蓋板零件塑料注塑模具設(shè)計【復(fù)蓋件】【一模兩腔】【說明書+CAD】
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華東交通大學(xué)理工學(xué)院畢業(yè)設(shè)計(論文) 華東交通大學(xué)理工學(xué)院畢業(yè)設(shè)計說明書設(shè)計題目: 蓋板塑料模具設(shè)計 設(shè)計編號: 學(xué) 院:華東交大理工學(xué)院系 別: 機電分院 專 業(yè): 材料成型及控制工程班 級: 06材料(2)班學(xué) 號:20060410210211 姓 名: 黃俊杰 指導(dǎo)教師: 莊文瑋 完成日期: 年 月 日 答辯日期: 年 月 日摘 要本復(fù)蓋件模具設(shè)計模具較大,模架為標準的4070工字模架。大模具成型時成形壓力也較大,所以為了保證模具在成型產(chǎn)品時的鎖模效果,本模具采用了模具原身止口鎖模。本模具主要有澆注系,導(dǎo)向系統(tǒng),頂出系統(tǒng),冷卻系統(tǒng),頂板復(fù)位系統(tǒng)。關(guān)鍵詞:大型模具;復(fù)蓋件;流道設(shè)計;對稱件;模具材料;模具設(shè)計AbstractThis cover design moulds, formwork for standard 4070 workers make word-model frame. Big mould molding forming is larger also, so in order to guarantee the products in molding mould clamping effect, the mould adopted mould clamping and check the mouth. The main casting mould department, guiding system, the system, cooling system, roof reduction system.Key words: large-scale die, Cover; Flow design, Symmetrical parts, Mould material, Mould design目 錄中文摘要1英文摘要2目 錄 31.引言2 塑件的工藝性分析2.1塑件的原材料分析2.2成型特性及條件2.3塑件的結(jié)構(gòu)和尺寸精度及表面質(zhì)量分析2.4塑件體積和重量的計算2.5初選注射機的型號和規(guī)格2.6塑件注射工藝參數(shù)的確定3.注射模的結(jié)構(gòu)設(shè)計3.1分型面確定3.2確定澆注系統(tǒng)3.2.1主流道設(shè)計3.2.2冷料穴設(shè)計3.2.3分流道設(shè)計.3.2.4澆口設(shè)計4確定型腔、型芯的結(jié)構(gòu)及固定方式4.1型腔、型芯的結(jié)構(gòu)設(shè)計4.2型腔和型芯的工作尺寸計算4.3型腔壁厚底版厚度計算4.3.1型腔壁厚4.3.2推出方式的設(shè)計4.3.3確定模具的導(dǎo)向機構(gòu)5.冷卻系統(tǒng)的設(shè)計5.1螺旋隔水片式5.2吸管式5.3隔水片式5.4導(dǎo)熱針式5.5直通式6.校核計算6.1注射壓力的校核6.2鎖模力校核6.3模具厚度H與注射機閉合高度的校核6.4頂出行程的校核7.結(jié) 語8.參考文獻- 5 -華東交通大學(xué)理工學(xué)院畢業(yè)設(shè)計(論文)1.引 言在經(jīng)歷了“十五”期間和“十一五”頭兩年高速發(fā)展(這七年間年均增長速度達18%)之后,由于受到國際金融危機影響,2008年下半年開始,中國模具工業(yè)發(fā)展速度己明顯放緩,致使2008年全年模具總銷售額與上年同比增長率跌進了個位數(shù),只達到9.2左右,總量約為950億元左右。2009年,發(fā)展進一步受阻,預(yù)計全年的模具總銷售額只能接近1000億元,而很難突破,基本與去年持平或略有增長。國家GDP增長是保八爭九,看來保八是有把握的,那么模具為什么達不到這個水平?這主要是國內(nèi)外模具市場總體不夠景氣所致。國家4萬億元投資主要投向于基礎(chǔ)設(shè)施建設(shè)和民生工程及改善民生等方面,GDP增加了,模具需求卻基本沒有增加或增加效應(yīng)滯后,汽車、家電、農(nóng)機等工業(yè)品下鄉(xiāng)以及以舊換新等政策措施的出臺,使GDP也增加了,模具需求雖也有增加,但增幅有限。例如汽車,年初猜測今年將突破1000萬輛,現(xiàn)在猜測是突破1200萬輛,比去年增長20%以上,但汽車模具卻沒有增加那么多,這是因為與模具需求最關(guān)聯(lián)的新車型投放與汽車銷售量之間并不成正比關(guān)系所致。但不管怎么說,在經(jīng)歷了一年多的金融危機之后,我們的模具工業(yè)經(jīng)受住了嚴重考驗,2009年全年不出現(xiàn)負增長的預(yù)計將可實現(xiàn),而且我們還在結(jié)構(gòu)調(diào)整等方面取得了不少成績,全行業(yè)積聚了力量,為今后發(fā)展打下了良好的基礎(chǔ)。那么在世界金融危機一年多的時間里,或者從更長一段時間來說,除了模具銷售額等數(shù)量方面以外,我們行業(yè)還有些什么發(fā)展特點和進步呢?我認為主要有以下幾點:一、結(jié)構(gòu)調(diào)整取得一定成效這主要有三方面表現(xiàn):一是體制改革與機制轉(zhuǎn)換的成效,目前國有企業(yè)少,無論從數(shù)量還是產(chǎn)銷來說,都只占全行業(yè)的不足3,股份制、私營和三資企業(yè)已占絕對優(yōu)勢,整個行業(yè)的活力進一步增強;二是以大型、精密、復(fù)雜、長壽命模具為主要代表的高技術(shù)含量的中高檔模具比例一直在穩(wěn)步提高;三是市場結(jié)構(gòu)不斷改善,新興行業(yè)受到普遍重視,例如新能源領(lǐng)域、醫(yī)療設(shè)備(器具、器械)領(lǐng)域、自動化領(lǐng)域、航空航天領(lǐng)域及快速經(jīng)濟模具領(lǐng)域等。