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南京理工大學(xué)泰州科技學(xué)院
畢業(yè)設(shè)計(jì)(論文)外文資料翻譯
系 部： 機(jī)械工程系
專 業(yè)： 機(jī)械工程及自動(dòng)化
姓 名： 王 鋒
學(xué) 號(hào)： 05010230
外文出處： 中國(guó)機(jī)械資訊網(wǎng)
BBS.CMIW.CN
附 件： 1.外文資料翻譯譯文；2.外文原文。
指導(dǎo)教師評(píng)語(yǔ)：
譯文基本符合翻譯原文,個(gè)別詞匯不符合語(yǔ)境。語(yǔ)句較為通順，條理比較清楚，專業(yè)用語(yǔ)翻譯基本恰當(dāng)，符合中文語(yǔ)法，整體翻譯質(zhì)量較好。
簽名：
年 月 日
附件1：外文資料翻譯譯文
在注塑模應(yīng)用方面，外形電鑄鎳的技術(shù)注釋
摘要 在過去幾年，快速成型技術(shù)及快速模具在發(fā)達(dá)國(guó)家已廣泛應(yīng)用。在這篇文章中,作為一種范例，分析電芯塑料注射模具。通過快速成型，利用差分系統(tǒng)得到鎳殼模型。主要目的是分析鎳殼力學(xué)特征，學(xué)習(xí)不同方面的金相組織、硬度、內(nèi)壓，失敗的可能性。以這些特色的有關(guān)參數(shù)生產(chǎn)鎳殼電設(shè)備，終于得到了一個(gè)注塑模具核心部分。
關(guān)鍵詞：電鍍； 電制；顯微組織； 鎳
文章概要
1. 引言
2. 注塑模具制造過程
3. 電鑄殼獲?。涸O(shè)備
4. 獲得硬度
5. 金相組織
6. 內(nèi)壓
7. 測(cè)試的注塑模具
8. 結(jié)論
1．引言
現(xiàn)代工業(yè)遇到的最重要的挑戰(zhàn)之一是在很短的時(shí)間內(nèi)向消費(fèi)者提供更好的產(chǎn)品。因此,現(xiàn)代工業(yè)必須有更強(qiáng)的競(jìng)爭(zhēng)性和適應(yīng)更合理的生產(chǎn)成本。 毫無(wú)疑問，結(jié)合時(shí)間和質(zhì)量并不容易,因?yàn)樗麄兘?jīng)?；ハ嘧儞Q。生產(chǎn)系統(tǒng)的科技進(jìn)步，在方式將可更有效和可行的促進(jìn)組合,例如,如果是演化的觀測(cè)系統(tǒng)和注塑技術(shù)、我們得出的結(jié)論是事實(shí)上可以用很少的時(shí)間和高質(zhì)量把新產(chǎn)品推向市場(chǎng)。在模具制造領(lǐng)域中，先進(jìn)的快速模具制造技術(shù)有可能改善設(shè)計(jì)和制造過程注入部分?？焖倌＞咧圃旒夹g(shù)基本上是由程序集中組成，在短短的時(shí)間里，以可接受的精度水平使我們獲取小型系列的塑料模具零件。其應(yīng)用領(lǐng)域不僅包括制作塑膠件注，而且他們研制并創(chuàng)造了最高產(chǎn)量。
本文包括在廣泛試圖研究確定分析測(cè)試和建議的科研第一線，在產(chǎn)業(yè)層次形成從注塑模具獲取鎳殼核心的可能性，同時(shí)用差分模型快速成型設(shè)備取得了初步的模型。
也將不得不說(shuō)，無(wú)數(shù)業(yè)內(nèi)人士事前并沒有應(yīng)用任何新電鑄技術(shù)，但很大程度上，在快速模具的生產(chǎn)技術(shù)上使用這種試圖調(diào)查研究工作.，運(yùn)用所有準(zhǔn)確，制度化的方式方法并提出了工作。
