外文翻译--注塑成型优化方法

1 A technical note on the characterization of electroformed nickel shells for their application to injection molds Universidad de Las Palmas de Gran Canaria, Departamento de Ingenieria Mecanica, Spain Abstract The techniques of rapid prototyping and rapid tooling have been widely developed during the last years. In this article, electroforming as a procedure to make cores for plastics injection molds is analysed. Shells are obtained from models manufactured through rapid prototyping using the FDM system. The main objective is to analyze the mechanical features of electroformed nickel shells, studying different aspects related to their metallographic structure, hardness, internal stresses and possible failures, by relating these features to the parameters of production of the shells with an electroforming equipment. Finally a core was tested in an injection mold. Keywords: Electroplating； Electroforming； Microstructure； Nickel Article Outline 1. Introduction 2. Manufacturing process of an injection mold 3. Obtaining an electroformed shell: the equipment 4. Obtained hardness 5. Metallographic structure 6. Internal stresses 7. Test of the injection mold 8. Conclusions References 1. Introduction One of the most important challenges with which modern industry comes across is to offer the consumer better products with outstanding variety and time variability (new designs). For this reason, modern industry must be more and more competitive and it has to produce with acceptable costs. There is no doubt that combining the time variable and the quality variable is not easy because they frequently condition one another； the technological advances in the productive systems are going to permit that combination to be more efficient and feasible in a way that, for example, if it is observed the evolution of the systems and techniques of plastics injection, we arrive at the conclusion that, in fact, it takes less and less time to put a new product on the market and with higher levels of quality. The manufacturing technology of rapid tooling is, in this field, one of those technological 2 advances that makes possible the improvements in the processes of designing and manufacturing injected parts. Rapid tooling techniques are basically composed of a collection of procedures that are going to allow us to obtain a mold of plastic parts, in small or medium series, in a short period of time and with acceptable accuracy levels. Their application is not only included in the field of making plastic injected pieces 1, 2 and 3, however, it is true that it is where they have developed more and where they find the highest output. This paper is included within a wider research line where it attempts to study, define, analyze, test and propose, at an industrial level, the possibility of creating cores for injection molds starting from obtaining electroformed nickel shells, taking as an initial model a prototype made in a FDM rapid prototyping equipment. It also would have to say beforehand that the electroforming technique is not something new because its applications in the industry are countless 3, but this research work has tried to investigate to what extent and under which parameters the use of this technique in the production of rapid molds is technically feasible. All made in an accurate and systematized way of use and proposing a working method. 