矩形線(xiàn)圈骨架塑件注射模設(shè)計(jì)【一模兩腔】【側(cè)抽芯】【說(shuō)明書(shū)+CAD】

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編號(hào)： 畢業(yè)設(shè)計(jì)(論文)外文翻譯 （譯文） 院 （系）： 國(guó)防生學(xué)院 專(zhuān) 業(yè)：機(jī)械設(shè)計(jì)制造及其自動(dòng)化 學(xué)生姓名： 蔡秀濱 學(xué) 號(hào)： 1001020105 指導(dǎo)教師單位： 機(jī)電工程學(xué)院 姓 名： 郭中玲 職 稱(chēng)： 高級(jí)工程師 2014年 3 月 9 日 目 錄 1.注塑模設(shè)計(jì) 1 2.基于注塑模具鋼研磨和拋光工序的自動(dòng)化表面處理 12 第 19 頁(yè) 共 20 頁(yè) 桂林電子科技大學(xué)畢業(yè)（論文）報(bào)告專(zhuān)用紙 注塑模設(shè)計(jì) Alp Tekin Ergen? Deniz ?zde Koca Yildiz Tecnical大學(xué)機(jī)械工程系,內(nèi)燃發(fā)動(dòng)機(jī)實(shí)驗(yàn)室,土耳其 模具簡(jiǎn)介 模具型腔可賦予制品其形狀，因此在塑料加工過(guò)程中模具處于非常重要的地位，這使得模具對(duì)于產(chǎn)品最終質(zhì)量的影響與塑化機(jī)構(gòu)和其他成型設(shè)備的部件一樣關(guān)鍵，有時(shí)甚至更重要。 模具材料 根據(jù)成型方法和模具使用周期（即要生產(chǎn)的產(chǎn)品數(shù)量）的不同，塑料成型模具要滿(mǎn)足不同的需求，模具可以由多種材料制成，甚至于可以使比較特殊的材料如紙張和石膏。然而，由于大多數(shù)成型過(guò)程需要高壓，通常還有高溫條件限制，金屬迄今為止時(shí)最重要的材料，其中剛才居首位。很多時(shí)候，模具材料的選擇不僅關(guān)系到性能和最佳性?xún)r(jià)比，還影響到模具的加工方法，甚至是整體設(shè)計(jì)。 典型的例子是金屬鑄造模具的材料選擇，與機(jī)械加工模具相比，不同材料的金屬鑄造模具冷卻系統(tǒng)存在很大的差異。另外，不同的制造方法也會(huì)對(duì)材料的選擇產(chǎn)生影生產(chǎn)，原型模具的制造常常采用一些新技術(shù)，如計(jì)算機(jī)輔助設(shè)計(jì)和計(jì)算機(jī)集成制造，將固體毛配制成原型模具。與以前以模型為基礎(chǔ)的方法相比，用CAD和CIMS方法會(huì)更經(jīng)濟(jì)，這是因?yàn)檫@類(lèi)模具廠(chǎng)家自身就能制作，而用其他技術(shù)，只能由外面的供應(yīng)商來(lái)加工生產(chǎn)。 總之，雖然模具生產(chǎn)中經(jīng)常會(huì)用到一些高性能材料，但用得最多的仍然是那些常規(guī)材料。像陶瓷這類(lèi)高性能材料幾乎不能用于模具制造，這可能是因?yàn)槠鋬?yōu)點(diǎn)（如高溫下性能不會(huì)改變）在模具中并不需要，相反，像燒結(jié)類(lèi)陶瓷材料，具有低抗張強(qiáng)度和熱傳遞性差的缺點(diǎn)，在模具中也只有少量應(yīng)用。這里所用的零件不是采用粉末冶金和熱等壓工藝生產(chǎn)，而是指燒結(jié)成的多空、透氣性零件。 在很多成型方法中，都必須將行腔中的氣體排出去，人們已經(jīng)多次嘗試使用多孔金屬材料排氣。與專(zhuān)門(mén)設(shè)置的排氣裝置相比，其優(yōu)點(diǎn)是顯而易見(jiàn)的，尤其是在熔料前鋒處如有熔接線(xiàn)的地方，這里是最容易出現(xiàn)問(wèn)題的區(qū)域：一方面能防止在制品表面有明顯的熔接線(xiàn)，還能避免溢流料等殘余物堵塞微孔。采用這類(lèi)材料制造模具時(shí)，在設(shè)計(jì)和成型工藝上都會(huì)出現(xiàn)新的問(wèn)題。 A．設(shè)計(jì)原則 模具設(shè)計(jì)的原則很多，這些原則都是基于邏輯、以往經(jīng)驗(yàn)、加工的方便性和經(jīng)濟(jì)性考慮，在設(shè)計(jì)、模具制造和模塑成型過(guò)程遵守這些規(guī)則是很有用的，但有時(shí)，忽略某一原則而遵守另一原則往往會(huì)更好些。本文將介紹最常用的設(shè)計(jì)原則，但設(shè)計(jì)人員只有從實(shí)踐經(jīng)驗(yàn)中才能有所收獲。設(shè)計(jì)者應(yīng)隨時(shí)關(guān)注與這些設(shè)計(jì)原則有關(guān)的新觀點(diǎn)、模塑方法、材料。 B．模具基礎(chǔ) 1．模腔 模腔指的是通過(guò)機(jī)加工在模具材料內(nèi)部挖出的空間，以供模塑材料，即塑料填充，并獲取該空間形狀得到需要的制品。模具的歷史幾乎與人類(lèi)文明一樣悠久，通過(guò)在沙型這類(lèi)的模具中注入液體金屬如鐵、青銅，生產(chǎn)出工具、武器、鐘、塑像和廚房用具，如今在鑄造廠(chǎng)仍使用這類(lèi)模具，為了取出固化后的制品，需要將模具打碎，因此這種模具只能用一次，我們一直在尋求可以反復(fù)使用的永久模具，現(xiàn)在可以用堅(jiān)固耐用的材料如鋼材、軟質(zhì)鋁及其他合金材料生產(chǎn)模具，當(dāng)生產(chǎn)量不是很大、模具壽命要求不是很高時(shí)，甚至可以用某些塑料制品模具。注塑生產(chǎn)時(shí)，熔料以高壓注入型腔，因此就需要模具足夠結(jié)實(shí)以抵御變形。 2．型腔數(shù)量 多數(shù)模具，尤其生產(chǎn)大型制品的模具多為單腔模，但是大批量生產(chǎn)時(shí)的模具，會(huì)有兩個(gè)或更多型腔，這純粹是出于經(jīng)濟(jì)考慮。注射多型腔的時(shí)間并不比單腔模多，例如四腔模注射一個(gè)產(chǎn)品的時(shí)間大約僅是單腔模的1/4，而產(chǎn)量卻與型腔數(shù)成正比。多腔模比單腔模貴，并不是說(shuō)要貴四倍，但需要帶有大模板和鎖模能力的注塑機(jī)，而且該例所需總的塑料量是單腔模的四倍，需要有較大的注射裝置，較大設(shè)備的單位成本要比用小型模具的設(shè)備高。目前多型腔模大多選擇2、4、6、8、12、16、24、32、48、64、96、128這樣的數(shù)字。選擇這些數(shù)字（偶數(shù)）的原因是為了方便在長(zhǎng)方形區(qū)域內(nèi)布置型腔，這樣有利于設(shè)計(jì)、定尺寸以方便加工制造，也有利于圍繞機(jī)器中心對(duì)稱(chēng)分布型腔，這種對(duì)稱(chēng)分布對(duì)保證每個(gè)型腔分配到相同的鎖模力非常重要。也可以在圓形范圍內(nèi)設(shè)置較少量的型腔數(shù)，甚至于是3，5，7，9這樣的奇數(shù)，還可用任意型腔數(shù)排布，但要注意圍繞注塑機(jī)中心線(xiàn)投影面積對(duì)稱(chēng)分布。 3．型腔形狀及收縮 型腔形狀實(shí)際上是塑件形狀的“反”形狀。尺寸需要家上塑料的收縮量。型腔形狀可以用切削設(shè)備或電火花、化學(xué)腐蝕及任何新型加工方法進(jìn)行加工和制造，如電鍍工藝，也可以將銅或鋅基合金澆鑄到具有制品形狀的石膏?；蛴菜芰夏Ｈ绛h(huán)氧樹(shù)脂中，再機(jī)加工成規(guī)定形狀。型腔可以直接在模板上切挖出來(lái)，也可做成嵌件攘入模板中。 C．型腔和型芯 通常模具的凹部叫型腔，與之相配的凸起部分叫型芯。大多塑料制品是杯狀的，這并不是它們看起來(lái)像水杯，而是有內(nèi)外兩面，其外部由型腔成型，內(nèi)部由型芯制得。另一種是平板狀制品，模具沒(méi)有明顯的凸起，型腔有時(shí)看起來(lái)像鏡面，這類(lèi)制品有塑料小刀、游戲籌碼、圓片狀制品如唱片，產(chǎn)品外表看起來(lái)很簡(jiǎn)單，但注塑成型時(shí)卻有很多嚴(yán)重問(wèn)題出現(xiàn)。通常將型腔設(shè)置在注塑一側(cè)的半模上，而將型芯設(shè)置在動(dòng)模一側(cè)。這樣放的原因是所有注塑機(jī)在動(dòng)模側(cè)都設(shè)置有頂出機(jī)構(gòu)，而且制品通常易于收縮并包覆在型芯上，隨后被頂出。絕大多數(shù)注塑機(jī)在注射側(cè)不安置頂出機(jī)構(gòu)。 聚合物成型過(guò)程 聚合物成型加工是將固體 (有時(shí)是液體狀) 粉末、粒狀、珠粒等形狀的樹(shù)脂轉(zhuǎn)變成具有一定形狀、尺寸和性能的固體塑料制品，通常包括：擠出、模塑、壓延、涂布、熱成型等。為了實(shí)現(xiàn)上述目標(biāo)，成型過(guò)程通常包括一下步驟：國(guó)體物料輸送、壓縮、加熱、熔融、混合、成型、冷卻、固化、修飾。很顯然，這些操作不一定順序完成，其中有一些是同時(shí)進(jìn)行的。 為了賦予塑料材料規(guī)定的幾何形狀和尺寸，需要通過(guò)成型加工來(lái)完成。還要綜合考慮黏彈性形變和若傳遞，他們和溶體的固化有關(guān)。 成型加工包括下述兩種方式：二維成型如口模成型、壓延和涂布；三維成型。二維成型既包括連續(xù)穩(wěn)定的操作也包括間歇式操作，連續(xù)式如薄膜和片材擠出、線(xiàn)纜包裹、紙張和片材涂布、壓延、纖維紡絲、管材和異型材基礎(chǔ)等，間歇式操作如擠出吹塑成型。通常，模塑成型是間歇式的，所以工作條件有時(shí)會(huì)不穩(wěn)定。熱成型、真空成型及其他類(lèi)似方法常可以被看作是對(duì)已有的二次加工，例如在吹塑成型中，就包括預(yù)成型（型胚的生成）和二次成型（型胚的吹脹）兩部分。 成型過(guò)程中既有同步的液體流動(dòng)和熱傳遞，也有交錯(cuò)的流動(dòng)和熱傳遞。在二維成型過(guò)程中，一般成型后再接著固化，而在三維成型時(shí)，固化和成型往往在模具內(nèi)同時(shí)進(jìn)行。根據(jù)材料的性質(zhì)、設(shè)備和成型條件，結(jié)合流動(dòng)面的情況（自由與否），流動(dòng)通常包括剪切、拉伸及壓縮流動(dòng)（國(guó)內(nèi)一般將流動(dòng)形式只分為剪切和拉伸流動(dòng)）。聚合物流動(dòng)和固化時(shí)的熱力學(xué)－機(jī)械性能決定了制品的微觀結(jié)構(gòu)變化如形態(tài)、結(jié)晶度和取向分布等，制品的最終性能與期微觀結(jié)構(gòu)密切相關(guān)。