板材三维曲面多点成形技术

多点成形是一种板材柔性成形新技术。它在新产品的试制开发、多品种、小批量板类件生产、大型板材成形等多方面都显示出良好的潜力。本文探讨了多点成形的基本原理、技术特点和系列实用技术,并对多点成形的应用前景作了阐述。     

多点成形压力机及成形工艺的最新进展

多点成形技术是金属板材三维曲面成形的新技术 ,与传统的整体模具板材成形工艺相比 ,多点成形压力机有许多优点 ,可以实现三维板类件既经济又快速的柔性成形。本文介绍了多点成形压力机系列规格参数、设备构成原理及其成形工艺。重点论述了几个现有的多点成形压力机的技术参数、调形方式的重大改进及多点成形技术应用领域的不断扩大。     

板类件多点成形专用CAD／CAM软件

多点成形压力机是一种新型板材柔性加工设备,因具有实现无模成形、小设备成形大型件等特点,在大型板材加工、多品种工件生产、新产品开发等诸多方面显示出良好的应用前景。要把多点成形用于三维曲面成形井使其向实用化、自动化方向     

名词解释

<正>多点成形技术多点成形技术是金属板料三维曲面成形的一种柔性加工方法,其基本思想是将传统的整体模具离散成一系列规则排列、高度可调的基本体(或称冲头)。在整体模具成形中,板材由模具曲面来成形,而多点成形中则由基本体群(或称冲头群)所构成的包络面(或称成形曲面)来完成。多点成形中各基本体的行程可以分别调节,改变各基本体的位置就改变了成形曲面,也就相当于重新构造了成形模具,由此体现了多点成形的柔性特点。该技术利用多点成形设备的柔性特点,无需换模就可进行     

板材无模多点成形技术

无模多点成形是由可调整高度的基本体群随意形成各种曲面形状进行板材三维曲面成形的先进制造技术。板材无模多点成形设备是以计算机辅助设计、辅助制造、辅助测试(CAD/CAM/CAT)技术为主要手段的柔性锻压设备。它利用计算机控制基本体的高度来形成所需要的曲面形状,不用模具实现板材的自动无模成形,而且,利用分段多点成形法可以实现用小设备成形大型件。     

杆系柔性成形模具及其板成形加工关键技术

提出了一种可重构、低成本、高效率的板件成形加工模具———杆系柔性成形模,该装置可以快速重构各种形状的板件成形加工模具。详细地分析了杆系柔性成形模的结构及其重构方案,采用可更换的“变形冲压头”与离散杆配合,较好地构成模具成形面,保证板件有较好的成形精度;提出了一种新颖的板成形方法———模内压板与成形复合工艺,通过这种工艺方法与杆系柔性成形模相结合,可以抑制板件在成形过程中的受压屈曲与起皱,并可以减小成形板件的回弹量。该模具对复杂曲面板件的成形加工具有明显的优越性。     

大型3维板类件多点闭环成形的研究

以多点成形技术为核心,为CAD／CAM／CAT为基础,提出了3维板类件的多点闭环成形。在多点成形过程中,3维曲面形状的离散傅里叶变换描述能够反映成形件的整体变形特性。以此为基础,给出多点成形过程的传递函数,并通过非参数化系统辨识方法获得每次循环中成形过程的非参数模型,从而预测出下次成形的基本体群形状,实现板类件的多点闭环成形。实验研究表明,在不考虑材料非线性、几何非线性和成形条件的情况下,金属板材通过闭环成形快速收敛的目标形状,实现了3维曲面的精确柔性造型。     

多点闭环成形中基本体群曲面描述方法的研究

探讨了在多点闭环成形中，基本体群曲面的数值矩阵描述和离散傅里叶变换描述方法；通过实例验证了离散傅里叶变换描述方法的有效性和对随机测量误差的鲁棒性；从闭环成形的实验结果可以看出，应用离散傅里叶变换描述能够体现板材多点成形时各基本体之间的相互耦合关系，提高了多点成形工件的精度。     

连续多点成形中的成形载荷分析

研制了连续多点成形装置来完成三维曲面工件的高效、柔性加工,并对其成形载荷的变化趋势以及不同工艺参数对成形载荷的影响进行了研究.首先,介绍了连续多点成形原理;基于一定的假设条件,建立了成形载荷的理论公式;以双曲率元件为研究对象,建立有限元模型,分析了y方向载荷、z方向载荷以及合成载荷的变化情况.接着,分析了上辊压下量、板材厚度以及柔性辊曲率半径对成形载荷的影响.最后,设计出成形装置并进行实验.结果表明,y方向载荷最大值为6.693 kN,成形载荷的最大值为6.716 kN,成形载荷主要由y方向载荷决定;z方向载荷最大值为1.412 kN,为驱动工件运动的力;随上辊压下量的增加、板材厚度的增加以及柔性辊曲率半径的减小,y方向载荷均增加.成形载荷的变化情况与实际情况吻合,为成形装置的研制提供了指导作用.实验结果证明,连续多点成形是一种连续、高效、柔性的三维曲面成形方法.     

基于多点成形的液压成形工艺关键技术的研究

介绍了基于液压成形和多点成形原理的板材成形新工艺.该工艺凸模用液体代替,凹模采用多点基本体调形而成.并用凹模垫技术提高多点成形技术中板材面轮廓度形状精度.对该工艺的液压系统、基本体的调形及压边圈等关键技术问题进行了深入研究.研制出了成形装置,并进行模拟试验.     

汽车覆盖件冲压成形仿真的研究及其工程应用

拉延是板料冲压成NAFORM建立有限元冲压仿真系统,对板料拉延成形过程进行了研究.结果表明,坯料形状、压边力大小和拉延筋布置是影响板料拉延成形的关键因素;典型仿真范例验证了研究结果的可靠性,并从成形极限图(FLD)上进行了工艺方案的改进.     

