Development of a Highly Flexible Incremental Roll Forming Process for the Manufacture of a Doubly Curved Sheet Metal

A flexible incremental roll forming process has been developed by adopting the advantages of the incremental forming process and the roll forming process: i.e., inherent flexibility of the incremental forming process and continuous bending deformation of the roll forming process. It has an adjustable roll set as a forming tool composed of one upper center roll and two pairs of lower support rolls, which plays a key role. Through the experiments, it is shown that the improved forming method of the proposed process is effective in the manufacture of various doubly curved sheet metals, and the proposed relationship of the experimental parameters and the radius of curvature of the formed sheet boundary is useful to control the final shape     

An Incremental Roll Forming Process for Manufacturing Doubly Curved Sheets from General Quadrilateral Sheet Blanks with Enhanced Process Features

In order to manufacture a doubly curved sheet metal effectively, a flexible incremental roll forming process has been developed by adopting the advantages of the incremental forming process and the roll forming process by combining inherent flexibility of the incremental forming process and continuous deformation of the roll forming process. In the proposed roll forming system, a newly designed gripper system is attached in order to achieve automation and more precision manufacturing of the required sheet intended double curvature. The forming method has been further enhanced to form general quadrilateral blanks (including a square, a rectangle, a symmetrical trapezoid and an asymmetrical trapezoid, etc.) into doubly curved shapes by controlling the forming schedule developed by various experiments.     

精锻成形技术的现状及其发展

本文首先介绍了我国的精锻成形技术,该技术在国际上并不十分落后,特别详细介绍了与我国台湾地区的情况对比。然后介绍了用传统的锻压设备及新型局部连续成形锻压设备进行精密成形的国内外情况,例如冷摆辗、辗环、楔横轧、螺旋轧制、辊锻、径向锻造……等。最后介绍了发展精锻技术必须注意的几个问题。     

Investigation of a new incremental counter forming in flexible roll forming to manufacture accurate profiles with variable cross-sections

A roll-formed profile with variable cross-sections fabricated by flexible roll forming has a shape error, such as warping, because of geometrical deviations in transitional zones of the profile between the initial metal strip and the roll-formed profile. To reduce the shape error, a new process called incremental counter forming (ICF) is proposed. Our investigation of the ICF process shows that the longitudinal strain distribution at the flange of the roll-formed profile can be controlled by combinations of forming parameters of the ICF process. As the forming parameters increase the longitudinal strain distribution in the concave zone, the shape error decreases. However, when the longitudinal strain distribution in the straight zone reaches a critical limit, the additional longitudinal strain works as an excessive longitudinal strain to worsen the shape error. An analytical model, which describes the longitudinal strain at the flange during roll forming, is adopted to reveal that the increase of the longitudinal strain is induced by increasing derivatives of a bending angle, which is controlled by the forming parameters of the ICF process. Finally, the FE simulation has been carried out to compare with the experimental results, which show that the ICF process is effective for reducing the shape error of the profile with variable cross-sections in flexible roll forming.     

Three-dimensional sheet metal continuous forming process based on flexible roll bending: Principle and experiments

To effectively manufacture three-dimensional sheet metal parts with various curvatures produced in small batch quantities, continuous sheet metal forming, a new flexible forming technology is being developed. This process employs an upper flexible roll and two lower flexible rolls as a forming tool, and the shape of a flexible roll can be changed in vertical direction. With the rotation of flexible rolls, the sheet metal is bent in longitudinal and transverse directions simultaneously and is formed continuously. In the present study, the three-dimensional surface of formed part is described by sweep surface based on the characteristic of the forming process and the arc-length parametric equation for describing continuous forming part is developed. The three-roll bending deformation of sheet metal in longitudinal direction is analyzed and the longitudinal curvature equation of the formed part is derived. The shape of flexible roll axis controlled at a number of points is represented by the cubic spline curve and the transverse curvature of the formed part after springback is then calculated piecewise. Typically experiments for forming concave shape surface and saddle-type surface have been performed, the experiment results are measured and analyzed by a binocular stereo vision measurement system, it is demonstrated that the formed surfaces are in good agreement with the desired shapes and the presented equations are useful for the continuous forming process design.     