國際市場也史為廣闊,除了歐美和東南亞傳統(tǒng)市場之外,印度、俄羅斯、巴西、澳大利亞、中東和南非等新興市場都己開始拓展。二、海外模具向我國內(nèi)地轉(zhuǎn)移的趨向不斷發(fā)展海外模具向我國內(nèi)地轉(zhuǎn)移的趨向不斷發(fā)展帶動了行業(yè)水平的不斷提高及出口的快速增長。由于我國模具生產(chǎn)的成本優(yōu)勢繼續(xù)存在,因此一方面是外資,同時還有模具采購,國際模具都在進一步向我國內(nèi)地轉(zhuǎn)移發(fā)展。由于要與國際接軌,這就加速了我們的進步。三、集群式生產(chǎn)方式得到進一步發(fā)展據(jù)我所知,目前全國已有不同種類和各種不同形式的模具城(園、區(qū)、集聚生產(chǎn)基地)30多個,其中半數(shù)以上己形成一定規(guī)模,2008年模具城的產(chǎn)出己達270億元左右,其中模具約為170億元左右,規(guī)模效應(yīng)己得到體現(xiàn)。而且,集群式生產(chǎn)方式的發(fā)展,為發(fā)展我國模具行業(yè)中的現(xiàn)代制造服務(wù)業(yè)和以模具為核心的產(chǎn)業(yè)鏈的發(fā)展作出了重大貢獻,其意義是很大的。目前集群式生產(chǎn)方式仍在不斷發(fā)展之中,總體態(tài)勢良好。四、模具生產(chǎn)周期進一步縮短,模具價格繼續(xù)下降這對模具生產(chǎn)企業(yè)來說,確實是造成了很人壓力,但對模具用戶來說,這就是成績。同時,這也是模具行業(yè)技術(shù)進步的表現(xiàn)。但是這里也有一個市場不規(guī)范,過度的價格競爭和中低檔產(chǎn)品產(chǎn)能過剩的問題,應(yīng)該引起我們的足夠重視。我國模具行業(yè)的水平我國“十一五”模具行業(yè)發(fā)展規(guī)劃中提出的目標是至2010年進入亞洲先進水平的行列。我認為這個目標是可以達到的。從數(shù)量上來說,我們目前已經(jīng)是世界模具生產(chǎn)大國。從產(chǎn)品水平上來說,為B級及以下檔次轎車及其他乘用車和商用車等配套的全套汽車模具,為電子行業(yè)配套的精度達2m,壽命達2億次以上的精密高速多工位級進模,單套模具重量超過100噸的巨型模具,長達6米的大型多工位級進模具,導(dǎo)光板模具、光盤模具、生物芯片模具等許多高水平模具己都能生產(chǎn)。然而中國地域廣闊,各地眾多模具企業(yè)水平不齊,相互之間差距很大,從綜合水平來說,與國際先進水平相比,還確實存在不少差距j差距促使我們進一步努力,差距促使我們奮進!向世界模具強國不斷邁進,將仍然是我們在較長時間內(nèi)的奮斗目標。模具發(fā)展趨勢我認為這主要取決于兩個方面,即一方面是模具為之服務(wù)的各行各業(yè)的發(fā)展趨勢,另一方面是整個社會和世界科學(xué)技術(shù)的發(fā)展趨勢,這實際上就是需要和可能。模具是為制件,也就是成形產(chǎn)品服務(wù)的,因此模具必然要以制件(成形產(chǎn)品)的發(fā)展趨勢為自己的發(fā)展趨勢,模具必須滿足他們的要求。制件發(fā)展趨勢主要是輕便、精美、快速高效生產(chǎn)、低成本與高質(zhì)量,每一項都預(yù)示了模具發(fā)展趨勢?,F(xiàn)簡要分析如下: 要輕便就會增加使用塑料及開發(fā)新材料,包括各種新型塑料、改性塑料、金屬塑料、鎂合金、復(fù)合材料等等,這就要求有新的成形工藝,從而也就要求有與之相適應(yīng)的新型模具。例如,汽車上越來越多地采用高強度板也是為了減輕重量,對一些超高強度板進行熱成形及與之相適應(yīng)的熱成形模具也就自然而然成為發(fā)展趨勢等等。要精美,就要求外形美觀大方,內(nèi)部無缺陷,這就要求有精細、精密和高質(zhì)量模具與之相適應(yīng)。目前我們在精細化方面差距很大,精細化往往被忽視,功虧一簣??焖俑咝a(chǎn),這一方面是要求模具企業(yè)要盡量縮短模具生產(chǎn)周期,盡快向模具用戶交付模具,另一方面更重要的是要使用戶能用你提供的模具來快速高效地生產(chǎn)制品。例如一模多腔多件生產(chǎn)、疊層模具、利用好熱流道技術(shù)來縮短成形時間以及使用多層復(fù)合技術(shù)、模內(nèi)裝飾技術(shù)、高光無痕注塑技術(shù)、在線檢測技術(shù)、多工序復(fù)合技術(shù)、多排多工位技術(shù)等等。同時制件成形過程智能化還要求有智能化的模具來適應(yīng)。低成本,這既要通過模具生產(chǎn)的設(shè)計、加工、裝配來實現(xiàn)模具的低成本制造和低成本供給,更重要的是要使模具用戶能使用模具來實現(xiàn)低成本生產(chǎn)。這就對模具提出了更高的要求。模具生產(chǎn)企業(yè)必須做到先使模具用戶賺錢,然后才能使自己賺錢。在要求低成本的過程中,無論是模具生產(chǎn)企業(yè)還是使用模具的企業(yè),不斷改善治理,逐步實現(xiàn)信息化治理都是企業(yè)的共同要求及進步和發(fā)展的方向。高質(zhì)量,要做到制品的高質(zhì)量,首先必須是模具的高質(zhì)量,模具的穩(wěn)定性一定要好,保證制品的一致性也要好,而且還要保證壽命。高質(zhì)量模具與技術(shù)休戚相關(guān)。除上述各點外,許多新領(lǐng)域、新興產(chǎn)業(yè)、新制件和個性化要求也都會對模具不斷提出新要求。所以發(fā)展趨勢的本身也是在不斷發(fā)展的。從科技發(fā)展趨勢來看模具發(fā)展趨勢可以先從下列最基本的六個方面進行分析:新材料模具新材料及為成形產(chǎn)品新材料成形的新型模具新工藝新的成形工藝及模具加工的新工藝新技術(shù)技術(shù)進步帶動模具生產(chǎn)逐步向超高速、超精和高度自動化方向發(fā)展信息化數(shù)字化生產(chǎn)、信息化治理、充分利用IT技術(shù)網(wǎng)絡(luò)化溶入和利用好世界全球化網(wǎng)絡(luò)循環(huán)經(jīng)濟與綠色制造一用盡量少的資源來創(chuàng)造盡量多的價值,包括再利用與環(huán)保等,不但模具要能這樣,而且更要使模具用戶也能這樣。