Improvement of thickness deposition uniformity in nickel electroforming for micro mold inserts

Thickness deposition is a crucial issue on the application of electroformed micro mold inserts. Edge concentration effect is the main source of the non-uniformity. The techniques of adopting a non-conducting shield, a secondary electrode and a movable cathode were explored to improve the thickness deposition uniformity during the nickel electroforming process. Regarding these techniques, a micro electroforming system with a movable cathode was particularly developed. The thickness variation of a 16 mm×16 mm electroformed sample decreased respectively from 150% to 35%, 12% and 18% by these three techniques. Combining these validated methods, anickelmold insert for microlens array was electroformed with satisfactory mechanical properties and high replication precision. It could be applied to the following injection molding process.

Numerical simulation method for weld line development in micro injection molding process

In order to reduce the "trial-mold" risk and cost,numerical simulation method was applied to micro injection molding weld line development investigation. The micro tensile specimen which has the size of 0.1 mm(depth) ×0.4 mm(width) ×12 mm(length) in test area was selected as the objective part,and polypropylene(PP) as the experimental material. Respectively with specific commercial software(Mold Flow) and general computational fluid dynamic(CFD) software(Comsol Multiphysics) ,the simulation experiments for development of weld line in micro injection molding process were executed and the real comparison experiments were also carried out. The results show that during micro injection molding process,the specific commercial software for normal injection molding process is not valid to describe the micro flow process,the shape of flow front in micro cavity flowing which is important in weld line developing study and the contact angle due to surface tension are not able to be simulated. In order to improve the simulation results for micro weld line development,the general CFD software,which is more flexible in user defining function,is applied. The results show better effects in describing micro fluid flow behavior. As a conclusion,as for weld line forming process,the numerical simulation method can give a characteristic analysis results for processing parameters optimizing in micro injection molding process;but for both kinds of softwares quantitative analysis cannot be obtained unless the boundary condition and micro fluid mathematic model are improved in the future.

Microstructure of Zn-Al4 alloy microcastings by micro precision casting based on metal mold

Metal mold micron scale precision casting technology was developed successfully,and three-dimension complicated microgear castings in micron scale were produced.Evolvement regularity of microgear castings were observed by optical microscope and scanning electron microscope.Compared with conventional casting,microcasting is characterized by typical nonequilibrium solidification,for example,its grain size can be refined significantly,eutectic structure is transformed from lamellar morphology to rod eutectic,and the ratio of primary phase is increased.This kind of microstructure can promote mechanical properties of microcasting.

Rapid manufacturing of SiC molds with micro-sized holes using abrasive water jet

Silicon carbide (SiC) is highly wear resistant with good mechanical properties, including high temperature strength, excellent chemical resistance, and high thermal conductivity and thermal shock resistance. SiC molds, which can be produced with diverse microstructural features, are now widely used in glass molding owing to their excellent characteristics, and also have potential applicability in IT industries. SiC molds are traditionally fabricated by silicon micromachining or dicing. The fabrication cost of silicon micromachining is very high, however, because several expensive masks are needed. Furthermore, the fabrication time is very long. Meanwhile, it is difficult to make micro-patterned molds with arbitrary shapes using dicing saws. Abrasive water jet (AWJ) is widely applied to cut and drill very brittle, soft and fibrous materials. It offers high energy density, the absence of a heat affected zone(HAZ), high performance, and an environment friendly process. In spite of these advantages, micro-hole drilling via conventional AWJ processing suffers from notable shortcomings. We proposed a new abrasive supplying method of AWJ. The proposed method reduces frosting phenomena, and provides micro-machining of AWJ. The characteristics of a hole machined was investigated by the proposed AWJ process according to the ratio of water and abrasives. With the optimal experimental conditions, 3×3 array SiC molds with the diameter of 700 μm and depth of 900 μm were successfully manufactured.

Flowing simulation of injection molded parts with micro-channel

In the micro-molding of component with a micro-sized channel, the ability for polymer melt to flowing into the micro-channel in a macro-sized part is a big challenge. The multidimensional flow behaviors are included in the injection molding the macro-component with a micro-channel. In this case, a simplified model is used to analyze the flow behaviors of the macro-sized part within a micro-channel. The flow behaviors in the macro-cavity are estimated by using the finite element and finite difference methods. The influence of the injection rate, micro-channel size, heat transfer coefficient, and mold temperature on the flowing distance is investigated based on the non-isothermal analytic method. The results show that an increase in the radius of the micro-channel and mold temperature can improve effectively the flowing distance in the micro-channel.

