塑料油壺蓋注塑模具設(shè)計(jì)【一模兩腔】【說(shuō)明書+CAD】

塑料油壺蓋注塑模具設(shè)計(jì)【一模兩腔】【說(shuō)明書+CAD】,一模兩腔,說(shuō)明書+CAD,塑料油壺蓋注塑模具設(shè)計(jì)【一模兩腔】【說(shuō)明書+CAD】,塑料,油壺,注塑,模具設(shè)計(jì),說(shuō)明書,仿單,cad 畢業(yè)設(shè)計(jì)說(shuō)明書 塑料油壺蓋模具設(shè)計(jì) 華東交通大學(xué)理工學(xué)院 畢業(yè)設(shè)計(jì)說(shuō)明書 設(shè)計(jì)題目： LDPE塑料油壺蓋注射模 設(shè)計(jì)編號(hào)： 學(xué) 院：華東交通大學(xué)理工學(xué)院 系 別：機(jī)電分院 專 業(yè)：材料成型及控制工程 班 級(jí)：（二）班 學(xué) 號(hào)： 姓 名： 指導(dǎo)教師： 完成日期：2010年5月 日 答辯日期：2010年6月 日 摘 要 隨著現(xiàn)代社會(huì)的發(fā)展，模具行業(yè)也發(fā)展越來(lái)越快，模具加工精度，模具的應(yīng)該范圍都越來(lái)越廣，因此模具在社會(huì)發(fā)展中的作用和地位也越來(lái)越大，越來(lái)越高。本次畢業(yè)設(shè)計(jì)以塑料油壺蓋為例，講述了模具的設(shè)計(jì)過(guò)程與設(shè)計(jì)方法。 油壺蓋的模具設(shè)計(jì)主要分為六個(gè)步驟。1分析制品及材料工藝性，2初選注射機(jī)的型號(hào)和規(guī)格，3.塑件注射工藝參數(shù)的確定，4.注射模的結(jié)構(gòu)設(shè)計(jì)，5.模具裝配和試模，6.校核計(jì)算。 關(guān)鍵詞：塑料油壺蓋模具；細(xì)水口；；二次開模；拉料桿，螺紋強(qiáng)脫，試模 目 錄 中文摘要…………………………………………………………………………… 英文摘要………………………………………………………………………………… 目 錄 ……………………………………………………………………………… 引 言……………………………………………………………………………… 1.分析制品及材料工藝性……………………………………………………… 1.1LDPE材料分析………………………………………………………………… 1.2塑件的結(jié)構(gòu)和尺寸精度及表面質(zhì)量分析………………………………………… 1.3塑件體積和重量的計(jì)算…………………………………………………………… 2.初選注射機(jī)的型號(hào)和規(guī)格…………………………………………………………… 3.塑件注射工藝參數(shù)的確定…………………………………………………………… 4.注射模的結(jié)構(gòu)設(shè)計(jì)…………………………………………………………………… 4.1分型面確定………………………………………………………………………… 4.2確定澆注系統(tǒng)……………………………………………………………………… 4.2.1主流道設(shè)計(jì)……………………………………………………………………… 4.2.2點(diǎn)澆口設(shè)計(jì)料穴設(shè)計(jì)………………………………………………………… 4.3確定型腔、型芯的結(jié)構(gòu)及固定方式……………………………………………… 4.3.1型腔、型芯的結(jié)構(gòu)設(shè)計(jì)………………………………………………………… 4.3.2固定方式……………………………………………………………………… 4.4型腔和型芯的工作尺寸計(jì)算…………………………………………………… 4.5型腔壁厚和底版厚度計(jì)算……………………………………………………… 4.5.1型腔壁厚……………………………………………………………………… 4.5.2型腔底版厚…………………………………………………………………… 4.6螺紋脫出方式的設(shè)計(jì)……………………………………………………………… 4.7確定模具的導(dǎo)向機(jī)構(gòu)…………………………………………………………… 5.模具裝配和試?！? 6.校核計(jì)算…………………………………………………………………………… 小 結(jié)…………………………………………………………………………………… 謝 辭…………………………………………………………………………… 參考文獻(xiàn)…………………………………………………………… - 4 - 畢業(yè)設(shè)計(jì)說(shuō)明書 塑料油壺蓋模具設(shè)計(jì) 引 言 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(shì)為自己的發(fā)展趨勢(shì)，模具必須滿足他們的要求。制件發(fā)展趨勢(shì)主要是輕巧、精美、快速高效生產(chǎn)、低成本與高質(zhì)量，每一項(xiàng)都預(yù)示了模具發(fā)展趨勢(shì)?，F(xiàn)簡(jiǎn)要分析如下： 要輕巧就會(huì)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(lái)越多地采用高強(qiáng)度板也是為了減輕重量，對(duì)一些超高強(qiáng)度板進(jìn)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(shì)等等。 要精美，就要求外形美觀大方，內(nèi)部無(wú)缺陷，這就要求有精細(xì)、精密和高質(zhì)量模具與之相適應(yīng)。目前我們?cè)诰?xì)化方面差距很大，精細(xì)化往往被忽視，功虧一簣。 快速高效生產(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(lái)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(lái)縮短成形時(shí)間以及使用多層復(fù)合技術(shù)、模內(nèi)裝飾技術(shù)、高光無(wú)痕注塑技術(shù)、在線檢測(cè)技術(shù)、多工序復(fù)合技術(shù)、多排多工位技術(shù)等等。同時(shí)制件成形過(guò)程智能化還要求有智能化的模具來(lái)適應(yīng)。 低成本，這既要通過(guò)模具生產(chǎn)的設(shè)計(jì)、加工、裝配來(lái)實(shí)現(xiàn)模具的低成本制造和低成本供應(yīng)，更重要的是要使模具用戶能使用模具來(lái)實(shí)現(xiàn)低成本生產(chǎn)。這就對(duì)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(guò)程中，無(wú)論是模具生產(chǎn)企業(yè)還是使用模具的企業(yè)，不斷改善管理，逐步實(shí)現(xiàn)信息化管理都是企業(yè)的共同要求及進(jìn)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(diǎn)外，許多新領(lǐng)域、新興產(chǎn)業(yè)、新制件和個(gè)性化要求也都會(huì)對(duì)模具不斷提出新要求。所以發(fā)展趨勢(shì)的本身也是在不斷發(fā)展的。 從科技發(fā)展趨勢(shì)來(lái)看模具發(fā)展趨勢(shì)可以先從下列最基本的六個(gè)方面進(jìn)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(jìn)步帶動(dòng)模具生產(chǎn)逐步向超高速、超精和高度自動(dòng)化方向發(fā)展 ????信息化——數(shù)字化生產(chǎn)、信息化管理、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(jì)與綠色制造一用盡量少的資源來(lái)創(chuàng)造盡量多的價(jià)值，包括回收再利用與環(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(shuō)的發(fā)展趨勢(shì)之我見以外，同時(shí)我們還認(rèn)為，從與模具用戶的關(guān)系來(lái)說(shuō)，模具和模具生產(chǎn)企業(yè)向來(lái)是比較依賴和比較被動(dòng)的，發(fā)言權(quán)很少。我認(rèn)為，這一現(xiàn)象應(yīng)逐漸適當(dāng)改變 上面所述的發(fā)展趨勢(shì)還只是一個(gè)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(jì)算機(jī)模擬仿真技術(shù)的進(jìn)一步發(fā)展和三維設(shè)計(jì)的全面推廣應(yīng)用，高速與超高速加工、精密與超精細(xì)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(shì)是動(dòng)態(tài)的，它必須不斷地來(lái)滿足模具用戶不斷發(fā)展的新趨勢(shì)，同時(shí)，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(jìn)和相得益彰。當(dāng)然，對(duì)于整個(gè)模具來(lái)說(shuō)模具技術(shù)發(fā)展趨勢(shì)只是其中的一個(gè)部分，諸如生產(chǎn)組織形式、市場(chǎng)經(jīng)營(yíng)模式以及管理等等，都有其一定的發(fā)展趨勢(shì)，也是很值得研討的. 1.分析制品及材料工藝性 1.1LDPE材料工藝分析 低密度聚乙烯（LDPE）是高壓下乙烯自由基聚合而獲得的熱塑性塑料。LDPE是樹脂中的聚乙烯家族中最老的成員，二十世紀(jì)四十年代早期就作為電線包皮第一次商業(yè)生產(chǎn)。