749 瓶塞注射模設(shè)計【全套14張CAD圖+文獻(xiàn)翻譯+說明書】

749 瓶塞注射模設(shè)計【全套14張CAD圖+文獻(xiàn)翻譯+說明書】,全套14張CAD圖+文獻(xiàn)翻譯+說明書,749,瓶塞注射模設(shè)計【全套14張CAD圖+文獻(xiàn)翻譯+說明書】,瓶塞,注射,設(shè)計,全套,14,cad,文獻(xiàn),翻譯,說明書,仿單 前 言 模具是利用其特定形狀去成型具有一定型狀和尺寸的制品的工具，按制品 所采用的原料不同，成型方法不同，一般將模具分為塑料模具，金屬沖壓模具， 金屬壓鑄模具，橡膠模具，玻璃模具等。因人們?nèi)粘Ｉ钏玫闹破泛透鞣N機 械零件，在成型中多數(shù)是通過模具來制成品，所以模具制造業(yè)已成為一個大行 業(yè)。在高分子材料加工領(lǐng)域中,用于塑料制品成形的模具,稱為塑料成形模具,簡 稱塑料模.塑料模優(yōu)化設(shè)計,是當(dāng)代高分子材料加工領(lǐng)域中的重大課題。塑料制 品已在工業(yè)、農(nóng)業(yè)、國防和日常生活等方面獲得廣泛應(yīng)用。為了生產(chǎn)這些塑料 制品必須設(shè)計相應(yīng)的塑料模具。在塑料材料、制品設(shè)計及加工工藝確定以后， 塑料模具設(shè)計對制品質(zhì)量與產(chǎn)量，就決定性的影響。首先，模腔形狀、流道尺 寸、表面粗糙度、分型面、進(jìn)澆與排氣位置選擇、脫模方式以及定型方法的確 定等，均對制品（或型材）尺寸精度形狀精度以及塑件的物理性能、內(nèi)應(yīng)力大 小、表觀質(zhì)量與內(nèi)在質(zhì)量等，起著十分重要的影響。其次，在塑件加工過程中， 塑料模結(jié)構(gòu)的合理性，對操作的難易程度，具有重要的影響。再次，塑料模對 塑件成本也有相當(dāng)大的影響，除簡易模外，一般來說制模費用是十分昂貴的， 大型塑料模更是如此。 塑料摸是塑料制品生產(chǎn)的基礎(chǔ)之深刻含意，正日益為人們理解和掌握。當(dāng) 塑料制品及其成形設(shè)備被確定后，塑件質(zhì)量的優(yōu)劣及生產(chǎn)效率的高低，模具因 素約占 80%。由此可知，推動模具技術(shù)的進(jìn)步應(yīng)是不容緩的策略。尤其大型塑 料模的設(shè)計與制造水平，常常標(biāo)志一個國家工業(yè)化的發(fā)展程度。本課題研究的 是塑料注射模具的設(shè)計。 本設(shè)計的研究目的是檢驗理論知識掌握情況，將理論與實踐結(jié)合。進(jìn)一 步掌握進(jìn)行模具設(shè)計的方法、過程，為將來走向工作崗位進(jìn)行科技開發(fā)工作和 撰寫科研論文打下基礎(chǔ)。培養(yǎng)自己的動手能力、創(chuàng)新能力、計算機運用能力。 研究意義是對于模具的設(shè)計可以從選材到設(shè)計到成型有一個完整的了解和初步 的掌握。以及進(jìn)一步的熟練掌握 AutoCAD、Pro\E 相關(guān)設(shè)計軟件。鍛煉自己的獨 立思考能力和創(chuàng)造能力，為更好更快的適應(yīng)工作作準(zhǔn)備。 塑料件的模具設(shè)計結(jié)構(gòu)設(shè)計，應(yīng)充分考慮實際生產(chǎn)的具體要求。特別是小 型塑件的模具設(shè)計，受位置的限制，抽芯機構(gòu)的選擇十分有限，這就產(chǎn)生了抽 芯機構(gòu)的設(shè)計與模具尺寸相互制約的問題，澆口位置的選擇也會直接影響塑件 的表面質(zhì)量。本設(shè)計通過一個實際塑料傳動機架模具的設(shè)計對此進(jìn)行分析。同 時也說明了模具設(shè)計的流程，及怎樣設(shè)計一套模具 在本設(shè)計編寫的過程中，遇到了很多問題，通過與同學(xué)的交流和制導(dǎo)老師 的耐心講解，都已得到解決，在此特別感謝。 