旋鈕零件注射模具設(shè)計(jì)【說明書+CAD】
旋鈕零件注射模具設(shè)計(jì)【說明書+CAD】,說明書+CAD,旋鈕零件注射模具設(shè)計(jì)【說明書+CAD】,旋鈕,零件,注射,模具設(shè)計(jì),說明書,仿單,cad
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： 張宜雄
學(xué) 號(hào)： 05010148
外文出處： http://www.sciencedirect.com
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)：
譯文基本能表達(dá)原文思想，語(yǔ)句較流暢，條理較清晰，專業(yè)用語(yǔ)翻譯基本準(zhǔn)確，基本符合中文習(xí)慣，整體翻譯質(zhì)量一般。
簽名：
年 月 日
附件1：外文資料翻譯譯文
下沉指數(shù)最小翹曲、注塑件熱塑性田口優(yōu)化方法
——大加那利島拉斯帕爾馬斯大學(xué)，機(jī)械工程學(xué)院，西班牙
摘要：
在過去幾年里快速成型和快速模具技術(shù)已被廣泛開發(fā)利用。在本文中，使用電芯作為核心程序分析塑料注塑模具。通過差分系統(tǒng)快速成型制造外殼模型。主要目的是分析電鑄鎳殼力學(xué)特點(diǎn)，研究相關(guān)的金相組織，硬度，內(nèi)部壓力等不同方面，由這些特征參數(shù)來生產(chǎn)電鑄設(shè)備的外殼。最后一個(gè)核心是檢驗(yàn)注塑模具。
關(guān)鍵詞：電鍍，電鑄，微觀結(jié)構(gòu)，鎳
文章大綱：
1 、導(dǎo)言
2 、制造過程的注塑模具
3 、獲得電殼：設(shè)備
4 、獲得硬度
5 、金相結(jié)構(gòu)
6 、內(nèi)部壓力
7 、檢驗(yàn)注塑模具
8 、結(jié)論
正文：
1 、導(dǎo)言
現(xiàn)代工業(yè)面臨巨大的挑戰(zhàn)，其中的最重要的挑戰(zhàn)是怎樣解決提供給消費(fèi)者更好的產(chǎn)品，更多的種類和更新?lián)Q代（更新設(shè)計(jì)）的問題 。出于這個(gè)原因，現(xiàn)代工業(yè)必定產(chǎn)生越來越激烈的競(jìng)爭(zhēng)性。毫無疑問，結(jié)合時(shí)間變量和質(zhì)量變量是不容易的，因?yàn)樗麄兘?jīng)常彼此互為條件，先進(jìn)的生產(chǎn)系統(tǒng)將允許該組合以更加有效可行的方式進(jìn)行，例如，如果是觀察注塑系統(tǒng)的演變，我們得出的結(jié)論是，事實(shí)上一個(gè)新產(chǎn)品在市場(chǎng)上具有較好的質(zhì)量它需要越來越少的時(shí)間。快速模具制造技術(shù)是在這一領(lǐng)域中可以改善設(shè)計(jì)和制造注入部分的技術(shù)進(jìn)步。快速模具制造技術(shù)基本上是一個(gè)中小型系列的收集程序，在很短的時(shí)間內(nèi)在可接受的精度水平基礎(chǔ)上讓我們獲得模具的塑料部件。其應(yīng)用不僅僅在決策領(lǐng)域的塑料注射件[1] -[3]，然而這是真的。
本文包含了很廣泛的研究路線，并試圖在那里學(xué)習(xí)，定義，分析，測(cè)試，提出在工業(yè)水平方面的可行性，從核心的注塑模具制造獲取電鑄鎳殼，同時(shí)作為一個(gè)初始模型的原型在一個(gè)FDM設(shè)備上的快速成型。
不得不說的是，先進(jìn)的電鑄技術(shù)應(yīng)用在無數(shù)的行業(yè)，這一研究工作調(diào)查到什么程度，并根據(jù)這些參數(shù)，使用這種技術(shù)生產(chǎn)快速模具在技術(shù)上是可行的。所有取得準(zhǔn)確的和系統(tǒng)化的使用方式，并提出了工作方法。