LDPE綜合了一些良好的性能：透明、化學(xué)惰性、密封能力好，易于成型加工。這決定了LDPE是當(dāng)今高分子工業(yè)中最廣泛使用的材料之一。 　　化學(xué)和性能 　　乙烯是聚乙烯制品的基本結(jié)構(gòu)單元。它是從煉油廠氣、液化的石油氣或液態(tài)烴中獲得的無(wú)色氣體。因?yàn)樗窃S多其它工業(yè)化學(xué)品和聚合物的成分，所以不斷地存在乙烯供應(yīng)的競(jìng)爭(zhēng)。這種獲得乙烯的競(jìng)爭(zhēng)具有戲劇性地影響著聚乙烯的價(jià)格和有效價(jià)值。例如：1990年，國(guó)內(nèi)乙烯生產(chǎn)能力約為465億磅，其中 51％用于象聚乙烯這樣的聚合物的生產(chǎn)。 　　常規(guī)的LDPE可用兩種方法生產(chǎn)：管式法或釜式法。兩種制法都是將高純度乙烯通入高壓（103到276MPa）高溫（300到500F）含有引發(fā)劑的反應(yīng)器中。引發(fā)劑或是氧氣或是一種有機(jī)過(guò)氧化物。反應(yīng)終止的實(shí)現(xiàn)是通過(guò)加入鏈終止劑或靠?jī)蓚€(gè)分子鏈的連結(jié)。 　　與其它聚乙烯（HDPE和LLDPE）制法獲得的線性結(jié)構(gòu)不同，通過(guò)高壓手段制得的聚合物是分支結(jié)構(gòu)。這種分支結(jié)構(gòu)賦與常規(guī)LDPE優(yōu)異的透明性、曲撓性及易于擠出的性能。為滿足不同應(yīng)用而特制的LDPE樹脂是通過(guò)分子量、結(jié)晶度及分子量分布MWD的平衡與控制而得到的。 　　分子量是表示構(gòu)成聚合物的所有分子鏈的平均長(zhǎng)度。為了方便，熔融指數(shù)（MI）被選作塑料工業(yè)分子量大小的量度。熔融指數(shù)用克/10分鐘給出，它與分子量的大小成反比。對(duì)于LDPE，熔融指數(shù)反映了樹脂的流動(dòng)性能和涉及成品大形變的性質(zhì)。降低MI（增大分子量）在增加大部分強(qiáng)度性能的同時(shí)，降低了LDPE的流動(dòng)性和制造過(guò)程中樹脂流向薄壁的能力。LDPE中的結(jié)晶度是樹脂中存在的分支短鏈數(shù)量的函數(shù)。對(duì)于LDPE，結(jié)晶度正常浮動(dòng)范圍為 30—40％。 　　增加 LDPE的結(jié)晶度將增大 LLDPE的剛度、抗化學(xué)腐蝕性、透氣性能、拉伸強(qiáng)度、耐熱性；同時(shí)，降低了LDPE的沖擊強(qiáng)度、撕裂強(qiáng)度和抗應(yīng)力開裂性。分子量分布（MWD）或聚合度分布性定義為重均分子量與數(shù)均分子量的比值。塑料工業(yè)中，MWD值3—5的樹脂被認(rèn)為是具有窄的分子量分布，MWD值6—12為中等分子量分布，MWD值在13以上視為寬分子量分布。MWD主要反映與流動(dòng)相關(guān)的性能。具有相等平均分于量的樹脂，寬分子量分布的在加工過(guò)程顯示了比窄分子量分布的樹脂具有更好的流動(dòng)性。WD對(duì)最終使用性能有些影響。但是，MWD的影響一般都被分子量的變化影響掩蓋。 　　加工 　　LDPE級(jí)別可以滿足大部分熱塑性成型加工技術(shù)的要求。包括：薄膜吹制、薄膜鑄制、擠壓貼膠、電線電纜貼膠、注射成型、吹塑成型。 　　應(yīng)用 　　LDPE可單獨(dú)使用或與聚乙烯家族其它成員共混使用。廣泛應(yīng)用于包裝。建筑、農(nóng)業(yè)、工業(yè)和消費(fèi)市場(chǎng)。擠出薄膜。LDPE最大的銷路是制作薄膜（＜12毫?xí)r）。吹塑或鑄壓工藝生產(chǎn)出的單一和復(fù)合LDPE薄膜占LDPE國(guó)內(nèi)消費(fèi)總量的 55％以上。LLDPE制做的薄膜表現(xiàn)了良好的光學(xué)性能、強(qiáng)度、曲撓性、密封性以及緩慢的氣味擴(kuò)散性和化學(xué)穩(wěn)定性。LDPE用來(lái)包裝面包、農(nóng)產(chǎn)品、快餐食品、紡織品、經(jīng)久性消費(fèi)品及一些工業(yè)制品。LDPE也可用作非包裝薄膜，比如：一次性尿布、農(nóng)用薄膜和縮水膜。 　　擠壓貼膠。它是LDPE的另一個(gè)主要市場(chǎng)。由于LDPE分子的結(jié)構(gòu)特點(diǎn)，它是聚乙烯樹脂家族中唯一能夠滿足擠壓貼膠加工工藝要求的樹脂。貼膠提供了有助于成品包裝密封的防護(hù)層，必不可少的優(yōu)良的拉伸性能、持久的覆蓋性和低的氣味擴(kuò)散性。典型的熔融指數(shù)范圍為3—15克／1O分鐘。LDPE貼膠可覆蓋在很多基質(zhì)上面，如：紙、板，布料和其它高分子材料。LDPE貼膠是保證基質(zhì)熱密封性和防濕性的一個(gè)經(jīng)濟(jì)而有效的手段。使用LDPE貼膠的市場(chǎng)有盛牛奶的盒子，無(wú)菌防腐包裝，食品包裝。膠帶和紙制品。 　　LDPE復(fù)合擠壓廣泛作為高阻隔復(fù)合層壓板的一種組分。重要的要求就是防濕和密封。滿足不同的要求，樹脂的性能隨之不同。它可用于無(wú)菌包裝、藥品與日用品的包裝。 　　模塑。在聚乙烯樹脂家族的競(jìng)爭(zhēng)中，吹塑成型與注射成型使用常規(guī)LDPE已經(jīng)相對(duì)穩(wěn)定。LDPE樹脂由于它的抗曲撓性和加工特性而被用于模塑成型。樹脂熔融指數(shù)范圍為0.5—2.0克／10分鐘，密度變化范圍 0.918—0.922克／立方厘米。LDPE模塑應(yīng)用于制做要求擠壓性能的醫(yī)用和日用消費(fèi)瓶以及封密件。 　　電線與電纜。LDPE最初是用作電線、電纜的包皮材料。LDPE顯示了優(yōu)異的電性能和抗磨性能，這些性能是市場(chǎng)上嚴(yán)格要求的。樹脂熔融指數(shù)范圍為0.25-2.0克／10分鐘，密度為0.918一0.932克／立方厘米。當(dāng)今，LDPE樹脂被用作電訊電纜的外皮。 商業(yè)用的PE-LD材料的密度為0.91~0.94 g/cm3。PE-LD對(duì)氣體和水蒸汽具有滲透性。PE-LD 的熱膨脹系數(shù)很高不適合于加工長(zhǎng)期使用的制品。 如果PE-LD的密度在0.91~0.925 g/cm3之間，那么其收縮率在2%~5%之間；如果密度在 0.926~0.94 g/cm3之間，那么其收縮率在1.5%~4%之間。當(dāng)前實(shí)際的收縮率還要取決于注塑工藝參數(shù)。 PE-LD在室溫下可以抵抗多種溶劑，但是芳香烴和氯化烴溶劑可使其膨脹。同PE-HD類似，PE-LD容易發(fā)生環(huán)境應(yīng)力開裂現(xiàn)象。 1.2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： 二維圖 三維模型圖 產(chǎn)品結(jié)構(gòu)較為簡(jiǎn)單，主要結(jié)構(gòu)特點(diǎn)表現(xiàn)為，外側(cè)有12個(gè)防滑筋，內(nèi)側(cè)有內(nèi)螺紋M50X3。 該零件尺寸均為一般重要性尺寸，這些尺寸精度為MT7級(jí)（GB/T1486—1993）便可，螺紋主，大徑，小徑要控制好，保證以后好裝配。 產(chǎn)品外面要求較高，所以采用細(xì)水口進(jìn)料，去澆口后，澆口痕很小 該零件不屬于受力部件，無(wú)特殊受力要求。 1.3計(jì)算塑件的體積和重量： 查設(shè)計(jì)手冊(cè)后得知LDPE的密度為0.91g/cm^3, 通過(guò)三維軟查詢本產(chǎn)品的質(zhì)量特性得知產(chǎn)品體積V=23817.240850588 mm^3=23.8cm3 ，根據(jù)公式M=ρ V=0.89x23.8=106.37.85=21.66(g) 2.初選注射成型機(jī)的型號(hào)和規(guī)格 初選取注塑成型設(shè)備的原則是產(chǎn)品質(zhì)量，根據(jù)證計(jì)算得知產(chǎn)品的重量21.66g 因?yàn)楫a(chǎn)品為一模二腔，產(chǎn)品的質(zhì)量為21.66gx2=43.32g,所以我們初步選用HTF58x1/G,它的具體參數(shù)如下圖, 3.塑件注射工藝參數(shù)的確定 注塑模工藝條件: 干燥：一般不需要 熔化溫度：180~280C 模具溫度：20~40C 為了實(shí)現(xiàn)冷卻均勻以及較為經(jīng)濟(jì)的去熱，建議冷卻腔道直徑至少為8mm，并且從冷卻腔道到 模具表面的距離不要超過(guò)冷卻腔道直徑的1.5倍。 注射壓力：最大可到1500bar。 保壓壓力：最大可到750bar。 注射速度：建議使用快速注射速度。 4.注射模的結(jié)構(gòu)設(shè)計(jì) 4.1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(duì)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. 有利于保證開模后產(chǎn)品留在動(dòng)模側(cè)。 本模具的分型面為產(chǎn)品底面，如下圖： 4.2確定澆注系統(tǒng) 4.2.1 主流道設(shè)計(jì)　　 噴嘴前端孔徑：d2=Φ3。6mm； 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(jì)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(shí)的壓力損失和塑料損耗，應(yīng)盡量縮短主流道的長(zhǎng)度， 澆口套主要有如下三種樣式，在模具設(shè)計(jì)中可根據(jù)實(shí)際須要選擇 4.2.2 點(diǎn)澆口設(shè)計(jì)料穴設(shè)計(jì)　　 點(diǎn)澆口優(yōu)點(diǎn)：開模時(shí)澆口自動(dòng)拉斷，澆口處的摻于應(yīng)力小，可實(shí)現(xiàn)自動(dòng)化生產(chǎn)，提高生產(chǎn)效率，便模具制造成本相對(duì)較高。 