計(jì)算機(jī)按鈕注塑模具設(shè)計(jì)【一模四腔】【說(shuō)明書(shū)+CAD】

購(gòu)買(mǎi)設(shè)計(jì)請(qǐng)充值后下載，資源目錄下的文件所見(jiàn)即所得，都可以點(diǎn)開(kāi)預(yù)覽，資料完整，充值下載可得到資源目錄里的所有文件?！咀ⅰ浚篸wg后綴為CAD圖紙，doc,docx為WORD文檔，原稿無(wú)水印，可編輯。具體請(qǐng)見(jiàn)文件預(yù)覽，有不明白之處，可咨詢QQ:12401814 河南機(jī)電高等專(zhuān)科學(xué)校學(xué)生畢業(yè)設(shè)計(jì)（論文）中期檢查表學(xué)生姓名黃林波學(xué) 號(hào)061304339指導(dǎo)教師杜 偉選題情況課題名稱(chēng)計(jì)算機(jī)按鈕注塑模具設(shè)計(jì)難易程度偏難適中偏易工作量較大合理較小符合規(guī)范化的要求任務(wù)書(shū)有無(wú)開(kāi)題報(bào)告有無(wú)外文翻譯質(zhì)量?jī)?yōu)良中差學(xué)習(xí)態(tài)度、出勤情況好一般差工作進(jìn)度快按計(jì)劃進(jìn)行慢中期工作匯報(bào)及解答問(wèn)題情況優(yōu)良中差中期成績(jī)?cè)u(píng)定：所在專(zhuān)業(yè)意見(jiàn)： 負(fù)責(zé)人： 年 月 日 河南機(jī)電高等專(zhuān)科學(xué)校畢業(yè)設(shè)計(jì)任務(wù)書(shū)系 部： 專(zhuān) 業(yè)： 學(xué)生姓名: 學(xué) 號(hào): 設(shè)計(jì)(論文)題目：計(jì)算機(jī)按鈕模具設(shè)計(jì) 起 迄 日 期: 指 導(dǎo) 教 師: 2009年 3 月11 日畢 業(yè) 設(shè) 計(jì)任 務(wù) 書(shū)1本畢業(yè)設(shè)計(jì)課題來(lái)源及應(yīng)達(dá)到的目的：本畢業(yè)設(shè)計(jì)的課題來(lái)源：來(lái)自于工廠工件；目的：設(shè)計(jì)一副合格的計(jì)算機(jī)按鈕注塑模具，能有效的來(lái)注塑出零件，注塑生產(chǎn)出合格的零件。2本畢業(yè)設(shè)計(jì)課題任務(wù)的內(nèi)容和要求（包括原始數(shù)據(jù)、技術(shù)要求、工作要求等）：計(jì)算機(jī)按鈕1.計(jì)算機(jī)按鈕塑件的結(jié)構(gòu)工藝分析；2.注塑模具設(shè)計(jì)，繪制模具總裝圖及全部的工作零件圖；3. 編寫(xiě)設(shè)計(jì)說(shuō)明書(shū)；所在專(zhuān)業(yè)審查意見(jiàn)：負(fù)責(zé)人： 年 月 日系部意見(jiàn)：系領(lǐng)導(dǎo)： 年 月 日河南機(jī)電高等專(zhuān)科學(xué)校畢業(yè)設(shè)計(jì)說(shuō)明書(shū)畢業(yè)設(shè)計(jì)題目：計(jì)算機(jī)按鈕模具設(shè)計(jì)系 部 材 料 工 程 系 專(zhuān) 業(yè) 模具設(shè)計(jì)與制造 班 級(jí) 模 具 063 學(xué)生姓名 黃 林 波 學(xué) 號(hào) 061304339 指導(dǎo)教師 杜 偉 年 月 日河南機(jī)電高等專(zhuān)科學(xué)校材料工程系畢業(yè)設(shè)計(jì)說(shuō)明書(shū)插圖清單1. 塑件圖62. 型腔分布圖83. 分型面圖94. 澆注系統(tǒng)圖105. 