数控渐进成形下压点分散的等高线成形轨迹生成

为解决在数控渐进成形中由于挤压工具压入点集中而使工件局部凹陷的问题,研究了基于商用UG软件的挤压工具下压点沿工件轮廓均布的等高线成形轨迹生成方法,并通过数字模拟和实际成形实验分析了所生成下压点分散成形轨迹的成形效果。结果表明,该方法能够解决工件局部凹陷问题,提高成形质量。     

金属板料单点渐进成形下压点分散的等高线混合成形轨迹生成

等高线成形轨迹是现行金属板料单点渐进成形的主要加工方式。针对板料渐进成形过程中由于成形工具头挤压造成的工具头下压点过于集中产出的成形件局部凹陷、破裂及成形件整体扭曲和板厚分布不均匀等问题,提出了一种结合商业Unigraphics NX 10.0(UG 10.0)软件轮廓铣削加工中混合加工策略和沿部件斜进刀方式结合的金属板料单点渐进成形等高线成形轨迹生成的方法。Abaqus有限元数值模拟和实验分析表明,使用上述方法成形的成形件不仅避免了成形表面局部凹陷和破裂问题,还解决了成形件整体扭曲和板厚分布不均匀等问题。     

面向数控渐进成形鼓包问题的成形轨迹生成与规划

针对数控渐进成形中鼓包的问题,提出了基于STL(Sterolithography)模型的等高线轮廓扫描、等高线轮廓与底面扫描、各等高层由外向内全扫描和各等高层由内向外全扫描4种挤压工具扫描运动轨迹类型,并给出了基于STL模型顶点偏置算法和多边形边偏置算法的各类型挤压运动轨迹生成方法;同时,采用有限元分析软件对这4种扫描运动轨迹的数控渐进成形效果进行了数字模拟仿真分析。研究结果表明,采用各等高层由内向外全扫描的轨迹进行数控渐进成形时不发生鼓包现象,并且能够减少制件的整体厚度差。     

基于 ＵＧ 的五轴数控渐进成形轨迹生成研究

针对金属板材五轴数控渐进成形轨迹生成的需求,研究了基于UG的五轴数控渐进成形轨迹生成方法.为使挤压工具能够按照用户所希望的方向挤压板材,给出了五轴数控渐进成形中基于前倾角和侧倾角的挤压工具姿态定义方法.研究了基于等残留高度的五轴不等层间距等高线轨迹生成方法以及交错运动轨迹生成方法,并给出了五轴数控渐进成形加工轨迹应用实例仿真.     

成形轨迹对数控渐进成形质量的影响

为了研究数控渐进成形过程中不同的成形轨迹对成形质量的影响,在给出下压点集中的等高线轨迹、下压点分散的等高线轨迹、等螺距螺旋线轨迹和不等螺距螺旋线轨迹这4种成形轨迹的生成方法的基础上,采用ANSYS/LS-DYNA软件,对基于这4种成形轨迹的数控渐进成形过程进行数值模拟,并根据数值模拟结果,对比分析了基于这4种成形轨迹的...     

金属板材数控渐进成形技术及加工轨迹坐标对位研究

金属板材数控渐进成形技术，是一种通过三轴数控成形机对金属板材进行逐层辗压而成形工件的柔性加工技术。本文探讨了金属板材数控渐进成形技术的过程、原理，同时，为了有效地排除成形过程中坐标对位对零件上出现的拉裂、材料堆积、材料硬化等现象的影响，本文提出了一种基于机器视觉的非接触式加工轨迹坐标对位方法，完成了金属板料数字化渐进成形中支撑模型的非接触式高精度快速定位。     

双凸板材件的数控渐进成形研究

针对数控渐进反向成形中无法直接成形加工双凸板材件的问题,提出了基于双面挤压的双凸板材件数控渐进反向成形方法。该方法通过设计从正反两面可接近各形体的支撑模,并把板材用两个支撑模装夹,从正反两面挤压板材来实现双凸板材件成形。给出了双凸板材件的成形工艺方案和支撑模设计方法,研究了双凸板材件数控渐进反向成形过程数字模拟分析的方法并运用数值模拟分析了该方案的可行性,并且通过成形试验,完成了双凸板材件的制作。研究结果表明,基于双面挤压的数控渐进反向方法可应用于双凸板材件的制作。     

三轴与五轴数控渐进复合成形

由于现有的数控渐进成形都采用三轴数控系统,无法成形加工包含有从Z轴正方向或负方向不可见且成形角大于90°曲面的复杂钣金件,针对此问题,提出一种基于三轴数控渐进成形与五轴数控渐进成形复合的成形方法。综合考虑成形效率和可成形性,将形状特征分为三轴数控渐进成形和五轴数控渐进成形可成形加工的特征,并分别采用三轴数控渐进成形和五轴数控渐进成形依次完成其成形。基于ANSYS/LS-DYNA的有限元分析和实际成形实验表明,所提出的方法具有可行性,能够制作出包含有从Z轴正方向或负方向不可见曲面复杂钣金件。     