除上述所說的發(fā)展趨勢之我見以外,同時我還認為,從與模具用戶的關(guān)系來說,模具和模具生產(chǎn)企業(yè)向來是比較依靠和比較被動的,發(fā)言權(quán)很少。我認為,這一現(xiàn)象應(yīng)逐漸適當(dāng)改變。這就要求我們模具行業(yè)要自強,要通過充分展示自己的實力和能力,以及創(chuàng)新發(fā)展來逐步變被動為主動。國慶前,我在海爾模具公司參觀,感慨很深。海爾模具公司的口號是“你給我一個概念,我給你一個產(chǎn)品”和“決不對市場說不”。他們在市場方面“無內(nèi)不穩(wěn),無外不強”,在觀念方面“把模具當(dāng)藝術(shù)品來做”(現(xiàn)在,模具是依靠技藝制造出來的藝術(shù)品的概念己被模具是依靠技術(shù)生產(chǎn)出來的高新技術(shù)產(chǎn)品所替代,但把模具當(dāng)藝術(shù)品來做的觀念并不過時,而且卻是認真和敬業(yè)的表現(xiàn),應(yīng)該提倡。),提出的目標是要成為“全球最先進的模具試制中心”,這些都可供我們借鑒。海爾模具公司也做到了模具設(shè)計的模塊化、參數(shù)化、標準化,以及生產(chǎn)方面的專業(yè)化和標準化。在轉(zhuǎn)型方面他們提出要從企業(yè)信息化向信息化企業(yè)轉(zhuǎn)型,要從生產(chǎn)型制造業(yè)向服務(wù)型(為用戶提供全套解決方案)制造業(yè)轉(zhuǎn)變。我認為這些思想也已經(jīng)在。一定程度上反映了模具企業(yè)的發(fā)展趨勢。上面所述的發(fā)展趨勢還只是一個概念性和東西,我們可以不斷的具體化和不斷的深化,例如CAD/CAE/CAM一體化,軟件的集成化、智能化、網(wǎng)絡(luò)化,計算機模擬仿真技術(shù)的進一步發(fā)展和三維設(shè)計的全面推廣應(yīng)用,高速與超高速加工、精密與超精細微加工和復(fù)合加工及五軸加工等等,不再一一列舉??傊?,模具技術(shù)的發(fā)展趨勢是動態(tài)的,它必須不斷地來滿足模具用戶不斷發(fā)展的新趨勢,同時,它也與世界科技發(fā)展密切關(guān)聯(lián)。它們相互之間可以互相促進和相得益彰。當(dāng)然,對于整個模具來說模具技術(shù)發(fā)展趨勢只是其中的一個部分,諸如生產(chǎn)組織形式、市場經(jīng)營模式以及治理等等,都有其一定的發(fā)展趨勢,也是很值得研討的。2塑件的工藝性分析2.1塑件的原材料分析本復(fù)蓋件產(chǎn)品材料為PE聚乙烯英文名為:Polythylene或polythene,簡稱PE(以下或稱PE)。PE為乳白色半透明至不透明的熱塑性樹脂。以密度的大小分為:低密度聚乙烯(LDPE),密度為0.9100.925g/cm2,因其為高壓法(ICI)聚合所得的聚乙烯,也稱為高壓聚乙烯;高密度聚乙烯(HDPE),密度為0.9410.965g/cm2;因其為低壓聚合(齊格勒法)所得的聚乙烯,也稱為低壓聚乙烯,也可以采用中壓法(菲利普法)制得,密度在0.965g/cm2以上;中密度聚乙烯(MDPE),密度為0.9160.940g/cm2;此外還有線型低密度聚乙烯(LLDPE)、超高分子量聚乙烯(HMW-HDPE),甚低密度聚乙烯(VLDPE)等。 HDPE是一種由乙烯共聚生成的熱塑性聚烯烴。雖然HDPE在1956年就已推出,但這種塑料還沒達到成熟水平。這種通用材料還在不斷開發(fā)其新的用途和市場。高密度聚乙烯通常使用Ziegler-Natta聚合法制造,其特點是分子鏈上沒有支鏈,因此分子鏈排布規(guī)整,具有較高的密度。該過程在管式或釜式低壓反應(yīng)器中以乙烯為原料,用氧或有機過氧化物為引發(fā)劑引發(fā)聚合反應(yīng)。高密度乙烯屬環(huán)保材質(zhì),加熱達到熔點,即可回收再利用。須知塑膠原料可大分為兩大類:“熱塑性塑膠”(Thermoplastic)及“熱固性塑膠”(Thermosetting),“熱固性塑膠”是加熱到一定溫度后變成固化狀態(tài),即使繼續(xù)加熱也無法改變其狀態(tài),因此,有環(huán)保問題的產(chǎn)品是“熱固性塑膠”的產(chǎn)品(如輪胎),并非是“熱塑性塑膠”的產(chǎn)品(如 塑膠棧板 注:棧板在港澳被稱為“夾板”),所以并非所有“塑膠”皆不環(huán)保。 【主要特性】HDPE是一種結(jié)晶度高、非極性的熱塑性樹脂。原態(tài)HDPE的外表呈乳 白色,在微薄截面呈一定程度的半透明狀。PE具有優(yōu)良的耐大多數(shù)生活和工業(yè)用化學(xué)品的特性。某些種類的化學(xué)品會產(chǎn)生化學(xué)腐蝕,例如腐蝕性氧化劑(濃硝酸),芳香烴(二甲苯)和鹵化烴 (四氯化碳)。該聚合物不吸濕并具有好的防水蒸汽性,可用于包裝用途。HDPE具有很好的電性能,特別是絕緣介電強度高,使其很適用于電線電纜。中到高分子量等級具有極好的抗沖擊性,在常溫甚至在-40F低溫度下均如此。各種等級HDPE的獨有特性是四種基本變量的適當(dāng)結(jié)合:密度、分子量、分子量分布和添加劑。不同的催化劑被用于生產(chǎn)定制特殊性能聚合物。這些變量相結(jié)合生產(chǎn)出不同用途的HDPE品級;在性能上達到最佳的平衡。 【密度】這是決定HDPE特性的主要變量,雖然被提到的4種變量確實起到相互影響作用。乙烯是聚乙烯主要原料,少數(shù)的其它共聚單體,如1一丁烯、l一己烯或1一辛烯,也經(jīng)常用于改進聚合物性能,對HDPE,以上少數(shù)單體的含量一般不超過12。共聚單體的加入輕微地減小了聚合物的結(jié)晶度。這種改變一般由密度來衡量,密度與結(jié)晶率呈線性關(guān)系。