模溫調(diào)節(jié)系統(tǒng)圖13摘要熱塑性塑件的注塑，是注射模中最基本的一種，根據(jù)計(jì)算機(jī)按鈕的造型，分析可得，結(jié)構(gòu)比較簡(jiǎn)單，沒(méi)有特殊工藝要求，公差等級(jí)低，易于實(shí)現(xiàn)大批量注塑生產(chǎn)，總體構(gòu)思過(guò)程；首先收集資料，根據(jù)塑件結(jié)構(gòu)工藝性、材料收縮率、注射機(jī)器的規(guī)格、壽命措施、分型面設(shè)置、澆口形式、本廠的加工設(shè)備和技術(shù)、其他相關(guān)資料等。其次是模具結(jié)構(gòu)，型腔、型芯配置及結(jié)構(gòu)、冷卻系統(tǒng)、抽芯機(jī)構(gòu)、推出機(jī)構(gòu)、澆道系統(tǒng)、排氣方式、模具材料、模架形式、標(biāo)準(zhǔn)間的選用。根據(jù)PS的性能，通過(guò)查閱機(jī)械制造手冊(cè)，合理控制塑件的收縮率，確定模具型腔、型芯的設(shè)計(jì)尺寸及強(qiáng)度計(jì)算校核，鎖模力平衡的確定、澆道系統(tǒng)設(shè)計(jì)、澆道和澆口平衡校核；計(jì)算機(jī)按鈕結(jié)構(gòu)不需要側(cè)抽芯機(jī)構(gòu)，抽芯力的計(jì)算；冷卻系統(tǒng)設(shè)計(jì)；推出機(jī)構(gòu)設(shè)計(jì)、計(jì)算推頂力；排氣方式選用。關(guān)鍵字：計(jì)算機(jī)按鈕 澆道系統(tǒng) 分型面 AbstractThermoplastic injection molding of plastic parts, injection mold is the most basic kind of button in accordance with computer modeling, analysis available, relatively simple structure, there is no special process requirements, a low tolerance level, easy to achieve high-volume injection molding production, the overall idea of the process; First of all, the collection of information technology in accordance with the structure of plastic parts, material shrinkage, injection machine specifications, life measures set up surface, gate the form of factory processing equipment and technology, other relevant information. Followed by the mold structure, cavity, core configuration and structure, cooling system, core-pulling mechanism, the introduction agencies, runner system, the exhaust means, mold materials, mold form of the choice of standard room. Reasonable control of the contraction rate of plastic parts to determine the mold cavity, the design of core size and strength check calculation, runner