Computer aided preform design in forging using the inverse die contact tracking method

The inverse die contact tracking method presented in this paper utilizes both the forward and inverse finite element simulations to design the preform shapes in forging processes. The procedure starts with the forward simulation of a candidate preform into the final forging shape. A record of the boundary condition changes is produced by identifying when a particular segment of the die makes contact with the workpiece surfaces in forward simulation. This recorded time sequence is then optimized according to the material flow characteristics and the state of die fill to satisfy the requirement of material utilization and forging quality. The modified boundary conditions are finally used as the boundary condition control criterion for the inverse deformation simulation. Additionally, a procedure to determine process staging points using trial forward simulation is given. As an example, the preform design of a plane strain forging process is performed. The fuller, buster and blocker dies are designed by using the inverse deformation simulation.     

汽车差速器半轴齿轮新型锻模设计

论述了精锻汽车差速器半轴齿轮原模具结构存在的问题,改进了锻造工艺和锻件设计,设计了新型粗锻模和精压模.新型粗锻模的齿模设在上模,半轴凹模设在下模,坯料定位准确迅速,可实现无飞边粗锻;齿模与热锻件接触时间短,模具温升小,模具寿命高.新型精压模的上模设有顶件装置,锻件半轴的拔模斜度小,锻件半轴的金属敷料少.新型模具可显著提高模具寿命和生产效率,降低材耗和生产成本.     

Pattern density and pitch effects on chemical-mechanical polishing

Test masks for characterizing pattern dependent variations in the thickness remaining after chemical-mechanical polishing (CMP) were designed taking the experimentally obtained interaction distance into consideration. Polishing behaviors were characterized with layout pattern density and pitch variations using these masks. The deposition profile effects were also compared between PETEOS (Plasma Enhanced Tetra Ethyl Ortho Silicate) and HDP (High Density Plasma) oxide. Both measured post-CMP thickness and the expected oxide pattern density from a consideration of the deposition profile effects showed good correlation with respect to pitch variation for a constant layout pattern density. Also, the relationship between the remaining thickness and true layout pattern density were deduced. Secondly, chip-level CMP modeling was investigated to obtain the post-CMP thickness distributions across a die from its design layout and a few oxide film and CMP parameters. The experimental CMP results agreed well with the modeling results. The effective dummy filling results were shown to achieve a smaller pattern density variation, which resulted in uniformly better post-CMP thickness. Finally, whether the resulting oxide thickness can be predicted for any location on a die for an arbitrary layout if the effective pattern density distributions are calculated is discussed.     

压铸模定模侧组合型芯反推式斜抽机构设计

为解决铸件气缩孔问题,在压铸模定模侧设计了一种组合型芯反推式斜抽机构.在铸件定模侧存在大量斜孔无法直接出镶针的情况下,采用该机构能够将这些孔位做成整体斜抽.该新型反推式斜抽机构设计精巧,运行平稳,故障率低,使用可靠,值得推广应用.     

Static compensation for elastic tool and press deformations during deep drawing

Although today’s deep drawing tools are thoroughly designed and calculated by means of computer-aided design (CAD), finite element (FE) simulation and computer-aided manufacturing (CAM), the sequence of operations to put a tool into production still encompasses manual and irreproducible labor. In particular, the die spotting is empirical and is almost entirely dependent on the toolmaker’s experience. This fine-tuning of the drawing tool consumes a large amount of time. In minimizing manual die spotting, a large potential to decrease time and costs exists. This article presents error compensation methods to create deep drawing tools, which require less manual die spotting in order to produce sound quality stampings. In FE simulations of deep drawing operations, it is general practice to assume rigid tool and press properties. The fact that die and punch design are based on these simplifications might be one of the main causes that empirical die spotting is still imperative. Therefore, the authors developed a methodology to compensate the tool face for effects of elastic press and tool deformations, which occur under applied process load. The authors demonstrate the static compensation with two examples. The first shows the static compensation for ram tilting caused by an unbalanced load, which can originate from asymmetric part design and/or eccentric mounted tools. The second example describes the compensation for elastic die deformation caused by local and global deflections. In either case, the compensated die face, under applied process load, deformed into the desired die face. This research work shows the potential and limits of a static compensation for effects of elastic tool and press deformations on the final shape of the stamping.     

An innovative extrusion die layout design approach for single-hole dies

To avoid distortion of complex extrudate profiles, it is essential that the exit velocity of the metal is uniform. The most important design parameter that controls the exit velocity is bearing length. However, this factor is not sufficient to achieve optimal design settings. This paper proposes an innovative layout design approach using a geometry based bearing length design methodology to minimise variations in exit velocity. This paper focuses on single hole extrusion dies and develops an optimisation algorithm suitable for any die profile. Since the optimised die design produces less bearing length difference, more uniform exit velocity and higher design quality would be achieved using the proposed approach.     