美國一般分類按ASTM D1248規(guī)定, HDPE的密度在 0940g。C以上;中密度聚乙烯(MDPE)密度范圍09260940gCC。其它分類法有時把MDPE歸類于HDPE或LLDPE。均聚物具有最高密度、最大的剛度,良好的防滲透性和最高的熔點,但一般具有很差抗環(huán)境應(yīng)力開裂(ESCR)。ESCR是PE抗由機械或化學(xué)應(yīng)力所引起的開裂性的能力。更高的密度一般改進了機械強度性,例如拉伸強度、剛度和硬度;熱性能如軟化點溫度和熱變形溫度;防滲透性,如透氣性或水蒸氣透過性。較低的密度改進其沖擊強度和ESCR。聚合物密度主要是受共聚單體加入的影響,但較少程度也受分子量影響。高分子量百分數(shù)使密度略有降低。例如,在一個較寬分子量范圍內(nèi)均聚物具有不同的密度。 【生產(chǎn)和催化劑】PE最通常的生產(chǎn)方法是通過淤漿或氣相加工法,也有少數(shù)用溶液相加工生產(chǎn)。所有這些加工過程都是由乙烯單體、a-烯烴單體、催化劑體系(可能是不止一種化合物)和各種類型的烴類稀釋劑參與的放熱反應(yīng)。氫氣和一些催化劑用來控制分子量。淤漿反應(yīng)器一般為攪拌釜或是一種更常用的大型環(huán)形反應(yīng)器,在其中料漿可以循環(huán)攪拌。當(dāng)乙烯和共聚單體(根據(jù)需要)和催化劑一接觸,就會形成聚 乙烯顆粒。除去稀釋劑后,聚乙烯顆?;蚍哿1桓稍锊磩┝考尤胩砑觿蜕a(chǎn)出粒料。帶有雙螺桿擠出機的大型反應(yīng)器的現(xiàn)代化生產(chǎn)線,可每小時生產(chǎn)PE40000磅以上。新的催化劑的開發(fā)為改進新等級HDPE的性能作出貢獻。兩種最常用的催化劑種類是菲利浦的鉻氧化物為基礎(chǔ)的催化劑和鈦化合物一烷基鋁催化劑。菲利浦型催化劑生產(chǎn)的HDPE有 中寬度分子量分布;鈦一烷基鋁催化劑 生產(chǎn)的分子量分布窄。用復(fù)式反應(yīng)器生產(chǎn)窄MDW的聚合物所用催化劑也可用 于生產(chǎn)寬MDW品級。舉例來說,生產(chǎn)顯著不同分子量產(chǎn) 品的兩個串聯(lián)反應(yīng)器可以生產(chǎn)出雙峰分子量聚合物,這種聚合物具有全寬域的分子量分布。 【分子量】較高的分子量導(dǎo)致較高的聚合物粘度,不過粘度也與測試所用的溫度和剪切速率有關(guān)。用流變或分子量測量對材料的分子量進行表征。HDPE的品級一般具有的分子量范圍是40 000300 000,重均分子量大致與熔融指數(shù)范圍相對應(yīng),即從100 0 02910min。通常地,更高的MW(更低的熔融指數(shù)MI)增強了熔體強度、更好韌性和ESCR,但是更高MW使加工過程更難或且需要更高的壓力或溫度。分子量分布(MWD):PE的WD根據(jù)使用的催化劑和加工過程而有從窄到寬的不同。最常用的MWD測量指數(shù)是不勻度指數(shù)(HI),它等于重均分子量(MW)除以數(shù)均分子量(Mn)。所有HDPE品級的這個指數(shù)范圍是430。窄MWD提供了在模塑過程中的低翹曲性和高沖擊性。中到寬MWD提供了對多數(shù)擠塑過程的可加工性。寬MWD也可改進熔體強度和抗蠕變性。 【添加劑】抗氧劑的加入可防止聚合物在加工過程中降解,并防止制成品在使用中氧化??轨o電添加劑用于許多包裝品級以減少瓶子或包裝物對灰塵和污物的粘附。特定的用途需要特殊的添加劑配方,例如與電線、電纜用途相關(guān)的銅抑制劑。優(yōu)良的耐氣候性和抗紫外線(或日光)可通過添加抗UV添加劑。沒有添加抗紫外線或炭黑的PE,建議不要持續(xù)在戶外使用。高等級的炭黑顏料提供了優(yōu)良的抗UV性并可經(jīng)常在戶外應(yīng)用,如電線、電纜、槽池村層或管子。 【加工方法】PE可用很寬的不同加工法制造。以乙烯為主要原料,丙烯、1-丁烯、己烯為共聚體,在催化劑的作用下,采用淤漿聚合或氣相聚合工藝,所得到的聚合物經(jīng)閃蒸、分離、干燥、造粒等工序,獲得顆粒均勻的成品。包括諸如片材擠塑、薄膜擠出、管材或型材擠塑,吹塑、注塑和滾塑。擠塑:用于擠塑生產(chǎn)的品級一般具有小于1的熔體指數(shù)和中寬到寬的MWD。在加工過程中,低的MI可獲得適宜的熔體強度。更寬MWD品級更適于擠塑,因為它們具有更高的生產(chǎn)速度,較低的??趬毫Χ胰垠w斷裂趨勢減少。PE有許多擠塑用途,如電線、電纜、軟管、管材和型材。管材應(yīng)用范圍從用于天然氣小截面黃管到48in直徑用于工業(yè)和城市管道的厚壁黑管。大直徑中空壁管用作混凝土制成的雨水排水管和其它下水道管線的替代物增長迅速。板材和熱成型:許多大型野餐型冷藏箱的熱成型襯里是由PE制成的,具有韌性、重量輕和耐用性。其它片材和熱成型產(chǎn)品包括擋泥板、槽罐襯里、盤盆防護罩、運輸箱和罐。一種大量的增長迅速的片材應(yīng)用是地膜或池底村里,這是基于MDPE具有韌性、耐化學(xué)性和不滲透性。吹塑:在美國銷售的 HDPE13以上用于吹塑用途。這些范圍從裝漂白劑、機油、洗滌劑、牛奶和蒸餾水的瓶子到大型冰箱、汽車燃料箱和筒罐。吹塑品級的特性指標,如熔體強度、ESCR和韌性,與用于片材和熱成型應(yīng)用級相似,故相似品級可以采用。注射-吹塑通常用于制造更小的容器(小于16oz),用于包裝藥品、洗發(fā)液和化妝品。這種加工過程的一個優(yōu)點是生產(chǎn)瓶子自動去邊角,不需象一般吹塑加工那樣的后期修整步驟。盡管有某些窄MWD品級用于改進表面光潔度,一般使用中寬到寬MWD品級。注塑:HDPE有數(shù)不清的應(yīng)用,范圍從可重復(fù)使用的薄壁飲料杯到5gsl罐,消費國內(nèi)生產(chǎn)的HDPE的15。注塑品級一般熔體指數(shù)510,有具有韌性較低流動性品級和具有可加工性的較高流動性品級。用途包括日用品和食品薄壁包裝物;有韌性、耐用的食品和涂料罐;高抗環(huán)境應(yīng)力開裂應(yīng)用,如小型發(fā)動機燃料箱和90gal垃圾罐。