II 摘 要 模具技術(shù)已成為衡量一個國家工業(yè)發(fā)展水平高低的重要標(biāo)志，而注塑模具越來 越顯示出不可比擬的優(yōu)越性。此文首先介紹了國內(nèi)外模具技術(shù)的現(xiàn)狀及存在的問題， 并提出了今后模具技術(shù)的發(fā)展趨勢，其次，以瓶塞注射模設(shè)計為例，闡述了注射模 設(shè)計的詳細(xì)過程。設(shè)計中運用了先進(jìn)的 CAD/CAM/CAE 技術(shù)，對注塑模進(jìn)行了優(yōu)化， 理論上分析了注射成型中塑料制品易出現(xiàn)的問題，比如澆口尺寸、注射壓力和注射 速率對收縮和翹曲的影響，并提出了相應(yīng)的解決對策。 關(guān)鍵詞： 注塑模具；模具 CAD/CAM/CAE；注射成型；塑料制品 III ABSTRACT The level of a cuntry’s industry was mostly determined by die 模內(nèi)冷卻的塑件 p 約取 0.8~1.2×107Pa。 所以:經(jīng)計算，A=379.94mm 2 ,μ 取 0.25,p 取 1×107Pa,取 α=45 ， 。 Ft=379.94×10-6×1×107(0.25×cos45`-sin45`) =900.04N. 因此，脫模力的大小隨塑件包容型芯的面積增加而增大，隨脫模斜度的增加而 減小。由于影響脫模力大小的因素很多，如推出機構(gòu)本身運動時的摩擦阻力、塑料 與鋼材間的粘附力、大氣壓力及成型工藝條件的波動等等，因此要考慮到所有因素 的影響較困難，而且也只能是個近似值。 20 9. 溫控系統(tǒng)設(shè)計 在塑料注射成形中，注射模具不僅是塑料熔體的成形設(shè)備，還起著熱交換器的 作用。模具溫度調(diào)節(jié)系統(tǒng)直接影響到制品的質(zhì)量和生產(chǎn)效率。由于各種塑料的性能 和成形工藝要求不同，對模具溫度的要求也不同。對于大多數(shù)要求較低模溫的塑料， 僅設(shè)置模具的冷卻系統(tǒng)即可。但對于要求模溫超過 80C°的塑料以及大型注射模具，均需要設(shè)置加熱裝置。 9.1 冷卻系統(tǒng) 一般注射到模具內(nèi)塑料溫度為 200oC 左右，而塑件固化后從模具型腔中取出時 其溫度在 60oC 以下。熱塑性塑料在注射成型后，必須對模具進(jìn)行有效的冷卻，使熔 融塑料的熱量盡快地傳給模具，以使塑料可靠冷卻定型并可迅速脫模。 對于粘度低、流動性好的塑料（例如：聚乙烯、聚丙烯、聚苯乙烯、尼龍 66 等） ，因為成型工藝要求模溫都不太高，所以常用常溫水對模具進(jìn)行冷卻。 ABS 的成型溫度和模具溫度分別為 200～260oC、40～60oC。 9.2 冷卻介質(zhì) 冷卻介質(zhì)有冷卻水和壓縮空氣，但用冷卻水較多，因為水的熱容量大，傳熱系 數(shù)大，成本低。用水冷卻，即在模具型腔周圍或內(nèi)部開設(shè)冷卻水道。 9.3 冷卻系統(tǒng)設(shè)計原則 冷卻水道的開受模具上鑲塊和頂出桿等零件幾何形狀的限制，必須根據(jù)模具的 特點，靈活地設(shè)置冷卻裝置，其設(shè)計要點如下： 1) 盡量保證塑件收縮均勻，維持模具的熱平衡。 2) 冷卻水孔的數(shù)量越多，孔徑越大，則對塑件的冷卻效果越均勻。根據(jù)經(jīng)驗， 一般冷卻水孔中心線與型腔壁的距離應(yīng)為冷卻水孔直徑的 1~2 倍（常為 12~15mm） ，冷卻水孔中心距約為水孔直徑的 3~5 倍，水孔直徑一般為 8~12mm。進(jìn)水管直徑的選擇應(yīng)使水流速度不超過冷卻水道的水流速度.避免 產(chǎn)生過大的壓力降應(yīng)，應(yīng)根據(jù)模具的具體大小和產(chǎn)品大小狀況而定。 