一种PMMA非球面透镜零件成型工艺优化研究

非球面塑料透镜壁厚变化大,收缩不均匀,容易产生翅曲变形,其成型技术的关键是精密模具的结构设计和成型工艺参数的合理选择.以一种PMMA非球面透镜零件典型成型工艺为例,说明在注射成型中进行工艺改进的方法,以给加工同类零件的企业提供参考.     

实验验证用股骨柄假体样件的加工

金属在CT图像上会产生伪影,在需要分析人工髋关节股骨柄假体样件与相应股骨腔匹配情况实验中,股骨柄假体样件不能采用金属材料。由于光敏树脂成形后具有一定硬度,光敏树脂材料的股骨柄假体样件能够植入相应股骨腔而不会发生变形。此外,树脂材料样件加工方便,加工成本较低。提出采用光敏树脂作为实验验证用股骨柄假体样件材料,并介绍了采用SLA快速成型方法加工股骨柄假体样件的方法。实验中,光敏树脂材料的股骨柄假体样件被植入股骨腔中并拍摄了CT图像。CT图像中光敏树脂材料股骨柄假体样件与股骨松质骨之间分界明显,采用边缘检测方法很容易从CT图像中检测出股骨柄假体样件轮廓曲线。这使股骨柄假体样件与相应股骨腔之间的匹配程度得以定量分析。上述结果表明,采用光敏树脂作为股骨柄假体样件材料来分析股骨柄假体样件与股骨腔的匹配程度切实可行,较好地解决了金属股骨柄假体样件不能用来分析在股骨腔中的匹配程度问题。     

光固化光敏树脂蜂窝结构试样动态力学行为及本构模型

为明确光固化成型技术制备的蜂窝状结构光敏树脂材料的力学性能,使用万能材料试验机和分离式霍普金森压杆实验装置对原始实心试样和不同胞元直径的圆形蜂窝结构试样进行不同应变率的力学性能测试.结果表明:光敏树脂的弹性模量和屈服极限随应变率的增加而增加.低应变率下,光敏树脂达到屈服极限后出现了应变软化和应变硬化现象,体现出光敏树脂的粘弹性.高应变率下,光敏树脂呈现出显著的应变率效应以及应变率敏感性.蜂窝结构试样的弹性模量和屈服极限随着胞元直径的增加而降低.最后建立了高应变率下光敏树脂的ZWT非线性粘弹性本构模型,拟合的数据与实际数据能够较好地吻合.     

立体光造型成型材料的制备

以环氧树脂E-51和丙烯酸为基本原料,合成了立体光造型成型材料光敏树脂,通过比较不同树脂体系的固化度及显微硬度,优化了光敏树脂合成工艺;用硅烷偶联剂处理后的SiC纤维对光敏树脂进行了增强,比较了光敏树脂增强前后固化件的抗拉强度.结果表明:预聚物与单体三翔甲基丙烷三丙烯酸的质量比为2:1、光引发剂质量分数为3.5%时,树脂体系固化度最高,硬度指标较理想;光敏树脂经SiC纤维增强后,抗拉强度得到提高.     

激光快速成型加工中扫描路径的研究

通过对激光快速成型加工中现有的激光扫描方式进行的实验研究和理论分析，找出了零件产生翘曲和引起其他误差的原因，提出了一种新的扫描方法，从而有效地解决了由于树脂收缩而引起的零件翘曲和形状误差，并且由于采用这种扫描方式，可以使得该技术省去光开关     

一种高效率低成本制作微透镜阵列的方法

通常采用的多次掩模光刻和离子束刻蚀制作微透镜阵列的方法不但制作效率低,而且易产生较大的制作误差。提出了一种在硅基底聚合物薄膜上热压制作微透镜阵列的工艺方法,并利用自制的热压印设备进行了热压制作衍射微透镜阵列的试验,讨论了影响压印精度的温度和压力等工艺参数,对压印的衍射微透镜阵列进行了轮廓测试和部分光学性能测试。测试结果表明,压印制作微透镜阵列的复形误差小于10%,衍射效率高于90%,为高效率低成本制作微透镜阵列提供了一种新的方法。     

光固化快速成型机液位控制机构优化设计

光固化快速成型是一种堆加材料新型快速成型加工方法,成型过程中,成型精度是零件加工的关键,液槽树脂Z轴方向液位控制影响成型精度及制作效率。针对光固化成型(SL)中树脂液位控制和树脂利用率的问题,Z轴升降系统采用三副滚珠丝杆螺旋副机构来粗、微调节液面高度,控制液位和提高树脂利用率。实践证明,采用滚珠丝杆螺旋副传动,产品成型精度提高,满足整机对液位控制精度要求,树脂的利用率提高27.2%。     

增强光电图像传感器紫外探测薄膜的制备

传统的CCD、COMS等光电成像器件并不响应紫外光,在CCD、CMOS传感器光敏面镀上"紫外-可见"变频薄膜是增强其紫外响应的一种非常有效的方法.Zn2SiO4: Mn由于粒子直径小,稳定性好,荧光量子效率高等优点,在增强光电器件紫外响应领域有着很广泛的应用前景.实验用"旋涂法"在石英基底上生成Zn2SiO4: Mn紫外增强薄膜,并对其透射光谱、吸收光谱、激发光谱与发射光谱等光学性质进行测量分析.实验测得薄膜在300 nm以下透过率极低,在300 nm以上透过率很高且平稳;对300 nm以下的光具有很强的吸收,对300 nm以上的光吸收很弱且很平稳;激发峰在265 nm,发射峰在525 nm,即能将紫外光转化为可见光.实验结果表明Zn2SiO4: Mn薄膜是一种适用于增强CCD等图像传感器紫外响应的紫外增强薄膜.     