因此，只有了解樹(shù)脂性能、設(shè)備、操作條件、熱力學(xué)－力學(xué)性能、微觀結(jié)構(gòu)和制品最終性能之間的相互作用，才能更好的實(shí)現(xiàn)生產(chǎn)過(guò)程和制品的質(zhì)量控制。已經(jīng)運(yùn)用數(shù)學(xué)模型和計(jì)算機(jī)模擬來(lái)研究它們之間的相互作用，鑒于CAD/CAM/CAE系統(tǒng)在塑料成型中應(yīng)用越來(lái)越廣泛，此種研究思路也越來(lái)越重要。 注塑成型 將粒狀、粉末及液體塑料轉(zhuǎn)變?yōu)橹破酚泻芏喾N方法，塑料材料處于可模塑狀態(tài)并可適用于多種成型方法。大多數(shù)情況下，熱塑性材料可以用某些方法成型，而熱固性材料需要用其他方法。這是因?yàn)闊崴苄圆牧霞訜岷髸?huì)軟化，冷卻前可被重塑，而熱固性材料在加工前未聚合，成型過(guò)程中會(huì)發(fā)生化學(xué)反應(yīng)，這種反應(yīng)通常是在熱、催化劑或壓力的作用下完成的，在進(jìn)行塑料加工研究和應(yīng)用時(shí)，了解這一點(diǎn)尤為重要。 注塑成型是迄今為止用得最多的一中熱塑性材料的成型方法，同時(shí)也是歷史悠久的一種方法，目前占到塑料成型總量的30%。由于原料可惜此一步成型，注塑方法適于大批量和一步自動(dòng)成型復(fù)雜幾何形狀的塑料制品，大多數(shù)情況下不需要后續(xù)加工。典型制品有玩具、汽車(chē)配件、家庭用具和電子產(chǎn)品。 由于注塑成型時(shí)有很多相互關(guān)聯(lián)的變量，這種方法是相當(dāng)復(fù)雜的。成功的注塑生產(chǎn)不僅有賴(lài)于設(shè)備參數(shù)的正確設(shè)置，還在于要消除每次注射時(shí)的潑動(dòng)，這種潑動(dòng)是由液壓系統(tǒng)、料筒溫度及材料黏度變化引起的。提高每次注射時(shí)設(shè)備參數(shù)的穩(wěn)定性，可得到公差小、次品率低和質(zhì)量高的產(chǎn)品。 任何成型加工最根本的目標(biāo)都是：提高產(chǎn)品質(zhì)量，縮短成型周期，采用重復(fù)性和自動(dòng)化程度高的循環(huán)過(guò)程。模具人員在生產(chǎn)過(guò)程中總是想盡辦法降低或消除不合格。用注塑法生產(chǎn)那些精度要求很高的化學(xué)產(chǎn)品，或者附加值很高的產(chǎn)品如電器外殼，降低次品率的好處很大。 典型的注塑成型過(guò)程由五個(gè)階段組成： 1.注射與充模； 2.補(bǔ)料或壓縮； 3.保壓； 4.冷卻； 5.頂出制品。 注塑概況 工藝 注射成型是一個(gè)塑料在壓力下進(jìn)入一個(gè)空腔中成為理想形狀的的循環(huán)過(guò)程。塑造，是通過(guò)冷卻（熱塑性塑料）或由一個(gè)化學(xué)反應(yīng)（熱固性）來(lái)實(shí)現(xiàn) 的。這是一個(gè)為大規(guī)模生產(chǎn)具有優(yōu)良尺寸精度的復(fù)合塑料零部件最常見(jiàn)和最靈活方式。它需要極少或根本沒(méi)有整理或裝配作業(yè)。除了熱塑性塑料和熱固性， 這個(gè)進(jìn)程現(xiàn)在通過(guò)用聚合物粘結(jié)劑被擴(kuò)展到象纖維，陶器，金屬粉末這樣的材料。 應(yīng)用 按重量計(jì)算大約所有塑料加工的32%是通過(guò)注塑成型機(jī)器的。 歷史上， 注入成型的主要里程碑包括往復(fù)移動(dòng)螺絲機(jī)器和各種新的替代過(guò)程， 和應(yīng)用電腦仿真，以及設(shè)計(jì)和制造的塑料零部件的發(fā)明。 注射機(jī)的發(fā)展 從19世紀(jì)70年代初注入成型機(jī)器問(wèn)世以來(lái)它已經(jīng)經(jīng)歷了顯著的修改和改進(jìn)。 尤其是往復(fù)移動(dòng)螺桿機(jī)器的發(fā)明使熱塑性塑料注塑成型過(guò)程的多功能性和生產(chǎn)力得到了徹底改革。 往復(fù)移動(dòng)螺桿的好處 除在機(jī)器控制方面和機(jī)器起動(dòng)功能上有明顯改進(jìn)外， 注塑成型機(jī)器的一個(gè)主要發(fā)展是從一個(gè)活塞機(jī)器到一個(gè)往復(fù)移動(dòng)螺絲桿的變化。 雖然活塞機(jī)本身簡(jiǎn)單，它的普及受到限制歸咎與它僅僅通過(guò)純傳導(dǎo)的緩慢的加熱速度。 往復(fù)移動(dòng)螺桿用它旋轉(zhuǎn)的運(yùn)動(dòng)能使材料塑化更迅速而均勻，如圖1中所示使可塑材料。另外，它能把這個(gè)熔融的聚合物注入在一個(gè)向前的方向，就像一個(gè)活塞。 注塑成型過(guò)程的發(fā)展 注塑成型過(guò)程開(kāi)始只與熱塑性塑料聚合物一起使用在活性材料方面的發(fā)展， 在塑造設(shè)備方面的改進(jìn)，并且由于特殊工業(yè)的需要已經(jīng)把工藝的用途擴(kuò)展到超出了他原先的范圍 供選擇的注塑工藝 在過(guò)去二十年期間發(fā)展注射模塑已經(jīng)被做出許多嘗試，隨著特殊設(shè)計(jì)發(fā)展道具生產(chǎn)零件的工序可用作替換過(guò)程，從傳統(tǒng)的注射模塑中派生而來(lái)的應(yīng)用策劃新時(shí)代，它有更多自由設(shè)計(jì)和特殊結(jié)構(gòu)上特征 通過(guò)這些努力產(chǎn)生了許多類(lèi)型，包括： 級(jí)進(jìn)注射（夾心）成型 易熔芯注塑成型 氣體輔助注塑成型 壓縮注塑成型 層狀（微）注射 交替供料的注塑成型 低壓注入成型 推拉注塑成型 反應(yīng)注塑成型 結(jié)構(gòu)泡沫注塑成型 薄壁件成型 計(jì)算機(jī)模擬注塑成型過(guò)程 由于他們的擴(kuò)展性和希望性,電腦仿真也已經(jīng)擴(kuò)展超出早期的"外行-扁平物" 現(xiàn)在,復(fù)雜程序在過(guò)程期間模仿填充后行為,反作用動(dòng)力學(xué)和兩材料的不同性質(zhì)或者二維的使用。 仿真部分提供關(guān)于使用C-類(lèi)型產(chǎn)品的信息 在設(shè)計(jì)題目有中間幾例子,其給你怎樣能使用CAE工具改進(jìn)你的部分和塑造設(shè)計(jì)和使處理狀況最優(yōu)化配上插圖。 級(jí)進(jìn)注射（夾心）成型 總體上說(shuō) 級(jí)進(jìn)注塑成型是通過(guò)兩種不同的材料連續(xù)的和或同時(shí)地由同一澆口注射完成的。材料層板和凝固。 這工藝生產(chǎn)零件,其隨著在層皮材料之間把型芯材料嵌入有一層積的結(jié)構(gòu)中. 這項(xiàng)創(chuàng)新過(guò)程為用最優(yōu)性能的每一種材料或修改模的一部分屬性提供了固有的靈活性。 圖1 四個(gè)階段的級(jí)進(jìn)注塑成型(a)短球的皮合物融化(顯示在里深綠色)注入進(jìn)那些模型 (b)核心聚合物的注射熔化，直到型腔被差不多填補(bǔ) 如(c)中所示皮聚合物再次被注入，以便把離開(kāi)的這個(gè)核心聚合物從澆注系統(tǒng)中清除出去 熔心注射成型 熔芯工藝在單個(gè)產(chǎn)品中，空的部分用復(fù)雜內(nèi)部結(jié)構(gòu)的易熔(丟失，可溶)如下圖。這個(gè)工藝在塑造核芯內(nèi)部完成，核芯將自身融化或者化學(xué)消失，留下它的外部結(jié)構(gòu)作為塑料部分的內(nèi)部形狀。 圖1。 易熔(失芯，熔芯)核心注射成型 氣體輔助注塑成型 氣體輔助工藝 氣體輔助注塑成型過(guò)程的是樹(shù)脂聚合物熔體欠料進(jìn)入模腔。壓縮氣體，然后注入的聚合物核心部分幫助填滿(mǎn)模具。這個(gè)過(guò)程如下所示。 圖1 。氣體輔助注射成型(a)電氣系統(tǒng)(b)液壓系統(tǒng)，，(c)控制面板，(d)汽缸。 注射--壓縮成型 注射壓縮成型工藝是傳統(tǒng)注射成型的延續(xù)。在把一種預(yù)調(diào)裝置量的聚合物熔化注入一個(gè)開(kāi)放型腔,如同下面展示那樣,聚合物注射的時(shí)候被壓緊,這過(guò)程的最重要特點(diǎn)是相對(duì)于無(wú)壓力部件要在低夾具方面保證尺寸上穩(wěn)定,(百分之20到50甚至更低). 層狀（微層）注塑成型 層狀注射成型通過(guò)同步注射和層倍增加的綜合了供擠出和注射成型，如同在圖下面1中展示那樣,層狀注射成型同時(shí)實(shí)施不同的樹(shù)脂注射.不同樹(shù)脂疊加在一起提高其性能，例如阻隔氣密性,尺寸穩(wěn)定性，耐熔性和光學(xué)透明性。 交替注射成型 交替注射成型過(guò)程是在入口壓力下引起聚合物熔化擺動(dòng)，如這下面的插圖中所示。當(dāng)不同的層分子或者纖維由于凝固而被在模具里增加時(shí)，活塞的行動(dòng)保持材料在門(mén)里熔融，、。 這個(gè)過(guò)程提供簡(jiǎn)單的方法使簡(jiǎn)單或者復(fù)雜部分從空間中釋放出來(lái)，下沉標(biāo)明，以及結(jié)合處缺陷。 低壓注射成型 低氣壓注塑成型，基本上是一種優(yōu)化并延長(zhǎng)的常規(guī)注塑成型（見(jiàn)圖1 ） 。低壓可以通過(guò)正確的螺桿轉(zhuǎn)/分的編程， 水壓支持壓力和螺桿速度來(lái)控制熔化的溫度和注射速度。它也利用很多閥門(mén)的連續(xù)關(guān)閉來(lái)縮小流程。填料階段以一般慢并且控制注射速度來(lái)消除，低氣壓注塑成型的優(yōu)點(diǎn)包括減少較大的夾緊力，利用成本較低的模具和壓力機(jī)和降低模塑制品成型應(yīng)力。 推拉注射成型 該推拉注射成型過(guò)程中使用了傳統(tǒng)的兩套注射液系統(tǒng)和雙澆口模具，推動(dòng)材料在母主注射裝置和輔助注射裝置中來(lái)回流動(dòng)，如下所示。這個(gè)過(guò)程中消除熔體縫，空隙，裂紋，并控制纖維方向。 反應(yīng)注塑成型 工藝 多數(shù)反應(yīng)注塑成型工藝，包括反應(yīng)注射成型（ RIM ），以及混合成型 加工，如樹(shù)脂傳遞模塑（ RTM）和結(jié)構(gòu)反應(yīng)注射成型（SRIM ）。 與熱塑性塑料塑造相比具有典型的低粘性，模具壓力低，模具成本低的特點(diǎn)?；钚詷?shù)脂也可以在混合過(guò)程中使用。