為了模具結(jié)構(gòu)簡(jiǎn)單本點(diǎn)澆品拉斷采用發(fā)下圖方式， 如上圖利用分流道未端斜度倒扣拉斷點(diǎn)澆口 點(diǎn)澆口入膠處如下圖： 如上圖進(jìn)膠處選用0。6mm 5.3 4.3確定型腔、型芯的結(jié)構(gòu)及固定方式 4.3.1型腔、型芯的結(jié)構(gòu)設(shè)計(jì)　　 為了加長(zhǎng)模個(gè)使用壽命，型腔采用P20鑲塊結(jié)構(gòu).。 4.3.2固定方式： 如下圖型腔鑲塊用碰模好后用螺釘緊固在動(dòng)模模板上。 型腔鑲塊的固定 4.4型腔和型芯的工作尺寸計(jì)算 成型零件工作尺寸計(jì)算公式如下 型腔徑向尺寸計(jì)算公式為L(zhǎng)+δz =[(1+)L－χΔ] +δz 型腔深度尺寸計(jì)算公式為H+δz =[(1+)H－χΔ] +δz 型芯徑向尺寸計(jì)算公式為= 型腔深度尺寸計(jì)算公式為= 其中為L(zhǎng)+δz模具型腔的徑向尺寸；H+δz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(gè)設(shè)計(jì)中,產(chǎn)品成形部分的工作尺寸按產(chǎn)品的收縮值計(jì)算,這種方法實(shí)用,且效率高 4.5型腔壁厚和底板厚度計(jì)算 4.5.1動(dòng)模墊板厚度理論計(jì)算公式如下 h=K（FL/2B[δ彎]）1/2 F=Ap h——?jiǎng)幽|板厚（mm）； K——修正系數(shù)，取0.6~0.75； F——?jiǎng)幽|板受的總壓力（N）； L——支承塊間距（mm）； B——?jiǎng)幽|板寬度（mm）； [δ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25~45MPa。 在本模具設(shè)計(jì)中采用下面的經(jīng)驗(yàn)數(shù)把確定 4.6螺紋強(qiáng)脫方設(shè)計(jì) 內(nèi)螺紋采用推件板強(qiáng)脫方式，如下圖 動(dòng)定模分開后，由注塑機(jī)上的頂棍通過(guò)頂動(dòng)推板，推板向上運(yùn)動(dòng)帶動(dòng)推件板上運(yùn) 動(dòng)，使產(chǎn)品脫離型芯。 4.7確定導(dǎo)向機(jī)構(gòu) 導(dǎo)向機(jī)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。另為了更好的證合模精度，模具還設(shè)計(jì)了輔助導(dǎo)向機(jī)構(gòu)—矩形精定位組件，如下圖: 導(dǎo)柱，導(dǎo)套零件圖如下 導(dǎo)柱 導(dǎo)套 導(dǎo)柱外圓要求用磨削加工到尺寸，表面粗糙度在0.8以內(nèi)。直線度，圓度在0.01以內(nèi)，與導(dǎo)大套配合處要求開設(shè)油槽。 導(dǎo)套內(nèi)孔研磨到尺寸，粗糙度在0.6以內(nèi)。 5模具裝配和試模 模具裝配是模具制造過(guò)程中的關(guān)鍵工序。模具裝配的質(zhì)量將影響制件的質(zhì)量及模具的使用、維修和模具的壽命，又將影響模具的制造周期和生產(chǎn)成本，是模具制造中的重要環(huán)節(jié)。 A, 裝配目的 模具裝配是根據(jù)模具的結(jié)構(gòu)特點(diǎn)、各零件間的相互關(guān)系和技術(shù)條件，以一定的裝配順序和方法，將符合圖樣技術(shù)要求的模具零件連接固定為組件、部件，直至裝配成滿足使用要求的模具。模具裝配可分為組件裝配、部件裝配和總裝配等。 B, 裝配內(nèi)容 選擇裝配基準(zhǔn)，組件裝配、調(diào)整，修配、研磨拋光、檢驗(yàn)和試模等環(huán)節(jié)，通過(guò)裝配達(dá)到模具各項(xiàng)精度指標(biāo)和技術(shù)要求 2，試模產(chǎn)品質(zhì)量分析 當(dāng)注射成型得到了近乎完整的制件時(shí)，制件本身必然存在各種各樣的缺陷，這種缺陷的形成原因是錯(cuò)綜復(fù)雜的，一般很難一目了然，要綜合分析，找出其主要原因來(lái)著手修正，逐個(gè)排出，逐步改進(jìn)，方可得到理想的樣件。下面就對(duì)度模中常見的成型制品主要缺陷及其改進(jìn)的措施進(jìn)行分析。 （1） 注射填充不足 所謂填充不足是指在足夠大的壓力、足夠多的料量條件下注射不滿型腔而得不到完整的制件。這種現(xiàn)象極為常見。其主要原因有： a. 熔料流動(dòng)阻力過(guò)大 這主要有下列原因：主流道或分流道尺寸不合理。流道截面形狀、尺寸不利于熔料流動(dòng)。盡量采用整圓形、梯形等相似的形狀，避免采用半圓形、球缺形料道。熔料前鋒冷凝所致。塑料流動(dòng)性能不佳。制品壁厚過(guò)薄。 b. 型腔排氣不良 這是極易被忽視的現(xiàn)象，但以是一個(gè)十分重要的問(wèn)題。模具加工精度超高，排氣顯得越為重要。尤其在模腔的轉(zhuǎn)角處、深凹處等，必須合理地安排頂桿、鑲塊，利用縫隙充分排氣，否則不僅充模困難，而且易產(chǎn)生燒焦現(xiàn)象。 c. 鎖模力不足 因注射時(shí)動(dòng)模稍后退，制品產(chǎn)生飛邊，壁厚加大，使制件料量增加而引起的缺料。應(yīng)調(diào)大鎖模力，保證正常制件料量。 （2） 溢邊（毛刺、飛邊、批鋒） 與第一項(xiàng)相反，物料不僅充滿型腔，而且出現(xiàn)毛刺，尤其是在分型面處毛刺更大，甚至在型腔鑲塊縫隙處也有毛刺存在，其主要原因有： a. 注射過(guò)量 b. 鎖模力不足 c. 流動(dòng)性過(guò)好 d. 模具局部配合不佳 e. 模板翹曲變形 （3） 制件尺寸不準(zhǔn)確 初次試模時(shí)，經(jīng)常出現(xiàn)制件尺寸與設(shè)計(jì)要求尺寸相差較大。這時(shí)不要輕易修改型腔，應(yīng)行從注射工藝上找原因。 a. 尺寸變大 注射壓力過(guò)高，保壓時(shí)間過(guò)長(zhǎng)，此條件下產(chǎn)生了過(guò)量充模，收縮率趨向小值，使制件的實(shí)際尺寸偏大；模溫較低，事實(shí)上使熔料在較低溫度的情況下成型，收縮率趨于小值。這時(shí)要繼續(xù)注射，提高模具溫度、降低注射壓力，縮短保壓時(shí)間，制件尺寸可得到改善。 b. 尺寸變小 注射壓力偏低、保壓時(shí)間不足，制在冷卻后收縮率偏大，使制件尺寸變?。荒剡^(guò)高，制件從模腔取出時(shí)，體積收縮量大，尺寸偏小。此時(shí)調(diào)整工藝條件即可。通過(guò)調(diào)整工藝條件，通常只能在極小范圍內(nèi)使尺寸京華，可以改變制件相互配合的松緊程度，但難以改變公稱尺寸。 對(duì)以上出現(xiàn)的缺陷調(diào)試時(shí)，盡可能先采用改變成形工藝條件，后采用修正模具來(lái)消除成形缺陷。以下的內(nèi)容均從這兩個(gè)方面來(lái)討論。 熱塑性塑料注射成形件的常見缺陷及消除措施如下。 1. 缺料（注射量不足） 消除措施如下： 工藝條件：增大注射壓力；延長(zhǎng)成形周期；延長(zhǎng)保壓時(shí)間；調(diào)整材料供給；提高熔料溫度；提高模具溫度；供給干燥過(guò)的熔料。 模具條件：加大主流道、分流道和澆口；減小澆口區(qū)面積；加大噴嘴；增加排氣槽；改變澆口位置。 2. 氣孔 消除措施如下： 工藝條件：增大注射壓力；延長(zhǎng)成形周期；調(diào)整材料供給；降低熔料溫度；降低模具溫度。 模具條件：加大主流道、分流道和澆口；改變冷卻水道位置；改變澆口位置。 3. 溢料飛邊 消除措施如下： 工藝條件：減小注射壓力；縮短保壓時(shí)間；降低熔料溫度；增大合模壓力。 模具條件：矯正修理分型面。 4. 著色不均勻 消除措施如下： 工藝條件：縮短保壓時(shí)間；降低熔料溫度；提高模具溫度；供給干燥過(guò)的物料；物料不得帶有雜質(zhì)、灰塵。 模具條件：加大主流道、分流道和澆口；減小澆口區(qū)面積。 5. 翹曲變形 消除措施如下： 工藝條件：增大注射壓力；延長(zhǎng)成形周期；延長(zhǎng)保壓時(shí)間；降低熔料溫度；降低模具溫度；使用矯正框架。 模具條件：加大噴嘴；改變冷卻水道位置。 6. 波狀痕跡 消除措施如下： 工藝條件：增大注射壓力；延長(zhǎng)成形周期；延長(zhǎng)保壓時(shí)間；調(diào)整原料供給；降低熔料溫度；降低模具溫度。 模具條件：加大噴嘴；改變冷卻水道位置。 7. 尺寸不穩(wěn)定 消除措施如下： 工藝條件：增大注射壓力；延長(zhǎng)成形周期；延長(zhǎng)保壓時(shí)間；降低熔料溫度；降低模具溫度。 模具條件：加大主流道、分流道和澆口；減小澆口區(qū)面積；加大噴嘴；改變冷卻水道位置；改變澆口位置。 8. 熔接痕強(qiáng)度低 消除措施如下： 工藝條件：減小注射壓力；延長(zhǎng)保壓時(shí)間；降低熔料溫度；減慢注射速度。 模具條件：增加排氣槽；檢查噴嘴加熱部分。 9. 表面質(zhì)量差 消除措施如下： 工藝條件：增大注射壓力；縮短保壓時(shí)間；增大合模壓力；提高模具溫度；降低模具溫度；減慢注射速度；物料不得帶有雜質(zhì)、灰塵；使用矯正框架。 模具條件：加大主流道、分流道和澆口；改變冷卻水道位置；增加排氣槽；改變澆口位置；研磨模腔表面；增加冷料穴容量；研磨主流道、分流道和澆口。 10. 塑件粘模 消除措施如下： 工藝條件：減小注射壓力；縮短保壓時(shí)間；降低熔料溫度；降低模具溫度。 模具條件：加大主流道、分流道和澆口；減小澆口區(qū)面積；研磨模腔表面。 11. 主流道凝料粘模 消除措施如下： 工藝條件：縮短保壓時(shí)間。 模具條件：改變噴嘴位置；研磨主流道襯套；改變主流道拉料桿形式。 12. 脆 消除措施如下： 工藝條件：縮短保壓時(shí)間；降低熔料溫度；提高模具溫度；供給干燥過(guò)的物料。 