and to perform the product optimization. The optimal setups of SLA manufacturing parameters for both individual features and a general part with various features have been concluded from this study.     

Form-accuracy analysis and prediction in computer-integrated manufacturing

The manufacturing of high-quality products at low costs is one of the greatest challenges of every company today. Form accuracy is among the quality parameters of machined parts and is directly related to functional performance. Control and improvement of form accuracy is to be performed under the computer-integrated manufacturing (CIM) concept. This paper investigates the form accuracy of mechanical machining and studies the essential aspects and procedures of form-accuracy simulation. The emphases are on the integration of form-accuracy analysis and the simulation into the CIM database construction and virtual manufacturing. Form-accuracy analysis in this paper reveals that the inherent drawbacks in design will directly affect the geometric quality of a workpiece, and proper process planning can enhance the manufacturability of parts with the required geometric quality. The simulation procedure implemented in this paper can be used at the design stage to predict the form accuracy of a machined part and functional performance. The procedure can also be used at the process planning stage to predict and control form accuracy during the machining process.     

梯度功能材料等离子熔积成形过程的Level-Set方法模拟

利用Level-Set方法与有限体积法(finite volume method,FVM)建立梯度功能材料(functionally graded material,FGM)等离子熔积制造(plasma deposition manufacturing,PDM)过程多相混态场统一模型;研究了在不同热输入功率下熔池形貌、温度场与流场以及溶质分布的变化规律.结果表明,热功率是影响梯度功能材料成分分布和性能的重要工艺参数.并用等离子熔积制造方法制备Al2O3-AISI316梯度功能材料,验证了模拟计算结果的正确性和可靠性.     

Preparation of Ti-Mo system functionally graded materials by co-sedimentation

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Study on the inner surface finishing of tubing by magnetic abrasive finishing

With the development of industry manufacturing technology, fine surface finish is in high demand in a wide spectrum of industrial applications. Presently, it is required that the parts used in manufacturing semiconductors, atomic energy parts, medical instruments and aerospace components have a very precise surface roughness. Amongst them, vacuum tubes, wave guides and sanitary tubes are difficult to polish by conventional finishing methods such as lapping, because of their shapes. The surface roughness of these tubes affects the performance of the entire system, but the finishing technology for these tubes is very scant in manufacturing fields. This project was proposed by a Shanghai Far East pharmaceutial and mechanical factory. They stated that the roughness of the inner surface must be less than 0.3 μm Ra after finishing. An internal magnetic abrasive finishing (MAF) process is proposed for producing highly finished inner surfaces of tubes used in this study. The process principle and the finishing characteristics of unbounded magnetic abrasive within internal tubing finishing are described first. MAF setup was designed for finishing three kinds of materials tubing, such as Ly12 aluminum alloy, 316L stainless steel and H62 brass. Experimental results indicated that finishing parameters such as polishing speed, magnetic abrasive supply, abrasive material, magnetic abrasive manufacturing process and grain size have critical effects on the material removal rate (MRR). How the inner surface micro shape changes course during finishing of an aluminous tube is demonstrated.     

梯度功能材料研究与应用

介绍了近年来梯度功能材料（ＦＧＭ）国外发展动态,较详细叙述了梯度功能材料制和协方法,如化学气相沉积法（ＣＶＤ）,放电等离子烧结法（ＳＰＳ）,复合离心铸造法（ＣＤＣ）等工艺方法,并介绍了样度磁性材料、封接合金、刀具材料及生体材料的制备、性能、特点及应用。     

Thermal process simulation of droplet based metal printing with aluminium

Droplet based additive manufacturing is a branch of novel processes to build full dense metal parts by adding material droplet by droplet on a build platform. As each droplet solidifies individually upon contact, the quality of bonding to the existing material is determined by the adjacent surface temperatures and the temperature of the arriving droplet. To design a manufacturing process that ensures good bonds between all droplets, it is necessary to understand the relations between process parameters, the part’s geometry and thermal conditions for each arriving droplet. This paper presents a thermal simulation model that is based on Flow 3D software. By adding a user routine to the solver, it is possible to simulate the building process of a part consisting of several thousand droplets with an acceptable effort. This simulation is used to study the effect of production parameters (substrate temperature, droplet temperature and deposition frequency) as well as the parts geometry (layer size and height) on the resultant temperature field. The model was successfully validated with experimental data and can deliver valuable information during further development of this additive manufacturing process.     