例如，制作高強(qiáng)度和小批量的大型零件，RTM和SRIM可用于長(zhǎng)纖維的預(yù)先成型。另一個(gè)領(lǐng)域是比以往任何時(shí)候接受的都是微電子集成電路芯片。 注塑成型的適應(yīng)性是在這些物質(zhì)中包括在機(jī)械上料（桶）中的一段溫度上升來(lái)避免固化。不過(guò)，腔通常是有足夠的熱來(lái)啟動(dòng)化學(xué)交聯(lián)。作為熱預(yù)聚合物是被迫進(jìn)入腔中，熱度是從腔墻中，流動(dòng)的粘性（摩擦）熱氣，和反應(yīng)元件所釋放的熱氣中補(bǔ)充的。零件的溫度往往超過(guò)模具的溫度。零件的固性(甚至在高溫中)的循環(huán)是當(dāng)反應(yīng)足夠強(qiáng)烈時(shí)完成的然后零件被彈出。 設(shè)計(jì)考慮 因?yàn)榉磻?yīng)是在填塞和充滿(mǎn)后的階段進(jìn)行的，所以活性材料的注塑成型的加工工藝是復(fù)雜的。例如，慢的填充經(jīng)常引起過(guò)早的膠化和一個(gè)合力，然而快速填充能引起內(nèi)部間隙混亂。模具壁溫度的不適當(dāng)控制和厚度不足要么引起的注射劑流動(dòng)性問(wèn)題或造成材料過(guò)熱。計(jì)算機(jī)仿真是普遍公認(rèn)的作為更具成本效益的工具，比傳統(tǒng)的時(shí)間短，試錯(cuò)能力強(qiáng)和高的改錯(cuò)能力。 結(jié)構(gòu)泡沫注塑成型 概況 結(jié)構(gòu)泡沫注塑生產(chǎn)的零件是有固體外表面周?chē)膰@內(nèi)部氣孔(或者泡沫)的核心組成的，在下面的圖1 說(shuō)明。這個(gè)工藝適合大型厚零件在最終用途應(yīng)用中承受彎曲負(fù)荷，結(jié)構(gòu)泡沫零件還可以高低壓生產(chǎn)或者是氮?dú)夂突瘜W(xué)填充劑。 薄壁成型 薄壁件是相對(duì)的，傳統(tǒng)的塑料零件通常是2到4毫米厚。當(dāng)厚度在1.2到2毫米時(shí)和邊緣尺寸低于1.2毫米的時(shí)候，薄壁設(shè)計(jì)被稱(chēng)為"先進(jìn)"。薄壁成型的另一個(gè)定義是根據(jù)流程/壁厚比，這些薄壁的應(yīng)用典型比率在100：1到150：1之間或更高。 典型的應(yīng)用范圍 薄壁件成型更適用于便攜式的通訊和計(jì)算設(shè)備，他們要求塑料殼得非常薄卻依然能夠同傳統(tǒng)零件一樣能夠承受同樣的機(jī)械強(qiáng)度 工藝 因?yàn)楸”诩鋮s速度非常快，他們需要高的溶化溫度，高的注射速度，和非常高的注射壓力，如果多種閥門(mén)或者順序閥門(mén)沒(méi)有一個(gè)理想的填充速度來(lái)幫助減少壓力的要求。 由于高的速度和剪切速率在薄壁件成型上更容易幫助減少薄壁件每個(gè)方向收縮，這對(duì)于充分的填充非常重要，然而核心的部分仍然是熔化。 注塑機(jī) 組成要素 對(duì)于熱塑性塑料，注塑機(jī)通過(guò)熔化，注塑，填充和冷卻把粒狀或丸?；限D(zhuǎn)換成最好的成型零件。一個(gè)典型的注塑機(jī)主要由以下部分組成，在下面圖1中說(shuō)明 機(jī)器功能 注塑機(jī)基于機(jī)器功能大致可分為三類(lèi)：一般用途的機(jī)器 精密機(jī)器超高速，薄壁件的機(jī)器 輔助設(shè)備 注塑機(jī)的主要輔助設(shè)備包括樹(shù)脂干燥機(jī)，材料處理設(shè)備，制粒機(jī)，模溫機(jī)，冷水機(jī)組，搬運(yùn)機(jī)械手以及零件處理設(shè)備。 基于注塑模具鋼研磨和拋光工序的自動(dòng)化表面處理 C. Apreaa, R. Mastrullob, C. Rennoa,* 薩勒諾大學(xué)機(jī)械工程系,通過(guò)Ponte Don Melillo 1、84084 菲夏諾( 薩勒諾)、意大利 那不勒斯大學(xué)DETEC費(fèi)德里科?二世,P。le Tecchio 80、80125 那不勒斯,意大利 完成于2002年8月8日,在修訂后完成于2003年12月18日, 通過(guò)是2004年2月18日 摘要: 本文研究了注塑模具鋼自動(dòng)研磨與球面拋光加工工序的可能性，這種注塑模具鋼P(yáng)DS5的塑性曲面是在數(shù)控加工中心完成的。這項(xiàng)研究已經(jīng)完成了磨削刀架的設(shè)計(jì)與制造。 最佳表面研磨參數(shù)是在鋼鐵PDS5 的加工中心測(cè)定的。對(duì)于PDS5注塑模具鋼的最佳球面研磨參數(shù)是以下一系列的組合：研磨材料的磨料為粉紅氧化鋁，進(jìn)給量500毫米/分鐘，磨削深度20微米，磨削轉(zhuǎn)速為18000RPM。用優(yōu)化的參數(shù)進(jìn)行表面研磨，表面粗糙度Ra值可由大約1.60微米改善至0.35微米。 用球拋光工藝和參數(shù)優(yōu)化拋光，可以進(jìn)一步改善表面粗糙度Ra值從0.343微米至0.06微米左右。在模具內(nèi)部曲面的測(cè)試部分，用最佳參數(shù)的表面研磨、拋光，曲面表面粗糙度就可以提高約2.15微米到0 0.07微米。 關(guān)鍵詞: 自動(dòng)化表面處理；拋光；磨削加工；表面粗糙度；Taguchi方法 一、引言: 塑膠工程材料由于其重要特點(diǎn),如耐化學(xué)腐蝕性、低密度、易于制造,并已日漸取代金屬部件在工業(yè)中廣泛應(yīng)用。 注塑成型對(duì)于塑料制品是一個(gè)重要工藝。注塑模具的表面質(zhì)量是設(shè)計(jì)的本質(zhì)要求,因?yàn)樗苯佑绊懥怂苣z產(chǎn)品的外觀和性能。 加工工藝如球面研磨、拋光常用于改善表面光潔度。 研磨工具(輪子)的安裝已廣泛用于傳統(tǒng)模具的制造產(chǎn)業(yè)。自動(dòng)化表面研磨加工工具的幾何模型將在[1]中介紹。自動(dòng)化表面處理的球磨研磨工具將在[2]中得到示范和開(kāi)發(fā)。 磨削速度, 磨削深度，進(jìn)給速率和砂輪尺寸、研磨材料特性（如磨料粒度大?。┦乔蛐窝心スに囍兄饕膮?shù)，如圖1（球面研磨過(guò)程示意圖）所示。注塑模具鋼的球面研磨最優(yōu)化參數(shù)目前尚未在文獻(xiàn)得到確切的依據(jù)。 近年來(lái) ，已經(jīng)進(jìn)行了一些研究，確定了球面拋光工藝的最優(yōu)參數(shù)(圖2) （球面拋光過(guò)程示意圖）。 比如，人們發(fā)現(xiàn), 用碳化鎢球滾壓的方法可以使工件表面的塑性變形減少,從而改善表面粗糙度、表面硬度、抗疲勞強(qiáng)度[3,4,5,6]。 拋光的工藝的過(guò)程是由加工中心 [3,4]和車(chē)床〔5,6〕共同完成的。對(duì)表面粗糙度有重大影響的拋光工藝主要參數(shù)，主要是球或滾子材料，拋光力， 進(jìn)給速率,拋光速度,潤(rùn)滑、拋光率及其他因素等。注塑模具鋼P(yáng)DS5的表面拋光的參數(shù)優(yōu)化，分別結(jié)合了油脂潤(rùn)滑劑，碳化鎢球,拋光速度200毫米/分鐘,拋光力300牛， 40微米的進(jìn)給量[7]。采用最佳參數(shù)進(jìn)行表面研磨和球面拋光的深度為2.5微米。 通過(guò)拋光工藝，表面粗糙度可以改善大致為40%至90%[3-7]。 此項(xiàng)目研究的目的是，發(fā)展注塑模具鋼的球形研磨和球面拋光工序，這種注塑模具鋼的曲面實(shí)在加工中心完成的。表面光潔度的球研磨與球拋光的自動(dòng)化流程工序，如圖3所示。 我們開(kāi)始自行設(shè)計(jì)和制造的球面研磨工具及加工中心的對(duì)刀裝置。利用Taguchi正交法，確定了表面球研磨最佳參數(shù)。選擇為T(mén)aguchiL18型矩陣實(shí)驗(yàn)相應(yīng)的四個(gè)因素和三個(gè)層次。 用最佳參數(shù)進(jìn)行表面球研磨則適用于一個(gè)曲面表面光潔度要求較高的注塑模具。 為了改善表面粗糙, 利用最佳球面拋光工藝參數(shù)，再進(jìn)行對(duì)表層打磨。 圖1.球狀研磨的過(guò)程的簡(jiǎn)圖 圖2.球面拋光的過(guò)程的簡(jiǎn)圖 PDS試樣的設(shè)計(jì)與制造 選擇最佳矩陣實(shí)驗(yàn)因子 確定最佳參數(shù) 實(shí)施實(shí)驗(yàn) 分析并確定最佳因子 進(jìn)行表面拋光 應(yīng)用最佳參數(shù)加工曲面 測(cè)量試樣的表面粗糙度 球研磨和拋光裝置的設(shè)計(jì)與制造 圖3.自動(dòng)球面研磨與拋光工序的流程圖 二、球研磨的設(shè)計(jì)和對(duì)準(zhǔn)裝置: 實(shí)施過(guò)程中可能出現(xiàn)的曲面的球研磨,研磨球的中心應(yīng)和加工中心的Z軸相一致。 球面研磨工具的安裝及調(diào)整裝置的設(shè)計(jì)，如圖4（球面研磨工具及其調(diào)整裝置）所示。電動(dòng)磨床展開(kāi)了兩個(gè)具有可調(diào)支撐螺絲的刀架。磨床中心正好與具有輔助作用的圓錐槽線(xiàn)配合。 擁有磨床的球接軌,當(dāng)兩個(gè)可調(diào)支撐螺絲被收緊時(shí)，其后的對(duì)準(zhǔn)部件就可以拆除。研磨球中心坐標(biāo)偏差約為5微米, 這是衡量一個(gè)數(shù)控坐標(biāo)測(cè)量機(jī)性能的重要標(biāo)準(zhǔn)。 機(jī)床的機(jī)械振動(dòng)力是被螺旋彈簧所吸收。球形研磨球和拋光工具的安裝，如圖5（a. 球面研磨工具的圖片. b.球拋光工具的圖片）所示。為使球面磨削加工和拋光加工的進(jìn)行，主軸通過(guò)球鎖機(jī)制而被鎖定。 三、矩陣實(shí)驗(yàn)的規(guī)劃 3.1Taguchi正交表: 利用矩陣實(shí)驗(yàn)Taguchi正交法，可以確定參數(shù)的影響程度[8]. 為了配合上述球面研磨參數(shù)，該材料磨料的研磨球(直徑10毫米),進(jìn)給速率，研磨深度,再次研究中電氣磨床被假定為四個(gè)因素(參數(shù))，指定為從A到D（見(jiàn)表1實(shí)驗(yàn)因素和水平）。三個(gè)層次(程度)的因素涵蓋了不同的范圍特征,并用了數(shù)字1、2、3標(biāo)明。挑選三類(lèi)磨料,即碳化硅(SiC),白色氧化鋁(Al2O3,WA),粉紅氧化鋁(Al2O3, PA)來(lái)研究. 這三個(gè)數(shù)值的大小取決于每個(gè)因素實(shí)驗(yàn)結(jié)果。