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編號(hào) 畢業(yè)設(shè)計(jì) 論文 開(kāi)題報(bào)告 題 目 塑料斜齒輪旋轉(zhuǎn)脫螺紋 注塑模具設(shè)計(jì) 院 系 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 題 目 類 型 理 論 研 究 實(shí) 驗(yàn) 研 究 工 程 設(shè) 計(jì) 工 程 技 術(shù) 研 究 軟 件 開(kāi) 發(fā) 2013 年 12 月 23 日 1 畢業(yè)設(shè)計(jì)的主要內(nèi)容 重點(diǎn)和難點(diǎn)等 畢業(yè)設(shè)計(jì)的主要內(nèi)容 模具在現(xiàn)代工業(yè)生產(chǎn)中占有非常重要的地位 隨著機(jī)械工業(yè) 電子工業(yè) 航空工業(yè) 儀器儀表工業(yè)和日常用品的發(fā)展 塑料成型制件的需求量越來(lái)越多 質(zhì)量要求也越來(lái)越高 模具生產(chǎn)技術(shù)水平的高低在很大程度上決定了一個(gè)國(guó)家 產(chǎn)品制造水平高低 本課題通過(guò)小模數(shù)塑料斜齒輪脫螺紋注塑模設(shè)計(jì)注塑模的 設(shè)計(jì)過(guò)程 學(xué)習(xí)掌握注塑模設(shè)計(jì)方法 并應(yīng)用設(shè)計(jì)軟件 完成注塑模的設(shè)計(jì) 本次畢業(yè)設(shè)計(jì)的主要內(nèi)容如下 1 分析已知工件的結(jié)構(gòu) 設(shè)計(jì)小模數(shù)塑料斜齒輪脫螺紋注塑模設(shè)計(jì) 在 分析工件結(jié)構(gòu) 工藝性和了解注塑模常用機(jī)構(gòu)及工作原理的基礎(chǔ)上 設(shè)計(jì)注塑 模 2 撰寫課題報(bào)告 3 通過(guò)對(duì)產(chǎn)品的性能和結(jié)構(gòu)的分析 完成模具結(jié)構(gòu)與零件設(shè)計(jì)及相關(guān)計(jì)算 4 認(rèn)真分析制件圖 確定注塑模設(shè)計(jì)的基本參數(shù) 設(shè)計(jì)模具的結(jié)構(gòu) 主要 零件結(jié)構(gòu) 卸料裝置 冷卻系統(tǒng)等 確定模具型腔 模具結(jié)構(gòu) 分型面和進(jìn)料 口形式 計(jì)算含收縮率的相關(guān)尺寸和模具的強(qiáng)度和剛度 5 繪制注塑模具總裝配圖和零件圖 6 根據(jù)主要零件結(jié)構(gòu) 技術(shù)參數(shù)要求 進(jìn)行工藝計(jì)算 制定主要零件加工 工藝 7 翻譯專業(yè)外語(yǔ)文獻(xiàn) 8 撰寫畢業(yè)設(shè)計(jì) 論文 說(shuō)明書 畢業(yè)設(shè)計(jì)的重點(diǎn)難點(diǎn) 1 塑件設(shè)計(jì)的合理性分析 工藝及結(jié)構(gòu)分析 2 材料的選擇 收縮率計(jì)算 模具強(qiáng)度及剛度分析 3 零件成型工藝考慮 保證獲得光潔完整美觀的表面 4 掌握齒輪傳動(dòng)等機(jī)械零件知識(shí) 合理設(shè)計(jì)自動(dòng)脫螺紋機(jī)構(gòu) 5 模具型腔數(shù)的確定 模具結(jié)構(gòu) 分型面和進(jìn)料口形式的選擇 6 繪制模具總裝圖 零件圖及尺寸標(biāo)注 完成各技術(shù)參數(shù)要求 2 準(zhǔn)備情況 查閱的文獻(xiàn)資料及調(diào)研情況 現(xiàn)有設(shè)備 實(shí)驗(yàn)條件等 模具工業(yè)是國(guó)民經(jīng)濟(jì)的重要基礎(chǔ)工業(yè)之一 模具是工業(yè)生產(chǎn)中的基礎(chǔ)工藝 裝備 是一種高附加值的高精密集型產(chǎn)品 也是高新技術(shù)產(chǎn)業(yè)化的重要領(lǐng)域 其技術(shù)水平的高低在很大程度上成為衡量一個(gè)國(guó)家制造業(yè)水平的重要標(biāo)志 專家預(yù)測(cè) 大型 精密 設(shè)計(jì)合理的注塑模具將受到市場(chǎng)普遍歡迎 調(diào)研情況 20 世紀(jì) 80 年代以來(lái) 國(guó)民經(jīng)濟(jì)的高速發(fā)展對(duì)模具工業(yè)提出了越來(lái)越高的要 求 同時(shí)為模具的發(fā)展提供了巨大的動(dòng)力 這些年來(lái) 中國(guó)模具發(fā)展十分迅速 模具工業(yè)一直以 15 