光敏树脂立体成型技术

据《Automotive Engineering》杂志1990年12月报道:光敏树脂立体成型技术是一项获得专利的最新设计方法。1987年在加拿大的维林西亚(Valencia)三维系统上首次试验成功并获得专利,目前国外已有200多家公司推广应用,获得了巨大经济和社会效益。光敏树脂立体成型技术是计算机、激光、光学扫描、光化学等多项科学技术的综合应用。光敏树脂立     

光学零件模具的有限元分析

以建筑仪器中透镜所常用的光敏树脂成型模具作为研究对象,运用有限元分析的方法,对其施加满足实际工况的约束,并选择精度高的单元和划分更细的网格密度,计算出模具的在有预应力情况下模态频率以及模态振型,为进一步的模具动力学分析打下了基础.     

台式快速成型装置的光学系统研究与开发

快速成型技术是光学、电子、材料、计算机等多学科集成的高新技术。研制的台式快速成型装置具有体积小、成本低的特点,其制造成本及运行成本仅为同类国外产品的1/10～1/20。论文主要论述了该装置的光学系统设计过程。在首先确定光学系统设计准则的基础上,通过几种类型的光源比较,选择性价比高的紫外灯,并实现了计算机对紫外灯的自动控制,如光的开启、关闭、能量调节等。该光学系统采用椭球镜及圆锥面透镜等使光束聚焦耦合入光纤,在锥度光纤输出端,光束经扩束、准直、聚焦、滤除杂散光后照射在液面处,由计算机控制的工作台带动光纤,实现零件的自动加工。设计的光学系统成本低,光束质量高,性能稳定。     

Applying the one-column, many pencil local scanning maskless lithography technology to micro-RP system

This paper introduces an innovative one column, many pencil local scanning maskless lithography technology used in dynamic mask and applies it to rapid prototyping (RP) system. By using this technology in micro RP system, the resolution of the 3-D microstructures can be upgraded remarkably. In addition, some relevant experiments are conducted on this micro rapid prototyping system. In the experiment, light beam is projected onto a digital mirror device (DMD) chip [Hornbeck LJ. Digital light processing: A new MEMS-based display, 4th Sensor Symp, p. 297–304 (1996)], and the image is reflected through a micro mirror. Meanwhile, by making use of zoom lens and pins array mask (PAM), the continuing pixels can be scattered. Moreover, in order to project scattered pixels onto the resin surface, the optical system is exploited. Additionally, by using a micro-stage, it is able to control the micro X-Y movement between the scattered pixels. Furthermore, this paper makes use of the spray coating technology to improve the build up capability of the overhand structures of the traditional deep dip liquid-type RP system. Finally, combining the fore-mentioned technologies, one can produce 3-D prototypes with overhand structures in higher resolution.     

Slant beam rotation UV scanning to eliminate stair-steps in stereolithography fabrications

Stair-stepping is one of the major causes of poor surface finish in stereolithography (SLA) and other rapid prototyping (RP) systems. Taking this effect as an inability of conventional scanning systems, which can only fabricate layers with straight edges, the authors have studied and implemented a new SLA scanning technique. In the new method, termed slant beam rotation (SBR) scanning, an inclined beam of ultra violet (UV) light fabricates slant edges of individual layers, while an additional degree of freedom (DOF) in the scan head is used to rotate the beam inside the resin through 360 degrees to change the build angle. The data format needed to complete this scanning process has also been prepared and reported along-with the development of the stereolithography system. Through fabrications and analyses, it has been found that average surface roughness of a typical stair-stepped object reduced to 1.1 μm from 18.0 μm otherwise.     

光固化快速成形过程中树脂固化零件变形的数值模拟

根据光固化快速成形过程中的零件变形机理及薄板小挠度温度应力理论,详细分析板状零件成形的翘曲变形,得到光固化快速成形过程中树脂相变收缩的力学等效模型,给出板状零件在成形过程中的时变刚度表达式、光固化等效相变收缩力与树脂材料常数间的关系式。结合力学等效模型利用有限元软件ABAQUS对双层板状零件和桥式零件的成形过程进行了数值模拟,并与试验结果进行对比,结果表明数值模拟结果与试验结果相当一致,从而可实现成形零件实际变形的可预测性,也可为改进工艺、提高成形零件的精度提供理论支持和量化依据。     