模具CAPP系统研究与探讨

在分析CAPP技术现状及发展趋势的基础上,结合模具零件加工工艺设计现状和存在的问题,提出了面向模具制造的CAPP系统的总体框架结构及各功能模块主要实现功能,编制了模具CAPP系统基础支撑软件——面向模具制造的工艺数据库管理系统,开发了模具结构件和标准件典型工艺检索系统和模具成形零件工艺生成系统。     

Numerical analysis of the process chain for the production of PM components with integrated information storage

The powder metallurgical production offers a number of advantages compared to other manufacturing technologies. A few examples are the high level of material utilization, the production of net-shape parts and an extensive amount of alloying options. This paper describes the production process to integrate component relevant information in the component to increase its functional range. The analysis of the production process is done by means of numerical simulation. Therefore, the process chain, consisting of die pressing and sintering, is modeled based on a finite-element-analysis.     

A study of the microstructural evolution during selective laser melting of Ti–6Al–4V

Selective laser melting (SLM) is an additive manufacturing technique in which functional, complex parts can be created directly by selectively melting layers of powder. This process is characterized by highly localized high heat inputs during very short interaction times and will therefore significantly affect the microstructure. In this research, the development of the microstructure of the Ti–6Al–4V alloy processed by SLM and the influence of the scanning parameters and scanning strategy on this microstructure are studied by light optical microscopy. The martensitic phase is present, and due to the occurrence of epitaxial growth, elongated grains emerge. The direction of these grains is directly related to the process parameters. At high heat inputs it was also found that the intermetallic phase Ti₃Al is precipitated during the process.     

Investigation of the coating thickness of plasma-transferred arc deposition welded and cross wedge rolled hybrid parts

Most of today’s technical parts and components are made of monolithic materials. These mono-material components produced in established production processes reach their limits due to their respective material characteristics. Thus, a significant increase in production quality and efficiency can only be achieved by combining different materials in one part. Bulk forming of previously joined semi-finished products to net shape hybrid components that consist of two different materials is a promising method to produce parts with locally optimized characteristics. This new production process chain offers a number of advantages compared to conventional manufacturing technologies. Examples are the production of specific load-adapted forged parts with a high level of material utilization, an improvement of the joining zone caused by the following forming process and an easy to implement joining process due to the simple geometries of the semi-finished products. This paper describes the production process of hybrid steel parts, produced by combining a plasma-transferred arc deposition welding process with a subsequent cross wedge rolling process. This innovative process chain enables the production of hybrid parts. To evaluate the developed process chain, coating thickness of the billet is analysed before and after cross wedge rolling. It could be shown, that the forming process leads to an improvement of the coating, meaning a more homogeneous distribution along the main axis.     

The inverse of material properties of functionally graded pipes using the dispersion of guided waves and an artificial neural network

Using guided circumferential wave dispersion characteristics, an inverse method based on artificial neural network (ANN) is presented to determine the material properties of functionally graded material (FGM) pipes. The group velocities of lowest modes at six lower frequencies are used as the inputs of the ANN model. The distribution function of the volume fraction of the FGM pipe is fitted to a polynomial, then the outputs of the ANN are the coefficients of the fitting polynomial. The Legendre polynomial method is employed as the forward solver to calculate the dispersion curves for the FGM pipe. Levenberg–Marquardt algorithm is used as numerical optimization to speed up the training process of the ANN model.     