左右的增長(zhǎng)速度快速發(fā)展 目前 我國(guó)模具生產(chǎn)廠點(diǎn)約有 3 萬(wàn)多家 從業(yè)人數(shù) 80 多萬(wàn)人 2005 年模具出口 7 4 億美元 比 2004 年的 4 9 億美元增長(zhǎng)約 50 均居世界前列 2006 年 我國(guó)塑料模具總產(chǎn)值約 300 多億 元人民幣 其中出口額約 58 億元人民幣 市場(chǎng)銷售方面 2006 年中國(guó)塑料模具 總需求約為 313 億元人民幣 國(guó)產(chǎn)模具總供給約為 230 億元人民幣 市場(chǎng)滿足 率為 73 5 在我國(guó) 廣東 上海 浙江 江蘇 安徽是主要生產(chǎn)中心 廣東占 我國(guó)模具總產(chǎn)量的四成 注塑模具比例進(jìn)一步提高 塑料制品在機(jī)電 儀表 汽車 航天航空等國(guó)家支柱產(chǎn)業(yè)及與人民日常生 活相關(guān)的各領(lǐng)域中得到了廣泛應(yīng)用 塑料制品成形的方法雖然很多 但最主要 的是注塑成形 在世界塑料模具市場(chǎng)中塑料成形模具產(chǎn)量中注塑模具約占一半 國(guó)內(nèi)注塑模在質(zhì)與量上都有了較快的發(fā)展 但是與國(guó)外的先進(jìn)技術(shù)相比 我國(guó) 仍有大部分企業(yè)處于需要技術(shù)創(chuàng)新 技術(shù)改造 提高產(chǎn)品質(zhì)量 加強(qiáng)現(xiàn)代化管 理以及體制轉(zhuǎn)軌的關(guān)鍵時(shí)期 總的來(lái)看我國(guó)塑料模具在數(shù)量 質(zhì)量 技術(shù)和能力等方面都有了很大進(jìn)步 但與世界先進(jìn)水平 國(guó)民經(jīng)濟(jì)發(fā)展的需求相比 差距仍很大 一些大型 精密 復(fù)雜 長(zhǎng)壽命的中高檔塑料模具每年仍需大量進(jìn)口 進(jìn)入 21 世紀(jì) 在經(jīng)濟(jì)全球化的新背景下 隨著技術(shù) 資本和勞動(dòng)力市場(chǎng)的 重新整合 中國(guó)裝備制造業(yè)在加入 WTO 以后 將成為世界裝備制造業(yè)的基地 而在現(xiàn)代制造業(yè)中 無(wú)論哪一行業(yè)的工程裝備 都越來(lái)越多地采用由模具工業(yè) 提供的產(chǎn)品 為了滿足市場(chǎng)需要 未來(lái)的塑料模具無(wú)論是品種 結(jié)構(gòu) 性能還 是加工都必將有較快發(fā)展 超大型 超精密 長(zhǎng)壽命 高效模具 多種材質(zhì) 多種顏色 多層多腔 多種成型方法一體化的模具將得到發(fā)展 隨著市場(chǎng)的發(fā) 展 塑料新材料及多樣化成型方式今后必然會(huì)不斷發(fā)展 因此對(duì)模具的要求也 越來(lái)越高 更高性能及滿足特殊用途的模具新材料將會(huì)不斷發(fā)展 隨之將產(chǎn)生 一些特殊的 更為先進(jìn)的加工方法 各種模具型腔表面處理技術(shù) 如涂覆 修 補(bǔ) 研磨和拋光等新工藝也會(huì)不斷得到發(fā)展 注塑模具在量和質(zhì)方面都有較快 的發(fā)展 我國(guó)最大的注塑模具單套重量己超過(guò) 50 噸 最精密的注塑模具精度己 達(dá)到 2 微米 制件精度很高的小模數(shù)齒輪模具及達(dá)到高光學(xué)要求的車燈模具等 也已能生產(chǎn) 多腔塑料模具已能生產(chǎn)一模 7800 腔的塑封模 高速模具方面已能 生產(chǎn)擠出速度達(dá) 6m min 以上的高速塑料異型材擠出模具及主型材雙腔共擠 雙 色共擠 軟硬共擠 后共擠 再生料共擠出和低發(fā)泡鋼塑共擠等各種模具 在 CAD CAM 技術(shù)得到普及的同時(shí) CAE 技術(shù)應(yīng)用越來(lái)越廣 以 CAD CAM CAE 一體 化得到發(fā)展 模具新結(jié)構(gòu) 新品種 新工藝 新材料的創(chuàng)新成果不斷涌現(xiàn) 特 別是汽車 家電等工業(yè)快速發(fā)展 使得注塑模的發(fā)展迅猛 目前 塑料模具在整個(gè)模具行業(yè)中所占比重約為 30 隨著中國(guó)汽車 家電 電子通訊 各種建材迅速發(fā)展 預(yù)計(jì)在未來(lái)模具市場(chǎng)中 塑料模具占模具總量 的比例仍將逐步提高 且發(fā)展速度將快于其他模具 專家預(yù)測(cè) 大型 精密 設(shè)計(jì)合理的注塑模具將受到市場(chǎng)普遍歡迎 據(jù)業(yè)內(nèi)人士分析 未來(lái)我國(guó)模具發(fā) 