2. Manufacturing process of an injection mold The core is formed by a thin nickel shell that is obtained through the electroforming process, and that is filled with an epoxic resin with metallic charge during the integration in the core plate 4 This mold (Fig. 1) permits the direct manufacturing by injection of a type a multiple use specimen, as they are defined by the UNE-EN ISO 3167 standard. The purpose of this specimen is to determine the mechanical properties of a collection of materials representative industry, injected in these tools and its coMParison with the properties obtained by conventional tools. The stages to obtain a core 4, according to the methodology researched in this work, are the following: (a) Design in CAD system of the desired object. (b) Model manufacturing in a rapid prototyping equipment (FDM system). The material used will be an ABS plastic. (c) Manufacturing of a nickel electroformed shell starting from the previous model that has been coated with a conductive paint beforehand (it must have electrical conductivity). (d) Removal of the shell from the model. (e) Production of the core by filling the back of the shell with epoxy resin resistant to high temperatures and with the refrigerating ducts made with copper tubes. 3 The injection mold had two cavities, one of them was the electroformed core and the other was directly machined in the moving platen. Thus, it was obtained, with the same tool and in the same process conditions, to inject simultaneously two specimens in cavities manufactured with different technologies. 3. Obtaining an electroformed shell: the equipment Electrodeposition 5 and 6 is an electrochemical process in which a chemical change has its origin within an electrolyte when passing an electric current through it. The electrolytic bath is formed by metal salts with two submerged electrodes, an anode (nickel) and a cathode (model), through which it is made to pass an intensity coming from a DC current. When the current flows through the circuit, the metal ions present in the solution are transformed into atoms that are settled on the cathode creating a more or less uniform deposit layer. The plating bath used in this work is formed by nickel sulfamate 7 and 8 at a concentration of 400 ml/l, nickel chloride (10 g/l), boric acid (50 g/l), Allbrite SLA (30 cc/l) and Allbrite 703 (2 cc/l). The selection of this composition is mainly due to the type of application we intend, that is to say, injection molds, even when the injection is made with fibreglass. Nickel sulfamate allows us to obtain an acceptable level of internal stresses in the shell (the tests gave results, for different process conditions, not superior to 50 MPa and for optimum conditions around 2 MPa). Nevertheless, such level of internal pressure is also a consequence of using as an additive Allbrite SLA, which is a stress reducer constituted by derivatives of toluenesulfonamide and by formaldehyde in aqueous solution. Such additive also favours the increase of the resistance of the shell when permitting a smaller grain. Allbrite 703 is an aqueous solution of biodegradable surface-acting agents that has been utilized to reduce the risk of pitting. Nickel chloride, in spite of being harmful for the internal stresses, is added to enhance the conductivity of the solution and to favour the uniformity in the metallic distribution in the cathode. The boric acid acts as a pH buffer. The equipment used to manufacture the nickel shells tested has been as follows: Polypropylene tank: 600 mm 400 mm 500 mm in size. Three teflon resistors, each one with 800 W. Mechanical stirring system of the cathode. System for recirculation and filtration of the bath formed by a pump and a polypropylene filter. Charging rectifier. Maximum intensity in continuous 50 A and continuous current voltage between 0 and 16 V. 4 Titanium basket with nickel anodes (Inco S-Rounds Electrolytic Nickel) with a purity of 99%. Gases aspiration system. Once the bath has been defined, the operative parameters that have been altered for testing different conditions of the process have been the current density (between 1 and 22 A/dm2), the temperature (between 35 and 55 C) and the pH, partially modifying the bath composition. 