3) 盡可能使冷卻水孔至型腔表面的距離相等，當(dāng)塑件壁厚均勻時，冷卻水孔 與型腔表面的距離應(yīng)處處相等。 4）澆口出加強冷卻。塑料熔體充填型腔時，澆口附近溫度最高，距澆口越遠(yuǎn)溫 度就越低，因此澆口附近應(yīng)加強冷卻，通常將冷卻水道的入口處設(shè)置在澆口附近， 使?jié)部诟浇哪＞咴谳^低溫度下冷卻，而遠(yuǎn)離澆口部分的模具在經(jīng)過一定程度熱交 換后的溫水作用下冷卻。 5)應(yīng)降低進(jìn)水與出水的溫差。一般進(jìn)水與出水溫度差不大于 5°。 6）合理選擇冷卻水道的形式。對于聚乙稀等收縮率較大的成型樹脂，必須沿制 21 品收縮大的方向設(shè)置冷卻回路。 7）合理確定冷卻水管接頭位置。 8）冷卻系統(tǒng)的水道盡量避免與模具上其他結(jié)構(gòu)（如推桿孔、小型芯孔等）發(fā)生 干涉現(xiàn)象。 9）冷卻水管進(jìn)出接頭應(yīng)埋入模板內(nèi)，以免模具在搬運過程中造成損壞。 10）冷卻水道的設(shè)計必須盡量避免接近塑件的熔接部位，以免產(chǎn)生熔接痕，降 低塑件強度；冷卻水道要易于加工清理一般水道孔徑為 10mm 左右，不小于 8mm。據(jù) 此套模具結(jié)構(gòu)，采用孔徑為 8mm 的冷卻水道。 圖 7 冷卻水管 22 10.注射機的校核 10.1 塑件在分型面上的投影面積與鎖模力校核 注射成型時，塑件在模分型面的投影面積是影響鎖模力的主要因素，其數(shù)值越大， 需鎖模力也就越大，若超過注射機的允許最大成型面積，則在成型過程中會出現(xiàn)漲模 溢料現(xiàn)象。因此有： 塑件總的投影面積 nA 與澆注系統(tǒng)的投影面積 之和要小于最大成型面積 1 A2 A。 nA +A A12 4x5.5*5.5*3.14+4x0.6x6=394.34mm29000mm2 滿足要求 應(yīng)使塑料熔體對型腔的成型壓力與塑件和澆注系統(tǒng)在分型面上的投影面積 之和的乘積小于注射機額定鎖模力： （nA +A ）PF12 T=394.34*55 =21688.7N=21.68KN250KN 滿足要求 10.2 模具厚度校核 模具厚度 H 必須滿足：H minHHmax 式中 H min——注射機允許的最小模厚，即動，定模板之間的最小開距； Hmax——注射機允許的最大模厚。 H=210mm,H =200mm,M =300mm。符合條件。minmax 10.3 開模行程校核 由于注射模最大開模行程 S 與模厚無關(guān)，因此有：ax S≥H 1+H2+a+(5~10)mm 式中 H 1——推出距離（脫模距離） （mm） ； H2——包括澆注系統(tǒng)凝料在內(nèi)的塑件高度（mm） ； a——取出澆注系統(tǒng)凝料必須的長度（mm） 。 H1=40mm, H2=40mm,a=24mm 所以 s=114mm,遠(yuǎn)小于注射機的最大開模行程 300mm,合適。綜上所述，所選 擇的注射機滿足注射要求。 23 11.模具材料的選用 11.1 模具材料選用原則 用于注塑模具的鋼材，大致應(yīng)滿足如下要求： 1）機械加工性能優(yōu)良：易切削，適于深孔、深溝槽、窄縫等難加工部位的加工 和三維復(fù)雜形面的雕刻加工； 2）拋光性能優(yōu)良：沒有氣孔等內(nèi)部缺陷，顯微組織均勻，具有一定的使用硬度 （40HRC 以上） ； 3）良好的表面腐蝕加工性：要求鋼材質(zhì)地細(xì)而均勻，適于花紋腐蝕加工；但對 一些特殊 塑料； 4）耐磨損，有韌性：可以在熱交變負(fù)荷的作用下長期工作，耐摩擦； 5）熱處理性能好：具有良好的淬透性和很小的變形，易于滲氮等表面處理； 6）焊接性好：具有焊接性，焊后硬度不發(fā)生變化，且不開裂、變形等； 7）熱膨脹系數(shù)小，熱傳導(dǎo)效率高：防止變形，提高冷卻效果； 8）性能價格比合理，市場上容易買到，供貨期短。 