多点对压成形技术的应用现状

多点对压成形是一种先进的板料数字化成形技术．其基本原理是由上、下两套规则排列的冲头点阵代替传统的;中压模具．实现板料三维曲面的快速成形。冲头点阵中每一个冲头的高度都由计算机自动调整．所有冲头调整到需要高度后形成成形面．用于板料冲压成形。用一套装置可以成形不同几何形状、不同厚度．不同材质的钣金零件．从而实现柔性成形：成形过程由CAD数据信息驱动．只要设计出所需要的几何形状,就能够调整;中头点阵型面进行成形．     

铝合金型材多点拉弯成形的数值模拟

多点成形技术的核心是实体模具被离散的多点模具代替,实现了柔性成形。铝合金型材的拉弯成形中,可以用多点模具代替实体模具,实现了一套模具成形多种零件的可能,节省大量的费用和时间。本文提出了多点拉弯成形的构想,比较了多点模具和实体模具成形铝合金型材的成形效果,结果表明,多点模具可以用于型材的拉弯成形;并分析了多点拉弯成形过程中产生压痕缺陷的原因,提出通过弹性垫技术消除压痕的方法;对比了多点拉弯件的轮廓曲线和目标轮廓曲线,验证了多点拉弯成形技术的成形精度。     

板材加工柔性工具技术研究

针对成形后金属三维曲面零件的测量、装配等后续加工的支撑问题,提出了多点柔性工具技术。该柔性工具由按矩阵排列的数控调整冲头单元组成,可以根据CAD数据任意改变型面。本文对由多点柔性工具支撑的工件在自重下的变形规律进行了有限元分析,得到了工件最大变形量与板材厚度及冲头单元间距之间的关系,为多点柔性工具的设计开发提供了理论依据。     

蒙皮拉形可重构柔性模具模面生成系统开发及应用研究

针对飞机蒙皮零件多品种、小批量、形状复杂、成形精度要求高的特点,对可重构柔性模具蒙皮拉形关键技术进行了深入分析,基于CATIA二次开发技术开发了蒙皮拉形可重构柔性模具模面生成系统,实现了蒙皮零件数模在可重构柔性模具制造坐标系中的调形计算,具备了冲头高度干涉检查和虚拟模具三维仿真功能。经过应用验证,系统稳定可靠,能准确调形出蒙皮零件拉形所需的模具包络面。本系统的建立,为可重构柔性模具蒙皮拉形工艺研究提供了技术保障。     

复合垫层在多点模蒙皮拉形中的应用

采用柔性垫层是抑制和消除多点模拉形过程中零件表面缺陷的重要措施。文章设计和制造了3种具有不同增强结构的新型柔性垫层,使用这些新型垫层进行了实际蒙皮拉形实验,并在拉形过程中使用三维非接触光学测量方法进行了零件型面数据的在线测量。实验结果表明,各种复合结构垫层仅以较小的厚度即可有效地抑制各种零件型面缺陷的产生,并且各种复合垫层在成形时的厚向变形均匀度均优于单纯橡胶垫层,其中,以离散钢板条为增强结构的复合垫层效果最佳。     

多点成形中的柔性压边技术研究

对于薄板类零件而言,无论是利用整体模具成形还是多点成形,影响成形零件质量的关键因素是起皱。为了防止薄板类零件成形过程中产生起皱,尽量提高薄板类零件的变形量,研制了一种适合于多点成形的新型柔性压边装置,依据成形件的工艺特点、变形大小、材料特性及其弹性模量和成形零件形状,可以确定压边力的大小,且与板料直接接触的柔性压边圈随成形零件的形状不同而有所变形。介绍了多点成形压力机专用的柔性压边装置的工作原理、工作过程、布置结构、力学分析、成形力及压边力的计算。阐述了实际使用过程中的压边力和成形力的调节方法及柔性压边力,实现了数字无级调压,通过调节柔性压边力,明显改善了薄板类零件的成形质量。     

多点技术在飞机板类部件制造中的应用

多点技术是一种机电一体化的柔性制造技术,其核心是高度由计算机控制的基本体单元。多个基本体单元紧密排列在一起,构成型面可变的多点模具,用于板类零件成形。由于多点模具型面可由计算机任意调整,可代替传统模具用于不同形状的飞机板类部件的对压成形、蒙皮拉形等。基本体单元按照一定距离排列在一起,构成多点柔性工装,不仅可用于飞机大型板类零件成形后的测量、切割等操作的支撑与定位,还可用于飞机部件的柔性装配过程。应用多点技术,可以实现飞机板类部件生产过程的数字化。     