微细光成型固化工艺参数优化

为了分析紫外光对液态光敏树脂进行曝光固化成型过程中工艺参数对固化物的形状和精度的影响,根据自行研制的实验系统的大量数据,对线形固化中的主要工艺参数进行了分析和优化。结果表明,在单层液态树脂膜厚30 μm,曝光光束功率0.15 μW,扫描速度15 μm/s以及工作距650 μm时能够得到具有较高精度线宽和线高的固化直线段,利用优化的工艺参数,成功实现了三维微小实体结构的成型制造。     

高速下摆式光学透镜抛光机的研发

传统光学透镜抛光机存在主轴摆动惯性大,机架易产生振动,整机稳定性差等严重影响产品精度的问题。本文在充分研究传统光学透镜加工设备性能的基础上,利用虚拟样机技术,研发了一套能够克服上述设备缺陷的新型高精度光学透镜抛光机。通过虚拟样机技术,不仅能解决传统研发方法的不足,而且能有效地降低抛光机的研发成本、缩短研发周期。     

SU-8 紫外深度光刻的误差及修正

在深紫外LIGA加工中,制作高精度大高宽比的微器件是很困难的。难点在于SU-8 光刻胶对紫外光的吸收系数随着波长变短而很快变大,而且其穿透深度也相应迅速变小;同时由于紫外光的衍射效应,获得高精度的大高宽比结构并不容易。本文深入研究了影响紫外深度光刻图形转移精度的如下因素:衍射效应、曝光剂量、紫外光波长和蝇眼透镜的分布等等。建立了基于模型区域的校正系统,该校正系统采用了分类分区域的思想将掩模图形按其畸变的特点进行了分类,在校正过程中对不同的类别分别建立校正区域,在每一校正区域内进行校正优化处理和校正评价,这种基于模型的分类分区域评价思想,使得校正过程有效且实时,该校正方法不仅降低了校正的复杂性,同时提高了校正的效率。     

紫外光快速成形系统扫描策略研究

紫外光快速成形机是国内自主开发的经济型快速成形机，介绍了紫外光快速成形机的光路构成与扫描策略，分析了平面扫描时边界过固化问题的成因及危害，并针对此问题提出了改进的扫描策略。     

An investigation into the rapid prototyping of moulds for expanded polystyrene foam

Expanded polystyrene foam, a packaging material, is traditionally injection-moulded by classical moulding techniques. However, the design and fabrication of these moulds is both intricate and time-consuming. In today's manufacturing environment of short time-to-market, the luxury of producing a mould for, often, a first-off article for client approval, is virtually untenable. Rapid prototyping technologies appear to offer an alternative method of fabrication which promises to drastically reduce the time for mould fabrication. When rapid prototyping of the mould is combined with microwave curing of the polystyrene, as an alternative source of energy to traditional steam heating, the benefit of considerably short throughput times can be expected. This paper describes the computer-integrated design and fabrication of both the mould and foam product, and discusses the main issues associated with rapid prototyping the mould, viz. accuracy of the prototype mould and the suitability of acrylic resin used in stereolithography apparatus for fabricating the mould, as well as the parameters for moulding expanded polystyrene using microwave energy. Initial results suggest that both the stereolithography process, and the acrylic resin used to build the stereolithographic model, can be used for rapid prototyping expanded foam products and their associated mould.     

Curing Characteristics of the Photopolymer Used in the Solid Laser-Diode Plotter RP System

Most stereolithography (SL) processes employ ultraviolet (UV) or diode pumped solid state lasers to cure the associated photopolymer to build a 3D part. A UV or diode pumped solid state laser is more expensive in initial cost and maintenance than a semiconductor laser. A semiconductor laser is used in the solid laser-diode plotter (SLP) rapid prototyping system to cure a specific photopolymer (DF2000). The DF2000 photo-polymer is formulated from a based resin, hardening agent, and powder. The wavelength of the semiconductor laser used in the SLP system is 680 nm and is in the range of red colour light. In this work, the curing effect of the visible wavelength spectrums generated by a lamp on the DF2000 photopolymer was investigated, using differential scanning photo calorimetry (DSPC). The DSPC result indicates that the curing degree of the photopolymer using blue light is better than that when using red light. The result also seems showing that the shorter the wavelength, the better the curing effect of the photopolymer. Hence, a blue semiconductor laser (405 nm) or a shorter wavelength laser or even a higher-power lamp, instead of a red laser, can be employed to increase the curing degree of the photopolymer used in the SLP system. The quantitative effect of the SLP processing parameters on the curing degree of DF2000 photopolymer and the mechanical property of the SLP test specimen was studied using the Taguchi method. The results show that the mechanical property of a fabricated part is proportional to the curing degree of the photopolymer. The results also indicate that the scanning pitch of processing parameters is the most sensitive parameter of the SLP system affecting the curing degree and, hence, also affecting the mechanical property. Therefore, the curing characteristics of the photopolymer used in SLP system could be used as an index of the mechanical property of a fabricated part. Also, the employment of a shorter wavelength laser rather than red laser can further improve the part mechanical property and fabrication speed of the part.