FEA-aided design of multi-stage drawing process and tooling for production of a miniature sheet metal component

This paper presents the design of multi-stage drawing process and tooling aided by finite element analysis (FEA) for fabrication of a miniature sheet metal component, made of a cold-reduced carbon steel material (SPCC). To design such a tooling, it is essential to figure out how many intermediate drawing steps are needed to produce the final part without deformation defect. First of all, a four-stage drawing process and a set of four-station tooling are designed. This pre-designed process is then analyzed by simulation, and the deformation behavior and formability in each stage is revealed. Based on the revealed deformation behavior and formability, the design of the process and tooling is confirmed. The reasonable drawing ratio and drawing depth in each drawing operation are determined. The size, clearance, and the corner radii of punch and die in each stage are also identified. The designed process and tooling are finally implemented. Through experiment, the “right design in the first time” is realized, and the simulation and experiment are found to have a good agreement. The research further demonstrates that the FEA simulation can be used as an effective tool to aid the design of metal-formed component, tooling, and process in upfront design process.     

Tooling design in sheet metal forming using springback calculations

A method to design tooling in sheet metal forming using springback calculations is presented. The designed tooling produces a part which matches the desired shape, thereby compensating for springback. To design the appropriate tooling, traction distributions on the sheet in the fully loaded deformed state are computed using the finite element method. The calculated tractions are then used to numerically reproduce springback of the desired part shape by elastic unloading of the part in a reverse manner. The method is examined for materials covering a range of steel strength and hardening, and is found to produce parts with negligible shape error. The success of the tooling design algorithm leads to a proposal for an experimental method to design tooling based on traction distribution measurements.     

Characterising material and process variation effects on springback robustness for a semi-cylindrical sheet metal forming process

Variation in the incoming sheet material and fluctuations in the press setup is unavoidable in many stamping plants. The effect of these variations can have a large influence on the quality of the final stamping, in particular, unpredictable springback of the sheet when the tooling is removed. While stochastic simulation techniques have been developed to simulate this problem, there has been little research that connects the influence of the noise sources to springback. This paper characterises the effect of material and process variation on the robustness of springback for a semi-cylindrical channel forming operation, which shares a similar cross-section profile as many automotive structural components. The study was conducted using the specialised sheet metal forming package AutoForm™ Sigma, for which a series of stochastic simulations were performed with each of the noise sources incrementally introduced. The effective stress and effective strain scatter in a critical location of the part was examined and a response window, which indicates the respective process robustness, was defined. The incremental introduction of the noise sources allows the change in size of the stress–strain response window to be tracked. The results showed that changes to process variation parameters, such as BHP and friction coefficient, directly affect the strain component of the stress–strain response window by altering the magnitude of external work applied to forming system. Material variation, on the other hand, directly affected the stress component of the response window. A relationship between the effective stress–strain response window and the variation in springback was also established.     

An accelerated springback compensation method

Part shape error due to springback is usually considered to be a manufacturing defect in sheet metal forming process. This problem can be corrected by adjusting the tooling shape to the appropriate shape and/or active process control. In this paper, the focus will be on tooling shape design. The traditional trial-and-error methods are inefficient for complex dies. Several analytical methods have been proposed in recent years. Each of these has their advantages and disadvantages. As expected, all these methods required a few iteration steps before converting to the desired tooling shape. Here, we put all of these proposed methods under the same framework. Additionally, built upon existing methods, a new methodology is proposed by incorporating pure geometry correction with fundamental mechanics analysis. Consequently, the convergence becomes much faster and certain. Tooling design results from the new method, together with three existing methods, are compared with each other and an experiment.     