基于双NURBS曲线的叶轮叶片工业机器人GMAW增材制造

以双NURBS曲线获得的直纹面广泛存在于各行业复杂零件中,如何实现复杂直纹面的增材制造一直是增材制造领域中极为关心的问题。以双NURBS曲线描述叶片模型,进一步获得直纹面,采用优化工艺参数,以GMAW方法实现了叶轮叶片的增材制造,增材获得的叶片完整,成形良好,表明以GMAW工艺实现双NURBS曲线叶片增材制造是可行的。为叶片模型构建、复杂形状叶片的电弧增材制造提供了新方法,对复杂形状零件增材制造过程控制具有借鉴意义。     

Interactive surface modelling, an implementation of an expert system for specification of surface roughness and topography

Making roughness a useful tool for obtaining optimally functional surfaces demands a high quality foundation for surface specifications. Erroneous specifications in many cases lead to costly production and perhaps nonfunctional surfaces. The Interactive Surface Modelling system, ISM, presented in this paper, addresses those problems with an approach where functional demands control the route from specification of parameters through manufacturing preparation to measurement of the machined surface. Here, the operator, be it the designer, the production engineer, or the quality control engineer, can interactively reason with the system to reach a suitable specification with the aid of integrated software in a PC-Windows environment controlled by an expert system software. The representation of the surface's 3D geometry then is a natural component. The access to depiction and literature references and standards is implemented together with the ability to serve the user with graphic feedback by generating synthetic surfaces from the specification made. The described features have been implemented in a prototype developed in cooperation between Volvo and Chalmers on two functional surfaces: cylinder liners and synthetic leather for the automotive industry. Problems with specifying correct roughness and topography actually have emerged when changes have been made of material or manufacturing process for an old and proven product. This has shown that knowledge is missing or incomplete about proper intervals for roughness parameter values for definition of the relationship between a surface's function and its parameters . The result is misunderstandings and errors. By letting ISM be a base for continuous updating and modification of knowledge, opportunities will be created for increased quality of surface roughness specifications through this systematic approach to the complex, expanding field of Surface Roughness and Surface Topography.     

板冲锻成形新工艺及其在轿车飞轮盘加工中的应用

该文提出一种新的冲锻复合塑性加工方法,来成形中空且厚差较大的板材零件或者管材零件。其特点是以冲压工序成形出空间形状,并在需要的部位储备金属,随后的锻造工序对该部位压缩增厚,从而得到大厚差整体塑性成形件。并以轿车飞轮盘为实例,进行了有限元分析与试验研究,结果显示,采用该方法进行零件加工,降低了对设备吨位的要求,材料的利用率、加工效率以及零件质量大大提高。     

An approach to selection of material and manufacturing processes for rocket motor cases using weighted performance index

Material selection is a very critical design decision, which has a profound influence on the entire development program for rocket motor cases. In the selection process, the main performance parameters and the most appropriate fabrication technology with proven processes must be considered. Many years of practical experience in material selection process with a thorough understanding of materials behavior under various loading environments and hands-on experiences with various available manufacturing processes are of immense help to the design and development engineer for successful completion of the development program. In this paper, an attempt has been made to present an approach for selecting appropriate material and manufacturing process for rocket motor case based on method of Weighted Performance Index (WPI) with the hope that this approach will also provide additional aid to the design engineer for the selection of material and manufacturing process for rocket motor cases. In this method, different properties are assigned a certain weight depending upon their importance to the service requirements. Different properties are normalized using a scaling factor, and finally a weighted property index is computed. The material that scored the maximum numerical value is chosen as the material for fabrication. This approach closely matches with the actual performance. Maraging steel and D6AC are found to be the preferred materials for rocket motor cases for critical missions. HSLA steels are appropriate for less-critical applications, in which rocket motor cases are required in very large numbers (e.g., flow-formed AISI 4130 motor cases^[8]). For the selection of an appropriate manufacturing method, the major parameters considered are dimensional accuracy, cost of production, minimum material waste, and flexibility in design. Again, these properties are given a relative grading, which is then converted into a scaled property. Finally, the weighted performance indices are estimated. The flow-forming method has emerged as the manufacturing method of choice for motor tubes.