2 、制造過程的注塑模具
薄鎳外殼的核心是電鑄，獲得一個(gè)充滿epoxic金屬樹脂的一體化的核心板塊[4]模具（圖1 ）允許直接制造注射型多用標(biāo)本，因?yàn)樗鼈兇_定了新英格蘭大學(xué)英文國(guó)際標(biāo)準(zhǔn)化組織3167標(biāo)準(zhǔn)。這樣做的目的是確定力學(xué)性能的材料收集代表行業(yè)。
圖 1 注塑模具制造與電的核心
該階段取得的核心[4] ，根據(jù)該方法研究了這項(xiàng)工作，如下：
（a）CAD系統(tǒng)的理想對(duì)象。
（b）示范制造業(yè)的快速成型設(shè)備（頻分多路系統(tǒng)） 。所使用的材料將是一個(gè)ABS塑料。
（c）電鑄鎳殼的模式，已事先涂有導(dǎo)電涂料（它必須有導(dǎo)電性） 。
（d）無外殼的模式。
（e）制作的核心是背面外殼的環(huán)氧樹脂抗高溫與銅管的制冷。
注塑有兩個(gè)腔的具，其中一個(gè)是電核心和其他直接加工的移動(dòng)板。因此，在同一工藝條件下，同時(shí)注入兩個(gè)標(biāo)準(zhǔn)腔技術(shù)制造，獲得相同的工件。
3 、獲得電殼：設(shè)備
電[5] [6]是電解質(zhì)時(shí)電流的化學(xué)變化。電解所形成的直流電有兩個(gè)電極，陽(yáng)極和陰極。當(dāng)電流流經(jīng)電路，在離子溶液中轉(zhuǎn)化為原子。
電鍍液用于這項(xiàng)工作是由氨基磺酸鎳[ 7 ] [ 8 ]400毫升/升，氯化鎳（ 10克/升） ，硼酸（ 50克/升） ， Allbrit SLA（ 30毫升/ l ）和Allbrite 703 （ 2毫升/升） 。選擇這一成分，主要是由于我們考慮注塑模具程序是玻璃纖維。氨基磺酸鎳使我們能夠獲得一個(gè)可以接受水平的內(nèi)部壓力（測(cè)試了不同的工藝條件結(jié)果，而不是最佳工藝條件為約2兆帕最高為50兆帕）。然而，這種內(nèi)部壓力，是由toluenesulfonamide衍生物和甲醛水溶液使用的Allbrite添加劑的結(jié)果，
添加劑也增加了殼的阻力。 Allbrite 703是一種可生物降解的水溶液作用劑。氯化鎳，有利于統(tǒng)一解決金屬分布在陰極，提高導(dǎo)電性的問題。硼酸作為pH值的緩沖區(qū)。
該設(shè)備用于制造殼的測(cè)試如下：
?聚丙烯： 600毫米× 400毫米× 500毫米大小。
?三個(gè)800瓦聚四氟乙烯電阻器
?機(jī)械攪拌系統(tǒng)的陰極。
?系統(tǒng)的循環(huán)和過濾用的泵和聚丙烯過濾器。
?充電整流器。最大強(qiáng)度在連續(xù)50個(gè)A和連續(xù)電流電壓介于0和16V
?籃鈦鎳陽(yáng)極（鎳硫回合電解鎳） ，純度99 ％以上。
?氣體注系統(tǒng)
一旦電流密度（ 1至22 A/dm2 ） ，溫度（ 35至55 ° C ）和pH值已經(jīng)確定，執(zhí)行參數(shù)，測(cè)試的進(jìn)程部分就不可改變。
4 、獲得硬度
電殼硬度的測(cè)試一直保持的相當(dāng)高和穩(wěn)定結(jié)果。如圖 2?？梢钥吹剑弘娏?
密度值2.5到A/dm2 ，硬度值介于540到580高壓，pH值為4 ± 0.2和溫度為45攝氏度，如果pH值減少到3.5和溫度為55 ℃，硬度為520以上，高壓低于560 。這一測(cè)試使常規(guī)組成不同于其他氨基磺酸鎳，允許其運(yùn)營(yíng)更加廣泛;然而，這種operativity將是一定的取決于其他因素，如內(nèi)部壓力，因?yàn)樗淖儺惪赡?