2．注塑模具制造過程
核心是透過電進(jìn)程的鎳殼。這是一個(gè)主管充滿金屬環(huán)氧樹脂的一核心板塊。模具(圖1)制造時(shí)可以直接注射A型多用標(biāo)本，確定SO3167標(biāo)準(zhǔn)的甲狀旁腺恩目的是要確定這個(gè)試樣的力學(xué)性能和通過常規(guī)手段收集工業(yè)材料。
圖1注塑模具制造與電核心
根據(jù)這一方法研制工作，該階段取得核心有以下幾方面：
(一) CAD系統(tǒng)預(yù)期目標(biāo)的設(shè)計(jì)
(二) 快速原型設(shè)備制造模型(頻分多路復(fù)用)。該材料將被用于ABS塑料
(三) 以以往的模式生產(chǎn)事前已經(jīng)涂了導(dǎo)電涂料的鎳電殼(必須有導(dǎo)電)
(四) 從模型中清理殼牌
(五) 生產(chǎn)背面填充著隨著銅管與冷凍槽流動(dòng)具有抗高溫殼牌環(huán)氧樹脂的核
心
注塑模具有兩個(gè)空洞，他們一個(gè)是電加工的核心，另一個(gè)是直接在機(jī)械上移動(dòng)壓板。因此，它獲得了與同一工具及同一工藝條件同時(shí)在空洞里注入兩種不同的標(biāo)本制造技術(shù)。
3．電鑄殼獲?。涸O(shè)備
電鍍是一個(gè)電化學(xué)過程中的化學(xué)變化, 當(dāng)電流通過，它起源于電解質(zhì)。該電解槽是由金屬鹽溶液淹沒兩個(gè)電極，一個(gè)陽(yáng)極(鎳)、陰極(示范)。通過來(lái)自一定強(qiáng)度的直流電。當(dāng)電流流經(jīng)電路，目前在溶液中金屬離子轉(zhuǎn)化為原子，堆積于陰極或多或少的創(chuàng)造沉淀層。
這項(xiàng)工作采用的鍍液是由鎳、磺酸集中在400 毫升/公升，氯化鎳(10微克/公升)、硼酸(50微克/公升),allbrite SLA (30立方厘米/公升),703allbrite(2立方厘米/公升)。這種合成物的選擇主要取決于我們打算的應(yīng)用類型即注塑模具，即使注射了玻璃纖維?；撬徭囎屛覀儷@得可以接受的殼內(nèi)壓 (測(cè)試結(jié)果，不同工藝條件，不高于50兆帕和2兆帕左右最佳條件)。 不過這種程度的內(nèi)部壓力也是使用添加劑Allbrite SLA強(qiáng)硝酸脂、甲醛水溶液產(chǎn)生的后果。這種添加劑當(dāng)允許較小殼顆粒增加阻力。703allbrite是降解水溶液以減少表面腐蝕。氯化鎳,盡管內(nèi)壓有害，增強(qiáng)導(dǎo)電溶液中的金屬均勻分布在陰極。硼酸作為pH值的緩沖。一旦已確定浴，有效驗(yàn)的參數(shù)測(cè)試改變不同條件過程的電流密度(在1至22a/立方分米)，溫度(35至55℃)和pH值, 部分的改變鍍液組成。
4．獲得硬度
在測(cè)試期間已獲得一個(gè)非常有趣的結(jié)論，對(duì)不同程度硬度的鎳殼一直保持在相當(dāng)高的穩(wěn)定價(jià)值。在圖2，在pH4±0.2，攝氏45℃時(shí)，可以觀察到電流密度值為2.5和22℃之間。硬度值的范圍從高壓540至580。如果pH值降為3.5，氣溫下降55℃，硬度值的范圍從高壓520以上至高壓560以下。由磺酸鎳組成的這一特點(diǎn)使得測(cè)試不同于其他傳統(tǒng)業(yè)務(wù)，觀念是允許經(jīng)營(yíng)范圍更廣；然而這種有限性的將取決于其他因素。