選定L18型正交矩陣進(jìn)行實(shí)驗(yàn)，進(jìn)而研究四——三級(jí)因素的球形研磨過(guò)程。 圖4.球狀研磨的工具的概要例證和它調(diào)節(jié)裝置 圖5.a 球面研磨的工具的照片 b 球拋光工具的的照片 3.2數(shù)據(jù)分析的意義: 工程設(shè)計(jì)問(wèn)題,可以分為較小而好的類(lèi)型,象征性最好類(lèi)型,大而好類(lèi)型，目標(biāo)取向類(lèi)型等[8]。 信噪比(S/N)的比值，常作為目標(biāo)函數(shù)來(lái)優(yōu)化產(chǎn)品或者工藝設(shè)計(jì)。 被加工面的表面粗糙度值經(jīng)過(guò)適當(dāng)?shù)亟M合磨削參數(shù)，應(yīng)小于原來(lái)的未加工表面。 因此,球面研磨過(guò)程屬于工程問(wèn)題中的小而好類(lèi)型。這里的信噪比（S/N）,η,按下列公式定義[8]: η =?10 log （平方等于質(zhì)量參數(shù)) =?10 log 這里， y——不同噪聲條件下所觀察的質(zhì)量參數(shù) n——實(shí)驗(yàn)次數(shù) 從每個(gè)L18型正交實(shí)驗(yàn)得到的信噪比（S/N）數(shù)據(jù)，經(jīng)計(jì)算后，運(yùn)用差異分析技術(shù)(變異)和殲比檢驗(yàn)來(lái)測(cè)定每一個(gè)主要的因素 [8]。 優(yōu)化小而好類(lèi)型的工程問(wèn)題問(wèn)題更是盡量使η最大而定。各級(jí)η選擇的最大化將對(duì)最終的η因素有重大影響。 最優(yōu)條件可視研磨球而待定。 表1。 實(shí)驗(yàn)性因素和等級(jí) 四、實(shí)驗(yàn)工作和結(jié)果: 這項(xiàng)研究使用的材料是PDS5工具鋼(相當(dāng)于艾西塑膠模具)[9]， 它常用于大型注塑模具產(chǎn)品在國(guó)內(nèi)汽車(chē)零件領(lǐng)域和國(guó)內(nèi)設(shè)備。 該材料的硬度約HRC33(HS46)[9]。 具體好處之一是, 由于其特殊的熱處理前處理，模具可直接用于未經(jīng)進(jìn)一步加工工序而對(duì)這一材料進(jìn)行加工。式樣的設(shè)計(jì)和制造,應(yīng)使它們可以安裝在底盤(pán)，來(lái)測(cè)量相應(yīng)的反力。 PDS5試樣的加工完畢后，裝在大底盤(pán)上在三坐標(biāo)加工中心進(jìn)行了銑削，這種加工中心是由楊*鋼鐵公司所生產(chǎn)(中壓型三號(hào)),配備了FANUC-18M公司的數(shù)控控制器(0.99型)[10]。用hommelwerket4000設(shè)備來(lái)測(cè)量前機(jī)加工前表面的粗糙度,使其可達(dá)到1.6微米。 圖6試驗(yàn)顯示了球面磨削加工工藝的設(shè)置。 一個(gè)由Renishaw公司生產(chǎn)的視頻觸摸觸發(fā)探頭，安裝在加工中心上，來(lái)測(cè)量和確定和原始式樣的協(xié)調(diào)。 數(shù)控代碼所需要的磨球路徑由PowerMILL軟件產(chǎn)。這些代碼經(jīng)過(guò)RS232串口界面，可以傳送到裝有控制器的數(shù)控加工中心上。 完成了L18型矩陣實(shí)驗(yàn)后，表2 （PDS5試樣光滑表層的粗糙度）總結(jié)了光滑表面的粗糙度RA值，計(jì)算了每一個(gè)L18型矩陣實(shí)驗(yàn)的信噪比（S/N）,從而用于方程1。通過(guò)表2提供的各個(gè)數(shù)值，可以得到4種不同程度因子的平均信噪比（S/N），在圖7中已用圖表顯示。 表2.PDS5試樣光滑表層的粗糙度 圖6.確定最佳球面磨削參數(shù)的實(shí)驗(yàn)設(shè)置 表3.由因素水平(dB)的平均S/N比率 圖7.控制因素作用的曲線(xiàn)圖 球面研磨工藝的目標(biāo)，就是通過(guò)確定每一種因子的最佳優(yōu)化程度值，來(lái)使試樣光滑表層的表面粗糙度值達(dá)到最小。因?yàn)? log是一個(gè)減函數(shù)，我們應(yīng)當(dāng)使信噪比（S/N）達(dá)到最大。因此，我們能夠確定每一種因子的最優(yōu)程度使得η的值達(dá)到最大。因此基于這個(gè)點(diǎn)陣式實(shí)驗(yàn)的最優(yōu)轉(zhuǎn)速應(yīng)該是18000RPM，如表4（優(yōu)化組合球面研磨參數(shù)）所示。 通過(guò)使用數(shù)據(jù)方差分析的技術(shù)和F比檢驗(yàn)方法，進(jìn)一步確定了每一種因子有什么主要的影響，從而確定了它們的影響程度(見(jiàn)表5信噪比和表面粗糙度)。F0.1，2，13的F比的比值是2.76，相當(dāng)于10%的影響程度。（或者置信水平為90%）這個(gè)因子的自由度是2，自由度誤差是13，根據(jù)F分布表[11]。如果F比值大于2.76，就可以認(rèn)為對(duì)表面粗糙度有顯著影響。結(jié)果，進(jìn)給量和磨削深度都對(duì)表面粗糙度有顯著影響。 為了觀察使用最優(yōu)磨削組合參數(shù)的重復(fù)性能，進(jìn)行了5種不同類(lèi)別的實(shí)驗(yàn)，如表6所示。獲得被測(cè)試樣的表面粗糙度值RA大約是0.35微米。使用球研磨組合參數(shù)，可使表面粗糙度提高了78%。使用球面拋光的優(yōu)化參數(shù)，光滑表面進(jìn)一步被拋光。經(jīng)過(guò)球面拋光可獲得粗糙度RA值為0.06微米的表面。被改善了的拋光表面，可以在30×光學(xué)顯微鏡觀察下進(jìn)行觀察，如圖8.（未加工表面、光滑面和拋光面的測(cè)試樣品的顯微鏡象(30×)的比較）所示。經(jīng)過(guò)拋光工藝，工件機(jī)加工前的表面粗糙度改善了近95%。 從Taguchi矩陣實(shí)驗(yàn)獲得的球面研磨優(yōu)化參數(shù)，適用于曲面光滑的模具，從而改善表面的粗糙度。選擇香水瓶為一個(gè)測(cè)試載體。對(duì)于被測(cè)物體的模具數(shù)控加工中心，由PowerMILL軟件來(lái)模擬測(cè)試。經(jīng)過(guò)精銑，通過(guò)使用從Taguchi矩陣實(shí)驗(yàn)獲得的球面研磨優(yōu)化參數(shù)，模具表面進(jìn)一步光滑。緊接著,使用打磨拋光的最佳參數(shù)，來(lái)對(duì)光滑曲面進(jìn)行拋光工藝，進(jìn)一步改善了被測(cè)物體的表面粗糙度。(見(jiàn)圖 9)。模具內(nèi)部的表面粗糙度用hommelwerket4000設(shè)備來(lái)測(cè)量。模具內(nèi)部的表面粗糙度RA的平均值為2.15微米，光滑表面粗糙度RA的平均值為0.45微米，拋光表面粗糙度RA的平均值為0.07微米。被測(cè)物體的光滑表面的粗糙度改善了：(2.15-0.45)/2.15=79.1%，拋光表面的粗糙度改善了：(2.15-0.07)/2.15=96.7%。 表4. 優(yōu)化組合球面研磨參數(shù) 表5. 信噪比和表面粗糙度 ?F比率值> 2.76對(duì)地面粗糙度有很大影響 圖8.未加工表面、光滑面和拋光面的測(cè)試樣品的顯微鏡象(30×)的比較 圖9.香水瓶樣品 五、結(jié)論: 在這項(xiàng)工作中,對(duì)注塑模具的曲面進(jìn)行了自動(dòng)球面研磨與球面拋光加工，并將其工藝最佳參數(shù)成功地運(yùn)用到加工中心上。 設(shè)計(jì)和制造了球面研磨裝置(及其對(duì)準(zhǔn)組件)。通過(guò)實(shí)施TaguchiL18型矩陣進(jìn)行實(shí)驗(yàn)，確定了球面研磨的最佳參數(shù)。對(duì)于PDS5注塑模具鋼的最佳球面研磨參數(shù)是以下一系列的組合：材料的磨料為粉紅氧化鋁，進(jìn)給量料500毫米/分鐘，磨削深度20微米，轉(zhuǎn)速為18000RPM。通過(guò)使用最佳球面研磨參數(shù)，試樣的表面粗糙度RA值從約1.6微米提高到0.35微米。應(yīng)用最優(yōu)化表面磨削參數(shù)和最佳拋光參數(shù)，來(lái)加工模具的內(nèi)部光滑曲面，可使模具內(nèi)部的光滑表面改善79.1%，拋光表面改善96.7%。 鳴謝： 作者感謝中國(guó)國(guó)家科學(xué)理事會(huì)對(duì)本次研究的支持, NSC 89-2212-E-011-059. 編號(hào)： 畢業(yè)設(shè)計(jì)(論文)外文翻譯 （原文） 院 （系）： 　國(guó)防生學(xué)院 專(zhuān) 業(yè)：機(jī)械設(shè)計(jì)制造及其自動(dòng)化 學(xué)生姓名： 蔡秀濱 學(xué) 號(hào)： 1001020105 指導(dǎo)教師單位： 機(jī)電工程學(xué)院 姓 名： 郭中玲 職 稱(chēng)： 高級(jí)工程師 2014年 3 月 9 日 Contents 1.The Injection Molding 1 2.Automated surface ?nishing of plastic injection mold steel with spherical grinding and ball burnishing processes 14 第 22 頁(yè) 共 23 頁(yè) 桂林電子科技大學(xué)畢業(yè)（論文）報(bào)告專(zhuān)用紙 The Injection Molding Alp Tekin Ergenc , Deniz Ozde Koca Yildiz Tecnical University, Mechanical Engineering Department, IC Engines Laboratory, Turkey The Introduction of Molds The mold is at the core of a plastic manufacturing process because its cavity gives a part its shape. This makes the mold at least as critical-and many cases more so-for the quality of the end product as, for example, the plasticiting unit or other components of the