基于有限元分析的铝合金板料弯曲回弹的影响因素研究

铝合金材料的弯曲成形是飞机板材和型材零件常用的加工方式之一,在卸载过程中,由于板料的弹性回复,不可避免的会出现回弹现象,在实际加工中如何预测工件回弹后的形状,并对模具进行适当修正仍是一个比较难解决的问题。本文利用非线性有限元软件MARC对不同厚度的铝合金板材弯曲加工过程进行了模拟分析,给出了相对弯曲半径,弯曲中心角,及不同弯曲模式与回弹角度之间的关系,并与实验数据进行了比较。结果表明,有限元分析结果与实验结果比较吻合,有限元模拟能有效地分析和预测铝合金板料的弯曲回弹,为实际生产加工过程中工艺参数的选择提供有力的参考。     

<Emphasis Type="Italic">Rapid Moulding Using Epoxy Tooling Resin</Emphasis>

Rapid prototyping (RP) is fast becoming a standard tool in today’s product design and manufacturing environment. Significant benefits in terms of lead time and cost savings have been reported with the use of RP technology. However, these benefits can be derived only during the design and planning stages of a new product where RP parts are produced in small quantities for design evaluation, form fitting, and marketing analysis. The high cost of raw material stock used in current RP systems makes them economically unsuitable even for small-batch production during the product evaluation and manufacturing stages. Further to this, the difference between the mechanical and physical properties of RP and traditional manufacturing materials limits the functionality of RP end products. Rapid tooling (RT) technology has opened up new cost-effective solutions for small-batch production. In this paper, a technique using a rapid soft-tooling approach, namely, aluminium filled epoxy resin tooling for injection mould preparation is successfully explored. An aluminium filled epoxy resin mould is evaluated and the characteristics of the injection-moulded end products are presented.     

Feasibility study of a new rapid tooling process

The requirements for faster product development cycles, lower product cost and environmental sustainability are ever increasing in today’s globally competitive market. Tooling is a very important phase in the product manufacturing cycle. To overcome the shortcomings of long lead-time and high cost associated with conventional tooling processes, new tooling methods with shorter lead-time and lower cost are strongly under demand. In this study, the feasibility of the proposed new rapid tooling process based on back support of a metal shell with packed metal powders is examined. First, the effect of metal powder properties, such as powder shape, size, and size distributions, on powder-packing behaviour is investigated experimentally. Then, the compressive behaviours of the metal shell and the shell-powder assembly are analysed numerically with different compressive loading. The study indicates that the proposed new rapid tooling method can potentially be used for injection moulding applications.     

Investigation of the effect of roll forming pass design on main redundant deformations on profiles from AHSS

The tooling design in the roll forming process plays a major role in the quality and successful mass production of a variety of complex profiled products, in many industrial sectors. The roll forming line is comprised of consecutive forming passes. Each roll forming pass consists of a set of rotating rollers able to bend the material as it passes through them. The roll forming pass design plays a major role in the production of profiles. The introduction of advanced high strength steels (AHSS), such as the DP-series and TRIP-series, has also posed new challenges for the design of the roll passes. The current paper exploits explicitly the finite elements (FE) method and investigates the effect of the roll forming passes design on main redundant deformations, such as longitudinal stains at the edge of the profile, shear strains on strips plane, thickness reduction, and final produced cross section with springback. The profiles discussed are symmetrical V- and U-sections from the AHSS Dual Phase series (DP780). The gradual lowering of the flower pattern design, known as ??downhill pass flow??, is discussed. The calculated decrease in the peak longitudinal strains of up to 28%, and the decrease in thickness of up to 38% are also presented and discussed.     

新型汽车玻璃滑槽拉弯成形工艺

针对汽车玻璃滑槽的拉弯成形工艺,设计开发了一种基于张臂式拉弯机上安装的一次拉弯工装和非标二次拉弯设备相结合的新型加工工艺。该工艺通过二次拉弯工序,利用机械、电气和液压相结合的控制技术,实现了汽车玻璃滑槽的拉弯成形工艺。采用该工艺来加工汽车玻璃滑槽,具有调试简单和产品状态稳定等优点。     