例如內(nèi)應(yīng)力，因?yàn)槠涔ぷ鳡顟B(tài)可能在某些變性的pH值、電流密度和溫度下。在另一方面，傳統(tǒng)的硬度介于200-250高壓磺酸浴，遠(yuǎn)低于在測(cè)試中獲得的。有必要要考慮到對(duì)于注塑模具，接受300高壓硬度。其中最常見的材料就可以找到注塑模具鋼(高壓290)，積分硬化鋼(高壓520-595)，casehardened鋼(高壓760-800)等。這樣可以觀察到中高幅度硬度水平的鎳殼注塑模具材料，有償殼牌是反對(duì)用低延性的環(huán)氧樹脂填充。因?yàn)樽⑺苁且粋€(gè)內(nèi)壓控制進(jìn)程， 這也是為什么必須要?dú)ず穸缺M可能均勻(以上最低值)，避免重大失誤。如圖：
圖2．硬度變化與電流密度．4+0.2pH值．45℃
5．金相組織
主要是為了改良而分析金相結(jié)構(gòu)、電流密度、溫度值。樣品分析、橫向部分(垂直于沉積)為實(shí)現(xiàn)準(zhǔn)備便捷，樹脂被方便的封裝在含有硝酸，醋酸混合物的瓶子，進(jìn)行每隔15，25，40，50秒收盤后擦拭。為了事后在奧林匹斯金相顯微鏡碲下觀察PME3-ADL 3.3×/10×。
在評(píng)論文中的照片之前，有必要討論用差分快速成型機(jī)械制造逐層貫通的熔融塑料 (ABS) 殼模具。 每一層擠出模具留下的螺紋直徑約0.15毫米即橫向和縱向的中間媒介。因此，在機(jī)器的主要表面可以觀察到薄線標(biāo)明的道路。這些線路將作為參考解決水平鎳重復(fù)性顯示。重復(fù)性模式將是一個(gè)評(píng)估注塑模具基本內(nèi)容的基本要素：表面紋理。
該系列測(cè)試表1所示：
表1．
檢驗(yàn)系列
系列
pH
溫度(℃)
電流密度A/mm2
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
圖3顯示第一次蝕刻的系列表面樣本。它顯示了頻分多路復(fù)用機(jī)的原理，也就是說(shuō)有一個(gè)良好的重復(fù)性。 它仍無(wú)法察覺圓形的顆粒結(jié)構(gòu)，在圖4系列2之后的第二蝕刻可以觀察到一條線道較前明顯減少。在圖5系列2°和3，雖然這時(shí)路徑很難查出，蝕刻已開始出現(xiàn)了一批顆粒結(jié)構(gòu)。另外，最黑暗的地方顯示含有合成物浴的蝕刻過程。
圖 3. 系列1(×150)、蝕刻1
圖 4. 系列2(×300), 蝕刻2
圖 5. 系列3(×300),蝕刻2
這一行為表明，工作在低電流密度、高溫下，殼以良好的再現(xiàn)能力獲得粒度即適當(dāng)?shù)膽?yīng)用。如果進(jìn)行了平面沉積的橫向分析，它可以在所有的樣品和一切條件下測(cè)試，沉淀物的增長(zhǎng)結(jié)構(gòu)是由薄片組成的(圖6)。雖然延展性低，但是取得了高機(jī)械阻力。這取決于質(zhì)量,，首先存在添加劑。因?yàn)榛撬徭囋]有添加劑，通常制造纖維和非層結(jié)構(gòu)[5]。更正直到近似于空值的潤(rùn)濕劑，在任何情況下保持層結(jié)構(gòu)表明這種結(jié)構(gòu)的應(yīng)力消脂(allbrite習(xí)得)。在另一方面，據(jù)測(cè)試根據(jù)不同層結(jié)構(gòu)層厚度的計(jì)算電流密度。
圖 6. 機(jī)橫向系列2 (×600),蝕刻2.