多向加载近净成形研究动态

通过主动控制不同方向、不同成形阶段的多向加载条件并配合模具、变形温度等成形条件,可有效控制变形,提高坯料的成形性能,以获得预期的结构形状及组织状态的零件,实现净成形或近净成形,为难变形材料的复杂整体构件的精确塑性成形提供了一条有效途径。多向加载技术在蒙皮拉形、管材挤胀、环件径轴向辗扩、多向模锻等塑性成形工艺中都得到体现,但其工艺通用性差,需要专门的设备,不同成形工艺甚至当成形零件不同时,其变形机理亦迥异。评述了目前多向加栽成形工艺的应用与国内外研究现状,指出了该工艺在体积成形中应用发展需要解决的关键技术问题。     

一种复杂弯曲长轴类件制坯辊锻工艺设计与调试

介绍一种具有复杂弯曲形状的长轴类汽车零件的制坯辊锻工艺,包括技术方案的确定,成形过程的模拟和工艺调试与应用情况。该工艺已经在实际生产过程中得到验证,取得了良好的使用效果。     

轴盘类零件差温无模锻造近净成形有限元模拟

轴盘类零件广泛应用于工业领域，其制造方法通常是分别加工轴和盘，然后组装而成，或是采用模锻工艺生产。这样，不仅生产周期长，而且生产成本也高。为了克服这个问题，拟采用一种新的加工方法，即差温无模锻造来实现此类零件的近净成形，以期达到减少生产成本，缩短生产周期之目的。本文采用热力耦合有限元方法，模拟了圆柱体坯料在环形热源局部加热下的无模锻造过程，从理论上证实了用这种方法预成形轴盘类零件的可行性。     

Investigation into forming sequences for the incremental forming of doubly curved plates using the line array roll set (LARS) process

The line array roll set (LARS) process [7] proposed by the authors is an effective metal forming process used to manufacture doubly curved metal plates. To obtain a final shape with the desired bend radii and to minimize any possible defects, the process for forming the desired shape should be systematically and accurately designed. The major purpose of the present work is to analyze the effect of the forming sequences in the LARS process. The experiments are conducted using three types of forming sequences, and the final bend radii and the quality of the formed plates produced by the LARS process are evaluated. It is found that it is more effective to form a doubly curved plate through a singly curved shape in order to improve the quality of the formed plate. A series of forming experiments with various bending radii are conducted and the interaction phenomena in double curvature bending are observed.     

Numerical and experimental investigation into cold incremental rolling of doubly curved plates for process design of a new LARS (line array roll set) rolling process

The line array roll set (LARS) rolling process is a new incremental sheet metal rolling process for effective manufacture of doubly curved metal plates. In this study, design equations were developed to predict the curvatures of formed plate shapes with complex curvatures using the experimental data. A series of experiments with various curvatures have been performed. The comparison of the finite element computation results with the design equations has shown that the design equations can be effectively used for process design of forming processes in forming of doubly curved plates over a wide range of input curvatures.     

十字轴小飞边精密成形工艺

针对十字轴热模锻成形过程中飞边大、成形力大的问题,根据十字轴形状尺寸及锻造成形工艺特点,提出十字轴小飞边精密成形工艺。采用Deform-3D对十字轴小飞边精密成形工艺过程进行数值模拟,对模拟成形的十字轴锻件及其金属速度场、等效应变、模具载荷-时间曲线进行分析。模拟结果显示,十字轴锻件成形完整,金属流动均匀,模具载荷减小。结合模拟结果,设计制造模具进行十字轴成形工艺试验。试验得到的十字轴锻件,填充饱满,无折叠、表面裂纹等缺陷,飞边明显减小,与模拟结果一致。结果表明:改变十字轴热模锻成形工艺,采用十字轴小飞边精密成形工艺,使锻件飞边减小,锻造过程成形载荷降低。     

ERW焊管辊弯成型过程的动态仿真研究

ERW焊管辊弯成型过程复杂,规律难以把握。为了获得高质量的ERW焊管,减少成型缺陷,降低开发成本,文章采用动力显式有限元法和实验获得材料模型,建立ERW焊管辊弯成型过程的弹塑性有限元模型,实现了对ERW焊管连续成型过程的全流程仿真,分析了带钢在成型过程中的应力、应变变化规律与形状变化规律以及带钢厚度对成型质量的影响。研究结果表明,整个辊弯成型过程应力变化较为平缓,在精成型段有较大变形量,产生较大应力;边部纤维纵向应变高于中部纤维,导致边部有少量"皱曲"产生;随着厚度的增加,纵向应变相应增大。     

拉杆锻件的辊锻制坯工艺研究与开发

研究了拉杆锻件的辊锻制坯技术,采用2道次体积分配辊锻模具和一次头部压形模具,得到拉杆锻件的坯料形状与尺寸。成功地解决了辊锻道次的确定和型槽系的选择,模具设计等问题。据此成果,完成了拉杆锻件的生产线。     