模具條件：加大主流道、分流道和澆口。 13. 表面硬度、強(qiáng)度不足 消除措施如下： 工藝條件：增大注射壓力；延長(zhǎng)保壓時(shí)間；縮短保壓時(shí)間；降低熔料溫度；提高模具溫度；供給干燥過(guò)的物料；減慢注射速度；物料不得帶有雜質(zhì)、灰塵。 模具條件：加大主流道、分流道和澆口；減小澆口區(qū)面積；改變冷卻水道位置；增加排氣槽；改變澆口位置；研磨模腔表面；增加冷料穴容量；研磨主流道、分流道和澆口。 3、注塑機(jī)操作過(guò)程注意事項(xiàng) 養(yǎng)成良好的注塑機(jī)操作習(xí)慣對(duì)提高機(jī)器壽命和生產(chǎn)安全都大有好處。 開機(jī)之前：（1）檢查電器控制箱內(nèi)是否有水、油進(jìn)入，若電器受潮，切勿開機(jī)。應(yīng)由維修人員將電器零件吹干后再開機(jī)。（2）檢查供電電壓是否符合，一般不應(yīng)超過(guò)±15%。（3）檢查急停開關(guān)，前后安全門開關(guān)是否正常。驗(yàn)證電動(dòng)機(jī)與油泵的轉(zhuǎn)動(dòng)方向是否一致。（4）檢查各冷卻管道是否暢通，并對(duì)油冷卻器和機(jī)筒端部的冷卻水套通入冷卻水。（5）檢查各活動(dòng)部位是否有潤(rùn)滑油（脂），并加足潤(rùn)滑油。（6）打開電熱，對(duì)機(jī)筒各段進(jìn)行加溫。當(dāng)各段溫度達(dá)到要求時(shí)，再保溫一段時(shí)間，以使機(jī)器溫度趨于穩(wěn)定。保溫時(shí)間根據(jù)不同設(shè)備和塑料原料的要求而有所不同。 （7）在料斗內(nèi)加足足夠的塑料。根據(jù)注塑不同塑料的要求，有些原料最好先經(jīng)過(guò)干燥。（8）要蓋好機(jī)筒上的隔熱罩，這樣可以節(jié)省電能，又可以延長(zhǎng)電熱圈和電流接觸器的壽命。 操作過(guò)程中：（1）不要為貪圖方便，隨意取消安全門的作用。（2）注意觀察壓力油的溫度，油溫不要超出規(guī)定的范圍。液壓油的理想工作溫度應(yīng)保持在45~50℃之間，一般在35~60℃范圍內(nèi)比較合適。（3）注意調(diào)整各行程限位開關(guān)，避免機(jī)器在動(dòng)作時(shí)產(chǎn)生撞擊。 工作結(jié)束時(shí)：（1）停機(jī)前，應(yīng)將機(jī)筒內(nèi)的塑料清理干凈，預(yù)防剩料氧化或長(zhǎng)期受熱分解。（2）應(yīng)將模具打開，使肘桿機(jī)構(gòu)長(zhǎng)時(shí)間處于閉鎖狀態(tài)。（3）車間必須備有起吊設(shè)備。裝拆模具等笨重部件時(shí)應(yīng)十分小心，以確保生產(chǎn)安全。 6. 注射機(jī)校核 本次模具設(shè)計(jì)中初選注塑機(jī)型號(hào)為HTF58X1/G，它的技術(shù)參數(shù)如下 6.1注射壓力的校核 注射機(jī)的額定壓力Pe=184MPa，塑料成型時(shí)所需的壓力Po=127MPa，Pe≥Po， 所以滿足要求。 6.2模具厚度H與注射機(jī)閉合高度的校核 Hmin＜H＜Hmax Hmin—注射機(jī)允許最小模厚（310mm） Hmax—注射機(jī)允許最大模厚（110mm） 而模具閉合的高度H為276mm. 因?yàn)?10＜276＜310 所以滿足要求 模具總高度如下圖 6.3頂出行程的校核 注射機(jī)最大頂出距離為70mm，產(chǎn)品的高度為30mm，所以頂出行程40到45。因此滿足要求。 結(jié)論：根據(jù)校核注射機(jī)，完全能夠滿足該模具的使用要求。 小 結(jié) 1.本模具內(nèi)螺紋采用了強(qiáng)脫方式脫模，螺紋脫模方很還有用齒輪旋轉(zhuǎn)脫模，用嵌件方式手動(dòng)脫模。 2.為了加長(zhǎng)模個(gè)使用壽命，型腔采用P20鑲塊結(jié)構(gòu). 通過(guò)對(duì)本模具的總體結(jié)構(gòu)的精心設(shè)計(jì)，加深了對(duì)模具各部件及模具生產(chǎn)中的條個(gè)環(huán)節(jié)的了解，加強(qiáng)了專業(yè)知識(shí)的實(shí)際運(yùn)用能力，綜合上述，本次設(shè)計(jì)較為成功。 謝 辭 參考文獻(xiàn) [1]廖月瑩.塑料模具設(shè)計(jì)指導(dǎo)與資料匯編.大連：大連理工大學(xué)出版社，2007 [2]曲華昌.塑料成型工藝與模具設(shè)計(jì).北京:高等教育出版社，2009 [3]任先明.塑料模具設(shè)計(jì)指導(dǎo).國(guó)防工業(yè)出版社，2006 [4]鄒繼強(qiáng).塑料模具設(shè)計(jì)參考資料匯編.北京:清華大學(xué)出版社，2005 [5]王鵬駒.塑料模具技術(shù)手冊(cè).北京:機(jī)械工業(yè)出版社，1999 [6]李德群.塑料成型模具設(shè)計(jì).武漢：華中理工大學(xué)出版社，1990 [7]許發(fā)樾主編.實(shí)用模具設(shè)計(jì)與制造手冊(cè).北京：機(jī)械工業(yè)出版社，2001 29 編號(hào)： 畢業(yè)設(shè)計(jì)(論文)外文翻譯 （原文） 學(xué) 院： 國(guó)防生學(xué)院 專 業(yè)： 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 學(xué)生姓名： 柯招軍 學(xué) 號(hào)： 1000110104 指導(dǎo)教師單位： 機(jī)電工程學(xué)院 姓 名： 曹泰山 職 稱： 講 師 2014年 3 月 9 日 桂林電子科技大學(xué)畢業(yè)設(shè)計(jì)（論文）外文翻譯原文 第37頁(yè) 共38頁(yè) Incorporating Manufacturability Considerations during Design of Injection Molded Multi-Material Objects Ashis Gopal Banerjee, Xuejun Li, Greg Fowler, Satyandra K. Gupta1 Mechanical Engineering Department and The Institute for Systems Research University of Maryland, College Park, MD 20742, U.S.A. ABSTRACT The presence of an already molded component during the second and subsequent molding stages makes multi-material injection molding different from traditional injection molding process. Therefore, designing multi-material molded objects requires addressing many additional manufacturability considerations. In this paper, we first present an approach to systematically identifying potential manufacturability problems that are unique to the multi-material molding processes and design rules to avoid these problems. Then we present a comprehensive manufacturability analysis approach that incorporates both the traditional single material molding rules as well as the specific rules that have been identified for multi-material molding. Our analysis shows that sometimes the traditional rules need to be suppressed or modified. Lastly, for each of the new manufacturability problem, this paper describes algorithms for automatically detecting potential occurrences and generating redesign suggestions. These algorithms have been implemented in a computer-aided manufacturability analysis system. The approach presented in this paper is applicable to multi-shot and over molding processes. We expect that the manufacturability analysis techniques presented in this paper will help in decreasing the product development time for the injection molded multi-material objects. Keywords: Automated manufacturability analysis, generation of redesign suggestions, and multi-material injection molding. 