在選擇注射模具鋼材時，要綜合考慮塑件的生產(chǎn)批量、尺寸精度、復(fù)雜程度、 體積大小和外觀要求等因素。對于塑件生產(chǎn)批量大、尺寸精度要求高的場合，應(yīng)選 用優(yōu)質(zhì)模具鋼。對于結(jié)構(gòu)復(fù)雜或體積比較大的塑件應(yīng)選用易切削鋼。外觀要求高的 塑件可以選用鏡面鋼材。 11.2 本套塑料模具的選材及熱處理 見表 3 表 3 模具零件及熱處理 零件名稱 材料牌號 熱處理方法 硬度 說明 動模小型芯 T8A 淬火 58HRC～62HRC 側(cè)向小型芯 T8A 淬火 58HRC～62HRC 形狀簡單的小型腔、型芯 下模仁 CrWMn 淬火 54HRC～58HRC 定模板 45 調(diào)質(zhì) 230～270HB 用于形狀簡單要求不高的型腔 動模板 45 調(diào)質(zhì) 230～270HB 脫澆板 45 調(diào)質(zhì) 230～270HB 動定模座板 45 調(diào)質(zhì) 230～270HB 推桿 T8A 淬火 54～58HRC 推桿 支撐板 45 淬火 43～48HRC 24 零件名稱 材料牌號 熱處理方法 硬度 說明 推板 45 淬火 43～48HRC 主流道襯套 T8A 淬火 50～55HRC 推板導(dǎo)柱 T8A 淬火 50～55HRC 定位圈 T8A 淬火 50～55HRC 復(fù)位桿 45 淬火 43～48HRC 水嘴 黃銅 各螺釘 45 楔緊塊 T8A 淬火 54～58HRC 斜導(dǎo)柱 T10A 淬火 54～58HRC 滑塊 T10A 淬火 54～58HRC 導(dǎo)套 T8A 淬火 50～55HRC 導(dǎo)柱 T8A 淬火 56～60HRC 拉料桿 T8A 淬火 50～55HRC 滑塊固定板 45 調(diào)質(zhì) 230～270HB 彈簧 65Mn 11.3 該套模具所用材料的性能比較 表 4 模具材料的性能比較 鋼號 切削加工性 淬透性 淬火不變形性 耐磨性 耐熱性 45 優(yōu) 差 差 中 差 T8A 優(yōu) 差 差 中 差 T10A 良 差 差 良 差 25 12.模具的工作過程 模具裝配試模完畢之后，模具進(jìn)入正式狀態(tài)，其基本工作過程如下： 1) 對塑料 ABS 進(jìn)行烘干，并裝入料斗。 2) 清理模具型芯、型腔，并噴上脫模劑，進(jìn)行適當(dāng)?shù)念A(yù)熱。 3) 合模、鎖緊模具。 4) 對塑料進(jìn)行預(yù)塑化，注射裝置準(zhǔn)備注射。 5) 注射過程包括充模、保壓、倒流、澆口凍結(jié)后的冷卻和脫模。 6) 塑件的后處理。去掉塑件上的毛刺，對塑件進(jìn)行調(diào)濕處理。 26 結(jié)束語 塑料工業(yè)是當(dāng)今世界上發(fā)展最快的工業(yè)門類之一，對于我國而言，它在整個國 民經(jīng)濟(jì)的各個部門中發(fā)揮了越來越大的作用。我們大學(xué)生對于塑料工業(yè)的認(rèn)識還是 很膚淺的，但是通過這次塑料模具課程設(shè)計，讓我更多的了解有關(guān)塑料模具設(shè)計的 基本知識，更進(jìn)一步掌握了一些關(guān)于塑料模具設(shè)計的步驟和方法，對塑料模有了一 個更高的認(rèn)識。這對我們在今后的生產(chǎn)實踐工作中無疑是個很好的幫助，也間接性 的為今后的工作經(jīng)驗有了一定的積累。 進(jìn)行塑料產(chǎn)品的模具設(shè)計首先要對成型制品進(jìn)行分析，再考慮澆注系統(tǒng)、型腔 的分布、導(dǎo)向推出機構(gòu)、抽芯機構(gòu)等后續(xù)工作。