Injection molding of micro patterned PMMA plate

A plastic plate with surface micro features was injection molded to investigate the effect of pressure rise of melt on the replication of the micro structures. Prism pattern, which is used in many optical applications, was selected as a model pattern. The prism pattern is 50 μm in pitch and 108° in the vertical angle. The overall size of the plate was 335 mm×213 mm and the thickness of the plate varied linearly from 2.6 mm to 0.7 mm. The prism pattern was firstly machined on the nickel plated core block using micro diamond tool and this machined pattern core was installed in a mold for injection molding of prism patterned plate. Polymethyl methacrylate (PMMA) was used as a molding material. The pressure and temperature of the melt in the cavity were measured at different positions in the cavity and the replication of the pattern was also measured at the same positions. The results show that the pressure or temperature profile through the process depends on the shape and the size of the plate. The replication is affected by the temperature and pressure profiles at the early stage of filling, which is right after the melt reaches the position to be measured.

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.

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.

Injection molding of ultra-fine Si_3N_4 powder for gas-pressure sintering

The ceramic injection molding technique was used in the gas-pressure sintering of ultra-fine Si3N4 powder. The feedstock＇s flowability, debinding rate, defect evolution, and microstructural evolution during production were explored. The results show that the solid volume loading of less than 50vol% and the surfactant mass fraction of 6wt% result in a perfect flowability of feedstock; this feedstock is suitable for injection molding. When the debinding time is 8 h at 40°C, approximately 50% of the wax can be solvent debinded. Defects detected during the preparation are traced to improper injection parameters, mold design, debinding parameters, residual stress, or inhomogeneous composition distribution in the green body. The bulk density, Vickers hardness, and fracture toughness of the gas-pressure-sintered Si3N4 ceramic reach 3.2 g/cm^3, 16.5 GPa, and 7.2 MPa·m^1/2, respectively.

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.

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.

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。

Micro powder injection molding——large scale production technology for micro-sized components

Micro powder injection molding (μPIM),a miniaturized variant of powder injection molding,has advantages of shape complexity,applicability to many materials and good mechanical properties. Co-injection molding has been realized between met-als and ceramics on micro components,which become the first breakthrough within the PIM field. Combined with the prominent characteristics of high features/cost ratio,micro powder injection molding becomes a potential technique for large scale production of intricate and three-dimensional micro components or micro-structured components in microsystems technology (MST) field.

Product Fingerprints for the Evaluation of Tool/Polymer Replication Quality in Injection Molding at the Micro/Nano Scale

Replication processes for the manufacturing of micro/nano-structured components are characterized by a certain degree of precision and accuracy.The transcription loss,or replication fidelity,defines the geometrical and dimensional correspondence of micro/nano-structure from metal tool inserts into plastic patterned products.The employment of a vast spectrum of micro/nano-structured geometries calls for methodologies that can be used for the estimation of replication fidelity.This study presents a number of product fingerprints,which propose multiple ways to characterize micro/nano structures in replication technologies.Replication fidelity yielded values above 80%and up to 96%depending on the considered product fingerprints and their definition.Thereafter,a correlation of the product fingerprint with the process parameters was found to optimize the replication process.Measurement uncertainty accompanies the analysis of the product fingerprints,enabling a standardized,robust,and quantitative methodology for process learning,modeling,and optimization.

A Study on Release Property through Self Coating in LSR Injection Process

This study explores the molding processes by using the Multi-component-injection molding (MCM) method, in which monolithic products are molded by attaching mixed liquid-silicone-rubbers (LSRs) to polybutylene terephthalate (PBT) that has the characteristic of self-binding while burning due to Pt catalysts. It is seen that this method increases the binding force between LSR and PBT. The surfaces coated with Polytetrafluoroethylene (PTFE), Cr, Ni, etc. have excellent peeling with plastic and such surfaces are compared with those treated with hot forging die and micro blasting without coating. When peeling tests are performed at the specified polymerization temperature and molding time after LSR molding on these surfaces of hot working die molds without coating, these surfaces show excellent peeling of molds and LSR products. In particular, they show better peeling after micro blasting than surfaces with Cr and Ni coating as well as surfaces without coating, and the peeling strength also decreases. The results of contact angle and XPS analysis indicate that the LSR binding force is enhanced as an effect of catalysts, though it is not found by SEM. According to the XPS analysis, the structures of the surfaces are close to methyl and vinyl materials that are produced while LSR molding.