滾塑:采用這種加工法的材料一般被粉碎成粉末料,使其在熱循環(huán)中熔融并流動。滾塑使用兩類PE:通用和可交聯(lián)類。通用級MDPEHDPE通常的密度范圍從 0935到 0945gCC,具有窄MWD,使產(chǎn)品具有高沖擊性和最小的翹曲,其熔體指數(shù)范圍一般為38。更高MI品級通常不適用,因為它們不具備滾塑制品希望的沖擊性和抗環(huán)境應(yīng)力開裂性。高性能滾塑應(yīng)用系利用其化學(xué)可交聯(lián)品級的獨特性能。這些品級在模塑周期的第一段,流動性好,而后交聯(lián)以形成其卓越的抗環(huán)境應(yīng)力開裂性、韌性。耐磨性和耐氣候性??山宦?lián)PE唯一適用于大型容器,范圍從500gal運輸各種化學(xué)品儲罐到20,000gal農(nóng)用儲箱。薄膜:PE薄膜加工一般用普通吹膜加工或平擠加工法。大多數(shù)PE用于薄膜,通用低密度PE(LDPE)或線性低密PE(LLDPE)都可用。HDPE薄膜級一般用于要求優(yōu)越的拉伸性和極好的防滲性的地方。例如,HDPE膜常用于商品袋、雜貨袋和食物包裝。 【主要特性】高密度聚乙烯為無毒、無味、無臭的白色顆粒,熔點約為130,相對密度為0.9410.960。它具有良好的耐熱性和耐寒性,化學(xué)穩(wěn)定性好,還具有較高的剛性和韌性,機械強度好。介電性能,耐環(huán)境應(yīng)力開裂性亦較好。熔化溫度220260。對于分子較大的材料,建議熔化溫度范圍在200250之間。 【包裝與儲運】貯存時應(yīng)遠離火源,隔熱,倉庫內(nèi)應(yīng)保持干燥、整潔,嚴禁混入任何雜質(zhì),嚴禁日曬、雨淋。運輸應(yīng)貯放在清潔、干燥有頂棚的車廂或船艙內(nèi),不得有鐵釘?shù)燃怃J物。嚴禁與易燃的芳香烴、鹵代烴等有機溶劑混運。例如,農(nóng)夫山泉的四升裝的礦泉水的大桶,就是此材料。 【回收利用】HDPE是塑料回收市場增長最快的一部分。這主要因為其易再加工,有最小限度的降解特性和其在包裝用途的大量應(yīng)用。主要的回收利用是將 25的回收材料,例如后消費回收物(PCR),與純HDPE經(jīng)再加工后用于制造不與食物接觸的瓶子。 管道系統(tǒng)發(fā)展簡史 本世紀在管道領(lǐng)域發(fā)生了一場革命性的進步,即“以塑代鋼”。隨著高分子材料科學(xué)技術(shù)的飛躍進步,塑料管材開發(fā)利用的深化,生產(chǎn)工藝的不斷改進,塑料管道淋漓盡致地展示其卓越性能。在今天,塑料管材已不再被人們誤認為是金屬管材的“廉價代用品”。在這場革命中,聚乙烯管道倍受青睞,日益發(fā)出奪目的光輝,廣泛用于燃氣輸送、給水、排污、農(nóng)業(yè)灌溉、礦山細顆粒固體輸送,以及油田、化工和郵電通訊等領(lǐng)域,特別在燃氣輸送上得到了普遍的應(yīng)用。2.2 PE成型特性及條件干燥:如果存儲恰當(dāng)則無須干燥。 熔化溫度:220260C。對于分子較大的材料,建議熔化溫度范圍在200250C之間。模具溫度:5095C。6mm以下壁厚的塑件應(yīng)使用較高的模具溫度,6mm以上壁厚的塑件使用較低的模具溫度。塑件冷卻溫度應(yīng)當(dāng)均勻以減小收縮率的差異。對于最優(yōu)的加工周期時間,冷卻腔道直徑應(yīng)不小于8mm,并且距模具表面的距離應(yīng)在1.3d之內(nèi)(這里“d”是冷卻腔道的直徑)。 注射壓力:7001050bar。 注射速度:建議使用高速注射。 流道和澆口:流道直徑在4到7.5mm之間,流道長度應(yīng)盡可能短??梢允褂酶鞣N類型的澆口,澆口長度不要超過0.75mm。特別適用于使用熱流道模具。典型用途 電冰箱容器、存儲容器、家用廚具、密封蓋 2.3塑件的結(jié)構(gòu)和尺寸精度及表面質(zhì)量分析 產(chǎn)品如下圖: 產(chǎn)品結(jié)構(gòu)較為簡單,尺寸均為一般性重要性尺寸。孔位尺寸為安裝尺寸外要求保證。 無須抽芯等模具結(jié)構(gòu),產(chǎn)品主要要求為外觀美觀漂亮,無變形等成型缺陷。該零件不屬于受力部件,無特殊受力要求。2.4計算塑件的體積和重量:首先用UG三維軟件把產(chǎn)品的三維模建立起來,模型如下圖用分析.質(zhì)量特性,查詢產(chǎn)品的體積為V= 1142842.6130650mm3=114.28cm3查設(shè)計手冊后得知PE的密度為0。94g/cm3,編輯產(chǎn)品密度,根據(jù)公式M= V=0。94x114.280=107.4232=107.4(g) 2.5初選注射成型機的型號和規(guī)格初選取注塑機:初選取注塑機時應(yīng)保證注塑機的注射量大于模具成型時產(chǎn)品的質(zhì)量,因為成型時會流道等廢料,原則為成型機的注注射量大于產(chǎn)品質(zhì)量的20%左右。因為產(chǎn)品為一模二腔,產(chǎn)品的質(zhì)量為107.4gx2=214.8g,所以我們初步選用HTF160x1/G,它的具體參數(shù)如下圖,2.6注射工藝參數(shù)的確定 料筒溫度 喂料區(qū) 4060(50) 區(qū)1 160180(180) 區(qū)2 180230(210) 區(qū)3 210260(240) 區(qū)4 210260(240) 區(qū)5 210260(240) 噴嘴 210260(240) 3.注射模的結(jié)構(gòu)設(shè)計3.1確定分型面確定分面選擇原則如下:1. 分型面的選擇應(yīng)便于脫模,此為必要條件。2. 分型面的選擇應(yīng)有利于保證塑件的精度要求3. 有利于塑料充模成型,有利于排氣。4. 分型面的選擇應(yīng)有利于側(cè)向抽芯。5. 不影響制品外觀,尤其對外觀有明確要求的制品,更應(yīng)該注意分型面。6. 分型面的選擇應(yīng)便于模具加工制造。7. 分型一般選取產(chǎn)品的最大輪廓處。8. 有利于保證開模后產(chǎn)品留在動模側(cè)。 