数控渐进成形板料尺寸自动确定方法研究

在板材数控渐进成形中,为满足节省材料、降低成形加工载荷的要求,提出了基于STL(Sterolithography)模型的数控渐进成形板料尺寸自动确定方法。利用板材件底面边界多边形的最小矩形包围盒确定了板料的长、宽;根据板材件厚度的正弦减薄规律确定了板料的厚度,并生成了板材件厚度分布颜色云图。通过对不同形状的板材件比较分析表明,本方法较传统方法能够节省板料9.4%~23.5%。基于有限元分析的数字模拟结果表明,采用本方法确定的板料尺寸完全可以加工成形出预期的板材件。     

基于NC代码的数控渐进成形有限元分析轨迹点提取研究

针对数控渐进成形有限元分析中非线性运动加载问题,提出了一种基于NC代码的数控渐进成形有限元分析轨迹点的提取方法。首先通过VC++编程对NC代码文件进行读取,识别出NC代码中刀具轨迹的插补形式;然后分别按照直线插补和圆弧插补两种插补形式,将刀具轨迹按给定的精度离散成点群,并将点的坐标连同设定的时间分别存储为有限元分析软件可读入的文本格式文件。基于ANSYS/LS-DYNA的应用实例表明,利用该方法从NC代码中获取的有限元分析所需轨迹点,可保证数控渐进成形有限元分析仿真稳定可靠地进行。     

板料数控渐进成形中变形力的研究

研究了板料数控渐进成形变形力的2种计算方法：按照纯剪切变形的方式计算变形力;按照剪切和弯曲综合变形的方式计算变形力。同时,通过实验测量出渐进成形的实际变形力。通过比较,实验测定的变形力与假定剪切弯曲变形计算的变形力相近,可以认为渐进成形是一种剪切弯曲变形。     

Single Point Incremental Forming and the Forming Criteria for AA3003

Single Point Incremental Forming (SPIF) is a modern method of forming sheet metal, where parts can be formed without the use of dedicated dies. The ability of SPIF to form a part is based on various forming parameters. Previous work was not accomplished with the help of design of experiments, thus reducing the number of parameters varied at any time. This paper presents two designs of experiments, which formalise the forming parameters critical in SPIF and the degree to which they affect formability.     

Forming Limit Curves in Single Point Incremental Forming

New experimental data is presented on Forming Limits in Single Point Incremental Forming (SPIF), which is a sheet metal forming process which does not require dies. A Box-Behnken Design of Experiment is used to develop the experimental plan and analyze data. In former work, the most critical factors affecting Single Point Incremental Forming were found to be material type, material thickness, formed shape, tool size, and incremental step size. In this experimental work, new results are presented as graphical response surfaces which show the forming limit for all the critical factors listed previously. In addition, forming limits are presented in terms of Forming Limit Diagrams.     

Forming strategies and Process Modelling for CNC Incremental Sheet Forming

Incremental Sheet Forming (ISF) is a process capable of producing complex sheet components by the CNC movement of a simple tool in combination with simplified dies. Earlier work revealed two major process limits, namely the limitation on the maximum achievable wall angle, and the occurrence of geometric deviations. The work detailed in this paper focuses on forming strategies to overcome these process limits, including the processing of tailor rolled blanks. Additionally, finite element modelling of the process is presented and discussed with respect to the prediction of the forming limits of ISF.     

Analysis of Material Formability in Incremental Forming

Incremental forming is an innovative sheet metal forming technology in which a blank is plastically deformed through the progressive action of a small-size punch, whose movement is governed by a CNC machine. In this way the tool locally deforms the material through an almost pure stretching deformation mechanics.The paper is focused on material formability in incremental forming. Several tests were developed, aimed to the achievement of different straining conditions in the material and consequently to the determination of Forming Limit Diagrams for progressive forming operations. The features and the application of such FLD are discussed in the paper.     

On-Line Control of Single Point Incremental Forming Operations through Punch Force Monitoring

Among the innovative sheet metal forming processes, Single Point Incremental Forming (SPIF) represents the simplest and the cheapest one. Despite its relevant advantages, up to now no specific CAE tools for SPIF were developed and the tool trajectory is generally defined utilizing CAD/CAM software developed for machining applications. In the paper an innovative monitoring and control approach, aimed to define and in-process update the most relevant process parameters during an industrial SPIF operation, is proposed. The strategy utilizes as monitoring variable the punch force trend: a set of preliminary tests demonstrated, in fact, its suitability as “spy variable” of the process mechanics and, in particular, of excessive sheet thinning and material failure approaching.