1 INTRODUCTION Over the last few years, a wide variety of multi-material injection molding (MMM) processes have emerged for making multi-material objects, which refer to the class of objects in which different portions are made of different materials. Due to fabrication and assembly steps being performed inside the molds, molded multi-material objects allow significant reduction in assembly operations and production cycle times. Furthermore, the product quality can be improved, and the possibility of manufacturing defects, and total manufacturing costs can be reduced. In MMM, multiple different materials are injected into a multi-stage mold. The sections of the mold that are not to be filled during a molding stage are temporally blocked. After the first injected material sets, then one or more blocked portions of the mold are opened and the next material is injected. This process continues until the required multi-material part is created. Nowadays, virtually every industry (e.g., automotive, consumer goods, toys, electronics, power tools, appliances) that makes use of traditional single-material injection molding (SMM) process is beginning to use multi-material molding processes. Some common applications include multi-color objects, skin-core arrangements, in-mold assembled objects, soft-touch components (with rigid substrate parts) and selective compliance objects. Typical examples of each class of application are shown in Fig. 1. There are fundamentally three different types of multi-material molding processes. Multi-component injection molding is perhaps the simplest and most common form of MMM. It involves either simultaneous or sequential injection of two different materials through either the same or different gate locations in a single mold. Multi-shot injection molding (MSM) is the most complex and versatile of the MMM processes. It involves injecting the different materials into the mold in a specified sequence, where the mold cavity geometry may partially or completely change between sequences. Over-molding simply involves molding a resin around a previously-made injection-molded plastic part. Each of the three classes of MMM is considerably different. Each specific MMM process requires its own set of specialized equipment; however, there are certain equipment requirements that are generally the same for all types of MMM. Techniques described in this paper are applicable to over-molding and multi-shot molding. Currently only limited literature exists that describes how to design molded multi-material objects. Consequently very few designers have the required know-how to do so. Consider an example of a two piece assembly consisting of part A and part B to be produced by multi-material molding. In fact, many new users believe that if part A and part B meet the traditional molding rules then assembly AB will also be moldable using multi-material molding. By moldable we mean that the assembly (or part) can be molded using one or more MMM (or SMM) processes such that basic functional and aesthetic requirements for the part or assembly are satisfied and the mold cavity shape can be changed (i.e. mold can be opened, pieces may be removed or inserted and then mold can be closed) without damaging the mold pieces. However, this notion is not always correct. Fig. 2 shows an assembly to be molded by MMM. In this case, both parts can be individually molded without any problem. However, molding them as an assembly using over-molding process leads to manufacturability problems. After molding the inner part in the first stage, it is not possible to carry out second stage molding as the injected plastic will flow over the inner part and damage the surfaces of the already molded component. This emphasizes the need for developing new design rules that are specific to addressing manufacturability problems encountered in multi-material molding. Detection of this problem and corresponding redesign suggestion will be described in sub-section 5.3. On the other hand, there are molded multi-material assemblies where at least one of the parts would have not been moldable as an individual piece using traditional molding. However, this part can be molded when done as a part of the assembly. Fig. 3 highlights such a case. Although application of traditional plastic injection molding rules would have concluded that component B cannot be manufactured, it is possible to mold assembly AB by choosing an