A die design method for springback compensation based on displacement adjustment

Springback is a major problem in sheet forming processes. This problem can be corrected by adjusting the tooling shape to the appropriate shape and/or active process control. In this paper, the focus will be on tooling shape design, of which compensation magnitude and compensation direction are the two important aspects. A new method, which takes compensation direction into account based on displacement adjustment, has been developed. The method, which we call “comprehensive compensation method” (CC) is general for it considers the fact that large rotation and displacement would occur during springback, which is more common for automotive panel stamping due to the application of advanced high strength steels (AHSS) and the complexity in automotive panel structure. An angle compensation factor was introduced to determine the compensation direction. Compared to the three existing methods, which compensate in different directions, the new method has a higher precision especially for complex panel with advanced high strength. Additionally, the suitability and application of those four methods is also discussed, along with the origin of the differences.     

基于有限元分析的二轴柔性滚弯过程影响因素的研究

利用弹性介质对钣金件进行二轴柔性滚弯成形是一种先进的钣金制造工艺,将弹性介质(聚氨酯橡胶)的冲压优势和传统滚弯原理结合,成为钣金成形领域的一个新的发展方向。本文利用有限元软件MARC建立二轴柔性滚弯过程的有限元分析模型,成功的模拟了板料滚弯成形及回弹的加工过程,对工件滚弯成形过程的主要影响因素进行了分析,给出了压入深度、柔性层厚度、刚性滚轴半径、材料性能与回弹后曲率半径的关系。分析结果表明,有限元模拟对滚弯过程的工艺参数选取有着一定的指导意义。     

一种特殊水冷板的工艺设计与实施

根据水冷板生产任务的要求,结合某公司车间现有的设备,对水冷板工艺流程和相应工装进行了详细设计,经过车间的生产验证,水冷板工艺流程和工装设计合理可行,具有指导性,对保证产品精度和质量起到了关键作用,使车间在现有条件下具有了水冷板批量生产的能力     

板料成形中的回弹计算和模具修正

利用动力显式有限元计算程序MSC／DYTRAN,采用动力松弛法模拟了板料成形及回弹过程,计算出板料成形后的回弹量：提出“位移描述－结点修正”法,以回弹量为依据通过反向位移补偿和插值算法,编制程序自动对模具网格结点进行修正,通过反复迭代计算,最终可获得生成理想形状制件所必需的凸,凹模尺寸。     

Rapid Sheet Metal Manufacturing. Part 2: Direct Rapid Tooling

The traditional methods adopted for tool design and production in the sheet metal forming industry usually carry a high cost and long lead time resulting in cost justification problems for short production runs. Rapid tooling (RT) technology is capable of justifying the cost of tooling suitable for short production runs or design evaluation purposes. In Part 1 of this work, a new process termed rapid sheet metal manufacturing (RSMM) for the production of soft tooling suitable for prototyping, tool development, and short production runs was introduced. In addition, an indirect RT method employing rapid prototyping (RP), rapid soft tooling, and casting for the fabrication of non-ferrous tools was presented. The current work, Part 2, presents an alternative technique for RSMM whereby metal forming tools are fabricated directly from the RP system via selective laser sintering (SLS).     

Automatic tooling design for rotary draw bending of tubes

Cold rotary draw bending of tubes is a CNC metal forming process widely used in industry. When planning a new process, trial and error is often required in order to calculate the proper overbending and to avoid wrinkling, excessive thinning and flattening. Process design is a critical, difficult, experience-based activity, that requires the selection of several variables. In this paper, a comprehensive, computer-based methodology, called Tube ProDes, is proposed for process design of the rotary draw bending of tubes. The approach can be described as follows. First, numerical calculations are carried out in order to compensate for springback, to evaluate the severity of the bend (i.e. the risk of the occurrence of defects), and to assess the sensitivity of the process to a change in the material properties. Then, the tooling setup is completely designed by fuzzy logic, using the tube material properties, the geometrical data of the bend and the variables previously calculated as input.     