and gate balance check; computer side buttons do not need to draw the structure of the core institutions, the calculation of core-pulling power; cooling system design; the introduction of mechanical design, push the top edge computing; exhaust mode selection. Keywords: plastic parts of the structure of process systems design runner runner system cavity, core河南機(jī)電高等專(zhuān)科學(xué)校畢業(yè)設(shè)計(jì)說(shuō)明書(shū)-計(jì)算機(jī)按鈕模具設(shè)計(jì)1緒 論 目前，我國(guó)注塑模具開(kāi)發(fā)比較晚，技術(shù)與工業(yè)發(fā)達(dá)國(guó)家相比還相當(dāng)?shù)穆浜?，主要原因是我?guó)在注塑成型基礎(chǔ)理論及成形工藝、模具標(biāo)準(zhǔn)化、模具設(shè)計(jì)、模具制造工藝及設(shè)備等方面與工業(yè)發(fā)達(dá)的國(guó)家尚有相當(dāng)大的差距，模具材料比較傳統(tǒng)，在新材料研發(fā)方面及模具加工技術(shù)與西方發(fā)達(dá)國(guó)家相差甚遠(yuǎn)，直接導(dǎo)致我國(guó)模具在壽命、效率、加工精度、生產(chǎn)周期等方面與工業(yè)發(fā)達(dá)國(guó)家的模具相比差距相當(dāng)大。1.1國(guó)內(nèi)模具的現(xiàn)狀和發(fā)展趨勢(shì)國(guó)內(nèi)模具的現(xiàn)狀我國(guó)模具近年來(lái)發(fā)展很快，據(jù)不完全統(tǒng)計(jì)，2003年我國(guó)模具生產(chǎn)廠點(diǎn)約有2萬(wàn)多家，從業(yè)人員約50多萬(wàn)人，2004年模具行業(yè)的發(fā)展保持良好勢(shì)頭，模具企業(yè)總體上訂單充足，任務(wù)飽滿，2004年模具產(chǎn)值530億元。進(jìn)口模具18.13億美元，出口模具4.91億美元，分別比2003年增長(zhǎng)18%、32.4%和45.9%。進(jìn)出口之比2004年為3.69:1，進(jìn)出口相抵后的進(jìn)凈口達(dá)13.2億美元，為凈進(jìn)口量較大的國(guó)家。在2萬(wàn)多家生產(chǎn)廠點(diǎn)中，有一半以上是自產(chǎn)自用的。在模具企業(yè)中，產(chǎn)值過(guò)億元的模具企業(yè)只有20多家，中型企業(yè)幾十家，其余都是小型企業(yè)。近年來(lái)，模具行業(yè)結(jié)構(gòu)調(diào)整和體制改革步伐加快，主要表現(xiàn)為：大型、精密、復(fù)雜、長(zhǎng)壽命中高檔模具及模具標(biāo)準(zhǔn)件發(fā)展速度快于一般模具產(chǎn)品；專(zhuān)業(yè)模具廠數(shù)量增加，能力提高較快；三資及私營(yíng)企業(yè)發(fā)展迅速；國(guó)企股份制改造步伐加快等。雖然說(shuō)我國(guó)模具業(yè)發(fā)展迅速，但遠(yuǎn)遠(yuǎn)不能適應(yīng)國(guó)民經(jīng)濟(jì)發(fā)展的需要。我國(guó)尚存在以下幾方面的不足: 第一，體制不順，基礎(chǔ)薄弱。 “三資”企業(yè)雖然已經(jīng)對(duì)中國(guó)模具工業(yè)的發(fā)展起了積極的推動(dòng)作用，私營(yíng)企業(yè)近年來(lái)發(fā)展較快，國(guó)企改革也在進(jìn)行之中，但總體來(lái)看，體制和機(jī)制尚不適應(yīng)市場(chǎng)經(jīng)濟(jì)，再加上國(guó)內(nèi)模具工業(yè)基礎(chǔ)薄弱，因此，行業(yè)發(fā)展還不盡如人意，特別是總體水平和高新技術(shù)方面。 第二，開(kāi)發(fā)能力較差，經(jīng)濟(jì)效益欠佳.我國(guó)模具企業(yè)技術(shù)人員比例低，水平較低，且不重視產(chǎn)品開(kāi)發(fā)，在市場(chǎng)中經(jīng)常處于被動(dòng)地位。我國(guó)每個(gè)模具職工平均年創(chuàng)造產(chǎn)值約合1萬(wàn)美元，國(guó)外模具工業(yè)發(fā)達(dá)國(guó)家大多是1520萬(wàn)美元，有的高達(dá)2530萬(wàn)美元，與之相對(duì)的是我國(guó)相當(dāng)一部分模具企業(yè)還沿用過(guò)去作坊式管理，真正實(shí)現(xiàn)現(xiàn)代化企業(yè)管理的企業(yè)較少。 第三，工藝裝備水平低，且配套性不好，利用率低雖然國(guó)內(nèi)許多企業(yè)采用了先進(jìn)的加工設(shè)備，但總的來(lái)看裝備水平仍比國(guó)外企業(yè)落后許多，特別是設(shè)備數(shù)控化率和CAD/CAM應(yīng)用覆蓋率要比國(guó)外企業(yè)低得多。由于體制和資金等原因，引進(jìn)設(shè)備不配套，設(shè)備與附配件不配套現(xiàn)象十分普遍，設(shè)備利用率低的問(wèn)題長(zhǎng)期得不到較好解決。裝備水平低，帶來(lái)中國(guó)模具企業(yè)鉗工比例過(guò)高等問(wèn)題。 第四，專(zhuān)業(yè)化、標(biāo)準(zhǔn)化、商品化的程度低、協(xié)作差 由于長(zhǎng)期以來(lái)受“大而全”“小而全”影響，許多模具企業(yè)觀念落后，模具企業(yè)專(zhuān)業(yè)化生產(chǎn)水平低，專(zhuān)業(yè)化分工不細(xì)，商品化程度也低。目前國(guó)內(nèi)每年生產(chǎn)的模具，商品模具只占45%左右，其馀為自產(chǎn)自用。模具企業(yè)之間協(xié)作不好，難以完成較大規(guī)模的模具成套任務(wù)，與國(guó)際水平相比要落后許多。模具標(biāo)準(zhǔn)化水平低，標(biāo)準(zhǔn)件使用覆蓋率低也對(duì)模具質(zhì)量、成本有較大影響，對(duì)模具制造周期影響尤甚。 第五，模具材料及模具相關(guān)技術(shù)落后模具材料性能、質(zhì)量和品種往往會(huì)影響模具質(zhì)量、壽命及成本，國(guó)產(chǎn)模具鋼與國(guó)外進(jìn)口鋼相比，無(wú)論是質(zhì)量還是品種規(guī)格，都有較大差距。塑料、板材、設(shè)備等性能差，也直接影響模具水平的提高。1.2國(guó)內(nèi)模具的發(fā)展趨勢(shì) 巨大的市場(chǎng)需求將推動(dòng)中國(guó)模具的工業(yè)調(diào)整發(fā)展。雖然我國(guó)的模具工業(yè)和技術(shù)在過(guò)去的十多年得到了快速發(fā)展，但與國(guó)外工業(yè)發(fā)達(dá)國(guó)家相比仍存在較大差距，尚不能完全滿足國(guó)民經(jīng)濟(jì)高速發(fā)展的需求。