安装扭矩对抱箍式锁模力仪测试结果影响的研究

注塑机锁模力监测系统主要用于在三板式注塑机中对锁模力的实时监测,以控制产品质量和防止设备的损坏。其中抱箍安装方式的锁模力实时监测仪由于价格低,安装可靠性高等特点,被广泛采用。在实际使用中,抱箍式注塑机锁模力传感器信号的准确度,在一定范围内与所施加的抱紧力(安装扭矩)有一定相关性,对后期维护会有较大影响。对抱箍式传感器在使用中的受力情况进行了分析,根据硅胶需要满足和格林柱之间无滑移的测试条件,分析了硅胶上的拉伸摩擦力以及正压力必须满足的条件,并根据传感器头的安装结构,推导了满足硅胶受力条件时,抱箍收紧时所需的理论最小扭矩公式,最后基于自行研发的抱箍式注塑机锁模力监测仪,进行了实验。实验结果表明,在扭矩较小时(100%理论最小扭矩),抱紧力的大小对测试结果影响很大;当抱紧力达到一定阶段后(150%最小理论扭矩),测试结果趋于稳定;当抱紧力达到一定值后(≥200%最小扭矩),测试结果的精度基本不再变化。

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。

3D打印技术和真空注型工艺在一体式软硬双材质零件制造上的应用

介绍了选择性激光烧结技术和真空注型工艺制造的过程,比较两种工艺的优势和不足,通过在车身加油口盖底座快速制造中的应用实例表明,在汽车研发阶段的样件制造中,选择性激光烧结技术和真空注型工艺相结合,可实现低成本,高效的小批量一体式软硬双材质零件制造。

脉冲熔融-红外/热导法测定钛合金粉末微注射成形脱脂坯中氧氮氢

准确测定钛合金粉末微注射成形脱脂坯中氧氮氢含量对钛合金的粉末微注射工艺改进有很大指导作用。采用工业镍板经过表面打磨、酸洗、加工成固定质量的镍粒来代替市售的镍助熔剂,通过自制镍粒预先加入设备预脱气减少空白影响的方式建立了脉冲熔融-红外/热导法测定钛合金粉末微注射成形的脱脂坯中氧氮氢含量的方法。实验表明,镍粒助熔剂与石墨坩埚经二次脱气,可确保镍粒助熔剂的空白降至极低值以代替市售的镍篮、镍屑等助熔剂。钛合金粉末微注射成形脱脂坯采用振动磨形式加工至0.178 mm以下,镍粒的加入量为1.5 g,分析功率为5 300 W时,可以获得稳定准确的结果。采用实验方法对脱脂坯实际样品进行测定,其相对标准偏差(RSD,n=6)分别为0.080%~0.47%、0.28%~1.3%和1.6%~2.0%;采用加入钛合金标准样品进行加标回收实验,氧氮氢加标回收率分别在95.7%~104%、97.8%~100%及96.6%~103%。方法满足脱脂坯中的氧氮氢快速检测要求的同时,极大地降低了分析成本。

氮化硅陶瓷的注射成型工艺研究

采用注射成型与气压烧结结合的工艺,可以低成本、大批量制备出体积小、精度高的陶瓷异形件。本文以低密度聚乙烯(LDPE)和乙烯-醋酸乙烯共聚物(EVA)为黏结剂,在注射温度165℃、注射压力85 MPa的条件下制备氮化硅坯体,通过热脱脂工艺和烧结动力学测试,得到了完整的氮化硅注射成型工艺路线,并研究了喂料固含量对坯体密度、烧结密度和维氏硬度的影响,以及喂料在140~160℃时的非牛顿指数变化。结果表明:喂料的最佳固含量为52.42%(体积分数),该条件下制备的氮化硅注射坯体密度为2.10 g/cm^(3),烧结密度为3.23 g/cm^(3),维氏硬度为(15.24±0.34)GPa;喂料在160℃时的非牛顿指数最小,即在该温度下喂料的流变性最好。

硅胶注塑成型的特点及工艺应用

主要介绍了液态硅胶的特点及其注塑成型的相关工艺,同时介绍了液态硅胶模具的特点以及用于硅胶注塑成型的注塑机所需要的特别配置。

加成型硅橡胶的研究进展

综述了近年来加成型硅橡胶在高强度、高耐热、加成注射成型等方面的研究进展。

微注塑成型中熔体充模流动的影响因素研究

针对微注塑成形中因熔体的质量小、所含的热量少及流动通道截面尺寸微小等特点所带来的不同于宏观注塑成形中的熔体流动问题及影响因素,进行了理论分析及相关试验研究。结果表明,微注塑成形中,模具温度是影响微尺度下熔体流动的重要工艺因素,且随通道截面尺寸的减小而逐渐增大;而壁面滑移对微小熔体流动行为的影响,也随通道尺寸的减小而增大。此外,模具排气、通道表面粗糙度等因素的对微注塑成形的影响也不可忽视,而表面张力等因素的影响可被忽略。

抽真空对微型塑件成型质量影响

针对微注塑成型过程中排气对塑件成型质量的影响,以细胞皿为研究对象,设计了带有抽真空装置的微注塑模具,通过测试,真空度达到-0.098 MPa.分别以聚丙烯(PP)和高密度聚乙烯(HDPE)进行成型工艺试验,当模具型腔未开设排气装置时,塑件流动前沿严重烧焦,严重影响了塑件质量.当有排气槽未抽真空时,在塑件的表面形成了微孔和暗纹;当抽真空时,塑件表面较光顺,成型质量较好.可见微型腔加工精度较高,熔体充模流动时气体不易排出,对熔体充填流动会产生严重影响,采用抽真空工艺对提高微塑件的成型质量至关重要.