Injection molding and debinding of micro gears fabricated by micro powder injection molding

Micro powder injection molding （μPIM） was investigated for possible mass production of micro-components at rela- tively low cost. However, scaling down to such a level produces challenges in injection molding and debinding. Micro gears were fabricated by μPIM from in-house feedstock. The effect of injection speed and injection pressure on the replication of the micro gear cavity was investigated. Solvent debinding and thermal debinding processes were discussed. The results show that micro gears can be successfully fabricated under the injection pressure of 70 MPa and the 60% injection speed. Either too low or too high injection speed can cause incomplete filling of micro gears. The same is the case with too low injection pressure. Too high injection pressure can bring cracks. Solvent debinding of micro gears was performed in a mixture of petroleum ether and ethanol. Subsequently, micro gears were successfully debound by a multistep heating schedule.

基于微注塑成型技术的PLA微针最佳成型工艺研究及其使用性能分析

为了提高聚合物微针的生产效率,提高成型质量,降低生产成本及适应大批量生产的要求,利用微注塑成型技术制备聚乳酸材料(PLA)的医美用微针贴片。通过正交实验法探究了注塑成型过程中的熔体温度、模具温度、注射速度、保压压力以及保压时间五项工艺参数对PLA微针顶端直径的影响。利用电子显微镜及测力计对PLA最佳工艺微针进行形貌尺寸表征及力学强度测试,并进行了体外皮肤穿刺测试及透皮渗透实验验证了其对皮肤的穿刺及渗透作用。结果表明,当工艺参数为熔体温度200℃、模具温度45℃、注射速度360 mm/s、保压压力50 MPa、保压时间4 s时,达到注塑成型PLA微针的最小顶端直径及成型效果,高度达到0.524 mm,顶端直径达到0.027 mm,针尖成型明显最优,且微针达到性能要求。

熔体黏弹特性对模内微装配成型制造精度影响

针对微细万向球形转动运动副的功能自润滑液膜辅助模内微装配成型,明晰其微装配界面直径制造公差—黏弹性热流固耦合冲击载荷、连续相变演化区厚度、热黏弹塑性应力—熔体黏弹弹性的多场协同耦合演化规律,是实现精密调控其制造精度的关键技术问题。结果表明,微装配界面直径制造公差受控于二次注射成型充填熔体的黏弹特性,当参考黏度由2267 Pa·s增至15000 Pa·s时,微装配界面直径制造公差由11μm增至19μm,增幅为72.7%;而当松弛时间由0.05 s增至0.25 s,则由31μm减至19μm,减幅38.7%;为了满足行业规范的尺寸制造公差技术指标≤30μm的要求,不宜采用松弛时间小于0.05 s的高弹性熔体进行其功能自润滑液膜辅助模内微装配成型。

超声塑化微注射成型技术研究现状及展望

简述了超声塑化中界面摩擦生热、黏弹性生热和空化效应3种生热机理及其研究现状,从超声塑化微注射成型(UPMIM)工艺参数的影响效果和成品性能的影响因素两个角度分析概括了UPMIM工艺的研究现状。介绍了现有UPMIM装置的结构及加工步骤,概括了UPMIM在精密药物输送装置、智能定制植入物和微流控设备等领域的应用研究现状,指出了UPMIM技术大规模工业化生产应用所具有的技术优势和面临的诸多技术挑战,对UPMIM未来的主要研究方向与应用领域进行了总结与展望。

湿型砂铸造中的旧砂微粉回用工艺

针对湿型砂铸造中旧砂循环混配再利用时型砂综合性能欠佳,铸件砂眼、夹砂结疤的缺陷率高,铸件质量不稳定等问题,对型砂进行了检测和数据分析,通过对双盘冷却机旋风分离后的微粉进行充分回用,调节了型砂粒度分布,改善了型砂中微粉含量比例,保证了型砂性能相对稳定受控,降低了混砂辅料用量比例,节约了生产成本,降低了型砂对水分的敏感性,促进了改善型砂流动性,提升了型砂综合性能和铸型质量,有效降低了铸件产生砂眼、夹砂结疤缺陷的风险。