Extrusion through controlled strain rate dies

The workability of a material during deformation processing is determined by (a) the die geometry which, in turn, determines the flow field during deformation, and, (b) the inherent workability of the material under the imposed processing conditions of strain rate and temperature. Most common alloys have good inherent workability and can be successfully formed over wide ranges of temperature and strain rate. Products can be successfully formed from these alloys even with dies which impose large variations in strain rate during deformation. However, many of the new alloys and composites can be deformed only in very narrow processing regimes, and control of the strain rate during deformation of such materials becomes important. For example, extrusion of a whisker-reinforced aluminum alloy composite is possible only when the strain rate is controlled to within one order of magnitude. This paper describes the development of a method for obtaining preliminary shapes of controlled strain rate extrusion dies, a special case being the constant strain rate die. The theoretical basis for such die design processes is presented, followed by some examples of die geometries. Since this design procedure ignores the material flow properties, the designed die shapes must be verified using the finite element method or physical modeling. Results of simulations with the program ALPID are also presented.     

钢管折叠式椅子模具设计

介绍钢管冲孔模具的设计,如何利用钳工的操作技能来制造上、下冲孔模具,降低制造成本,以及不同抽芯块的原理来设计钢管弯曲模具,从而提高工作效率。     

拉伸模结构设计

在相同材质条件下采用不同的孔型设计,拉伸模产品使用寿命相差甚远。因此,改进孔型设计是提高拉伸模具使用寿命的一条重要途径。采用ANSYS力学结构理论,以11-2.3、11-2.8、13-6.7、13-7.7型四种拉伸模结构为设计参考基准,计算拉伸模主要结构参数变化时,拉伸模各部位的应力、应变及位移变化,根据拉伸模结构有限元数值分析中关于各种参数对拉伸模结构变形和应力状态的影响规律,优选结构参数,以减小单重为目标,获得最优的拉伸模结构设计。     

Design of forging process variables under uncertainties

Forging is a complex nonlinear process that is vulnerable to various manufacturing anomalies, such as variations in billet geometry, billet/die temperatures, material properties, and workpiece and forging equipment positional errors. A combination of these uncertainties could induce heavy manufacturing losses through premature die failure, final part geometric distortion, and reduced productivity. Identifying, quantifying, and controlling the uncertainties will reduce variability risk in a manufacturing environment, which will minimize the overall production cost. In this article, various uncertainties that affect the forging process are identified, and their cumulative effect on the forging tool life is evaluated. Because the forging process simulation is time-consuming, a response surface model is used to reduce computation time by establishing a relationship between the process performance and the critical process variables. A robust design methodology is developed by incorporating reliability-based optimization techniques to obtain sound forging components. A case study of an automotive-component forging-process design is presented to demonstrate the applicability of the method.     

Integrated planning for precision machining of complex surfaces—III. Compensation of dimensionai errors

This paper presents an approach that compensates machining errors in ball-end milling processes using the control-surface strategy. In the proposed approach, machining errors induced by cutter deflections are predicted from a surface generation model so that actual machining experiments and dimensional inspections are not required. Therefore, the proposed approach can be integrated into an integrated framework for machining planning in which prediction and compensation of dimensional errors take place in the process development phase rather than in the manufacturing phase of the production cycle. Based on the predictive capability of the surface generation model, a sensitivity function is defined so as to characterize the variations of the machining errors when perturbing the control surface. Using the defined sensitivity function, a compensated control surface can be constructed, based on which new cutting paths can be planned and “near-zero” surface dimensional errors can be accomplished. In order to verify the proposed strategy, actual production of a turbine blade die using a CNC machining center was conducted. By using the control-surface strategy with the sensitivity function approach, the maximum surface dimensional error is reduced from ± 340 to ± 10 μm.     

Numerical simulation of thixoforming

Processing of alloys and composites in the solid plus liquid range has advantages over casting, forging, and powder metallurgy techniques. The sensitivity of semisolid slurries to temperature variations and their history and rate dependent behavior, however, make process design and control difficult. Precise selection of die velocity, process temperature, and die design is necessary to produce satisfactory products. Therefore, a computational capability for the prediction of the rheological behavior of semisolid materials would be an invaluable tool in process design. This work presents preliminary results on numerical simulations of thixoforming operations. Constitutive models that are able to describe qualitatively the transient flow behavior of semisolid materials are implemented in a finite element program. Simple but realistic thixoforming operations are simulated. Weaknesses of currently available constitutive models and numerical techniques are identified and discussed. This paper was originally presented at the Symposium “Paniculate Materials in Rheological Applications,” TMS 1993 Fall Meeting, Materials Week Program.     

