Water-Assisted Injection Molding System Based on Water Hydraulic Proportional Control Technique

Water-assisted injection molding（WAIM）, an innovative process to mold plastic parts with hollow sections, is characterized with intermittent, periodic process and large pressure and flow rate variation. Energy savings and injection pressure control can not be .attained based on conventional valve control system. Moreover, the injection water can not be supplied directly by water hydraulic proportional control system. Poor efficiency and control performance are presented by current trial systems, which pressurize injection water by compressed air. In this paper, a novel water hydraulic system is developed applying an accumulator for energy saving. And a new differential pressure control method is proposed by using pressure cylinder and water hydraulic proportional pressure relief valve for back pressure control. Aiming at design of linear controller for injection water pressure regulation, a linear load model is approximately built through computational fluid dynamics（CFD） simulation on two-phase flow cavity filling process with variable temperature and viscosity, and a linear model of pressure control system is built with the load model and linearization of water hydraulic components. According to the simulation, model based feedback is brought forward to compensate the pressure decrease during accumulator discharge and eliminate the derivative element of the system. Meanwhile, the steady-state error can be reduced and the capacity of resisting disturbance can be enhanced, by closed-loop control of load pressure with integral compensation. Through the developed experimental system in the State Key Lab of Fluid Power Transmission and Control, Zhejiang University, China, the static characteristic of the water hydraulic proportional relief valve was tested and output pressure control of the system in Acrylonitrile Butadiene Styrene（ABS） parts molding experiments was also studied. The experiment results show that the dead band and hysteresis of the water hydraulic proportional pressure relief valve are large, but the control precision and linearity can be improved with feed-forward compensation. With the experimental results of injection water pressure control, the applicability of this WAIM system and the effect of its linear controller are verified. The novel proposed process of WAIM pressure control and study on characteristics of control system contribute to the application of water hydraulic proportional control and WAIM technology.

Simulation and Experiment Research on the Proportional Pressure Control of Water-assisted Injection Molding

Water-assisted injection molding（WAIM）,a newly developed fluid-assisted injection molding technology has drawn more and more attentions for the energy saving,short cooling circle time and high quality of products.Existing research for the process of WAIM has shown that the pressure control of the injecting water is mostly important for the WAIM.However,the proportional pressure control for the WAIM system is quite complex due to the existence of nonlinearities in the water hydraulic system.In order to achieve better pressure control performance of the injecting water to meet the requirements of the WAIM,the proportional pressure control of the WAIM system is investigated both numerically and experimentally.A newly designed water hydraulic system for WAIM is first modeled in AMEsim environment,the load characteristics and the nonlinearities of water hydraulic system are both considered,then the main factors affecting the injecting pressure and load flow rate are extensively studied.Meanwhile,an open-loop model-based compensation control strategy is employed to regulate the water injection pressure and a feedback proportional integrator controller is further adopted to achieve better control performance.In order to verify the AMEsim simulation results WAIM experiment for particular Acrylonitrile Butadiene Styrene（ABS） parts is implemented and the measured experimental data including injecting pressure and flow rate results are compared with the simulation.The good coincidence between experiment and simulation shows that the AMEsim model is accurate,and the tracking performance of the load pressure indicates that the proposed control strategy is effective for the proportional pressure control of the nonlinear WAIM system.The proposed proportional pressure control strategy and the conclusions drawn from simulation and experiment contribute to the application of water hydraulic proportional control and WAIM technology.

Water modeling of mold powder entrapment in slab continuous casting mold

The optimal parameters were determined by the water modeling of slab casting. It was found that there are mainly three types of mold powder entrapment in slab continuous casting, i.e., the entrapment caused by the shearing flow near the narrow face of mold, the entrapment caused by vortexes around the submerged entry nozzle （SEN）, and the entrapment caused by the Ar bubbling. Both the velocity of the surface flow and the level fluctuation of the liquids are enlarged with increasing the casting speed, reducing the submersion depth of SEN, decreasing the downward angles of the nozzle outlets, and increasing the Ar flowrate, all of which increase the tendency of mold powder entrapment. Among the four above-mentioned factors, casting speed has the largest effect.

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.