processing equipment. Mold Material Depending on the processing parameters for the various processing methods as well as the length of the production run, the number of finished products to be produced, molds for plastics processing must satisfy a great variety of requirements. It is therefore not surprising that molds can be made from a very broad spectrum of materials, including-from a technical standpoint-such exotic materials as paper matched and plaster. However, because most processes require high pressures, often combined with high temperatures, metals still represent by far the most important material group, with steel being the predominant metal. It is interesting in this regard that, in many cases, the selection of the mold material is not only a question of material properties and an optimum price-to-performance ratio but also that the methods used to produce the mold, and thus the entire design, can be influenced. A typical example can be seen in the choice between cast metal molds, with their very different cooling systems, compared to machined molds. In addition, the production technique can also have an effect; for instance, it is often reported that, for the sake of simplicity, a prototype mold is frequently machined from solid stock with the aid of the latest technology such as computer-aided (CAD) and computer-integrated manufacturing (CIMS). In contrast to the previously used methods based on the use of patterns, the use of CAD and CAM often represents the more economical solution today, not only because this production capability is available pin-house but also because with any other technique an order would have to be placed with an outside supplier. Overall, although high-grade materials are often used, as a rule standard materials are used in mold making. New, state-of-the art (high-performance) materials, such as ceramics, for instance, are almost completely absent. This may be related to the fact that their desirable characteristics, such as constant properties up to very high temperatures, are not required on molds, whereas their negative characteristics, e. g. low tensile strength and poor thermal conductivity, have a clearly related to ceramics, such as sintered material, is found in mild making only to a limited degree. This refers less to the modern materials and components produced by powder metallurgy, and possibly by hot isocratic pressing, than to sintered metals in the sense of porous, air-permeable materials. Removal of air from the cavity of a mold is necessary with many different processing methods, and it has been proposed many times that this can be accomplished using porous metallic materials. The advantages over specially fabricated venting devices, particularly in areas where melt flow fronts meet, I, e, at weld lines, are as obvious as the potential problem areas: on one hand, preventing the texture of such surfaces from becoming visible on the finished product, and on the other hand, preventing the microspores from quickly becoming clogged with residues (broken off flash, deposits from the molding material, so-called plate out, etc.). It is also interesting in this case that completely new possibilities with regard to mold design and processing technique result from the use of such materials. A. Design rules There are many rules for designing molds. These rules and standard practices are based on logic, past experience, convenience, and economy. For designing, mold making, and molding, it is usually of advantage to follow the rules. But occasionally, it may work out better if a rule is ignored and an alternative way is selected. In this text, the most common rules are noted, but the designer will learn only from experience which way to go. The designer must ever be open to new ideas and methods, to new molding and mold materials that may affect these rules. B. The basic mold 1. Mold cavity space The mold cavity space is a shape inside the mold, “excavated” in such a manner that when the molding material is forced into this space it will take on the shape of the cavity space and, therefore, the desired product. The principle of a mold is almost as old as human civilization. Molds have metals into sand forms. Such molds, which are still used today in foundries, can be used only once because the mold is destroyed to release the product after it has solidified. Today, we are looking for permanent molds that can be used over and over. Now molds are made from strong, durable materials, such as steel, or from softer aluminum or metal alloys and even from certain plastics where a long mold life is not required because the planned production is small. In injection molding the plastic is injected into the cavity space with high pressure, so the mold must be strong enough to resist the injection pressure without deforming. 