Development of optimum process design system by numerical simulation

Now, the development of optimum forming process design system based on computer simulation to reduce the time consumption is strongly required in the industries. In this study, the optimum process design system is newly developed in conjunction with the nonlinear FEA code and the nonlinear optimization code. In the latter code, “Sweeping Simplex Method” is newly proposed, which can find the global minimum. The accuracy and quickness of this method to find the global minimum of objective function, which have several local minimum points, is confirmed by comparison with the grid method.

This numerical system is applied to the process design of complicate shaped cup deep drawing. In order to form the sheet metal with uniform thickness, “Deviation of thickness from uniform average thickness” is employed as the objective function, and the global minimum point in the design variable space is searched by “Sweeping Simplex Method”. For the design variables, the heights of two punches in first stage forming are employed. The optimum process condition was determined by using this numerical code and also the validity of this code was confirmed by the comparison with the experimental observation results.     

Rapid design of corner restraining force in deep drawn rectangular parts

With the development of finite element method and computer technology, the complete modeling of the forming of a 3D sheet metal part is becoming realistic. However, an accurate 3D simulation is usually too time-consuming to be used in the early stage of design. One solution is to model the straight side of a 3D part as a plane strain problem and the corner section as an axisymmetric problem. Unfortunately, the axisymmetric solution often over-predicts the severity of the deformation at the corner and leads to a very conservative design. In this study, a modified axisymmetric model with a center offset is proposed to predict tearing failure in the corner sections of 3D parts. The proposed offset is found to be a function of the center strains, failure height, and tooling/process parameters, including tooling geometry, material properties, friction coefficient, and restraining force provided by the binder. Finite element analyses of both 3D and 2D axisymmetric models for square and rectangular cup forming are utilized to verify the proposed concept and to define the function. Excellent predictions of the failure heights are obtained. The proposed model enables engineers to rapidly specify the right amount of the restraining force in the corner section based on the desired center strains and forming depth. A detailed design algorithm is provided.     

Optimum cooling system design of a free-form injection mold using an abductive network

This study uses the cooling system as the major control parameter to achieve an optimal design for a simulated injection-mold model. In this investigation, once the cooling system parameters, i.e. cooling channel diameters, cooling channel spacing and cooling line equations, are given, the product performance (warpage) can be predicted accurately by the developed abductive network model.To begin, the injection-mold part-line of the parameter equation is formulated by the abductive network method to limit the number of parameters in the cooling system. The optimal cooling system parameters can then be reached through a simulated annealing (SA) optimization algorithm with a performance index to obtain perfect parts.     

A fuzzy expert system for the design of machining operations

In this paper, a fuzzy expert system called Smart Assistant to Machinist, or SAM, is introduced. The system consists of four modules: a database, a cutter selection module, a cutting condition design module and a learning module. The database consists of four data files: work material data file, machine tool data file, machining plan data file (which defines desirable material removal rate, surface finish, cutting speed, feed, depth of cut, etc.) and cutter data file. The cutter selection module is developed based on fuzzy logic, in which the cutter selection is conducted in three steps. First, the input information is “fuzzyized” Next, using the fuzzy correlation functions, cutter grades and cutters are selected. Then, the selected grades and cutters are searched against the cutter data file to check the availability. The cutting condition design module is developed based on fuzzy non-linear programming and user interactive graphics. The learning module is developed so that users can fine-tune the fuzzy functions to further improve the performance of the system. The system has two distinct features: (1) it can select cutters and design cutting conditions based on partial and imprecise information, and (2) it selects commercial cutter products used on shop floors. The use of the system is demonstrated using two examples.     

