基于新LOM的金属功能零件分层快速制造研究

基于新LOM方法和热扩散工艺，以1.0mm数量级的不锈钢板做造型材料，尝试了金属功能零件的分层快速制造，介绍了新LOM方法的原理，进行了金属分层板的连接实验和样模制作。研究结果表明，新LOM方法加工的零件曲面光滑，没有明显的台阶效应；热扩散焊在堆积成形方向上尺寸变化小，且为系统误差，结合强度达到100MPa；零件最大综合制造误差为0.485mm，但大部分位置处的误差在0.3mm以下。     

基于新LOM技术的金属零件自适应切片软件的开发

针对以金属板材为造型材料的分层实体制造中存在的精度问题,提出了一种新LOM方法直接快速制造金属功能零件。在传统LOM切片算法的基础上推导出了新的分层切片算法,并开发了适用于新LOM方法的自适应切片软件。     

阻焊式分层实体制造技术研究

针对纸质材料的分层实体制造方法中存在的缺陷并结合模具的传统制作过程,提出电阻点焊金属分层板的新方法——阻焊式分层实体制造,以实现快速、直接制造金属模具的目的.介绍阻焊式分层实体制造双工位系统的基本原理和系统组成以及各部分的作用,重点分析该方法的工艺过程及焊头的位置控制,并用厚度为0.1mm的302不锈钢薄板为造型材料进行了试验验证,试验结果表明了该技术的可行性,所得成形件不需后处理便可作为模芯进行注塑,有效地缩短了模具的制作周期.     

基于薄片叠层连接的金属零件三维成型技术探索研究

为了制备具有复杂内腔的零件,近年来出现了通过不同焊接方法进行薄片叠层连接的技术工艺,如:热扩散焊接、电阻焊等。该工艺主要是通过线切割等机加工工艺获得金属薄片,再通过电阻焊或真空热扩散焊接等不同的焊接工艺焊接在一起。研究中,利用激光加工0.1 mm厚度的不锈钢片,从而获得单层二维图形结构,然后通过激光扫描焊接和热扩散焊接的方式来焊接经过叠加和固定的薄层,进而直接制造金属零件。通过研究激光加工与真空热扩散焊接两种工艺对薄片叠层后零件的外型轮廓以及片层间距的影响,探索薄片叠层连接技术对于复杂内腔零件制造的可行性。实验结果表明,进行薄片叠层时,真空热扩散焊接比激光焊接的零件成型效果更好,片层间间隙基本消失,贴合更加紧密,内腔层片状现象基本消失。因此真空热扩散焊接更适合于薄片叠层制造具有复杂内腔和精度要求较高的零件。     

基于CNC的自适应直接分层制造方法研究

将RP技术的增材制造理念与数控铣削加工技术相结合,提出了基于CNC机床的金属零件分层制造方法。为解决等厚分层方法存在的缺陷,提出了基于相邻层面积变化比率和轮廓法向矢量的自适应直接分层算法,并在Pro/E软件平台上,利用Pro/TOOLKIT进行了系统的开发。该方法采用定厚板材作为造型材料,在等厚分层的基础上对分层板进行自适应分层切削,有利于保证成型精度和提高成型效率,为复杂形面功能零件的快速成型制造提供了一种有效的方法。     

大厚度金属功能零件LOM技术的层厚分析

为了解决金属功能零件分层实体制造中的成型精度和强度问题，提出了基于大厚度切片的金属功能零件分层制造的概念。即在一定的成型精度条件下，通过综合优化分层和正反两面切削，最大限度地提高每一层板允许的厚度．并归整为若干种标准化厚度，以有效提高零件的强度和加工效率，获得具有较高精度和强度的金属功能零件。因此，分析了大厚度切片的金属功能零件分层制造中提高分层板厚度的方法层厚的标准化问题。     

基于LOM工艺快速成型的快速模具制造

本文系统地介绍了分层物体制造技术的原理、特点及其技术体系的基本环节,详细阐述了基于LOM工艺快速成型的快速模具制造技术。     

动态分区并行扫描方法研究

如何制造大型原型零件是目前快速成形技术(RP)研究的热点之一。分层实体制造工艺(LOM)在直接制造大型原型方面具有独特的优势。造型周期长是制造大型原型的困难之一,针对LOM工艺提出了动态分区并行扫描成形的方法。分析和试验结果表明,采用该方法可以有效提高成形效率,是实现直接制造大型原型的可行途径之一。     

基于分层实体制造的预分割成形

快速成形方法制造大型零件的一个共同难题是零件的翘曲变形。建立了描述分层实体制造(LOM)工艺中零件翘曲变形机理的数学模型，指出零件长度和层间粘接结是影响变形的关键因素．并由此提出了预分割方法来缩短零件参与变形的有效长度。开发了相关分层与控制软件。并制造了大型原型。实践证明预分割方法可有效避免大型原型的翘曲．保证成形原型的精度。     

分层实体制造(LOM)成形过程中的热力耦合有限元分析

在分层实体制造（LOM工艺）过程中,原型件存在着翘曲变形的问题,采用热力耦合的有限元分析方法对LOM成形过程进行分析,为优化工艺参数、获得高精度的原型件提供依据。在有限元分析过程中,针对LOM成形过程的特殊性,对其材料模型的选取、材料增长过程的描述、动态的边界条件等进行了特别的处理。采用了单元的activate/deactivate技术来对LOM成形过程的材料增长过程进行描述。     