2. Number of cavities Many molds, particularly molds for larger products, are built for only cavity space, but many molds, especially large production molds, are built with 2 or more cavities. The reason for this is purely economical. It takes only little more time to inject several cavities than to inject one. For example, a 4-cavity mold requires only one-fourth of the machine time of a single-cavity mold. Conversely, the production increases in proportion to the number of cavities. A mold with more cavities is more expensive to build than a single-cavity mold, but not necessarily 4 times as much as a single-cavity mold. But it may also require a larger machine with larger platen area and more clamping capacity, and because it will use 4 times the amount of plastic, it may need a large injection unit, so the machine hour cost will be higher than for a machine large enough for the smaller mold. 3. Cavity shape and shrinkage The shape of the cavity is essentially the “negative” of the shape of the desired product, with dimensional allowance added to allow for shrinking of the plastic. The shape of the cavity is usually created with chip-removing machine tools, or with electric discharge machining, with chemical etching, or by any new method that may be available to remove metal or build it up, such as galvanic processes. It may also be created by casting certain metals in plaster molds created from models of the product to be made, or by casting some suitable hard plastics. The cavity shape can be either cut directly into the mold plates or formed by putting inserts into the plates. C. Cavity and core By convention, the hollow portion of the cavity space is called the cavity. The matching, often raised portion of the cavity space is called the core. Most plastic products are cup-shaped. This does not mean that they look like a cup, but they do have an inside and an outside. The outside of the product is formed by the cavity, the inside by the core. The alternative to the cup shape is the flat shape. In this case, there is no specific convex portion, and sometimes, the core looks like a mirror image of the cavity. Typical examples for this are plastic knives, game chips, or round disks such as records. While these items are simple in appearance, they often present serious molding problems for ejection of the product. The reason for this is that all injection molding machines provide an ejection mechanism on the moving platen and the products tend to shrink onto and cling to the core, from where they are then ejected. Most injection molding machines do not provide ejection mechanisms on the injection side. Polymer Processing Polymer processing, in its most general context, involves the transformation of a solid (sometimes liquid) polymeric resin, which is in a random form (e.g., powder, pellets, beads), to a solid plastics product of specified shape, dimensions, and properties. This is achieved by means of a transformation process: extrusion, molding, calendaring, coating, thermoforming, etc. The process, in order to achieve the above objective, usually involves the following operations: solid transport, compression, heating, melting, mixing, shaping, cooling, solidification, and finishing. Obviously, these operations do not necessarily occur in sequence, and many of them take place simultaneously. Shaping is required in order to impart to the material the desired geometry and dimensions. It involves combinations of viscoelastic deformations and heat transfer, which are generally associated with solidification of the product from the melt. Shaping includes: two-dimensional operations, e.g. die forming, calendaring and coating; three-dimensional molding and forming operations. Two-dimensional processes are either of the continuous, steady state type (e.g. film and sheet extrusion, wire coating, paper and sheet coating, calendaring, fiber spinning, pipe and profile extrusion, etc.) or intermittent as in the case of extrusions associated with intermittent extrusion blow molding. Generally, molding operations are intermittent, and, thus, they tend to involve unsteady state conditions. Thermoforming, vacuum forming, and similar processes may be considered as secondary shaping operations, since they usually involve the reshaping of an already shaped form. In some cases, like blow molding, the process involves primary shaping (pair-son formation) and secondary shaping (pair son inflation). Shaping operations involve simultaneous