改變PH值，電流密度和溫度等。另一方面，傳統(tǒng)的硬度氨基磺酸高壓200-250之間，遠(yuǎn)低于取得的一個(gè)試驗(yàn)結(jié)果。這是必須考慮到的，對(duì)于一個(gè)注塑模具，硬度可以接受的起點(diǎn)300高壓。注塑模具中最常見的材料，有改善鋼（ 290高壓） ，整體鋼淬火（ 520-595高壓） ， casehardened鋼鐵（ 760-800高壓）等，以這樣一種方式，可以看到，注塑模具硬度水平的鎳是殼內(nèi)的高范圍的材料。因?yàn)檫@是一個(gè)負(fù)責(zé)內(nèi)部壓力的塑料注射液，這種方式與環(huán)氧樹脂灌漿將遵循它，相反對(duì)低韌性的殼補(bǔ)償，這就是為什么它是必定盡可能的外殼厚度均勻，并沒有重要的原因，如 腐蝕
圖 2 硬度隨電流密度 pH值為4 ± 0.2 ，溫度為45攝氏度
5 、金相結(jié)構(gòu)
為了分析金相結(jié)構(gòu)的電流密度和溫度主要變化。在正面橫向部分（垂直沉積）對(duì)樣品進(jìn)行了分析。為了方便地封裝在樹脂、拋光、銘刻，在不同階段的混合乙酸和硝酸。該蝕刻間隔為15 、 25 、 40和50之后再次拋光，為了在金相顯微鏡下觀察奧林巴斯PME3-ADL 3.3×/10×。
必須要說的是，這一條規(guī)定顯示了圖片之后的評(píng)論，用于制造該模型的殼在FDM快速成型機(jī)里溶化的塑料材料（澳大利亞統(tǒng)計(jì)局）鞏固和解決了該階層。后來在每一個(gè)層，擠出的模具都留下一個(gè)大約0.15毫米直徑橫向和縱向的線程。因此，在表面可以看到細(xì)線表明頭部的機(jī)器。這些線路將作為參考信息解決鎳的重復(fù)性問題。重復(fù)性的模型將作為一個(gè)基本要素來評(píng)估注塑模具表面紋理。
表1 測(cè)試系列
系列
pH
溫度
(°C)
電流密度
(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
圖3說明該系列第一蝕刻表面的樣本.
它顯示了流道起點(diǎn)的頻率復(fù)用機(jī)，這就是說，有一個(gè)很好的重復(fù)性。它不能仍然注意到四舍五入結(jié)構(gòu)。在圖 4 .系列2 ，經(jīng)過第二次，可以看到一條線的流道的方式與以前的相比不太清楚。在圖 5 .系列3,雖然第二次蝕刻開始出現(xiàn)圓形晶結(jié)構(gòu)是非常困難的。此外，最黑暗的部分表明蝕刻不足的進(jìn)程和組成。
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
這種現(xiàn)象表明，在低電流密度和高溫條件下工作，得到更小的晶粒尺寸和殼重現(xiàn)性好，就是所需的足夠的應(yīng)用程序。
如果分析橫向平面進(jìn)行的沉積，可以在所有測(cè)試樣品和條件增長(zhǎng)的結(jié)構(gòu)層（圖6 ） ，犧牲一個(gè)低延展性取得令人滿意的高機(jī)械阻力。最重要的是添加劑的使用情況，氨基磺酸鎳鍍液的添加劑通常創(chuàng)建一個(gè)纖維和非層狀結(jié)構(gòu)[9]。這個(gè)問題表明，在任何情況下改變潤(rùn)濕劑，由于該層結(jié)構(gòu)的決定因素是這種結(jié)構(gòu)的應(yīng)力減速器（ Allbrite SLA） 。另一方面，它也是測(cè)試的層狀結(jié)構(gòu)不同厚度層中的電流密度。
圖 6 橫向平面系列2 （ × 600 ） ，蝕刻2
6 、內(nèi)部壓力
殼的一個(gè)主要特點(diǎn)是應(yīng)該有其應(yīng)用，如插入是要有一個(gè)低水平的內(nèi)部壓力。測(cè)試不同的溫度和電流密度，所采取的措施取決于陰極彎曲張力計(jì)法。 A鋼測(cè)試控制使用側(cè)固定和其他自由度固定（160毫米長(zhǎng)， 12.7毫米寬和0.3毫米厚度）。金屬沉積只有在控制了機(jī)械拉伸力（拉伸或壓應(yīng)力），才能計(jì)算內(nèi)部壓力。彈性的角度來看，斯托尼模型[10]應(yīng)用，假定鎳基質(zhì)厚度，對(duì)部分鋼材產(chǎn)生足夠小（ 3微米）的影響。在所有的測(cè)試情況下，一個(gè)能夠接受的應(yīng)用程序在內(nèi)部壓力在50兆帕的極端條件下和2兆帕的最佳條件下產(chǎn)生。得出的結(jié)論是，內(nèi)部壓力在不同的工作條件和參數(shù)沒有明顯變化的條件下沒有太大變化。
7 、檢驗(yàn)注塑模具