Optimization design of wide face water slots for medium-thick slab casting mold

A three-dimensional finite-element model has been established to investigate the thermal behavior of the medium-thick slab copper casting mold with different cooling water slot designs. The mold wall temperatures measured using thermocouples buried in different positions of the mold with the original designed cooling system were analyzed to determine the corresponding heat flux profile. This profile was then used for simulation to predict the temperature distribution and the thermal stress distribution of the molds. The predicted temperatures during operation matched the plant measurements. The results showed that the maximum temperature, about 635 K in the wide hot surface, was found about 60 mm below the meniscus and 226 mm from the center of the mold. For the mold with the type I modified design, there was an insignificant decrease in temperature of about 5 K, and for the mold with the type II modified design, the maximum temperature was decreased by about 15 K and the temperature of the hot surface was distributed more uniformly along the length of the mold. The corresponding maximum thermal stress at the hot surface of the mold was reduced from 408 MPa to 386 MPa with the type II modified design. The results indicated that the modified design II is beneficial to the increase of mold life and the quality of casting slabs.

基于激光选区熔化技术的金属悬垂圆孔结构无支撑成形工艺优化与质量研究

基于激光选区熔化(SLM)技术制造的随形冷却模具,凭借其优异的冷却性能,能够显著提高加工效率,有效降低生产成本,成为未来注塑成型模具的重要发展方向,但目前在使用SLM技术成形随形冷却模具内部的圆形流道方面仍存在诸多挑战。在SLM成形时,随形冷却模具内部圆形流道的结构主要表现为悬垂圆孔结构,若直接使用传统工艺策略成形悬垂圆孔结构易出现翘曲、粘粉等缺陷,同时由于随形冷却模具内部流道复杂的特点,其内部流道无法通过添加支撑辅助成形。采用在模具外侧添加支撑结构的方法,可调整模具成形角度,增强悬垂圆孔结构自支撑性,但会增加额外成形时间与成形材料,导致生产成本增高。优化悬垂圆孔结构无支撑成形工艺,实现在不添加支撑结构的前提下满足随形冷却模具对流道成形质量要求,能够有效降低随形冷却模具生产成本并获得高质量成型件。本文对金属悬垂圆孔结构成形工艺策略进行优化,以316L不锈钢悬垂圆孔结构为对象,分析了工艺策略、孔径对悬垂圆孔成形质量的影响。采用一种基于加工层角度自适应的下表面工艺区域划分策略,研究该工艺区策略对于无支撑金属悬垂圆孔成形的适用性,并使用该工艺制造冷却模具样件,对成件的成形质量进行分析。结果表明采用基于加工层角度自适应的下表面工艺区域划分策略可明显抑制成形过程中的翘曲行为。使用该工艺策略成形的随形水冷模具样件无明显质量缺陷,内部流道的表面质量与成形精度满足使用要求。

壳聚糖/AKD乳液改善纸浆模塑制品防水防油性能的研究

目的以壳聚糖/AKD乳液替代传统的AKD乳液,作为安全无毒的防水防油剂,以改善纸浆模塑的防水防油性能。方法采用壳聚糖作为乳化剂,在高剪切分散乳化条件下与AKD蜡共混,获得稳定均一的壳聚糖/AKD乳液,然后通过浆内施胶的方式制备纸浆模塑制品,对纤维的滤水性能、纸浆模塑制品的力学性能以及防水防油性能进行研究。结果以壳聚糖质量分数为1.5%的壳聚糖醋酸溶液,可制备得到AKD蜡质量分数为5%的乳白色壳聚糖/AKD乳液;乳液的添加未影响纤维的滤水性能,且当其用量占绝干浆质量的7%时,纤维悬浮液的打浆度和保水值分别达到23°SR和(1.71±0.06)g/g,满足生产要求。对比未添加乳液的样品,添加了质量分数为7%的乳液后,纸浆模塑制品的力学性能,包括紧度、抗张强度、耐破指数和撕裂强度分别提高了26.2%、60.6%、152.6%和67.1%,Cobb_(60)值降低到了(18.5±0.68)g/m^(2),静态水接触角提高到了(119±4.1)°,体现防油性能的Kit值提高到了第8等级,油接触角提高到了(97.9±3.1)°。纸浆模塑制品具有良好的防热水和防热油的性能。结论壳聚糖/AKD乳液可作为一种新型防水防油助剂用于纸浆模塑制品生产,拓展了环保造纸助剂品类。

基于CAE的智能水表盖注塑模具设计

结合智能水表复杂结构特征,基于CAE软件对其进行注塑模具设计。通过Moldflow模流分析确定最佳的浇口位置,设计了浇注系统和冷却系统,并通过冷却+填充+保压+翘曲分析验证浇注系统和冷却系统设计的合理性;针对复杂结构特征,基于UG,通过设计斜顶+推杆机构实现侧凹成型,通过设计直顶+斜顶机构实现侧孔成型,通过设计滑块+弹簧的侧向抽芯机构实现侧凸成型。模具结构合理,动作可靠,可为同类设计提供参考。