or staggered fluid flow and heat transfer. In two-dimensional processes, solidification usually follows the shaping process, whereas solidification and shaping tend to take place simultaneously inside the mold in three dimensional processes. Flow regimes, depending on the nature of the material, the equipment, and the processing conditions, usually involve combinations of shear, extensional, and squeezing flows in conjunction with enclosed (contained) or free surface flows. The thermo-mechanical history experienced by the polymer during flow and solidification results in the development of microstructure (morphology, crystallinity, and orientation distributions) in the manufactured article. The ultimate properties of the article are closely related to the microstructure. Therefore, the control of the process and product quality must be based on an understanding of the interactions between resin properties, equipment design, operating conditions, thermo-mechanical history, microstructure, and ultimate product properties. Mathematical modeling and computer simulation have been employed to obtain an understanding of these interactions. Such an approach has gained more importance in view of the expanding utilization of computer design/computer assisted manufacturing/computer aided engineering (CAD/CAM/CAE) systems in conjunction with plastics processing. It will emphasize recent developments relating to the analysis and simulation of some important commercial process, with due consideration to elucidation of both thermo-mechanical history and microstructure development. As mentioned above, shaping operations involve combinations of fluid flow and heat transfer, with phase change, of a visco-elastic polymer melt. Both steady and unsteady state processes are encountered. A scientific analysis of operations of this type requires solving the relevant equations of continuity, motion, and energy (I. e. conservation equations). Injection Molding Many different processes are used to transform plastic granules, powders, and liquids into final product. The plastic material is in moldable form, and is adaptable to various forming methods. In most cases thermoplastic materials are suitable for certain processes while thermosetting materials require other methods of forming. This is recognized by the fact that thermoplastics are usually heated to a soft state and then reshaped before cooling. Theromosets, on the other hand have not yet been polymerized before processing, and the chemical reaction takes place during the process, usually through heat, a catalyst, or pressure. It is important to remember this concept while studying the plastics manufacturing processes and the polymers used. Injection molding is by far the most widely used process of forming thermoplastic materials. It is also one of the oldest. Currently injection molding accounts for 30% of all plastics resin consumption. Since raw material can be converted by a single procedure, injection molding is suitable for mass production of plastics articles and automated one-step production of complex geometries. In most cases, finishing is not necessary. Typical products include toys, automotive parts, household articles, and consumer electronics goods, Since injection molding has a number of interdependent variables, it is a process of considerable complexity. The success of the injection molding operation is dependent not only in the proper setup of the machine variables, but also on eliminating shot-to-shot variations that are caused by the machine hydraulics, barrel temperature variations, and changes in material viscosity. Increasing shot-to-shot repeatability of machine variables helps produce parts with tighter tolerance, lowers the level of rejects, and increases product quality ( i.e., appearance and serviceability). The principal objective of any molding operation is the manufacture of products: to a specific quality level, in the shortest time, and using a repeatable and fully automatic cycle. Molders strive to reduce or eliminate rejected parts, or parts with a high added value such as appliance cases, the payoff of reduced rejects is high. A typical injection molding cycle or sequence consists of five phases: 1 Injection or mold filling 2 Packing or compression 3 Holding 4 Cooling 5 Part ejection Injection Molding Overview Process Injection molding is a cyclic process of forming plastic into a desired shape by forcing the material under pressure into a cavity. The shaping is achieved by cooling (thermoplastics) or by a chemical reaction (thermosets). It is one of the most common and versatile operations for mass production of