4. Obtained hardness One of the most interesting conclusions obtained during the tests has been that the level of hardness of the different electroformed shells has remained at rather high and stable values. In Fig. 2, it can be observed the way in which for current density values between 2.5 and 22 A/dm2, the hardness values range from 540 and 580 HV, at pH 4 0.2 and with a temperature of 45 C. If the pH of the bath is reduced at 3.5 and the temperature is 55 C those values are above 520 HV and below 560 HV. This feature makes the tested bath different from other conventional ones composed by nickel sulfamate, allowing to operate with a wider range of values； nevertheless, such operativity will be limited depending on other factors, such as internal stress because its variability may condition the work at certain values of pH, current density or temperature. On the other hand, the hardness of a conventional sulfamate bath is between 200250 HV, much lower than the one obtained in the tests. It is necessary to take into account that, for an injection mold, the hardness is acceptable starting from 300 HV. Among the most usual materials for injection molds it is possible to find steel for improvement (290 HV), steel for integral hardening (520595 HV), casehardened steel (760800 HV), etc., in such a way that it can be observed that the hardness levels of the nickel shells would be within the mediumhigh range of the materials for injection molds. The objection to the low ductility of the shell is compensated in such a way with the epoxy resin filling that would follow it because this is the one responsible for holding inwardly the pressure charges of the processes of plastics injection； this is the reason why it is necessary for the shell to have a thickness as homogeneous as possible (above a minimum value) and with absence of important failures such as pitting. 5. Metallographic structure In order to analyze the metallographic structure, the values of current density and temperature were mainly modified. The samples were analyzed in frontal section and in transversal section (perpendicular to the deposition). For achieving a convenient preparation, they were conveniently encapsulated in resin, polished and etched in different stages with a mixture of acetic acid and nitric acid. The etches are carried out at intervals of 15, 25, 40 and 50 s, after being polished again, in order to be observed afterwards in a metallographic microscope Olympus PME3-ADL 3.3/10. 5 Before going on to comment the photographs shown in this article, it is necessary to say that the models used to manufacture the shells were made in a FDM rapid prototyping machine where the molten plastic material (ABS), that later solidifies, is settled layer by layer. In each layer, the extruder die leaves a thread approximately 0.15 mm in diameter which is compacted horizontal and vertically with the thread settled inmediately after. Thus, in the surface it can be observed thin lines that indicate the roads followed by the head of the machine. These lines are going to act as a reference to indicate the reproducibility level of the nickel settled. The reproducibility of the model is going to be a fundamental element to evaluate a basic aspect of injection molds: the surface texture. The tested series are indicated in Table. Table 1. Tested series Series pH Temperature (C) Current density (A/dm2) 1 4.2 0.2 55 2.22 2 3.9 0.2 45 5.56 3 4.0 0.2 45 10.00 4 4.0 0.2 45 22.22 Fig. 3 illustrates the surface of a sample of the series after the first etch. It shows the roads originated by the FDM machine, that is to say that there is a good reproducibility. It cannot be still noticed the rounded grain structure. In Fig. 4, series 2, after a second etch, it can be observed a line of the road in a way less clear than in the previous case. In Fig. 5, series 3 and 2 etch it begins to appear the rounded grain structure although it is very difficult to check the roads at this time. Besides, the most darkened areas indicate the presence of pitting by inadequate conditions of process and bath composition. This behavior indicates that, working at a low current density and a high temperature, shells with a good reproducibility of the model and with a small grain size are obtained, that is, adequate for the required