3.2確定澆注系統(tǒng)3.2.1 主流道設(shè)計噴嘴前端孔徑:d2=3.5mm;噴嘴前端球面半徑:SR1=16mm;主流道錐度為2度,為便于將凝料從主流道中拔出,將主流道設(shè)計成圓錐形,其斜度為2 4,取2,澆口套熱處理要求淬火50-60HRC。為減少熔體充模時的壓力損失和塑料損耗,應(yīng)盡量縮短主流道的長度, 為了減少澆口套的長度,澆口套設(shè)在第二塊板下,如下圖 3.2.2分流道設(shè)計分流道的截面形式有如下幾種形式,本模具采用第一種,圓形截面的分流道,由于PE收縮大,冷卻快,所以分流道應(yīng)該取較大值,本模具分流道直徑為12mm.3.2.3冷料穴設(shè)計在拉料桿于及,分流道尾部設(shè)置冷料井。冷料井一般為流道直徑的1.5到2倍。冷料井設(shè)計置成如下圖; 3.2.4 澆口設(shè)計采用進料,側(cè)澆口進料。由于產(chǎn)品較長,所以每個產(chǎn)品做二處過澆口,如下圖:澆口詳圖如下: 4確定型腔、型芯的結(jié)構(gòu)及固定方式4.1型腔、型芯的結(jié)構(gòu)設(shè)計型腔,型芯采用整體結(jié)構(gòu),成型產(chǎn)品上的通孔采用小鑲針式小型芯。如下圖4.2型腔和型芯的工作尺寸計算成型零件工作尺寸理論計算公式如下型腔徑向尺寸計算公式為L+z =(1+)L +z型腔深度尺寸計算公式為H+z =(1+)H +z型芯徑向尺寸計算公式為型芯深度尺寸計算公式為 其中為L+z模具型腔的徑向尺寸;H+z為模具型腔的深度尺寸;為模具型芯的徑向尺寸;為模具型芯的高度尺寸;本模個設(shè)計中,產(chǎn)品成形部分的工作尺寸按產(chǎn)品的收縮值計算,這種方法實用,且效率高,由于z、c與的關(guān)系隨塑件的精度等級和尺寸大小的不同而變化,因此式中前的系數(shù)x在塑件尺寸較大、精度級別較低時,z和c可忽略不計。其中收縮率為1.53%.把數(shù)據(jù)帶入上面的公式:型腔徑向尺寸:Lm(1+s)Ls-x= (1+0.0225)500-x*0=515.01型腔深度尺寸:Hm=(1+s)Hs-x=(1+0.0225)112-x*0=115.33型芯徑向尺寸:Am=(1+Scp)As-x=(1+0.025)495+0.5*0=509.86型芯高度尺寸:Bm=(1+Scp)Bs-x=(1+0.025)109.5+0.5*0=112.764.3型腔壁厚和底板厚度計算 4.3.1動模墊板厚度理論計算公式如下h=K(FL/2B彎)1/2F=Ap h動模墊板厚(mm); K修正系數(shù),取0.60.75; F動模墊板受的總壓力(N); L支承塊間距(mm); B動模墊板寬度(mm); 彎彎曲許用應(yīng)力(MPa); A塑件及澆注系統(tǒng)在分型面上的投影面積(mm2); p型腔壓力,一般取2545MPa。本模具為中大型模具,成型壓力大,所模板要厚些,模板厚度尺寸如下圖4.3.2推出方式的設(shè)計 頂出機構(gòu)就是克服產(chǎn)品包著模具的包緊力而頂出產(chǎn)品的機構(gòu)。頂出機構(gòu)一般用注塑機上的頂棍驅(qū)動。脫模力的理論計算公式如下:脫模力計算 1.1設(shè)計步驟: 計算正壓力 參數(shù):E=2900N/cm2; S=0.006mm/mm; t=0.713cm; =2.5; R=1.5cm; m(帕松比)=0.3813.3273 MPap正壓力(MPa);E塑料的彈性模量(N/cm2);S成形收縮率(mm/mm);t塑件平均壁厚(cm);脫模斜度();R凸模半徑(指圓形截面,矩形截面時可求其相等遠,即以其周長除以)(cm);m塑料的帕松比,約為0.380.39。1.2設(shè)計步驟: 初始脫模力 參數(shù):E=2900N/cm2; S=0.006mm/mm; t=0.713cm; L=2.2cm; f=0.3; m=0.38 Q=63.8285 NQ脫模力(N);E塑料彈性模量(N/cm2);S塑料平均成形收縮率(mm/mm);t塑件壁厚(cm);L包容凸模的長度(cm);f塑料與鋼的摩擦系數(shù);m塑料的柏松比。1.3設(shè)計步驟: 頂桿直徑 參數(shù):=3 l=14cm; n=2; E=2900N/cm2; Q=63.8285N1.2154 cm1.2 cmd圓形頂桿直徑(cm);頂桿長度系數(shù)0.7;l頂桿長度(cm);Q總脫模力(N);n頂桿數(shù)量;E頂桿材料的彈性模量(N/cm2), 鋼 E=21000000=2.11071.4 設(shè)計步驟:頂桿的應(yīng)力校核參數(shù):Q=63.8285N; n=4; d=1.2154cm; s=2900mm/mm2Q :總脫模力(N) n :頂桿數(shù)量 d :圓形頂桿直徑(cm):頂桿應(yīng)力(N/cm2) s: 頂桿鋼材的屈服極限強度(N/cm2) 一般中碳鋼 s=32000N/cm2 合金結(jié)構(gòu)鋼 s=42000N/cm2計算結(jié)果:=13.7543 N/cm21.5 設(shè)計步驟: 推件板的厚度 參數(shù):y=0.01cm; B=25cm; L=4.6cm; Q=63.8285N; E=2900N/cm2L頂桿間距(cm);Q總脫模力(N);E鋼材的彈性模量(N/cm2) 一般中碳鋼 E=2.1107;B頂板寬度(cm);y頂板允許最大變形量(cm) 頂桿應(yīng)均勻布置于推件板下,保證塑件被推出時受力均勻,推出平穩(wěn)、不變形。 推出機構(gòu)主要有,推板推出機構(gòu),頂桿頂出機構(gòu),氣頂,等。本模具設(shè)計中采用頂桿頂出機構(gòu)。模具采用頂桿方式推出產(chǎn)品,頂桿應(yīng)該對稱布置,且應(yīng)該布置在產(chǎn)品邊沿處,因為產(chǎn)品邊沿處的包緊力大。 4.3.3確定導(dǎo)向機構(gòu) 導(dǎo)向機構(gòu)主要就是導(dǎo)柱和導(dǎo)套配合,通常配合公差帶取H7/h6,導(dǎo)套和模板配合公差帶取為H7/n6。