正交试验法优选咽炎丸成型工艺

目的优选并确立咽炎丸的最佳制备工艺。方法以咽炎丸溶散时限为考察指标,采用正交试验法对丸剂生产过程中的药材粉碎细度(A)、整圆时间(B)、干燥温度(C)、干燥时间(D)4个因素进行优选研究。结果咽炎丸的最佳成型工艺为:中药饮片粉碎成150目细粉,制成的丸剂整圆10 min,在70℃干燥14 h。结论优选出的成型工艺稳定、重复性好,所得丸粒圆整、色泽均一,溶散时限短,适合于工业化生产。

《高分子材料成型模具》教学案例讨论

从两个教学案例出发,分别讨论了斜导柱滑块抽芯机构中滑块抽拔距和抽拔方向与开模方向之间倾角之间的关系,加深了对于模具工作原理的理解,及模具冷却水道设计中塑件壁厚、水道直径等因素与导热效果之间的关系。前一个教学案例有利于培养学生批判性思维,后一个案例将计算机编程与模具设计结合,系统地对比分析了各个因素对应的结果,减轻了繁杂的运算过程,提高了设计效率,培养了学生解决复杂工程问题的能力。

基于综合加权评分的后防擦条内板注塑参数多目标优化

在Moldflow2019模流分析软件中,对浇口位置进行充分模拟,综合比对后发现,后防擦条内板选择两浇口充填较合适。根据注塑机型号将模具设置为“1模2腔”结构;选用标准热流道,最大限度减少流道凝料,体现绿色设计理念。选取定模水路直径、隔水管直径、熔体温度、注射压力、保压压力、保压时间为研究对象,利用正交试验进行研究,通过综合加权评分对翘曲量及缩痕指数进行加权,得到第15组工艺参数综合评分最高,其值为0.998。当定模水路直径为10 mm、隔水管直径为12 mm、熔体温度为217℃、注射压力为115 MPa、保压压力为85%、保压时间为15 s时,制品的最大翘曲变形量为2.185 mm、总体翘曲率为0.105%~0.210%;缩痕指数为2.823%,与初始参数下的数值相比,减少了48.472%。试验证明了制品成型较好。

浆纤维对模塑墙体装饰材料物理性能的影响

通过设计并实施一系列试验,评估不同掺量(0%、5%、10%)的浆纤维对模塑材料密度、抗压强度和吸水率的影响。研究发现,随着浆纤维掺量的增加,模塑材料的密度显著下降,从1.798g/cm^(3)下降到1.708g/cm^(3);抗压强度显著提升,从50.04MPa增加到54.72MPa;吸水率显著增加,从1.22%上升到1.78%。因此,浆纤维的掺入对模塑材料的物理性能具有重要影响,可以在材料应用中根据具体需求进行相应调整。

LAZ811合金水冷凝固工艺设计与组织性能研究

对LAZ811合金水冷凝固模具与工艺进行了探索,主要包括熔铸工艺分析、水冷模具的结构设计及浇注参数的确定,并制备出了LAZ811合金铸锭。结果表明:真空感应熔炼+氩气保护,合理的水冷模具结构能够使合金快速凝固,有效防止铸锭内部缩孔及缩松的形成,并获得组织细小、拉伸性能优良的镁锂合金材料,并适用于类似合金的生产。

中药房小包装饮片储存养护常见问题浅析

目的通过阐述中药饮片水分含量的影响因素,探讨中药材小包装水分含量的定量指标,为提高中药房饮片管控水平提供了新的思路。方法通过引入蜜炙饮片含水量公式、水分自由度、包装材料化学成分迁移等概念,阐述中药饮片水分含量与炮制、贮藏、霉菌、薄膜包装之间的相互作用,系统性的总结了中药饮片水分含量的各项影响因子和质控指标。结果中药饮片水分含量与炮制、贮藏、霉菌、薄膜包装等内外因素之间有很大关联性。结论通过引入中药新鲜度,中药材小包装水分含量定量指标,为更好地控制中药材质量提供了参考。

铝合金金属型铸造用水基涂料研究

选用硅藻土、海泡石、高岭土、滑石粉作为复合耐火骨料,以水玻璃和快干硅溶胶作为复合粘结剂,海藻酸钠和羧甲基纤维素钠(CMC)作为复合悬浮剂,采用正交试验法和极差分析法确定了铝合金金属型铸造用水基涂料中各组份的最优配比,通过对涂料各项性能进行测定和试验验证发现,所得的最佳配方涂料性能良好,能够应用于实际生产中。