通過制品的零件圖就可以了解制品 的設(shè)計要求。對形態(tài)復(fù)雜和精度要求較高的制品，有必要了解制品的使用目的、外 觀及裝配要求，以便從塑料品種的流動性、收縮率，透明性和制品的機械強度、尺 寸公差、表面粗糙度、嵌件形式等各方面考慮注射成型工藝的可行性和經(jīng)濟(jì)性。模 具的結(jié)構(gòu)設(shè)計要求經(jīng)濟(jì)合理，認(rèn)真掌握各種注射模具的設(shè)計的普遍的規(guī)律，可以縮 短模具設(shè)計周期，提高模具設(shè)計的水平。 塑料制品成型及模具的設(shè)計還是個很專業(yè)性、實踐性很強的技術(shù)，而它的主要 內(nèi)容都是在今后的生產(chǎn)實踐中逐步積累和豐富起來的。因此，我們要學(xué)好這項技術(shù) 光靠書本上的點點知識還是不夠的，我們更多的還應(yīng)該將理論與實際結(jié)合起來，這 還需要我們以后更多的去實踐。 27 參考文獻(xiàn) [1] 葉久新，王群主編．塑料制品成型及模具設(shè)計[M]．湖南科學(xué)技術(shù)出版社， 2005，1-156 ． [2]黃毅宏、李明輝主編模具制造工藝.北京：機械工業(yè)出版社，1999.6 [3]. 何忠保，陳曉華，王秀英主編.典型零件模具圖冊.北京：機械工業(yè)出版社， 2000.9 [4]. 李紹林，馬長福主編.實用模具技術(shù)手冊.上海：上?？茖W(xué)技術(shù)文獻(xiàn)出版社， 2000.6 [5]. 王樹勛主編.注塑模具設(shè)計與制造實用技術(shù).廣州：華南理工大學(xué)出版社， 1996.1 [6]. 李紹林主編.塑料·橡膠成型模具設(shè)計手冊. 北京：機械工業(yè)出版社，2000.9 [7] 劉小寧，張永?。可w注射模設(shè)計[J]．模具工業(yè)，2006，32（5）：44-46． [8] 伍先明，王群，龐佑霞，張厚安編著[M]．國防工業(yè)出版社，2006． [9] 劉小寧，張永俊．瓶蓋注射模設(shè)計[J]．模具工業(yè)，2006，32（5）：44-46． [10] 付偉，張海，曹愛文．基于 Pro/E 的分模方法及技巧 [J]．模具工業(yè)， 2006，32（5）：65-70． [11] 杜智敏，何華妹 郭擎強編著．Pro/ENGINEER 野火版塑料注射模具設(shè)計實例 [M]．機械工業(yè)出版社，2005． [12] 付宏生，劉京華編著．注塑制品與注塑模具設(shè)計[M]．化學(xué)工業(yè)出版社，2003． [13] 模具實用技術(shù)叢書編委會編．塑料模具設(shè)計制造與應(yīng)用實例[M]．機械工業(yè)出 版社，2002，1-230． 28 致 謝 29 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 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. 30 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. 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: 31 ? 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. 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 32 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. 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