Computer simulation of stereolithographic curing reactions: phenomenological versus mechanistic approaches

A new phenomenological modelling approach to study, simulate and optimise the curing processes of thermosetting materials for stereolithographic processes is proposed. The model was developed for light-initiated, thermal-initiated, light-initiated accelerated by heat, and light and thermal-initiated systems. This model includes the effects of initiator concentration, temperature and light intensity, predicting the diffusion-controlled effects that occur after vitrification, the phenomenon of unimolecular termination and the shrinkage effects. The model is numerically implemented through the finite element method and solved using both the Galerkin method for spatial approximation and the Crank-Nicolson method for temporal approximation. The model was experimentally verified showing a good correlation between experimental and predicted values.     

激光快速成型及其固化树脂

简要介绍了快速制造技术 ,阐述了光固化成型原理 ,激光光源及所用光固化树脂。探讨了光固化树脂及工艺对成型精度的影响。     

可见激光立体光造型树脂光固化过程的研究

研究了在514nm Ar^2 激光下丙烯酸环氧村脂在染料，叔胺，紫外引发剂协同引发下的固化过程，研究发现，激光在树脂中的穿透服从Lambert-Beer定律，固化深度主要由光照射能量和染料浓度决定。在引发剂组成及浓度一定时，固化深度及固化质量随光照射能量的对数的增加而线性增加。     

激光快速成型中的几个问题

本文讨论了光阑形状、口径、光固化点的排列方式，激光扫描速度、路径、固化层厚度等因素对激光快速成型技术中光固化层积出模型速度的影响。对不同种类的光敏树脂与成型速度的关系进行了实验分析。并提出制作最佳模型的设想。     

新型LED光源快速成形系统精度研究

介绍了以大功率UV-LED为光源的光固化快速成形系统(LED-SL)的基本原理.针对UV-LED的光源特点,研究了光束发散角对树脂固化形态的影响,在Jacobs光固化理论的基础上,建立了发散光束固化单线形状的数学模型.分析比较了UV-LED、激光、汞灯光源固化单线形状的差异及其对零件精度的影响.通过比较,阐述了LED ...     

立体光固化3D打印成型碳化硅陶瓷的烧结特性

立体光固化(SLA)作为碳化硅陶瓷材料3D打印的主流方法之一,具有广泛的应用前景。本文针对立体光固化成型的碳化硅素坯,进行了脱脂与反应熔渗试验,通过烧结过程中密度、强度、收缩率、微观结构的变化,研究了立体光固化成型碳化硅素坯的烧结特性。结果表明:脱脂后样品具有较低的烧结收缩率,特别是增材方向,为0.88%,脱脂后的坯体强度为0.26 MPa;光敏(UV)树脂的残留热解碳(PyC)呈网状结构连接碳化硅颗粒,热解碳局部出现断裂,同时样品沿打印层间出现微裂纹;反应熔渗后残留热解碳与硅反应生成β-SiC,连续相硅填充孔隙与层间微裂纹,样品体积密度为2.79 g/cm³,抗弯强度为183.99 MPa。     

In‐line stepped ridge coaxial‐to‐rectangular waveguide transition with capacitive coupling

An original in‐line coaxial‐to‐rectangular waveguide transition including stepped ridged sections is presented. This device differs from the state of the art because of the coaxial inner conductor not being in electrical contact with the ridge, leading to considerable mechanical advantages. In addition to this, capacitive coupling can extend the bandwidth even with a few matching sections when compared with the traditional counterpart presenting DC contact with the first ridge. An ultra‐compact transition is designed, manufactured, and tested in back‐to‐back configuration. From measured data, a return loss better than 20 dB on a bandwidth of 1.27 GHz (12.2%) is observed in this configuration. An average insertion loss of 0.11 dB can be derived for the standalone transition.     

3D Printing of Viscoelastic Suspensions via Digital Light Synthesis for Tough Nanoparticle–Elastomer Composites

The rheological parameters required to print viscoelastic nanoparticle suspensions toward tough elastomers via Digital Light Synthesis (DLS) (an inverted projection stereolithography system) are reported. With a model material of functionalized silica nanoparticles suspended in a poly(dimethylsiloxane) matrix, the rheological-parameters-guided DLS can print structures seven times tougher than those formed from the neat polymers. The large yield stress and high viscosity associated with these high concentration nanoparticle suspensions, however, may prevent pressure-driven flow, a mechanism essential to stereolithography-based printing. Thus, to better predict and evaluate the printability of high concentration nanoparticle suspensions, the boundary of rheological properties compatible with DLS is defined using a non-dimensional Peclet number (Pe). Based on the proposed analysis of rheological parameters, the border of printability at standard temperature and pressure (STP) is established by resin with a silica nanoparticle mass fraction (ϕ_silica) of 0.15. Above this concentration, nanoparticle suspensions have Pe > 1 and are not printable. Beyond STP, the printability can be further extended to ϕ_silica = 0.20 via a heating module with lower shear rate to reduce the Pe < 1. The printed rubber possesses even higher toughness (Γ ≈ 155 kJ m⁻³), which is 40% higher over that of ϕ_silica = 0.15.     

用于面曝光快速成形系统的光照度测量系统研究

面曝光快速成形工艺中,视图平面上的光照度大小严重影响着零件的制作精度,为控制面曝光快速成形工艺中的制作精度,需要准确测量视图平面上的光照度,为此开发了基于硅光电池的光照度测量系统.系统采用硅光电池接收光信号并转换成微弱的电流信号,经I/V转换和放大后以电压信号传送至MCU进行A/D转换,再根据数字信号和硅光电池的线性灵敏度计算出实际光照度值.为能动态调整放大电路的增益,系统采用了数字电位器作为反馈元件.利用该系统测量了面曝光快速成形工艺中视图平面上的光照度,对测量数据用MATLAB进行3次曲线拟合,建立了光照度与灰度的模型关系,利用该关系,可方便地通过改变灰度来调整视图平面上的光照度.