不等厚多筋立柱面板注塑模结构设计及数值模拟

以细节特征多且壁厚不等的汽车立柱面板塑件为例,借助模具型腔传热模型,计算分析获取冷却系统设计参数,结合应用模流分析验证模具温度分布均衡性,获知型腔内外表面温差不到15℃,模具达到温度稳定的时间为450 s左右,稳定周期时间较短,冷却效率高,最后依据模流分析结果以及塑件工艺结构特点,进行立柱面板注塑模结构设计,采用曲面分型潜伏浇口内侧进料,侧滑块配合斜顶完成内外抽芯的两板式结构,实践表明,该模具符合产品生产需求。

玻纤质量分数对长玻纤增强聚丙烯水驱动弹头辅助注塑管件的影响

分别以玻纤质量分数10%,20%,30%和40%的长玻纤增强聚丙烯(LGFRPP)材料制取一系列水驱动弹头辅助注塑(W-PAIM)管件。探究了玻纤质量分数对玻纤断裂长度、纤维取向、壁厚以及耐压性的影响。结果表明,随着玻纤质量分数的增加,玻纤断裂长度在较长区间内占比降低;不同玻纤质量分数的W-PAIM制件在壁厚层的取向不同,水道层的玻纤沿流动方向取向较模壁层和中间层更好,当玻纤质量分数为10%与40%时,水道层玻纤取向度最好,玻纤质量分数为20%时,中间层取向最差,玻纤质量分数为30%时,模壁层的玻纤取向较好;随着玻纤质量分数的增加,WPAIM管件壁厚呈先增加后减小再增加的趋势;随着玻纤质量分数的增加,管件的耐压性先增加后减小最后又增加,当玻纤质量分数为20%时,耐压性最好。

200 mm厚度加氢反应器用特厚板12Cr2Mo1VR(H)的开发

介绍了加氢反应器特厚板12Cr2Mo1VR(H)钢的成分设计、冶炼、浇铸和轧制工艺,利用JMatPro软件计算热扩散率、热容量、钢板导热能力等重要相变参数,并分析了热处理制度对其组织、回火脆化性能、高温持久与蠕变性能的影响。生产过程中通过调整Cr、Mo(Mn)和V含量,控制各组织的形态和分布,促进晶内铁素体形核,利用洁净钢冶炼技术将有害元素控制在较低水平,减少有害元素晶界偏聚产生的回火脆化现象,利用水冷模浇铸技术和控制轧制技术控制原始晶粒度,性能检测结果显示,12Cr2Mo1VR(H)钢的抗回火脆化温度达到-51℃,钢板经模拟热循环后X向、Y向、Z向的三个位置拉伸性能差异范围在15 MPa以内,厚度截面表层、厚度1/4、厚度1/2、厚度3/4位置冲击功均达到280 J以上,无较大的位置趋向差异,在540℃温度下,加载力为210 MPa时,持续1 010 h未断裂,高温蠕变弹性伸长率为0.147 5%,总塑性伸长率1.454 5%。

水溶性化妆品霉菌和酵母菌快速检测替代方法

本文旨在研究采用测试片法进行水溶性化妆品霉菌和酵母菌快速检测的可行性。选取了6批化妆品面膜,参照《中国药典》2020年版非无菌产品微生物限度检查的微生物计数法,从专属性、定量限、重现性和耐用性几个方面对测试片法进行考察,并进行6批面膜测试片法的方法适用性试验。结果显示,测试片法与《化妆品安全技术规范》(2015年版)中平皿法在专属性、定量限、重现性和耐用性等方面无明显差异,6批面膜测试片法方法适用性试验结果回收率均在0.7~1.1之间,表明测试片法可作为快速检测法对水溶性化妆品中霉菌和酵母菌进行检测。

水驱动弹头辅助注塑弹头的穿透行为

残余壁厚(RWT)是表征水驱动弹头辅助注塑成型(WPAIM)管件质量的一个重要指标,直接受弹头的穿透行为影响。为了研究WPAIM过程中弹头的穿透行为及相应的RWT分布规律,文中基于计算流体动力学(CFD)方法对WPAIM过程进行了数值模拟,模拟结果与实验结果吻合较好。研究结果表明,WPAIM管在直线段的RWT相对均匀,而在曲线段,外凸侧RWT大于内凹侧RWT,两者之间的RWT差值小于水辅助注射成型(WAIM)管。通过对WPAIM中弹头穿透行为与WAIM中水的穿透行为分析发现:穿透前沿附近的压力分布WPAIM较WAIM更均匀,穿透两侧的速度差也更小,弹头能更好地沿型腔中心穿透,提高管件壁厚的均匀性;无论是在直段或是弯曲段,两者的穿透过程都是在不断加速的,WAIM穿透速度更快,而WPAIM的加速过程较稳定。