介绍一种多工位级进模的设计

介绍了一种生产材料薄，尺寸小、尺寸精度要求高的电位器零件的多工位级模设计实例。对该制件的冲压工艺性，经济性，排样方案及模具结构进行了分析。     

小型移动焊接机器人结构设计

针对狭窄空间自动焊接问题,设计了一种小型移动焊接机器人机构.根据机器人结构的运动特点,运用模块化设计方法,把机器人机构分为轮式移动平台、焊炬调节机构和电弧传感器三部分.其中,轮式移动平台采用三轮式差速驱动结构形式,底部安装一可调磁吸附力装置,且控制器集成于移动平台上;焊炬调节机构由十字滑块和焊炬连接装置组成,十字滑块由两电机分别驱动,实现焊缝水平和高低方向精确跟踪;电弧传感器采用圆锥摆形式,且与焊枪设计成一体,使用方便.同时,建立机器人运动学方程,并对直角焊缝不同的转弯中心进行分析,确定水平滑块的行程参数,为机器人的焊缝跟踪控制提供参考.结果表明,该机器人机构满足弯曲焊缝跟踪要求,焊接质量良好.     

Prediction of surface roughness profiles for milled surfaces using an artificial neural network and fractal geometry approach

Artificial neural networks (ANNs) models were developed for the analysis and prediction of the relationship between the cutting conditions and the corresponding fractal parameters of machined surfaces in face milling operation. These models can help manufacturers to determine the appropriate cutting conditions, in order to achieve specific surface roughness profile geometry, and hence achieve the desired tribological performance (e.g. friction and wear) between the contacting surfaces. The input parameters of the “ANNs” models are the cutting parameters: rotational speed, feed, depth of cut, pre-tool flank wear and vibration level. The output parameters of the model are the corresponding calculated fractal parameters: fractal dimension “D” and vertical scaling parameter “G”. The model consists of three-layered feed-forward back-propagation neural network. ANNs models were utilized successfully for modeling and predicting the fractal parameters “D” and “G” in face milling operations. Moreover, W–M fractal function was integrated with the developed ANNs models in order to generate an artificially fractal predicted profiles at different cutting conditions. The predicted profiles were found statistically similar to the actual measured profiles of test specimens.     

加油口冲压工艺设计

通过对圆筒形零件拉深工艺与缩口工艺的对照比较,介绍该零件成形的工艺方案及实验过程。阐述了缩口成形工艺的成形特点,根据成形前后材料体积不变的原则,利用积分计算管子的缩口毛坯高度。并对模具设计与制造中存在的关键技术进行了研究分析。实现了用简单的缩口模具,生产出了合格零件。该模具不仅能保证工艺稳定,而且提高材料利用率和生产效率。因此,对细长的管状类零件,有时用缩口工艺代替拉深工艺可取得更好的效果。     

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.     

T-shape upsetting–extruding test for evaluating friction conditions during rib–web part forming

Since the deformation features of existing friction testing methods are not as similar as those of the closed die forging process of rib–web parts, the friction conditions evaluated by these methods are not consistent with the actual situation. In this paper, a new friction testing method, the T-shape upsetting–extruding process employing a rectangular blank, is proposed for evaluating the friction conditions during rib–web part forming process. It was found that rib height and the web width are both sensitive to friction conditions. Therefore, the ratio of rib height to web width was chosen as a criterion for friction evaluation. With the utilization of a commercial FEM program, DEFORM, the effects of the geometrical parameters and testing variables on the friction sensitivity were investigated, and the friction conditions between different interfaces were analyzed. In order to verify the proposed method, friction factors of a water-based graphite lubricant measured by three different methods (the proposed one, the ring compression test and the double-cup extrusion test) at 723 K were used to simulate the isothermal deformation process of a cross-rib part. The experimental results suggest that the proposed method is more accurate than the other two methods for rib–web part forming process.     