導(dǎo)柱導(dǎo)套如下圖: 導(dǎo)套 5.冷卻統(tǒng)的設(shè)計冷卻水中路的常見方式:5.1螺旋隔水片式5.2噴管式5.3隔水片式5.4導(dǎo)熱針5.5直通式由于根據(jù)模具的特點,模具采用直通式冷水路,如下圖6. 注射機校核 本次模具設(shè)計中初選注塑機型號為HTF160X1/G,它的技術(shù)參數(shù)如下6.1注射壓力的校核 注射機的額定壓力Pe=159MPa,塑料成型時所需的壓力Po=137MPa, Po Pe,所以滿足要求。6.2鎖模力的校核注射時塑料熔體進入型腔內(nèi)仍然存在較大的壓力,它會使模具從分型面漲開。漲膜力等于塑件和澆注系統(tǒng)在分型面上不重合的投影面積之和乘以型腔的壓力。他應(yīng)小于注射機的額定鎖模力Fn,這樣才能使注射時不發(fā)生溢料和漲?,F(xiàn)象,即滿足下式:(nA1+Aj)p Fn,代入數(shù)據(jù)(238750+329.812+21259.48)15994.62KN1600KN符合要求。6.3模具厚度H與注射機閉合高度的校核HminHHmax Hmin注射機允許最小模厚(170mm)Hmax注射機允許最大模厚(490mm)而模具閉合的高度H為306mm. 因為170390490 所以滿足要求模具總高度如下圖6.4頂出行程的校核注射機最大頂出距離為140mm,頂出行程60到45。因此滿足要求。結(jié)論:注射機完全能夠滿足該模具的使用要求。結(jié) 論這次歷時三個月的畢業(yè)設(shè)計中,在指導(dǎo)老師的帶領(lǐng)下,歷經(jīng)了從設(shè)計思路的提出,到繪制模具草圖,到設(shè)計方案,最后設(shè)計出注塑模。在這個過程中我學(xué)到了許多關(guān)于模具設(shè)計的新知識,熟悉了模具設(shè)計的基本方法、基本步驟,從中培養(yǎng)和提高了我的設(shè)計能力和創(chuàng)新能力,也初步鍛煉了自己把所學(xué)理論知識用到實際工程中的能力。在這個過程中,繪圖也是我們設(shè)計中的一個重要環(huán)節(jié)。先是繪制草圖,再到計算機制圖,這加深和鞏固了我以前所學(xué)的制圖知識,例如:對視圖的表達,尺寸的標住等的掌握。而且這期間我學(xué)會了PRO/E軟件的應(yīng)用,更加熟練地使用CAD軟件制圖。總之,這次的設(shè)計培養(yǎng)了我最基本的工作實踐能力,進一步鞏固和加深了所學(xué)的基礎(chǔ)理論知識、基本技能和專業(yè)知識的理解,并使之理論化、系統(tǒng)化;培養(yǎng)了自己獨立工作、獨立思考并用所學(xué)的知識解決實際工程問題的能力,獲取了許多關(guān)于模具的新知識。在設(shè)計期間,指導(dǎo)老師的敬業(yè)精神、很強的責(zé)任心、嚴謹?shù)闹螌W(xué)態(tài)度等,這些對我以后的學(xué)習(xí)和工作都有很大的幫助。參考文獻1屈華昌.塑料成型工藝與模具設(shè)計.機械工業(yè)出版社,1998-12-252鄒維強.塑料膜典型結(jié)構(gòu)圖冊.模具制造雜志社3彭建生.模具設(shè)計與加工速查手冊.機械工業(yè)出版社4李建軍.模具設(shè)計基礎(chǔ)及模具CAD.機械工業(yè)出版社5屈華昌.塑料成型工藝與模具設(shè)計(修訂版).高等教育出版社- 33 - 編號: 畢業(yè)設(shè)計(論文)外文翻譯(原文)院 (系): 國防生學(xué)院 專 業(yè):機械設(shè)計制造及其自動化 學(xué)生姓名: 蔡秀濱 學(xué) 號: 1001020105 指導(dǎo)教師單位: 機電工程學(xué)院 姓 名: 郭中玲 職 稱: 高級工程師 2014年 3 月 9 日Contents1.The Injection Molding12.Automated surface nishing of plastic injection mold steel with spherical grinding and ball burnishing processes14第 22 頁 共 23 頁 桂林電子科技大學(xué)畢業(yè)(論文)報告專用紙 The Injection Molding Alp Tekin Ergenc , Deniz Ozde KocaYildiz Tecnical University, Mechanical Engineering Department, IC Engines Laboratory, TurkeyThe Introduction of MoldsThe 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 MaterialDepending 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 mold1. 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 filling2 Packing or compression3 Holding4 Cooling5 Part ejectionInjection Molding OverviewProcessInjection molding is a cyclic process of forming plastic into a desired shape by forcingthe 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 commonand versatile operations for mass production of complex plastics parts with excellentdimensional tolerance. It requires minimal or no finishing or assembly operations. Inaddition