非直壁外形筒体零件辊挤成形工艺设备研究

针对非直壁外形筒体零件的几何形状特点,在综合分析辊锻和挤压成形工艺的基础上,提出了集辊锻、挤压为一体的复合辊挤成形工艺。同时介绍了此工艺的设备设计,并进行了计算机辅助模拟验证。     

体积成形过程物理模拟技术的研究及应用

本文介绍了体积成形整体物理模拟技术的实施方案和主要技术要点 ,以及将该项技术用于模拟研究曲轴等典型锻件的成形过程 ,测定了变形力、错移力和关键部位的应变分布 ,提出了优化工艺设计、提高锻件成形质量及减少模具和设备磨损的具体措施     

Optimization of squeeze cast parameters of LM6 aluminium alloy for surface roughness using Taguchi method

The ability to produce near net shape components with good surface finish is made possible by means of squeeze casting, a hybrid metal forming process combining features of both casting and forging in a single operation. The primary objective of this paper is to analyze the influence of the process parameters on surface roughness in squeeze casting of LM6 aluminium alloy using Taguchi method. In Taguchi method, a three level orthogonal array has been used to determine the S/N ratio. Analysis of variance and the ‘F’-test values are used to determine the most significant process parameters affecting the surface roughness. The results indicated that the squeeze pressure and the die preheating temperature are the recognized parameters to cause appreciable improvement in the surface finish of the squeeze cast components.     

单曲率板材激光弯曲成形过程的有限元模拟

利用有限元软件MSC.Marc建立了单曲率板激光弯曲成形过程的热力耦合有限元模型。计算并分析了激光弯曲成形过程中板材内部的温度场、应力场和位移场。此外,还研究了扫描线的长度和单曲率板的初始形状对激光弯曲成形的影响。结果表明:随着扫描线长度的增加,板材的弯曲变形量增大;随着单曲率板曲率的增加,板材的弯曲变形量减小。实验结果验证了模型的可靠性。     

齿轮精密锻造技术的发展

研究和试验了圆柱直齿轮、圆柱斜齿轮和同步齿轮等 3种汽车用齿轮。制造工艺采用温锻加冷处理 ,用有限元模拟来分析锻造过程和设计模具 ,从而保证齿轮的精度。经过 3年的研究 ,已掌握其基本技术 ,下一步将进行工厂现场试验     

Production of low-volume aviation components using disposable electromagnetic actuators

Electromagnetic forming is commonly used to produce high strain rates to improve the formability of sheet metal. The objective of this paper is to discuss the feasibility of the use of disposable actuators during electromagnetic forming of two aluminum components: a very simple part with a one-dimensional curve, and a realistic part whose main feature is a convex flange with two joggles. The main forming complications after the parts were formed using conventional methods were the presence of wrinkles and excessive springback. The goal of this work is to use large controlled electromagnetic impulses to minimize the springback of these components from a rough-formed shape. The optimum test protocols for electromagnetic calibration of the components were determined by optimizing parameters such as actuator design, tool material, press force, and capacitor discharge energy. The use of disposable actuators for electromagnetic calibration of the parts showed significant reductions in springback compared to the parts which were only preformed using conventional techniques (hydroforming and rubber pad forming). Springback was decreased in the curved component by up to 87%. The wrinkles were eliminated on the flanged component, the joggles were formed properly, and the average bending angle of the part was improved from 95.3° to 90.3°, very near the target bending angle of 90°. This study demonstrates that these techniques can be used to improve current sheet metal production processes.     

Investigation of the cold orbital forging process of an AlMgSi alloy bevel gear

Orbital forging is a metal forming process in which one of the dies performs a complex rocking motion. It ensures reduction in required load and allows for the cold forming of a workpiece. One of the mechanical parts formed by means of this technology is a bevel gear. However, a numerical analysis of orbital forging bevel gears is very difficult to perform due to the complex rocking motion of the die, which is confirmed by numerous works investigating the orbital forging process. In the present work, investigation results of the cold orbital forging of aluminum alloy bevel gears are presented. In contrast to other works devoted to the process, this study proposes a new procedure for forming bevel gears and the workpiece used has a shape which is different from the previously applied ones. The obtained results apply to both theoretical and technological aspects of orbital forging. The FEM simulation results have been successfully verified in laboratory conditions using the industrial PXW-100A press.