Material removal and chip formation mechanisms of UHC-steel during grinding

Laser shock forming (LSF) is a sheet plastic forming technology, which employs laser-induced shock waves to make sheet metal duplicate a desired shape of the mold. In this paper, a finite element analysis (FEA) model was developed to simulate dynamic forming process with the commercial finite element code ABAQUS/Explicit, and a series of dynamic deformation behaviors of the metal sheet shaped into conical cup at the end of different periods of time were displayed and discussed in detail. The springback of conical cup and the distribution of residual stress were analyzed with ABAQUS/Standard. All these investigations could provide insight into the physics process of the ultra-fast deformation. The LSF experiment was further conducted to verify the results predicted by FEA. The experiment results are well consistent with the numerical predicted data, which validates the FEA model. It indicates that FEA can be used to simulate the forming process and optimize its parameters.     

基于几何补偿的高强板汽车覆盖件回弹优化控制

利用板料成形CAE软件DynaForm对高强板汽车覆盖件地板中通道进行回弹仿真分析,结合模具几何补偿,通过对成形工艺参数的正交优化,找到了最优参数组合及各因素对回弹的影响程度,有效地控制了零件在多工序冲压成形过程中产生的回弹.     

On bend-stretch forming of aluminum extruded tubes — II: analysis

Part II describes a two-dimensional model of the bend-stretch-pressure forming process, which assumes that the tube shape and all applied loads are uniform along the length. This simplification results in a significant improvement in computational time over corresponding three-dimensional models. The model is validated through comparisons with experimental results discussed in Part I and its application to the design process is illustrated. The model is then used to study the current manufacturing process and to evaluate some possible alternative loading histories. The effect of tension and pressure on the cross-sectional distortion, springback and net elongation are discussed in light of the predictions. Additionally, the merits of changing the tension and pressure after forming are discussed. The simulations and corresponding experiments are used as the basis for a design methodology for selecting the order and magnitude of the loads applied during the forming process.     

基于改进粒子群算法和小波神经网络的高强钢扭曲回弹工艺参数优化*

针对高强钢复杂件冲压后出现的扭曲回弹现象,运用有限元仿真软件DYNAFORM对复杂件的冲压、回弹过程进行数值模拟,提出了评价复杂件扭曲回弹程度的指标,并运用试验设计和小波神经网络代理模型方法对扭曲回弹进行了优化研究。以某弯曲梁为研究对象,以扭曲回弹为成形目标,通过正交试验设计筛选出对扭曲回弹影响较大的工艺参数作为影响因素。利用拉丁超立方对影响因素进行抽样,通过数值模拟获得样本数据,建立影响因素与成形目标之间的小波神经网络代理模型,利用改进的粒子群算法对该模型迭代寻优获得最优参数。结果表明：采用优化后的工艺参数能有效地减小该弯曲梁的扭曲回弹,该方法为减小复杂件的扭曲回弹提供一种有益的指导。     

Numerical simulations on reducing the unloading springback with multi-step multi-point forming technology

Multi-point forming (MPF) is an innovative flexible manufacturing technology for three-dimensional sheet metal forming. It replaces the conventional solid dies with a set of height-adjustable discrete punches, called the “punch group”. A set of punches can construct various three-dimensional curved surfaces freely and conveniently, through adjusting the relative position of each punch. MPF technology not only saves a significant amount of money and time in the design, manufacture, and adjusting of the dies but it can also be applied to change the deformation path and to improve the forming quality. Unloading springback is an inevitable phenomenon in sheet metal forming using MPF. To control and reduce springback, numerical simulations for the MPF process and the unloading springback are carried out using the explicit-implicit coupled finite element method. Subsequently, influencing factors such as thickness, deformation amount, and material properties of MPF springback are researched to investigate the MPF springback tendency. Next, the multi-step MPF technology is introduced to reduce MPF springback. Based on numerical simulation analysis, it is obviously validated that the unloading springback is decreased when the multi-step MPF method is applied. Finally, it is verified that the equidifferent deformation path and small deformation amount of each forming step can improve the workpiece stress state and minimize the unloading springback effectively by an evaluation result of the deformation path effect on the multi-step MPF.