to thermoplastics and thermosets, the process is being extended to suchmaterials as fibers, ceramics, and powdered metals, with polymers as binders.ApplicationsApproximately 32 percent by weight of all plastics processed go through injection moldingmachines. Historically, the major milestones of injection molding include the invention of thereciprocating 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 machineSince its introduction in the early 1870s, the injection molding machine has undergone significantmodifications 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 screwApart from obvious improvements in machine control and machine functions, the majordevelopment for the injection molding machine is the change from a plunger mechanism to areciprocating screw. Although the plunger-type machine is inherently simple, its popularity waslimited due to the slow heating rate through pure conduction only. The reciprocating screw canplasticize 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 processThe injection molding process was first used only with thermoplastic polymers. Advances in theunderstanding 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 processesDuring the past two decades, numerous attempts have been made to develop injection moldingprocesses 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 moldingComputer simulation of injection molding processesBecause 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) moldingOverviewCo-injection molding involves sequential or concurrent injection of two different butcompatible polymer melts into a cavity. The materials laminate and solidify. This processproduces parts that have a laminated structure, with the core material embedded betweenthe layers of the skin material. This innovative process offers the inherent flexibility ofusing the optimal properties of each material or modifying the properties of the moldedpart.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 moldingOverviewThe fusible (lost, soluble) core injection molding process illustrated below producessingle-piece, hollow parts with complex internal geometry. This process molds a coreinside the plastic part. After the molding, the core will be physically melted or chemicallydissolved, leaving its outer geometry as the internal shape of the plastic part.FIGURE 1. Fusible (lost, soluble) core injection moldingGas-assisted injection moldingGas-assisted processThe gas-assisted injection molding process begins with a partial or full injection ofpolymer melt into the mold cavity. Compre
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