appropriate molding sequence. For example, in this case we first need to mold part A and then mold part B using overmolding operation. The reason why MMM appears to be significantly different from SMM can be explained as follows. The part that has been molded first (component A) acts as the “mold piece” during the second molding stage. Thus, a plastic mold piece is present in addition to the metallic mold pieces during this molding stage. Hence, this second stage is fundamentally different in nature from conventional single-material injection molding. Fig. 4 illustrates this condition by depicting the two molding stages in rotary platen multi-shot molding. Although the shape of the core remains identical in both the stages, the cavity shape changes and already molded component A acts as an additional “mold piece” in the second shot. Moreover, the first stage part that acts as plastic “mold piece” is not separated from the final assembly. This forces us to avoid applying some of the traditional molding design rules on certain portions of the gross shape of the overall object also referred as gross object. By gross object, we mean the solid object created by the regularized union of the two components. That is why, simply ensuring that the first stage part and the gross shape are moldable do not solve this problem either. Fig. 5 illustrates this fact; blindly checking all the faces of the gross object for presence of undercuts leads us to wrongly conclude that it cannot be molded. In reality, this is not the case and we should only test the faces that need to be demolded (i.e., separated from the mold pieces) during that molding stage while determining a feasible molding sequence. Based on the above discussion, we conclude that a new approach needs to be developed to analyze manufacturability of molded multi-material objects. In the current paper we only consider manufacturability problems arising due to the shape of the components and the gross object. Fig. 6 shows an example where undercuts create problems; they need to be eliminated in order to form a feasible molding sequence. The gross object shown in that figure cannot be made by any MMM process, because neither of the two components is moldable due to the presence of deep, internal undercuts. Slight redesign of component A enables us to carry out MMM operation – component A can be injected first and then component B, provided they have similar melting points or A melts at a higher temperature than B. Section 3 systematically derives five such new manufacturability problems that arise in multi-material molding from the state transition diagram representing the process flow. The next task in developing a systematic manufacturability analysis methodology is to develop a detailed approach for applying these new rules. A comprehensive approach to outline how and when the new multi-material molding design rules need to be applied and traditional single material molding rules have to be applied, modified or suppressed has been proposed in Section 4. Finally, algorithms have been presented to detect violations of such rules and generate feasible redesign suggestions in Section 5. All the algorithms have been implemented in a computer-aided manufacturability analysis system. We conclude this paper by stating its contributions and limitations in Section 6. 2 RELATED RESEARCH A wide variety of computational methods have emerged to provide software aids for performing manufacturability analysis [Gupt97a, Vlie99]. Such systems vary significantly by approach, scope, and level of sophistication. At one end of the spectrum are software tools that provide estimates of the approximate manufacturing cost. At the other end are sophisticated tools that perform detailed manufacturability analysis and offer redesign suggestions. For analyzing the manufacturability of a design, the existing approaches can be roughly classified into two categories. In direct approaches [Ishi92, Rose92, Shan93], shape-based rules are used to identify infeasible design attributes from direct inspection of the design description. In indirect or plan-based approaches [Gupt95, Gupt97b, Gupt98, Haye89, Haye94, Haye96], the first step is to generate a manufacturing plan, and then to evaluate the plan in order to assess the manufacturability of design. This approach is useful in domains where there are complex interactions between manufacturing