未來(lái)的十年，中國(guó)模具工業(yè)和技術(shù)的主要發(fā)展方向包括以下幾方面: 1） 模具日趨大型化； 2）在模具設(shè)計(jì)制造中廣泛應(yīng)用CAD/CAE/CAM技術(shù)； 3）模具掃描及數(shù)字化系統(tǒng)； 4）在塑料模具中推廣應(yīng)用熱流道技術(shù)、氣輔注射成型和高壓注射成型技術(shù)； 5）提高模具標(biāo)準(zhǔn)化水平和模具標(biāo)準(zhǔn)件的使用率；6）發(fā)展優(yōu)質(zhì)模具材料和先進(jìn)的表面處理技術(shù)；7）模具的精度將越來(lái)越高； 8）模具研磨拋光將自動(dòng)化、智能化； 9）研究和應(yīng)用模具的高速測(cè)量技術(shù)與逆向工程；10）開(kāi)發(fā)新的成形工藝和模具。1.3國(guó)外模具的現(xiàn)狀和發(fā)展趨勢(shì)模具是工業(yè)生產(chǎn)關(guān)鍵的工藝裝備，在電子、建材、汽車(chē)、電機(jī)、電器、儀器儀表、家電和通訊器材等產(chǎn)品中，6080的零部件都要依靠模具成型。用模具生產(chǎn)制作表現(xiàn)出的高效率、低成本、高精度、高一致性和清潔環(huán)保的特性，是其他加工制造方法所無(wú)法替代的。模具生產(chǎn)技術(shù)水平的高低，已成為衡量一個(gè)國(guó)家制造業(yè)水平高低的重要標(biāo)志，并在很大程度上決定著產(chǎn)品的質(zhì)量、效益和新產(chǎn)品的開(kāi)發(fā)能力。近幾年，全球模具市場(chǎng)呈現(xiàn)供不應(yīng)求的局面，世界模具市場(chǎng)年交易總額為600650億美元左右。美國(guó)、日本、法國(guó)、瑞士等國(guó)家年出口模具量約占本國(guó)模具年總產(chǎn)值的三分之一。國(guó)外模具總量中,大型、精密、復(fù)雜、長(zhǎng)壽命模具的比例占到50%以上；國(guó)外模具企業(yè)的組織形式是大而專(zhuān)、大而精。2004年中國(guó)模協(xié)在德國(guó)訪問(wèn)時(shí)，從德國(guó)工、模具行業(yè)組織-德國(guó)機(jī)械制造商聯(lián)合會(huì)（VDMA）工模具協(xié)會(huì)了解到，德國(guó)有模具企業(yè)約5000家。2003年德國(guó)模具產(chǎn)值達(dá)48億歐元。其中（VDMA）會(huì)員模具企業(yè)有90家，這90家骨干模具企業(yè)的產(chǎn)值就占德國(guó)模具產(chǎn)值的90%，可見(jiàn)其規(guī)模效益。 隨著時(shí)代的進(jìn)步和技術(shù)的發(fā)展，國(guó)外的一些掌握和能運(yùn)用新技術(shù)的人才如模具結(jié)構(gòu)設(shè)計(jì)、模具工藝設(shè)計(jì)、高級(jí)鉗工及企業(yè)管理人才，他們的技術(shù)水平比較高故人均產(chǎn)值也較高我國(guó)每個(gè)職工平均每年創(chuàng)造模具產(chǎn)值約合1萬(wàn)美元左右，而國(guó)外模具工業(yè)發(fā)達(dá)國(guó)家大多1520萬(wàn)美元，有的達(dá)到 2530萬(wàn)美元。國(guó)外先進(jìn)國(guó)家模具標(biāo)準(zhǔn)件使用覆蓋率達(dá)70%以上，而我國(guó)才達(dá)到451.4計(jì)算機(jī)按鈕模具的設(shè)計(jì)與制造方面計(jì)算機(jī)模具的設(shè)計(jì)思路熱塑性塑件的注塑，是注射模中最基本的一種，根據(jù)計(jì)算機(jī)按鈕的造型，分析可得，結(jié)構(gòu)比較簡(jiǎn)單，沒(méi)有特殊工藝要求，公差等級(jí)低，易于實(shí)現(xiàn)大批量注塑生產(chǎn)，總體構(gòu)思過(guò)程；首先收集資料，根據(jù)塑件結(jié)構(gòu)工藝性、材料收縮率、注射機(jī)器的規(guī)格、壽命措施、分型面設(shè)置、澆口形式、本廠的加工設(shè)備和技術(shù)、其他相關(guān)資料等。