Direct laser fabrication of thin-walled metal parts under open-loop control

Direct laser fabrication (DLF) is an advanced manufacturing technology, which can build full density metal parts directly from CAD files without using any modules or tools. The investigation on the fabrication of thin-walled parts of nickel alloy using open-loop DLF process is introduced in this paper. The experimental setup consisted of a CO₂ laser, a 3-axis CNC table, a coaxial powder nozzle and a powder recycler. The 3D-CAD file of a thin-walled metal part was converted into the STL file format and imported into software HUST-RP to generate ‘pseudo-random’ scanning paths of laser beam. The influence of process parameters on the build height of thin-walled metal parts was studied by 1–10 layered single-bead stacks of nickel alloy. The result shows that the interference factors which affect the build height of thin-walled metal parts occur randomly during the process. For open-loop DLF process, thin-walled metal parts can achieve much better shape quality if the process parameters are suitable. Multilayer single-bead walls were built up with different scanning velocity to obtain the optimal process parameters of thin-walled parts of nickel alloy. It shows that thin walls of nickel alloy with uniform height can be built up layer by layer in a certain range of specific energy. However, it is difficult to control the build height of complex thin-walled metal parts in an accurate manner just using optimal parameters. A special coaxial powder nozzle was designed in this paper. In a certain range, the deposition thickness of the nozzle is nearly linearly increased with increase in the standoff distance between the powder focusing point of the nozzle and the deposition substrate. By means of the nozzle, a novel method to control the build height of thin-walled metal parts using open-loop DLF process was introduced. The difference in build height of a thin-walled part can be compensated automatically in one or several layers during the process. It is proved that the build height of a thin-walled metal part can be accurately controlled in theory using the nozzle. A complex single-bead part of nickel alloy whose geometry was designed to be the well-known Chinese ‘FU’ was fabricated and explained in this paper. The result shows that the shape quality of the sample is quite good, and actual build height of the sample is 53.54 mm while the designed value is 54 mm.     

精密级进模工作零件关联性设计研究

针对IT制件精密级进模工作零件设计非标准化问题,通过运用关联设计、面向对象方法和参数化技术建立了工作零件的特征结构模型和参数化驱动模型,并以AutoCAD2002为平台,开发出相应的CAD系统,实现了凸模、凹模镶块和卸料板镶块的关联性设计,提高了工作零件设计效率和质量。     

Optimal grey-fuzzy controller design for a constant turning force system

In this paper the grey-fuzzy control scheme is proposed to control the turning process with constant cutting force under various cutting conditions. The grey-fuzzy control scheme consists of two parts: the grey predictor and the fuzzy logic controller. When we use the grey-fuzzy control scheme to design the constant turning force system, it is necessary to adjust the control parameters of both the grey predictor and the fuzzy controller (i.e., the sample size and grey constants of the grey predictor, and the scaling factors of the fuzzy controller) for guaranteeing stability and obtaining optimal control performances. Therefore, in order to search for the optimal control parameters by way of systematic reasoning instead of the time-consuming trial-and-error procedure, in this paper the Taguchi method is applied to search for the optimal control parameters of both the grey predictor and the fuzzy controller such that the grey-fuzzy controller is an optimal controller. Computer simulations are performed to verify the effectiveness of the above optimal grey-fuzzy control scheme designed by the Taguchi method. It is shown that satisfactory performances have been achieved by the optimal grey-fuzzy control scheme designed in this way.     

Conceptual manufacturing system design based on early product information

This paper presents a new approach for the conceptual design of manufacturing systems based on early product information supported by model-based systems engineering. The approach consists of three parts: First, an integrated process model for product design and manufacturing systems planning, second, a systematic method for the conceptual design of manufacturing systems based on early product information, and third, a modelling approach based on a common design language for the collaboration between product design and manufacturing systems planning. The proposed approach is validated using an example from the automotive industry.     

Expansion and reduction of thin-walled tubes using a die: Experimental and theoretical investigation

The production of sound thin-walled tubular parts by expansion and reduction using a die is generally limited to components having geometrical features within a compact range. Basic design rules, providing the geometrical and material parameters that govern the process, are mainly derived from the accumulated experience of both manufacturers of tubular parts and suppliers of machine-tools. However, no information is generally available on the influence of interface friction on material flow and on the effect of material damage and strain path on the occurrence of fracture, wrinkling and local buckling. The aim of this paper is to refresh and extend the fundamentals of tube expansion and reduction using a die by means of a comprehensive theoretical and experimental investigation. The emphasis is focused on understanding modes of deformation and on establishing formability principles for the benefit of those who design tubular parts in daily practice. The theoretical investigation is accomplished by the utilization of virtual prototyping modelling techniques based on the finite element method and the experimental work is mainly utilized for supporting and validating the theoretical investigation.     