operations. Several leading professional societies have published manufacturability guidelines for molded plastic parts to help designers take manufacturability into account during the product design phase [Bake92, Truc87]. Poli [Poli01] has also described qualitative DFM rules for all the major polymer processing processes including injection molding, compression molding and transfer molding. Moreover, companies such as General Electric [Gene60] have generated their own guidelines for the design of plastic parts. Such guidelines show examples of good and bad designs. It is left to the designer’s discretion to apply them as and when necessary. Basically, there are two types of guidelines. The first type deals with manufacturability issues, whereas the second type deals with part functionality. We will only cover the first type of guidelines here. They are listed as follows. a) Fillets should be created and corners should be rounded so that the molten plastic flows smoothly to all the portions of the part. Use of radii and gradual transitions minimize the degree of orientation associated with mold filling, thereby resulting in uniform mold flow [Mall94]. Moreover, this also avoids the problem of having high stress concentration. Fig. 7 shows an example of how part design needs to be altered to get rid of sharp corners. b) The parting line must be chosen carefully so that “parting” and metal “shut-off” flashes can be minimized. Typically, flashes (solidified leakages of plastic material) occur along the parting line, where the mold pieces come in direct contact with each other. Fig. 8 illustrates how the stiffening ribs on a part have to be redesigned in order to change the location of the parting line. This consequently changes the flash formation position. In the first case, flashes run all along the part, destroying the part quality. However, they occur on the top surface of the part in the second design, and hence can be easily removed later on. c) Thin and uniform section thickness should be used so that the entire part can cool down rapidly at the same rate. Thick sections take a longer time to cool than thin sections. For example, in the first part shown in Fig. 9, the thicker, hotter sections of the molding will continue to cool and shrink more than the thinner sections. This will result in a level of internal stress in the portions of the part where the wall thickness changes. These residual, internal stresses can lead to warpages and reduced service performances. If possible, the part must be redesigned to eliminate such thickness variations altogether. Otherwise, tapered transitions can be used to avoid residual stresses, high stress concentrations and abrupt flow transitions during mold filling. Whenever feasible, wall section thickness must be reduced by coring out sections of the molding, and by using ribs to compensate for the loss in stiffness of a thinner part [Mall94]. d) Side actions (side cores, split cores, lifters etc.) must be used to create undercut features on the part or the part should be redesigned to eliminate undercut features. Fig. 10 shows an example of a plastic part, whose undercut region cannot be molded by any side action. A simple redesign shown in this figure solves this problem. e) Draft angles need to be imparted to vertical or near-vertical walls for ease of removal of the part from the mold assembly. Fig. 11 shows that incorrect draft angles make it impossible to eject the part. Tapering the side walls inward (towards the core side) resolves this issue satisfactorily. Drafting also reduces tool and part wear considerably – sliding friction as well as scuffing or abrasion of the outer (cavity) faces of the part are eliminated to a large extent. Typically, the required draft angle ranges from a fraction of a degree to several degrees and depends on a lot of parameters such as depth of draw, material rigidity, surface lubricity and material shrinkage [Mall94]. Computational work in the field of manufacturability analysis of injection molded parts mainly focuses on two different areas. The first area deals with demoldability of a single material part. The demoldability of a part is its ability to be ejected easily from the mold assembly (core, cavity and side actions) when the mold opens. Deciding if a part is demoldable is equivalent to deciding if there exists a combination of main parting direction, side