其次是模具結(jié)構(gòu)，型腔、型芯配置及結(jié)構(gòu)、冷卻系統(tǒng)、抽芯機(jī)構(gòu)、推出機(jī)構(gòu)、澆道系統(tǒng)、排氣方式、模具材料、模架形式、標(biāo)準(zhǔn)間的選用。根據(jù)PS的性能，通過(guò)查閱機(jī)械制造手冊(cè)，合理控制塑件的收縮率，確定模具型腔、型芯的設(shè)計(jì)尺寸及強(qiáng)度計(jì)算校核，鎖模力平衡的確定、澆道系統(tǒng)設(shè)計(jì)、澆道和澆口平衡校核；計(jì)算機(jī)按鈕結(jié)構(gòu)不需要側(cè)抽芯機(jī)構(gòu)，抽芯力的計(jì)算；冷卻系統(tǒng)設(shè)計(jì)；推出機(jī)構(gòu)設(shè)計(jì)、計(jì)算推頂力；排氣方式選用。 為了保證達(dá)到塑件要求 為了保證達(dá)到塑件形狀、精度、表面質(zhì)量要求。對(duì)分型面的設(shè)計(jì)方法、拼接縫的位置、抽芯措施、出模斜度數(shù)值、熔接縫的位置、防止出現(xiàn)氣孔和型芯偏斜的方法及型腔、型芯的加工方法。合理地確定型腔為了提高塑件的生產(chǎn)經(jīng)濟(jì)效益，在注塑機(jī)容量能滿足要求的前提下，應(yīng)計(jì)算出較合理的型腔數(shù)。隨型腔的數(shù)量增多，每一個(gè)塑件的模具費(fèi)用有所降低。型腔數(shù)的確定一般與塑件的產(chǎn)量、成型周期、塑件的質(zhì)量、成型設(shè)備、成型費(fèi)用等因素有關(guān)。澆口和澆道設(shè)置 由于澆口對(duì)塑件的形式、尺寸精度、熔接縫位置、二次加工和商品價(jià)格等有較大影響，因而必須首先對(duì)澆道和澆口與具體塑件的成型關(guān)系進(jìn)行探討?，F(xiàn)在可以用注射模CAE的流動(dòng)分析軟件對(duì)澆道和澆口系統(tǒng)進(jìn)行優(yōu)化。這對(duì)保證模具成功地進(jìn)行設(shè)計(jì)有很大作用。模具制造成本估算 在最合理型腔數(shù)的基礎(chǔ)上，設(shè)計(jì)人員根據(jù)塑件的總生產(chǎn)量對(duì)模具成本做出估算，并從選材料、加工難易程度等方面提出降低模具生產(chǎn)成本的措施。 同時(shí)，對(duì)所需的標(biāo)準(zhǔn)件及所采用特種加工方法的種類(lèi)進(jìn)行選擇。 2.塑料工藝與模具設(shè)計(jì)2.1塑件工藝性分析塑件的成型工藝性分析 如上圖1名稱(chēng)：計(jì)算機(jī)按鈕材料：PS2.1.1塑件材料特性PS聚苯乙烯是僅次于聚乙烯和聚氯乙烯的第三大塑料品種，聚苯乙烯無(wú)色無(wú)味、透明、有光澤、無(wú)毒無(wú)味，落地發(fā)出清脆的金屬聲音，密度為1.05g/cm3,聚苯乙烯是目前最理想的高頻絕緣材料，可以與熔融的石英相媲美。聚苯乙烯化學(xué)穩(wěn)定性良好。能耐堿、硫酸、磷酸、10%30%的鹽酸、稀硝酸及其他有機(jī)酸的腐蝕，但不耐硝酸及氧化劑的腐蝕，對(duì)水、乙醇、汽油、植物油及各種鹽溶液的也有足夠的耐腐蝕能力。但耐熱性低，只能在不高的溫度下使用，質(zhì)地硬而脆，塑件由于應(yīng)力而易開(kāi)裂，聚苯乙烯的透明性很好，透光率很高，光學(xué)性能僅次于有機(jī)玻璃，其著色能力優(yōu)良，能染成各種鮮艷的色彩。