complex plastics parts with excellent dimensional tolerance. It requires minimal or no finishing or assembly operations. In addition to thermoplastics and thermosets, the process is being extended to such materials as fibers, ceramics, and powdered metals, with polymers as binders. Applications Approximately 32 percent by weight of all plastics processed go through injection molding machines. Historically, the major milestones of injection molding include the invention of the reciprocating screw machine and various new alternative processes, and the application of computersimulation to the design and manufacture of plastics parts. Development of the injection molding machine Since its introduction in the early 1870s, the injection molding machine has undergone significant modifications and improvements. In particular, the invention of the reciprocating screw machine hasrevolutionized the versatility and productivity of the thermoplastic injection molding process. Benefits of the reciprocating screw Apart from obvious improvements in machine control and machine functions, the major development for the injection molding machine is the change from a plunger mechanism to a reciprocating screw. Although the plunger-type machine is inherently simple, its popularity was limited due to the slow heating rate through pure conduction only. The reciprocating screw can plasticize the material more quickly and uniformly with its rotating motion, as shown in Figure 1. Inaddition, it is able to inject the molten polymer in a forward direction, as a plunger. Development of the injection molding process The injection molding process was first used only with thermoplastic polymers. Advances in the understanding of materials, improvements in molding equipment, and the needs of specific industrysegments have expanded the use of the process to areas beyond its original scope. Alternative injection molding processes During the past two decades, numerous attempts have been made to develop injection molding processes to produce parts with special design features and properties. Alternative processes derivedfrom conventional injection molding have created a new era for additional applications, more designfreedom, and special structural features. These efforts have resulted in a number of processes,including: Co-injection (sandwich) molding Fusible core injection molding) Gas-assisted injection molding Injection-compression molding Lamellar (microlayer) injection moldin Live-feed injection molding Low-pressure injection molding Push-pull injection molding Reactive molding Structural foam injection molding Thin-wall molding Computer simulation of injection molding processes Because of these extensions and their promising future, computer simulation of the process has alsoexpanded beyond the early "lay-flat," empirical cavity-filling estimates. Now, complex programs simulate post-filling behavior, reaction kinetics, and the use of two materials with different properties, or two distinct phases, during the process. The Simulation section provides information on using C-MOLD products.Among the Design topicsare several examples that illustrate how you can use CAE tools to improve your part and molddesign and optimize processing conditions. Co-injection (sandwich) molding Overview Co-injection molding involves sequential or concurrent injection of two different but compatible polymer melts into a cavity. The materials laminate and solidify. This process produces parts that have a laminated structure, with the core material embedded between the layers of the skin material. This innovative process offers the inherent flexibility of using the optimal properties of each material or modifying the properties of the molded part. FIGURE 1. Four stages of co-injection molding. (a) Short shot of skin polymer melt (shown in dark green)is injected into the mold. (b) Injection of core polymer melt until cavity is nearly filled, as shown in (c). (d)Skin polymer is injected again, to purge the core polymer away from the sprue. Fusible core injection molding Overview The fusible (lost, soluble) core injection molding process illustrated below produces single-piece, hollow parts with complex internal geometry. This process molds a core inside the plastic part. After the molding, the core will be physically melted or chemically dissolved, leaving its outer geometry as the internal shape of the plastic part. FIGURE 1. Fusible (lost, soluble) core injection molding Gas-assisted injection molding Gas-assisted process The gas-assisted injection molding process begins with a partial or full injection of polymer melt into the mold cavity. Compre