疏水性微结构聚合物的高效注塑成形制备

针对微结构聚合物元件的高效成形制备,本工作采用金刚石砂轮在钛硅碳陶瓷模芯表面精密磨削加工出V形沟槽阵列结构,通过微注塑成形工艺将模芯表面的微结构快速成形复制到聚合物工件表面,实现微结构聚合物元件的批量化与制造,研究不同微结构尺寸对微结构聚合物表面疏水性的影响。结果表明,通过微细磨削加工技术和微注塑成形工艺,能够高效快速制备出微结构聚合物元件。微结构聚合物工件表面接触角随V沟槽间距的增加而逐渐减小,当V沟槽深度为150μm时,表面接触角可达123.19°。聚合物工件表面质量越高,其表面疏水性能越好。

超疏水微结构表面的制备工艺研究

针对装备表面大面积采用超疏水结构以实现减阻、防污的需求,考虑加工低成本、可重复及高效的目标,采用PDMS模塑工艺来实现超疏水微结构的制备,基于高速微小孔钻削工艺在铝合金表面加工阵列微孔结构作为PDMS浇铸的模具,成功在PDMS膜表面复印出阵列微柱结构,对制备的超疏水微结构PDMS膜进行了加工误差分析,误差为6%。

粉末微注射成形Catamold~ 316L喂料流变性能研究

采用Rosand RH7双柱塞高压毛细管流变仪对BASF Catamold316L奥氏体不锈钢喂料进行流变性能研究.讨论了在口模直径为1mm,长径比为16,Bagley校正条件下不同剪切速率、温度对喂料粘度、非牛顿指数、粘流活化能的影响,同时从理论上分析了粉末装载量及粘结剂选取对喂料流变性能的影响,并且对喂料的流变性能进行综合评价.实验结果表明,Catamold316L喂料呈现假塑性流体特征,200℃时非牛顿指数和粘流活化能最小,可塑性指数最大,更加适合注射成形;随着温度的升高、剪切速率的增大,粘度均逐渐降低,粘度对剪切速率具有很高的敏感性;在相同的剪切速率下,随着温度的升高,喂料综合评价指标呈现先增大后减小的趋势.

POM精密微型齿轮注射成型的Moldflow模拟分析

以聚甲醛(POM)精密微型齿轮注射成型为例,展示Moldflow在精密微型注塑制品加工中的指导作用。结果表明,模温是POM精密微型齿轮加工参数中最为重要的影响因素,齿轮的齿顶边缘是最容易产生制品缺陷的区域。使用Moldflow对精密微型注塑制品的加工过程进行模拟,对其加工工艺有着重要的指导作用,同时大大缩短了产品的开发周期和费用,具有显著的经济效益。

跨线连续钢—混组合梁桥负弯矩区抗裂措施设计与研究

为改善跨线连续钢—混组合梁桥负弯矩区的受力性能以解决桥面板开裂问题,以深圳某高速改扩建工程4×85 m连续钢—混组合梁桥为研究对象。基于有限元法,研究增设预应力筋、支点升降法、后浇成型、微膨胀混凝土以及增大配筋率对负弯矩区桥面板抗裂性能的影响。结果表明:桥面板后浇成型可消除一期恒载引起的桥面板拉应力;支点升降法和预应力筋均能在桥面板中引入预压应力,有效降低桥面板的应力水平;增大配筋率只能减小最大裂缝宽度,当配筋率小于1.2%时,随着截面配筋率的增加,桥面板的最大裂缝宽度迅速减小,当配筋率超过2.4%时,随着截面配筋率的增加,桥面板的最大裂缝宽度减小幅度变小;微膨胀混凝土可有效减小桥面板的拉应力。最后基于工程实际提出了综合抗裂措施,可为后续类似工程设计提供参考。

动模连续铸造巴氏合金微截面扁坯制备近终尺寸线材装置的设计及应用

巴氏合金用来铸造制作轴瓦减摩材料层,但存在结合强度、材料利用率低、偏析等。随着技术的发展,堆焊逐步替代铸造成为制备减摩层的主要技术,因此堆焊用巴氏合金线材替代铸造用巴氏合金锭,成为轴瓦领域的发展趋势。巴氏合金塑性差,难以用挤压、拉拔的常规工艺制备细线径线材,同时挤压制坯的“裹芯”等缺陷降低了堆焊质量。因此设计了动模连续铸造微截面巴氏合金扁坯装置。该装置可连续铸造截面面积为24.6mm^(2)的扁坯,经轧制与分切、去毛边、辊拉模减径等工序,可获得直径≤φ2.00mm的线材,其无夹杂气泡和裹芯,表面油脂残留少,经济性佳。