展趨勢(shì)包括 10 個(gè)方面 1 模具日趨大型化 2 快速經(jīng)濟(jì)模具的前景十分廣闊 3 模具的精度將 越來(lái)越高 4 熱流道模具在塑料模具中的比重也將逐漸提高 5 隨著塑料 成型工藝的不斷改進(jìn)與發(fā)展 氣輔模具及適應(yīng)高壓注塑成型等工藝的模具也將 隨之發(fā)展 6 標(biāo)準(zhǔn)件的應(yīng)用將日益廣泛 7 多功能復(fù)合模具將進(jìn)一步發(fā)展 8 隨著車輛和電機(jī)等產(chǎn)品向輕量化發(fā)展 壓鑄模的比例將不斷提高 同時(shí)對(duì)壓 鑄模的壽命和復(fù)雜程度也將提出越來(lái)越高的要求 9 以塑代鋼 以塑代木的進(jìn) 程進(jìn)一步加快 塑料模具的比例將不斷增大 由于機(jī)械零件的復(fù)雜程度和精度 的不斷提高 對(duì)塑料模具的要求也越來(lái)越高 10 模具技術(shù)含量將不斷提高 塑料模具盡管成為時(shí)下最為誘人的 奶酪 但櫻桃好吃樹(shù)難栽 由于塑 料零配件形狀復(fù)雜 設(shè)計(jì)靈活 對(duì)模具材料 設(shè)計(jì)水平及加工設(shè)備均有較高要 求 并不是人人都可以輕易涉足的 專家認(rèn)為 目前中國(guó)與國(guó)外水平相比還存 在較大差距 眼前需盡快突破制約模具產(chǎn)業(yè)發(fā)展的三大瓶頸 一是塑模企業(yè)應(yīng) 向園區(qū)發(fā)展 加快資源整合 二是加大塑料材料與注塑工藝的研發(fā)力度 三是 模具試模結(jié)果檢驗(yàn)等工裝水平必須盡快跟上 否則塑料模具發(fā)展將受到制約 本次課程研究的創(chuàng)新點(diǎn) 1 設(shè)計(jì)利用齒輪傳動(dòng)等機(jī) 械零件知識(shí) 合理設(shè)計(jì)自動(dòng)脫螺紋機(jī)構(gòu) 2 注塑模具方案的優(yōu)化 已查閱的文獻(xiàn)資料 1 屈華昌 塑料成型工藝與模具設(shè)計(jì) M 北京 高等教育出版社 2007 2 董燕 熊毅 定模推出結(jié)構(gòu)的設(shè)計(jì)與應(yīng)用 M 機(jī)械工業(yè)出版社 2007 8 3 許鶴峰 注射模具設(shè)計(jì)要點(diǎn)與圖例 M 北京 化學(xué)工業(yè)出版社 1999 4 王明強(qiáng) 計(jì)算機(jī)輔助設(shè)計(jì)技術(shù) M 北京 科學(xué)出版社 2002 5 肖 青 注射模設(shè)計(jì) J 北京 科學(xué)出版社 2005 6 李名堯 模具 CAD CAM M 北京 機(jī)械工業(yè)出版社 2004 7 潘寶權(quán) 模具制造工藝 M 北京 機(jī)械工業(yè)出版社 2004 8 張維合 注塑模具設(shè)計(jì)實(shí)用教程 M 北京 化學(xué)工業(yè)出版社 2007 9 李 學(xué) 鋒 塑 料 模 設(shè) 計(jì) 及 制 造 M 北 京 機(jī) 械 工 業(yè) 出 版 社 2002 10 廖念釗 互換性與技術(shù)測(cè)量 M 北京 中國(guó)計(jì)量出版社 2000 11 賈潤(rùn)禮 程志遠(yuǎn)主編 實(shí)用注塑模設(shè)計(jì)手冊(cè) M 北京 中國(guó)輕工業(yè) 出版社 2000 4 12 郭廣思主編 注塑成型技術(shù) M 北京 機(jī)械工業(yè)出版社 2002 4 13 Y Zhang W Hu and Y Rong et al Graph based set up planning and tolerance decomposition for computer aided fixture design International Journal of Production Research J 2001 39 14 3109 3126 現(xiàn)有設(shè)備及實(shí)驗(yàn)條件 計(jì)算機(jī)一臺(tái) 使用軟件為 Pro Engineer5 0 及 Auto CAD2008 Moldflow insight 以上實(shí)驗(yàn)條件可滿足本次畢業(yè)設(shè)計(jì)的要 求 3 實(shí)施方案 進(jìn)度實(shí)施計(jì)劃及預(yù)期提交的畢業(yè)設(shè)計(jì)資料 一 2013 年 12 月 9 日至 2013 年 12 月 22 日 理解消化畢設(shè)任務(wù)書要求并 收集 分析 消化資料文獻(xiàn) 根據(jù)畢設(shè)內(nèi)容完成并交開(kāi)題報(bào)告 二 2014 年 