多点成形原理与技术

多点成形技术属于计算机柔性加工范畴 ,可进行板材立体曲面成形的多品种少批量生产。该成形方法使用多个可调整高度的冲头形成所要求的成形曲面 ,而无需制作金属模型。但是 ,为了把多点成形方法应用于立体曲面成形 ,还存在着不少必须解决的技术问题 ,如冲头的控制方式和保证成形精度等。1　多点成形原理表 1描述了多点成形的基本原理。　　多点模型成形在成形前 ,要预先设定各冲头的高度。在成形中 ,由设定行程长的冲头开始 ,依次接触原料板材。由于负荷集中在少数点上 ,容易产生折皱压痕。而多点冲压成形在成形前 ,所有冲头挟住原料板材 ,…     

航空换热器封头成形工艺分析与模具设计

通过对航空换热器封头的结构进行分析,提出不同的成形方案,最终采用分割零件,补全型面,分别拉深成形,还介绍了分型面的选择和模具设计要点。实践证明:该模具解决了零件成形难的问题,满足零件成形精度的要求。     

材料和目标形状对多点拉形成形精度的影响分析

多点拉形是将整体拉形模具离散成多点模具,可以在一套多点拉形模具上实现不同形状零件的拉形,省去了模具的设计、制造等大量的生产成本,实现了蒙皮件的柔性成形。多点拉形主要适于成形小曲率、大变形的蒙皮件,材料和目标曲面形状都是影响多点拉形成形结果的重要因素。通过对3种材料成形不同曲率半径球形件的多点拉形过程进行数值分析,研究材料和成形件目标形状对多点拉形的影响。结果表明,在成形件中心区域的形状误差小于边缘区的形状误差,拉伸方向的形状误差大于垂直拉伸方向的误差,成形件的曲率半径越小,成形件的形状误差越大。     

马鞍形板材件多点“三明治”成形实验研究

多点“三明治”成形是一种针对小批量多曲率板材工件制造而提出的新成形方法。用该方法成形时,上模采用聚氨酯模具,下模为型面可调节的多点模具。为了使多点模具型面连续化和消除工件表面的压痕,在成形过程中使用了金属护板和弹性垫板。由于工件板材两侧都和聚氨酯相接触,因此成形后工件的表面质量好。为了研究采用多点“三明治”成形复杂三维曲面工件的成形过程以及成形可能会出现的表面缺陷,文章选用马鞍面作为目标形面进行了实验研究,提出了用于提高工件的贴模程度,通过改变上模形状的分步成形方法,并得到了Q235B板材厚度和可成形马鞍形工件深度之间的关系曲线。     

Use of micro ultrasonic vibration lapping to enhance the precision of microholes drilled by micro electro-discharge machining

In microhole machining of metal, micro electro-discharge machining (MEDM) is an effective method that can easily create a hole with a diameter under 100 μm. Due to the poor surface quality and shape of MEDM, a machining method that compounds MEDM and micro ultrasonic vibration lapping (MUVL) is proposed here to allow the production of high precision microholes with high aspect ratios. In our investigations, first, a circular or stepped circular microtool was made by the MEDM process, and the tool was used to create a microhole on a small piece of titanium plate in the same machining process. Finally, the abrasive particles driven by the same tool were utilized to grind this hole in the MUVL procedure, and a hole with a diameter about 100 μm can be obtained. Owing to the microtool and workpiece not taking apart from the clamping apparatus during different machining steps, the microhole was processed in the co-axial situation, so the precise shape and perfect surface can be obtained easily. For example, the diameter variation between the entrances and exits of the microholes could reach a value of about 5 μm when the workpiece had a thickness of 500 μm, if the circular microtools was used. Meanwhile, the roundness of the microholes clearly improved, regardless of whether circular or stepped tools were used. However, owing to the perfect grinding effect between the microholes and microtools, the stepped circular tools produced high quality surfaces more easily than the circular tools.     

High-pressure jet-assisted cooling: a new possibility for near net shape turning of decarburized steel

Ultra-high-pressure cooling (UHPC) in turning operations is an effective method for achieving higher productivity. Previous research has demonstrated that the introduction of a high-pressure fluid jet into the gap between the tool and chip interface can control chip form and breakage. The present work shows the effect of UHPC in the turning of near net shape (NNS) decarburized parts. The workpiece material properties are strongly influenced by the loss of carbon atoms to a depth of up to 1 mm, due to the aggressive atmosphere during forming (decarburization). The extremely soft material makes chips difficult to control. Consequently, productivity decreases since the machine must be frequently stopped in order to manually remove the chips from the working area. The results show the influence of UHPC on chip form, surface topography and tool life when turning decarburized parts close to NNS. An interesting observation was that the combination of small cutting depth (near net shape) and soft material (decarburization) allowed for the presence of built-up edge formation, even at a high cutting speed.     