application. If the analysis is carried out in a plane transversal to the deposition, it can be tested in all the samples and for all the conditions that the growth structure of the deposit is laminar (Fig. 6), what is very satisfactory to obtain a high mechanical resistance although at the expense of a low ductibility. This quality is due, above all, to the presence of the additives used because a nickel sulfamate bath without additives normally creates a fibrous and non-laminar structure 9. The modification until a nearly null value of the wetting agent gave as a result that the laminar structure was maintained in any case, that matter demonstrated that the determinant for such structure was the stress reducer (Allbrite SLA). On the other hand, it was also tested that the laminar structure varies according to the thickness of the layer in terms of the current density. 6 6. Internal stresses One of the main characteristic that a shell should have for its application like an insert is to have a low level of internal stresses. Different tests at different bath temperatures and current densities were done and a measure system rested on cathode flexural tensiometer method was used. A steel testing control was used with a side fixed and the other free (160 mm length, 12.7 mm width and thickness 0.3 mm). Because the metallic deposition is only in one side the testing control has a mechanical strain (tensile or compressive stress) that allows to calculate the internal stresses. Stoney model 10 was applied and was supposed that nickel substratum thickness is enough small (3 m) to influence, in an elastic point of view, to the strained steel part. In all the tested cases the most value of internal stress was under 50 MPa for extreme conditions and 2 MPa for optimal conditions, an acceptable value for the required application. The conclusion is that the electrolitic bath allows to work at different conditions and parameters without a significant variation of internal stresses. 7. Test of the injection mold Tests have been carried out with various representative thermoplastic materials such as PP, PA, HDPE and PC, and it has been analysed the properties of the injected parts such as dimensions, weight, resistance, rigidity and ductility. Mechanical properties were tested by tensile destructive tests and analysis by photoelasticity. About 500 injections were carried out on this core, remaining under conditions of withstanding many more. In general terms, important differences were not noticed between the behavior of the specimens obtained in the core and the ones from the machined cavity, for the set of the analysed materials. However in the analysis by photoelasticiy (Fig. 7) it was noticed a different tensional state between both types of specimens, basically due to differences in the heat transference and rigidity of the respective mold cavities. This difference explains the ductility variations more outstanding in the partially crystalline materials such as HDPE and PA 6. For the case of HDPE in all the analysed tested tubes it was noticed a lower ductility in the specimens obtained in the nickel core, quantified about 30%. In the case of PA 6 this value was around 50%. 8. Conclusions After consecutive tests and in different conditions it has been checked that the nickel sulfamate bath, with the utilized additives has allowed to obtain nickel shells with some mechanical properties acceptable for the required application, injection molds, that is to say, good reproducibility, high level of hardness and good mechanical resistance in terms of the 7 resultant laminar structure. The mechanical deficiencies of the nickel shell will be partially replaced by the epoxy resin that finishes shaping the core for the injection mold, allowing to inject medium series of plastic parts with acceptable quality levels. References 1 A.E.W. Rennie, C.E. Bocking and G.R. Bennet, Electroforming of rapid prototyping mandrels for electro discharge machining electrodes, J. Mater. Process. Technol. 