6．內(nèi)壓
其中一個(gè)主要特征是殼的應(yīng)用像輸入低水平內(nèi)壓。用陰極張力法在不同電流密度和鍍液溫度測(cè)量系統(tǒng)下做不同的測(cè)試。鋼鐵被用來(lái)測(cè)試與控制自由和固定(160毫米長(zhǎng)度 寬度12.7毫米,厚度0.3毫米)。因?yàn)槌练e金屬是唯一允許檢測(cè)控制機(jī)械應(yīng)變(拉伸或壓應(yīng)力)和計(jì)算內(nèi)壓。對(duì)于部分鋼鐵來(lái)說(shuō)，從彈性的角度來(lái)看Stoney模型應(yīng)用被假定鎳底層厚度不夠，表面影響小(3微米)。在所有測(cè)試情形中最佳條件是內(nèi)部壓力50和極端條件下為2兆帕，為所需的可接受值。最后的結(jié)論是在不同的條件和工作參數(shù)下電鍍?cè)≡试S無(wú)明顯變化內(nèi)壓。
7．測(cè)試的注塑模具
試驗(yàn)已在各種代表性熱塑性材料中進(jìn)行如聚丙烯、鎂、高密度聚乙烯和PC。分析零件的性能，如注射大小、重量、抗延性僵化。測(cè)試?yán)炝W(xué)性能和分析光破壞性。這一核心進(jìn)行約500注射量，其余條件下經(jīng)受更多。
一般而言，重大分歧都是未察覺樣本核心之間的行為。從加工腔到一整套的材料，但是在分析光彈性時(shí)(圖七)發(fā)現(xiàn)了兩種不同張標(biāo)本，基本上是取決于炎熱劃轉(zhuǎn)、澆注腔的剛度。這種差異說(shuō)明延性變化較突出的部分材料，如聚乙烯、六鎂。
圖 7．分析光注入標(biāo)本
在所有分析化驗(yàn)中發(fā)現(xiàn)高密度聚乙烯管案例是一個(gè)較低延性標(biāo)本。所得鎳核心，量化30%左右。在這種情況下六鎂值也接近50%。
8．結(jié)論
經(jīng)過連續(xù)的測(cè)試和不同的條件下已經(jīng)清查磺酸鎳浴已獲準(zhǔn)使用添加劑。鎳殼將獲得一些可以接受的注塑模具的機(jī)械性能。也就是說(shuō)，重復(fù)性好，高硬度及良好的機(jī)械阻力。因而機(jī)械層結(jié)構(gòu)不足的部分將取代鎳殼的環(huán)氧樹脂飾面。核心為注塑塑造，允許注入可接受質(zhì)量水平中型系列塑料零件。
附件2：外文原文（復(fù)印件）
A technical note on the characterization of electroformed nickel shells for their application to injection molds
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
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 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 ， 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 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 。 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.
Fig. 1.?Manufactured injection mold with electroformed core.
The stages to obtain a core, 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.
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 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 and 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.
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 200–250?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 (520–595?HV), casehardened steel (760–800?HV), etc., in such a way that it can be observed that the hardness levels of the nickel shells would be within the medium–high 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.
Fig. 2.?Hardness variation with current density. pH 4?±?0.2, T?=?45?°C.
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×.
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 1.
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.
Fig. 3.?Series 1 (×150), etch 1.
Fig. 4.?Series 2 (×300), etch 2.
Fig. 5.?Series 3 (×300), etch 2.
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. 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.
Fig. 6.?Plane transversal of series 2 (×600), etch 2.
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 was applied and was supposed that nickel substratum thickness is enough small (3?μm) 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.
Fig. 7.?Analysis by photoelasticity of injected specimens.
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 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