為了提高聚苯乙烯的耐熱性和降低其脆性，常用改性聚苯乙烯和聚苯乙烯為基體為的共聚物，從而大大擴(kuò)大了聚苯乙烯的用途。2.1.2塑件材料成型性能 聚苯乙烯性脆易裂，易出現(xiàn)裂紋，所以成型塑件脫模斜度不宜過(guò)小，頂出是受力要均勻；熱賬系數(shù)大，塑件中不宜有嵌件，否則會(huì)因兩者熱賬系數(shù)相差太大而開(kāi)裂；由于流動(dòng)性好，應(yīng)注意模具間隙，防止形成飛邊，且模具設(shè)計(jì)中大多用點(diǎn)澆口形式；適宜用高料溫、高模溫、低注射壓力成型，并延長(zhǎng)注射時(shí)間，以防止縮孔及變形，降低應(yīng)力，但料溫過(guò)高容易出現(xiàn)銀絲，料溫低或脫模多，則塑件透明性差。2.1.3.塑件成型工藝參數(shù)的確定查相關(guān)手冊(cè)得到PS（抗沖）塑件的成型工藝參數(shù)：密度： 1.031.05g/cm3;收縮率： 0.3%0.8%;預(yù)熱溫度：8085 預(yù)熱時(shí)間23h；料筒溫度 后段140160噴嘴溫度 160170模具溫度 2060注射壓力 60100Mpa成型時(shí)間 注射時(shí)間4090s,保壓時(shí)間1540s.冷卻時(shí)間2050s3.模具結(jié)構(gòu)方案及模架的選擇3.1模具的基本結(jié)構(gòu)塑件采用注射成型生產(chǎn)。為保證拼縫痕少和好澆注，采用側(cè)澆口澆注系統(tǒng)形式。3.2確定行腔數(shù)目及布置塑件形狀較簡(jiǎn)單，質(zhì)量較小，生產(chǎn)批量較大，所以應(yīng)使用多行腔注射模具。根據(jù)注射機(jī)的額定鎖模力F的要求來(lái)確定型腔數(shù)目n ，即 n式中 F注射機(jī)額定鎖模力（N）P型腔內(nèi)塑料熔體的平均壓力（MPa）A1、A2分別為澆注系統(tǒng)和單個(gè)塑件在模具分型面上的投影面積（mm2）所以模具采用一模四腔，平衡式的型腔布置，模具結(jié)構(gòu)尺寸較小，制造加工方便，生產(chǎn)效率高，塑件成本較低。型腔布置如下圖2 圖23.3選擇分型面塑件分型面的選擇應(yīng)保證塑件的質(zhì)量要求， 分型面位置選擇的總體原則，是能保證塑件的質(zhì)量、便于塑件脫模及簡(jiǎn)化模具的結(jié)構(gòu)，分型面受到塑件在模具中的成型位置、澆注系統(tǒng)設(shè)計(jì)、塑件的結(jié)構(gòu)工藝性及精度、嵌件位置形狀以及推出方法、模具的制造、排氣、操作工藝等多種因素的影響，因此在選擇分型面時(shí)應(yīng)綜合分析比較具體可以從以下方面進(jìn)行選擇。a) 分型面應(yīng)選在塑件外形最大輪廓處。b) 保證塑件的精度要求。c) 便于塑件順利脫模，盡量使塑件開(kāi)模時(shí)留在動(dòng)模一邊。d) 滿足塑件的外觀質(zhì)量要求。e便于模具加工制造。本實(shí)例中塑件的分型面位置如圖3所示：圖33.4確定澆注系統(tǒng)澆口可分為限制性和非限制性澆口兩種。我們將采用限制性澆口。限制性澆口一方面通過(guò)截面積的突然變化，使分流道輸送來(lái)的塑料熔體的流速產(chǎn)生加速度，提高剪切速率，使其成為理想的流動(dòng)狀態(tài)，迅速面均衡地充滿型腔，另一方面改善塑料熔體進(jìn)入型腔時(shí)的流動(dòng)特性，調(diào)節(jié)澆口尺寸，可使多型腔同時(shí)充滿，可控制填充時(shí)間、冷卻時(shí)間及塑件表面質(zhì)量，同時(shí)還起著封閉型腔防止塑料熔體倒流，并便于澆口凝料與塑件分離的作用。由公式：b=(0.60.9)/30 T=(0.60.9)可以求出澆口的各值：寬度b為1.6、澆口的厚度為t為0.2、澆口的長(zhǎng)度取1.0mm.