110 (2001), pp. 186196. 2 P.K.D.V. Yarlagadda, I.P. Ilyas and P. Chrstodoulou, Development of rapid tooling for sheet metal drawing using nickel electroforming and stereo lithography processes, J. Mater. Process. Technol. 111 (2001), pp. 286294. 3 J. Hart, A. Watson, Electroforming: A largely unrecognised but expanding vital industry, Interfinish 96, 14 World Congress, Birmingham, UK, 1996. 4 M. Monzn et al., Aplicacin del electroconformado en la fabricacin rpida de moldes de inyeccin, Revista de Plsticos Modernos. 84 (2002), p. 557. 5 L.F. Hamilton et al., Clculos de Qumica Analtica, McGraw Hill (1989). 6 E. Julve, Electrodeposicin de metales, 2000 (E.J.S.). 7 A. Watson, Nickel Sulphamate Solutions, Nickel Development Institute (1989). 8 A. Watson, Additions to Sulphamate Nickel Solutions, Nickel Development Institute (1989). 9 J. Dini, Electrodeposition Materials Science of Coating and Substrates, Noyes Publications (1993). 10 J.W. Judy, Magnetic microactuators with polysilicon flexures, Masters Report, Department of EECS, University of California, Berkeley, 1994. (cap. 3). 8 外文 资料 译文 注塑成型优化方法 tuncayerzurumlua 和巴布尔 ozcelik 厂房及制造工程 ,伊利诺斯工学院 41400、科贾埃利 ,土耳其 摘 要 快速成型技术及快速模具发达国家已广泛在过去几年 . 在这篇文章中 ,作为一种程序 ,使电芯塑料注射模具分析 . 贝壳制成模型 ,通过快速成型得到利用差分系统 . 主要目的是分析力学特征镍炮弹、 学习方面的不同金相组织 ,硬度 ,内部讲 ,可能失败 由这些特色的有关参数以生产贝壳电设备 . 终于引爆了一个核心注塑模具 . 文章概要 1. 引言 2. 注塑模具制造过程中的 3. 壳牌获取电 :设备 4. 获得硬度 5. 金相组织 6. 测 试的注塑模具 7. 结论 参考资料 1、引言 其中最重要的是现代工业遇到的挑战是提供更好的产品与消费者 ,优秀品种和时间变异 (新设计 ). 因此 ,现代工业必须有更多的竞争性和生产成本与接受 . 毫无疑问 ,结合时间变量 ,质量并不容易 ,因为他们经常变状态 互相 ； 科技进步生产许可证制度 ,将可更有效和可行的组合在 方式 ,例如 ,如果是演化的观测系统和注塑技术、 我们得出的结论是 ,事实上 需少时间把新产品的市场和较高素质 . 快速模具制造技术 ,在这一领域 , 其中的技术进步 ,使得有可能改善设计和制造过程注入部分 . 快速模具制造技术基本上是由程序集将允许我们获取 塑料模具零件 ,小型系列 在短短的时间里 ,以可接受的精度水平 . 其应用领域不仅包括制作塑胶件注 1,2,3但是 , 的确 ,这是他们研制并在那里找到更多的最高产量 本文包括在科研第一线 ,广泛试图研究确定 ,分析测试和建议 在产业层次 ,形成核心的可能性注塑模具从获取镍炮弹、 同时 ,作为一个初步的原型取得了差分模型快速成型设备 它也将不得不说 ,事前并没有任何新电铸技术的应用 ,因为它 业内人士无数、 但这种试图调查研究工作 ,并在多大程度上使用这一技术参数 ,其中 在生产技术上的 快速模具 . 所有在准确、制度化的方式方法的运用 ,并提出了工作 . 2、注塑模具制造过程中的核心是由镍壳薄 ,透过电进程 这是一个充满金属环氧树脂主管期间一体化这一核心板块 4 模具 (图 1)制造许可证直接注射 A 型多用标本、 他们确定的甲状旁腺恩的 SO3167 标准 . 目的是要确定这个试样力学性能的材料收集代表工业 在注入这些工具及其性能相比常规手段获得 该阶段取得核心根据这一方法研制工作 ,有以下几方面 : (一 ) 在设计 CAD 系统预期目标 (二 ) 在快速原型制造设备模型 (差分系统 ). 该材料将 ABS 塑料 9 (三 ) 生产镍电壳牌从以往的模式已 经涂了导电涂料 事前 (必须有导电 ). (四 ) 清理壳牌从模型 (五 ) 生产核心填写背面与壳牌环氧树脂抗高温 随着铜管与冷冻槽 有两个空洞的注塑模具、 他们一个是电加工的核心 ,一是直接在移动压板 . 因此 ,它获得了与同一工具及同一工艺条件、 同时注入两种不同制成标本蛀牙技术 . 3、壳牌获取电设备 电镀 5和 6是一个电化学过程中的化学变化 ,当它起源于一电解质 悠悠电流通过 . 该电镀 5和 6是一个电化学过程中的化学变化 ,当它起源于一电解质 悠悠电流通过 . 该电解槽是由金属盐两个电极淹没 ,一个阳极 (镍 )、阴极 (示范 ) 它是 通过把烈度来自直流 . 当电流流经电路 目前在金属离子的溶液转化为原子 ,是定居于创造一个更加阴极 存款少或制服层 镀液采用这项工作是由镍、磺酸 78集中在 400 毫升 /公升 ,氯化镍 (10微克 /公升 )、硼酸 (50 微克 /公升 ),allbrite 习得 (30 完工 /公升 ),703allbrite(2 完工 /公升 ). 选择这种组合主要原因是我们打算申请类别 ,即 注塑模具 ,即使注射了玻璃纤维 . 磺酸镍让我们获得可以接受的程度 ,在内部讲壳牌 (作了测试结果 不同工艺条件 ,不高于50 兆帕的最佳条件和 2 兆帕左右 ). 不过 ,这种 程度的内部压力也是作为添加剂使用后果 allbrite 习得、 这是由衍生 -T 强调消脂、甲醛水溶液 . 这种添加剂也赞成增加阻力较小壳当允许粮食 . 703allbrite 是降解水溶液表面代理商代理已经利用以减少蚀 . 氯化镍 ,尽管危害性的内部讲 加上增强导电溶液并赞成在金属均匀分布在 阴极 . 硼酸 pH 值的作为缓冲 该设备用于制造镍炮弹已测试如下： 聚丙烯坦克 :600 毫米 400 毫米 500 毫米的尺寸 三聚四氟乙烯电阻器 ,每一个有 800 特约阴极机械搅拌系统 再循环和过滤系统组成的水泵、浴聚丙烯过滤 充电整流器 . 最高强度和持续不断的电流电压 0 至 16 伏 镍钛篮 阳极 (镍矿公司的 S 轮电解镍 )具有纯度 99% 气体吸入系统 一旦已确定浴、 手术已更改参数测试不同条件的过程一直电流密度 (之间 1、 22 ),温度 (35 至 55 )和 pH 值 ,改变镀液组成部分 4、获得硬度 一个非常有趣的测试期间已获得结论 ,对不同程度的硬度 电炮弹一直保持在相当高的稳定价值观 . 在无花果 . 2,可以观察到哪种方式电流密度值为 2.5和 22 之间 , 硬度值从高压 540、 580、 在 pH0.2 和 4+摄氏 45 如果是浴的 pH 值为 3.5,气温下降 55 以上这些价值观 高压 520 以下 560 高压 . 这一特点使得测试洗澡不同于其他传统业务组成磺酸镍、 允许经营范围更广的价值观念 ； 然而 ,这种有限性的将取决于其他因素 , 例如内应力 ,因为其工作状况可能在某些变性的 pH 值、 电流密度和温度 . 在另一方面 ,传统的硬度介于 200-250 高压磺酸浴、 远比取得的一个考验 . 既要考虑到 ,对注塑模具、硬度接受高压 300 起 . 其中最常见的材料就可以找到注塑模具钢改善 (高压 290) 积分硬化钢 (高压 520-595),casehardened钢 (高压 760-800)等 这样可以观察到的硬度水平都将炮弹镍 中高幅度的注塑模具材料 . 反对低延性是有偿壳牌这样的环氧树脂填充 它表示 ,将依负责 ,因为这是一个内心压力控股收费进程 注塑 ； 这也是为什么必须要由有壳厚度为尽可能均匀 (以上 最低值 ),。 5、金相组织 为了分析金相结构、电流密度、温度值 ,主要是改良 . 样品分析、横向组额叶组 (垂 10 直于沉积 ). 实现便捷的准备 ,他们在方便的封装树脂 巧言镌刻在不同阶段有硝酸、醋酸混合物 . 瓶子的进行每隔 15,25,40,50收盘后擦拭 , 为了观察事后在奥林匹斯金相显微镜碲 -日常生活 330/10 以前的照片进行评论本文 说是要用来制造炮弹模型作了一个差分快速成型 当熔融塑料机械 (ABS)的 ,后来 ,坚固 ,逐