利用X射线微层析成像研究炸药造型颗粒随机堆积结构

通过X射线微层析成像(X-μCT)研究了5种炸药造型颗粒样品的随机堆积结构,获得了造型颗粒堆积体系的颗粒空间排列、颗粒堆积特性以及颗粒接触特征等堆积结构参量。结果表明,造型颗粒随机堆积体系存在不同程度的尺寸分离现象,粒径较大的颗粒倾向于分布在容器下方,颗粒装填过程会影响水平方向的颗粒分布取向;各样品平均堆积效率随颗粒间径向距离的增大连续变化,表明造型颗粒随机堆积结构长程无序;样品平均接触数为5~6,接近球形颗粒随机疏松堆积,而受颗粒粒径和形状的影响,造型颗粒随机堆积体系的体积分数能够超过球形颗粒随机紧密堆积的极限(0.64)。造型颗粒堆积体系构成局部接触的颗粒在数量、尺寸和形貌等方面分布不均匀,但各种接触结构中60°左右的接触角出现频次最高,形成了60°左右出现单一特征峰的接触角分布。

微挤出发泡堆叠成型制备多孔聚酯弹性体制件及其性能研究

在聚合物弹性体内部及表面引入多孔结构能够显著提升其弹性,同时兼具轻质、高比表面积、多功能化等优点。开发更经济、环保、简便及满足多样化需求的多孔制件制备方法具有重要意义。与传统制造技术相比,3D打印技术具有更高的成型自由度,在多样化定制、精细制造及高尖端领域具有明显优势。微挤出发泡联合熔融沉积成型(FDM)3D打印技术和高压流体发泡技术能够实现复杂三维多孔制件的原位发泡制造,是制备多孔发泡制件的有效方法。采用微挤出发泡技术,以高压CO_(2)作为物理发泡剂,制备了具有不同结构的多孔聚酯弹性体(TPEE)制件,并系统研究了多孔制件的弹性性能。研究结果表明,引入微发泡结构可使制品的减重最高达34.17%,通过针对性调节打印参数能够在长宽高方向实现FDM打印级别的精度水平。相较于未发泡制件,发泡多孔制件的落球回弹率明显增加,硬度和刚度大幅降低,制件柔软度和舒适性增加,压缩形变恢复率更高。采用微挤出发泡堆叠成型工艺制备的多孔制件内部及表面引入了微孔结构,增强了打印层之间的粘结强度,使其具有轻量化、高弹性、高柔软度和高精度成型的特点。此方法拓宽了多孔制件的应用领域,同时在低应力和应力敏感的应用场景显现潜在的应用前景。

可溶性微针在经皮给药系统中应用的研究进展

对微针在经皮给药系统中的优势进行了简单阐述,重点介绍了可溶性微针。可溶性微针由生物相容性和水溶性的基质材料制成,具有可生物降解、载药量大、不产生针尖废物等独特优势。从可溶性微针常用的基质种类和制备方法阐述了可溶性微针对药物经皮渗透和吸收的影响。对国内外研究中可溶性微针递送疫苗、降糖药、基因、麻醉剂、抗肿瘤药物和其他应用进行了介绍。总结出可溶性微针经皮给药系统可显著提高药物的经皮渗透量,能够安全、稳定地输送药物并达到良好的治疗效果。最后,对可溶性微针现研究阶段存在的问题进行了分析,并展望了未来发展的方向。

微纹处理技术(Micro matte)在仪表板表皮搪塑模具上的应用开发

主要讨论使用微纹处理技术对汽车仪表板表皮搪塑镍壳模具进行降低光泽度处理的应用开发。与现有的喷砂处理方式相比微纹处理技术具有均匀、皮纹磨损小、成本低等优势,试验结果表明:采用微纹处理技术处理后,不仅降低了光泽度,延长了模具的使用寿命,同时减少了由于自喷漆喷涂产生异味之后的市场不良反馈。一举实现了在提高品质的同时降低表皮生产的综合成本等多重目的。