大型原型快速制造中的并行加工技术

认为分层实体制造工艺（ＬＯＭ）是目前较成熟的几种快速成形工艺中加工效率最高的一种,最适合用于制造大型原型。提出了基于ＬＯＭ工艺的分区并行加工的思想,即将加工平面分为加工区域,并将被加工零件的数据进行分割,控制系统驱动多台扫描仪并行加工。对其关键技术进行了分析。采用分区并行加工技术可大幅度提高ＬＯＭ工艺的成形效率。     

分层实体制造中层间应力和翘曲变形的研究

分层实体制造(LOM)是一种典型的快速成形(RP)技术,该文对分层实体制造中的层间应力和翘曲变形进行了深入研究。建立了一种LOM工艺的简化模型,通过对模型的分析,给出了零件层间正应力和切应力的计算公式。通过试验现象,对翘曲变形的两种主要形式进行了说明。首次建立了翘曲变形过程描述模型,深入分析了翘曲变形的机理,认为内应力产生的等效弯矩是使零件翘曲变形的原因。最后从材料和成形工艺两个方面对减小内应力和翘曲变形的措施进行了论述。     

Al2O3 Ceramics Preparation by LOM (Laminated Object Manufacturing)

Al2 O3 ceramics green tape of 0.7 mm thickness was fabricated by a roll-forming technique. Ceramic green parts were formed by LOM (laminated object manufacturing), a kind of RP (rapid prototyping) technique. Final products were produced by a pressureless sintering process. Thermal analysis and SEM microstructure analysis of green tape were carried out to decide on the best process for removing the binder. Using a SEM, the microstructure of the ceramic parts was analysed. The mechanical properties of the parts were also analysed.     

Plaster casting process for prototyping of die casting based on rapid tooling

Rapid prototyping (RP) combined with a gravity casting process can provide a suitable substitute with steel tool die casting for prototyping metal casting. Due to differences between die casting and gravity casting, there are several drawbacks in RP simulated die casting. This paper is concerned with the development of a new plaster die casting process that combines pressurization and vibration for prototyping of die castings, and with a plaster die casting machine that has a structure similar to that of a die casting machine. The machine utilizes an oil cylinder for pressurization and a magnetic actuator for vibration. A rapid prototyped pattern is made by the laminated object manufacturing (LOM) process to prepare a plaster mold. In the process, a plunger in the developed machine simultaneously pressurizes and vibrates the molten metal to fill the plaster mold completely and to facilitate the creation of nuclei in the molten metal, respectively. The developed machine has produced a prototype of an end clutch cover with remarkable improvement in mechanical properties.     

<Emphasis Type="Bold">Development of Divisional Parallel Scan Technology in Large-Scale Laminated Object Manufacturing</Emphasis>

Many technological difficulties exist in the field of rapid prototyping (RP) technology when making large-scale prototypes. The manufacturing efficiency is the main problem, and the process implemention and RP equipment also present difficulties. In this paper, the concept of divisional parallel scan is presented. Laminated object manufacturing (LOM) technology is used for the basic forming process and has been improved continuously through practice. Static divisional scan technology was also better developed to dynamic divisional scan technology, which can help in achieving the object of improving work efficiency and optimising design.     

Study of laminated object manufacturing with separately applied heating and pressing

To improve the hot-pressing process currently employed in laminated object manufacturing (LOM), an innovative heating-and-pressing separation system is proposed, and heat transfer problems of this system are investigated. A thermal model is first established. It is solved numerically by the finite element method (FEM) software ANSYS, and verified by experiments. Based on the numerical solution under various operating conditions, it is found that the operating temperature of an adhesive can be reached quickly when the heater is maintained at a higher temperature, corresponding to a deeper heat-affected zone. This shortcoming can be effectively reduced if the speed of the heater is increased. Hence, a higher heater temperature together with a higher moving speed is suggested to shorten processing time and promote manufacturing efficiency. Through analysis, the appropriate distance between the roller and the heater, so as to obtain finished parts of high quality, is determined.     

A neural network solution for LOM process performance

A neural network (NN) modeling approach is presented for the prediction of laminated object manufacturing (LOM) process performance. A NN was developed using experimental data which were conducted on a LOM 1015 machine according to the principles of Taguchi design of experiments (DoE) method. The process parameters considered in the experiment to investigate LOM process performance were nominal layer thickness (NLT), heater temperature (HT), platform retract (PR), heater speed (HS), laser speed (LS), feeder speed (FS), and platform speed (PS). LOM process performance is divided in dimensional errors in X and Y directions (Ex and Ey), actual layer thickness (ALT), average surface roughness of vertical supporting frame (VSF-R_a), and tensile strength in X direction (TSx). It was found that NN approach can be applied in an easy way on designed experiments and predictions can be achieved, fast and quite accurate. The developed NN is constrained by the experimental region in which the designed experiment is conducted. Thus, it is very important to select parameters’ levels as well as the limits of the experimental region and the structure of the orthogonal experiment. The above analysis is useful for LOM users when prediction of process performance is needed. This methodology could be easily applied to different materials and initial conditions for optimization of other Rapid Prototyping (RP) processes.