基于UG的铝型材挤压分流模设计KBE系统

结合铝型材挤压特点,将KBE系统引入型材挤压分流模设计中,在基于知识工程的铝型材挤压分流模智能设计系统框架内,将铝型材挤压分流模设计知识通过UG系统用户界面实现同分流模几何特征构建的搭接。系统是以UG NX为CAD/CAE开发平台,以VC++、UG/API、UG/GRIP等为编程开发语言环境,以工程实际经验及专家知识为分流模设计指导,并综合运用UG多种二次开发手段开发各个功能模块,包含零件管理信息、材料分析、截面特征、挤压工艺参数确定、模具结构设计、模具强度校核以及模具其他尺寸设计。系统的开发是KBE与CAX系统融合的一次有益尝试,对于挤压分流模KBE及计算机辅助设计具有积极的推广作用。     

汽车覆盖件双动拉深模参数化设计中的概念设计

针对目前国内模具CAD结构设计效率低下而专用模具CAD软件适用面过窄的情况,以模具零部件间的尺寸链表为核心,用变参的方法开发汽车覆盖件双动拉深模具参数化设计系统,并完成了其中的概念设计部分,不仅降低了常规模具CAD系统的开发难度,而且极大地提高了模具设计效率。     

Internal inversion of thin-walled tubes using a die: experimental and theoretical investigation

The design of sound double-walled tubular parts by external inversion using a die is presently well established. Major parameters are identified, the influence of lubrication is sufficiently well understood and the typical modes of deformation that may occur during the forming process are fully characterized. In contrast to external inversion, there are almost no published works that comprehensively cover the conception of double-walled tubular parts by internal inversion using a die.This paper draws from fundamental research on the internal inversion of thin-walled tubes using a die to the establishment of formability diagrams in terms of the major process parameters. Fundamental research is based on a comprehensive theoretical and experimental investigation of a wide range of subjects, such as: development of plastic instability modes (local buckling), thickening of the tube-wall and occurrence of wrinkling phenomena at the free curved end of the inwardly inverted tubes. The influence of the frictional conditions prevailing at the contact interface between the tube and the die is also examined. The theoretical investigation is supported by numerical predictions based on the finite element flow formulation and the overall methodology is assessed by means of experimental tests on industrial Al6060 Aluminium alloy tubes (annealed and naturally aged) under laboratory-controlled conditions.     

Manufacturing feature-based cost estimation of cast parts

Seventy percent of new product cost is committed in the design phase. Therefore, the cost needs to be minimized. Incorporating accurate cost estimation capabilities into manufacturing processes can help industries to minimize the cost and optimize the design. The casting process has been employed as a key process to manufacture parts having the advantage of low cost and customized products in foundry industry. This paper presents a cost estimation system for the casting process based on the design features, which incorporates the casting information at the design stage of castings. It aims to deliver the best cost-effective choice for casting design features of a product. Two kinds of knowledge, namely economical knowledge(describing the relation between the casting design considerations and the cost) and technical knowledge(involving the material of the casting features) were structured in this research work. On the basis of the minimum product cost, casting material selection can be carried out in detail. The developed system has been validated through an industrial case study.     

细长轴楔横轧模具设计及仿真实验

细长、锥形阶梯轴类大断面收缩率零件(断面收缩率>75%)成形,是楔横轧新技术较特殊的一种成形形式,具有广阔的应用前景,其在成形建筑用材、汽车关键轴类零件等起着不可替代的作用。基于目前对细长、锥形阶梯轴的研究尚不多见,对其成形规律、缺陷的产生机理也缺少了解,该文根据细长轴的几何特殊性,进行了相应的模具设计和布楔设计;基于DEFORM有限元平台,对轧制全过程进行模拟,得到了各模具参数对应力应变的影响变化规律,并利用遗传算法对模具进行了多目标优化设计。