cores and split cores such that the criterion of demoldability is satisfied. Chen et al. [Chen93] describe a visibility map based approach to find a feasible parting direction that minimizes the number of side cores. Hui [Hui97] describes a heuristic search technique for selecting a combination of main parting, core and insert directions. Approaches based on undercut-feature recognition have also been developed [Gu99, Fu99, Lu00, Yin01]. The basic idea behind these approaches is to find potential undercuts on the part using feature recognition techniques. Each type of feature has its own set of candidate parting directions. The optimal main, parting direction is then chosen on the basis of some evaluation functions. Ahn et al. [Ahn02] describe mathematically sound algorithms to test if a part is, indeed, moldable using a two-piece mold (without any side actions) and if so, to obtain the set of all such possible parting directions. Building on this, Elber et al. [Elbe05] have developed an algorithm based on aspect graphs to solve the two-piece mold separability problem for general free-form shapes, represented by NURBS surfaces. McMains and Chen [McMa04] have determined moldability and parting directions for polygons with curved (2D spline) edges. Recently, Kharderkar et al. [Khar05] have presented new programmable graphics hardware accelerated algorithms to test the moldability of parts and help in redesigning them by identifying and graphically displaying undercuts. Dhaliwal et al. [Dhal03] described exact algorithms for computing global accessibility cones for each face of a polyhedral object. Using these, Priyadarshi and Gupta [Priy04] developed algorithms to design multi-piece molds. Other notable work in the area of automated multi-piece mold design includes that by Chen and Rosen [Chen02, Chen03]. The second area of active work deals with the simulation of molten, plastic flow in injection molding process. Many commercial systems are available to help designers in performing manufacturability analysis. Also, finite element analysis software like ANSYS, ABAQUS, FEMLAB etc. can be used to predict and solve some problems, such as whether the strength of some portion of the part is adequate. Since these types of problems arising during multi-material injection molding are the same as those experienced in case of single material molding, appropriate commercial packages can be used to overcome them. 3 IDENTIFYING SOURCES OF MOLDING PROBLEMS Many different reasons can contribute to manufacturability problems during MMM. These reasons include material incompatibility, interactions among cooling systems for different stages, placement of gates, demoldability, and ejection system problems. In this paper we mainly focus on the manufacturability problems that result from the shape of the multi-material objects. Specifically, we focus on those manufacturing complications that arise due to the presence of plastic material inside the mold cavity during the second shot. The work presented in this paper is applicable to multi-shot rotary platen (shown in Fig. 4 and Fig. 12), multi-shot index plate (shown in Fig. 13 and Fig. 14), and over-molding processes (shown in Fig. 15). Appendix A describes each of these processes in details. It is important to note here that part designs need to be modified significantly depending upon the nature of the MMM process that will be used to mold it. Fig. 16 illustrates this idea by using three different part designs. The first object can be molded by overmolding process only, whereas the second object can be molded using either overmolding or index plate multi-shot molding process. Rotary platen process should be used to mold the last part. Thus, it is clear that specific process-dependent design rules are essential in multi-material injection molding. Let us now try to systematically identify the manufacturability problems so that corresponding design rules can be framed to handle them. These design rules will be later utilized by the algorithms in Sections 4 and 5 to offer meaningful solutions once the problems have been detected. A new way of identifying all the potential sources of manufacturability problems using state transition diagrams and studying failure mode matrices is presented below. The effectiveness of this technique is first validated by comparing the identified failure modes and corresponding design rules wi