試驗(yàn)已進(jìn)行了各種代表性的熱塑性材料，如聚丙烯，高密度聚乙烯和PC材料，并進(jìn)行了注射部件性能的分析，如尺寸，重量，阻力，剛度和柔性。對(duì)殼的力學(xué)性能進(jìn)行了拉伸破壞性測(cè)試和分析。大約500個(gè)注射液在其余的條件下，進(jìn)行了更多的檢驗(yàn)。
總體而言，為分析一種材料，重要的是注意到行為標(biāo)本中的核心和那些加工腔之間的差異。然而在分析光彈注入標(biāo)本（圖7）有人注意到不同的國(guó)家之間的張力存在兩種不同類型的標(biāo)本，是由于不同的模腔熱傳遞和剛度。這種差異解釋了柔性的變化更加突出的部分晶體材料，如聚乙烯和聚酰胺6 。
圖 7 分析光彈注入標(biāo)本
有人注意到一個(gè)較低的柔性標(biāo)本在的高密度聚乙烯分析測(cè)試管在鎳核心的情況下，量化30 ％左右。如尼龍6這個(gè)值也接近50 ％ 。
8 、結(jié)論
經(jīng)過連續(xù)試驗(yàn)，注塑模具在不同的條件下檢查的氨基磺酸鎳鍍液使用添加劑，這就是說塑性好，硬度好和摩擦力好的層狀結(jié)構(gòu)，已取得的力學(xué)性能是可以接受的。機(jī)械缺陷的鎳殼將部分取代環(huán)氧樹脂為核心的注塑模具，使注入的一系列中型塑料零部件達(dá)到可接受的質(zhì)量水平。
參考文獻(xiàn)
[1] A.E.W. Rennie, C.E. Bocking and G.R. Bennet.電鑄電極快速成型軸的電火
花加工.學(xué)者材料,（2001年）. 186-196頁(yè).
[2] P.K.D.V. Yarlagadda, I.P. Ilyas and P. Chrstodoulou.模具的快速發(fā)展使
用鎳電鑄和立體光刻工藝.學(xué)者材料,（2001年）.286-294頁(yè).
[3] J. Hart, A. Watson, Electroforming:一種基本上未擴(kuò)大，但關(guān)鍵行業(yè)，
Interfinish 96 ， 14世界大會(huì)上，英國(guó)伯明翰， 1996年.
[4] M. Monzón .阿根廷布宜諾斯艾利斯國(guó)際塑料雜志Modernos , 84 （2002）.
第557頁(yè).
[5] L.F. Hamilton. 希爾的化學(xué)及分析.（1989年）.
[6] E. Julve. Electrodeposición德金屬. 2000年（ EJS ）.
[7] A. Watson.鎳氨基磺酸鹽解決方案.鎳發(fā)展研究所（1989年）.
[8] A. Watson.補(bǔ)充氨基磺酸鹽鎳解決方案.鎳發(fā)展研究所（1989年）.
[9] J. Dini.電鍍材料科學(xué)的涂膜及襯底.諾伊斯出版（1993年）.
[10] J.W. Judy.磁性微與多晶硅屈.信息科學(xué)技術(shù)部，加州大學(xué)伯克利分校， 1994
年.
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
——aUniversidad of Las Palmas of Gran Canaria, Departamento of 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 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.
Fig. 1.?Manufactured injection mold with electroformed core.
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.
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.
? 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 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 [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.
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 [10] 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 propert
收藏