Direct laser deposition of Cu alloy on forming tool surfaces—Process window and mechanical properties

Direct laser deposition offers a widespread spectrum of applications. Creating functional surfaces for forming tools is one of them where inexpensive material for the main tool body is complemented layer by layer with a second material to tune the desired properties and shape. Investigations on coating mild tool steel with copper alloy have been carried out to outline the chances and challenges in this cost effective way of producing forming tools for processing stainless steels, e.g. 1.4301. This paper reports on experimental investigations showing the influence of the absolute angle of the tool surface and the relative angle between surface and laser beam/powder nozzle on the process window and the mechanical properties that can be obtained.     

复杂锻件净成形过程温度场的数值模拟

本文以数值模拟方法为工具,以齿轮温态净成形（Ｎｅｔ－ＳｈａｐｅＦｏｒｍｉｎｇ）工艺为对象,研究了复杂锻件净成形过程热力学因素对工件／模具系统的影响。重点探讨了工件与模具的接触传热问题及使用有限元程序分析计算的实现方法,并验证了其正确性。模拟分析得到的温度场可用于模具寿命和锻件精度的预测。     

Application of computer aided upper bound method in forging and extrusion processes

This paper presents the development of a Computer Aided Upper Bound software for the plain-strain upset forging, and closed impression die processes. The upper bound method is applied by providing the number of plastic sections (triangles). friction conditions of the tool surfaces, and geometry parameters as inputs to a predefined tool and workpiece configuration. The program calculates the forming pressure and provides the upper bound metal flow field and hodograph as outputs. The forming pressure is calculated by an upper bounding algorithm which can be improved by increasing the number of plastic sections. The differences in tool and workpiece surface friction coefficients and variation of die angles can be considered in order to optimize the forming process.     

转向球销球面加工组合机床设计

根据球面形成原理，将工件回转轴线和刀具回转轴线形成交角，利用两个圆运动，合成转向球球销的不完整球面。通过铣剧和滚压，在一台机床上完成球面精加工。     

Effect of the lubrication-cooling technique, insert technology and machine bed material on the workpart surface finish and tool wear in finish turning of AISI 420B

The paper is focussed on the effects produced by cutting operations on workpiece surface finish and tool wear. To this end, finish turning of AISI 420B stainless-steel was carried out under wet, minimum quantity of lubricant and dry cutting conditions, using both conventional and wiper technology inserts, on turning centres equipped with beds made in polymer concrete and cast iron. The workpiece surface finish and tool wear versus cutting volume were measured, and the results analysed and discussed in detail. The most significant results were: (i) the lubrication-cooling technique does not significantly affect the tool wear, whilst wet cutting produces the worst surface finish, (ii) the wiper inserts allow obtaining of the best surface finish, and (iii) the use of polymer concrete bed leads to an improved behaviour in terms of tool wear and surface roughness.     

Mechanism investigation for the influence of tool rotation and laser surface texturing (LST) on formability in single point incremental forming

Single point incremental forming (SPIF) is a new sheet metal forming process which achieves higher formability, greater process flexibility and reduced forming force compared to conventional sheet forming operations due to its characteristic of localized deformation. In recent years, a novel SPIF process assisted by localized friction heat is developed to further improve the material formability. Physically, the frictional heat is generated by the high relative motion at tool–workpiece interface resulted from tool rotation. However, the mechanisms behind formability difference induced by tool rotation at both low and high speed ranges are required to investigate in detail. In this paper, a series of experiments with an increase of tool rotation speeds ranging from 0 to 7000 rpm are conducted to form AA5052-H32 aluminum alloy sheets into a truncated funnel. Additionally, the obtained results are analyzed in terms of formability, forming forces and temperature trends to find out the different roles of friction and heat during the forming process. As a result, the formability behaviors at varying tool rotation speeds can be categorized into four stages according to different reasons. It indicates that friction is the dominant factor in low tool rotation speed range (0–1000 rpm) but will be substituted by thermal effect and potential dynamic recrystallization in high tool rotation speed range (2000–7000 rpm). Furthermore, due to the proved lubrication enhancement and hydrodynamic enhancement generated by surface textures, a laser surface textured forming tool is also utilized to show its influence on forming forces, measured temperatures and the corresponding formability. Finally, it demonstrates that the fabricated laser surface texturing (LST) is capable to reduce the friction at tool–workpiece interface and change the magnitude of heat generation.     

利用TiC半烧结体电极进行电火花表面处理的实验研究

研究了一种在普通电火花加工机床上实现金属工件表面处理的新方法。它使用传统电火花加工方法，通过特制的半烧结体电极在加工过程中使工件表面迅速形成一层硬质碳化物陶瓷，从而达到改善工件表面性能的目的。对这种方法的原理进行了初步的探讨，并在大量实验的基础上，通过厚度测量、表面粗糙度测量、X射线衍射分析等一列实验手段，对沉积层的生成特性进行了详细的分析。实验与分析表明，用电火花加工的方法进行金属表面沉积陶瓷层技术是一种极具潜力的表面改性方法。