优化板料成形状态的新技术

为了解决一些形状复杂的薄板零件在实际生产中存在的问题，提出了优化板料成形状态的思想，介绍了一种既能有效地减小薄板成形时法兰面上流动阻力极大区域内的流动阻力，又不会增加起皱趋势，进而优化板料成形状态的新工艺措施。对这一措施进行了较为精确的有限元数值模拟和机理分析。     

Simulation and Experiment on Workability for Cold Pressure Forming of Sheet Metal Part with Step Cross-section

In modem manufacturing, a new type of sheet metal part with step cross-section in both inner hole and outer edge is proposed. The traditional stamping separating processes can only produce sheet metal part with vertical cross-section. According to the latest developing theory and potential of cold pressure forming: combination of pressure and cold forging, a new flow control forming of sheet metal(FCF) is excogitated based on blanking process of general stamping and combined with cold forging processes such as extrusion and coining, etc, which is aiming at the above-mentioned new type of sheet metal part. With utilization of this new process, the new type of sheet metal parts can be manufactured. In order to shorten the testing period, the numerical simulation was carried out by using DEFORM-3D software, and both deformation and mechanics rules were analyzed. Based on the simulation, both punching part and blanked parts of this new type were successfully developed. Then a new conception of optimal distance between the step walls of inner hole and outside edge was proposed and the design principle for its numerical value was inferred. Furthermore, a mold set for combination of stamping & cold forging was designed and manufactured, by which the technologic experiments were taken for validation with Aluminum plate of thickness 2.35 mm for power battery cover board, which verified the principle of the distance between the step walls. The research of cold pressure forming of thin sheet metal with step cross-section is significant, not only to the development of modem mechanical manufacture, but also to metal plastic forming science.     

汽车覆盖件模具冲压有限元仿真分析

针对汽车覆盖件难以成形以及在冲压过程中易产生各种质量问题等特点,采用基于动力显式算法的有限元分析软件DYNAFORM,以某汽车内覆盖件前隔板为例,对模拟得到的成形极限图（FLD）、材料厚薄图进行分析,优选工艺设计。阐述了CAE技术在模具开发中的重要作用。     

应用数值模拟技术研究摩擦对板料拉深成形的影响

本文论述了摩擦对板料成形的特点和重要性,应用数值模拟技术研究摩擦对板料拉深成形的影响。结果表明：模拟某复杂零件成形性能与摩擦系数关系密切;当摩擦系数为μ3时,冲压方向最大应力最小。研究结果表明采用数值模拟技术便于研究摩擦与板料冲压成形之间的相互关系。     

Generation and suppression of local severe plastic deformation in sectional multi-point forming

Sectional multi-point forming (SMPF) technology provides a new solution for forming large-size sheet metal. With this technique, large-size parts of sheet metal can be manufactured on a smaller multi-point forming press. But the force status and deformation of the workpiece are complicated in SMPF; the local severe plastic deformation will be produced easily in the transition region, and strain-hardening will be commonly produced subsequently. The hardening is difficult to eliminate in subsequent processes, which will largely affect the final deformation quality. In this paper, the generation of local severe plastic deformation was discussed; NURBS-based modeling method was used to construct the shape of the assortative region to suppress the defect. Experiments proved that the method is fairly effective. Finally, a plan was suggested to raise further the forming limit of materials and enhance the work efficiency by combining multi-point press forming with assortative region method.     

板料数控柔性成形工艺在新品开发中的应用研究

板料柔性成形是基于产品的数字化信息,由产品的三维CAD模型直接驱动,通过高度可调的基本体构成包络面,实现三维曲面零件成形的技术。典型的板料柔性成形方法是增量成形与多点成形。增量成形通过一个成形工具头沿x、y轴方向的运动及z轴方向的进给,逐层形成零件的三维包络面,从而实现板料的渐进成形;多点成形的核心是规则排列的基本体阵列,通过控制基本体z方向的位置坐标使其构成所需包络面,进行板料快速成形。介绍了以数控多点柔性成形新工艺进行新产品开发试制的应用。     

基于Dynaform对拉延筋在板材拉深中的应用研究

板材冲压工艺应用十分广泛,如何提高板材在拉深工艺中的成形质量,是从事冲压的技术人员和研究人员一直关注的热点问题。在板材拉深成形控制中设置拉延筋是既经济灵活又广泛运用的方法。在参考国内外资料的基础上,应用CAE中的专用分析软件Dynaform分别模拟了有拉延筋和无拉延筋存在的板材拉深成形过程,并对各自的数值模拟的结果进行对比分析,得出了拉延筋可以更有效地提高拉延件的成形质量的结论。     

Research on three-dimensional surface parts in multi-gripper flexible stretch forming

Multi-gripper flexible stretch forming (MGFSF) is a novel flexible forming process of sheet metal based on the multi-point forming principle. The straight jaws in traditional transverse stretch forming (TSF) are replaced by several discrete clamping mechanisms on both sides. To help understand the forming characters of MGFSF, spherical and concave–convex parts were selected as the research objects and finite element analyses on TSF and MGFSF were implemented using an explicit nonlinear finite element code. The influence of the transition length on the forming results in MGFSF was also taken into account in the present work. The simulation results reveal that a shorter transition length in MGFSF would result in an easier conformability of the sheet metal to the desired shape as well as a smaller strain variation in the forming zone. It is also found that, compared to TSF, the sheet metal can be formed without transition zone by utilizing MGFSF, which could significantly improve the material utilization and save the manufacturing costs. Finally, experimental validations were conducted on the self-developed MGFSF apparatus and the experimental results show a good agreement with the numerical results.