New Methods for Severe Plastic Deformation Processing

Several new concepts for possible methods of severe plastic deformation (SPD) of bulk quantities of materials are presented. The first of these are variations of equal channel angular extrusion (ECAE) in which the conventional fixed die is replaced by rotating tools, for the inner die corner, the outer die corner, or both corners. Other methods share some characteristics of ECAE in that they use shearing strains to deform the material; these are reversed shear spinning and transverse rolling. Deformation sequences for a cylindrical or annular workpiece that deform the workpiece while eventually restoring the initial workpiece geometry can be performed by numerous processes. These techniques can be used to accumulate high strains by repeated deformation cycles. These methods offer possible alternatives to ECAE and high-pressure torsion, with potential benefits that include different and larger workpiece geometries, simplified tooling design, lower tooling loads, ease of lubrication, automated or reduced part handling, and, in some cases, potentially continuous operation. It is hoped that these suggestions will prompt new examination of alternative methods for SPD. This article was presented at Materials Science & Technology 2006, Innovations in Metal Forming symposium held in Cincinnati, OH, October 15-19, 2006.     

Optimal design of die coating thickness using the Lewis—Ransing correlation

The objective of design optimisation in this context is to enforce directional solidification in the casting, i.e. to generate an optimal die design which will produce shrinkage-free castings with the minimum manufacturing cost. A large number of parameters can be listed which govern the directional solidification in a casting. The more important are the location of the feeders, interface conditions such as die coating thickness, insulation etc., feeder neck size, feeder volume and the cooling system. It is shown that the influence of the die coating thickness, or any other interface condition, can be considered using the correlation proposed by the authors. The correlation offers a natural choice for the design variables. The optimal design of the spatial and temporal variation of the interfacial heat-transfer coefficients is demonstrated using two examples.     

冲压件拉延方向分析方法及应用

文章研究了复杂曲面零件冲压方向分析时闭角寻找的数学算法和特征图构造方法,给出了在三维CAD环境下的具体实施措施,讨论了冲压方向调整时特征图的基本变化,提出了能定量调整冲压方向和判断零件闭角能否消除的方法,该方法可以有效地减少冲压方向调整时的盲目性。文章所得到的结果能用于零件、拉延件以及后续成形类工序件(再次成形、整形、翻边等)的冲压方向的分析。实例表明,该方法能够快速、合理地辅助冲压方向的确定。     

多腔小尺寸塑件去浇口冲模设计

分析了镜筒隔圈带浇口塑件冲裁工艺性,针对塑件1模多腔,尺寸小,不利取放,存在安全隐患的特点,设计了移动装取料装置。本文介绍了模具的结构特点和工作过程,并重点介绍了关键零件的设计特点。该模具结构合理,操作简单,轻便,安全可靠,生产的塑件完全可以满足装配要求。     

中心带长条孔紧固圈级进模设计

针对开口环类制件成形,介绍了一种级进成形模具,条料通过自动送料完成冲孔、切断、打弯,又经机械手送进卷圆,压缩空气吹出制件,全程实现自动生产。并且介绍了模具在设计失误后,通过制件结构分析,采取了相应的补救措施,达到了设计要求。     

The optimum die profile for the cylindrical bending of plates

This paper presents a methodology for the design of plate-forming dies in cylindrical bending using optimization techniques to reduce the cost of die production by reducing the trial-and-error procedure considerably in determining the final die geometry. The plate thickness is discretized by plane-strain finite-elements. The die is taken to be rigid and its profile is approximated by Bezier curves the control-point coordinates of which are the design variables. The die profile is varied to minimize the difference between the required shape and the shape of the bent plate, considering springback action. The unconstrained optimization problem is solved by the BFGS (Broyden-Fletcher-Goldfarb-Shanno) method. A numerical example is presented where the optimum die profile is obtained for a plate bent into a quarter circle.     

复杂工件多道次拉深成形数值模拟研究

以汽车门内板为例，在分析了复杂工件多道次拉深成形受力特点的基础上，阐述了复杂多道次板料拉深成形数值模拟思路，并举例说明数值模拟对模具设计的重要指导作用，最后用图例说明了凹模圆角半径对成形的影响规律。     

Investigation on Effects of Die Orifice Layout on Three-Hole Porthole Extrusion of Aluminum Alloy 6063 Tubes

Currently, with the increasing demand of high production output, much attention is paid to the research and development of multi-hole extrusion die. However, owing to the complexity of multi-hole porthole extrusion technology, it has not been applied widely in practice for the production of aluminum profiles, especially for porthole die with an odd number of die orifices. The purpose of this study is to design a three-hole porthole die for producing an aluminum tube and to optimize the location of die orifices based on computer-aided design and engineering. First, three-hole extrusion dies for different locations of die orifices are designed. Then, extrusion processes with different multi-hole porthole dies are simulated by means of HyperXtrude. Through numerical simulation, metal flow, temperature distribution, welding pressure, extrusion load, and die stress, etc. could be obtained, and the effects of the location of die orifices on extrusion process are investigated. With the increasing distance between die orifice and extrusion center (described as eccentricity ratio), metal flow becomes nonhomogeneous, and twisting or bending deformation of profile occurs, but the welding pressure rises, which improves the welding quality of profiles. However, the required extrusion force, billet and die temperature, die displacement, and stress induce no significant changes. In comparison with the extrusion force during single-hole porthole extrusion, there is 18.5% decrease of extrusion force during three-hole porthole extrusion. Finally, design rules for this kind of multi-hole extrusion dies are summarized.