1 月 6 日至 2014 年 1 月 13 日 開(kāi)展調(diào)研 了解塑件結(jié)構(gòu) 對(duì) 原材料進(jìn)行分析 考慮塑件的成型工藝性 模具的總體結(jié)構(gòu)的形式 并完成部分英文摘要翻譯 三 2014 年 3 月 4 日至 2013 年 3 月 31 日 查閱資料 熟悉注射模的結(jié)構(gòu) 及有關(guān)計(jì)算 擬定模具的方案設(shè)計(jì) 總體設(shè)計(jì)及主要零件設(shè)計(jì) 擬定 成型工藝過(guò)程 查閱有關(guān)手冊(cè)確定適宜的工藝參數(shù) 注射機(jī)的選擇及 確定注射設(shè)備及型號(hào)規(guī)格 四 2014 年 4 月 1 日至 2014 年 4 月 6 日 完成設(shè)計(jì)計(jì)算任務(wù) 總體結(jié)構(gòu)的 設(shè)計(jì)和完成總裝配圖及零件圖的設(shè)計(jì) 五 2014 年 4 月 7 日至 2014 年 4 月 21 日 完成設(shè)計(jì) 圖紙繪制任務(wù) 工 藝規(guī)程說(shuō)明書的編寫 六 2014 年 4 月 22 日至 2014 年 5 月 4 日 完善設(shè)計(jì)并完成論文的撰寫 七 2014 年 5 月 5 日至 2014 年 5 月 9 日 修改并打印畢業(yè)論文及整理相關(guān) 資料 交指導(dǎo)老師評(píng)閱 準(zhǔn)備論文答辯 指導(dǎo)教師意見(jiàn) 指導(dǎo)教師 簽字 2013 年 12 月 日 開(kāi)題小組意見(jiàn) 開(kāi)題小組組長(zhǎng) 簽字 2014 年 1 月 日 院 系 部 意見(jiàn) 主管院長(zhǎng) 系 部主任 簽字 2014 年 1 月 日 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 0 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 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 1 頁(yè) 共 38 頁(yè) 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 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 2 頁(yè) 共 38 頁(yè) 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 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 3 頁(yè) 共 38 頁(yè) 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 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 4 頁(yè) 共 38 頁(yè) 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 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 5 頁(yè) 共 38 頁(yè) 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 with the established guidelines for traditional injection molding Afterwards the same approach is adopted in order to detect and diagnose all the potential manufacturability problems in MMM processes This scheme is comprehensive with respect to the state transition model it does not overlook any of the potential problems that arises due to the geometry of the multiple heterogeneous objects Fig 17 shows the state transition diagram for SMM It is clear that five states have to be completed successfully so that an acceptab