分流道截面采用半圓截面流，其半徑為3mm，主流道為圓錐形。上端直徑為注射機(jī)噴嘴相配合，下端直為8mm.澆口的形式如下圖4：3.4.1澆口位置的選擇模具設(shè)計(jì)時(shí)，澆口的位置及尺寸要求比較嚴(yán)格，初步試模后還需進(jìn)一步修改澆口尺寸，無(wú)論采用何種澆口，其開(kāi)設(shè)位置對(duì)塑件成型性能及質(zhì)量影響很大，因此合理選擇澆口的開(kāi)設(shè)位置是提高質(zhì)量的重要環(huán)節(jié)，同時(shí)澆口位置的不同還影響模具結(jié)構(gòu)?？傊顾芗哂辛己玫男阅芘c外表，一定要認(rèn)真考慮澆口位置的選擇，通常要考慮以下幾項(xiàng)原則：1) 盡量縮短流動(dòng)距離。2) 澆口應(yīng)開(kāi)設(shè)在塑件壁厚最大處。3) 必須盡量減少熔接痕。4) 應(yīng)有利于型腔中氣體排出。5) 考慮分子定向影響。6) 避免產(chǎn)生噴射和蠕動(dòng)。7) 澆口處避免彎曲和受沖擊載荷。8) 注意對(duì)外觀質(zhì)量的影響這里我們選在制件的側(cè)面?？梢苑奖氵M(jìn)料。3.5成型零件結(jié)構(gòu)設(shè)計(jì)凹模采用整體嵌入式凹模，可以節(jié)約模具成本，也可方便以后的更換。這了防止嵌入件松動(dòng)和旋轉(zhuǎn)才用防脫胎吊緊螺釘。型芯由動(dòng)模板上的孔固定，型芯與推件板采用錐面配合以保證配合緊密，離止塑件產(chǎn)生飛。另外，錐面配合可以減小推件板在推出制件運(yùn)動(dòng)時(shí)與型芯的磨損。3.6推出方式由塑件形狀為圓殼形而且壁厚較薄，使用推桿出容易在塑件上留下推出痕跡，不宜采用。所以采用推件板推出機(jī)構(gòu)完成塑件的推出，這種方法結(jié)構(gòu)簡(jiǎn)單，推出力均勻，塑件在推出時(shí)變形小，推出可靠。推件板設(shè)計(jì)的要點(diǎn)a) 推件板與型芯應(yīng)呈310的推面配合，以減少遠(yuǎn)動(dòng)摩擦，并起輔助定位以防止推件板偏心而溢料；推件板與型芯側(cè)壁之間應(yīng)有0.200.25mm的間隙，以防止兩者間的擦傷而或卡死，推件板與型芯間的配合間隙以不產(chǎn)生塑料溢料為準(zhǔn)，塑料的最大溢料間隙可查表，推件板與型芯相配合的表面粗糙度可以取Ra0.80.4m。b) 推件板可用經(jīng)調(diào)質(zhì)處理的45鋼制造，對(duì)要求比較高的模具，也可以采用T8或T10等材料，并淬硬到5355HRC，有時(shí)也可以在推件板上鑲淬火襯套以延長(zhǎng)壽命。c) 當(dāng)用推件板脫出元通孔的大型深腔殼體類(lèi)塑件時(shí)，應(yīng)在型芯上增設(shè)一個(gè)進(jìn)氣裝置，以避免塑件脫模時(shí)在型芯與塑件間形成真空。d) 推件板復(fù)位后，在推板與動(dòng)模座板間應(yīng)留有為保護(hù)模具的23mm空隙。開(kāi)模行程與推出機(jī)構(gòu)的校核對(duì)雙分型面注射模，開(kāi)模行程為：S機(jī)H=H1+H2+a+(510)mm式中，H1為塑件推出距離 H2包括澆注系統(tǒng)在內(nèi)的塑件高度 S機(jī)注射機(jī)移動(dòng)板最大的行程 H所需開(kāi)模行程 a中間板與定模分開(kāi)距離其開(kāi)模行程H應(yīng)小于動(dòng)模移動(dòng)板與定模固定板之間的最大距離S0減去模具厚度H1，即，HS0-H1對(duì)于雙分型面注射模HS0-3.7確定模溫調(diào)節(jié)系統(tǒng)一般生產(chǎn)ABS材料塑件的注射模具不需要加熱。模具的冷分兩部分，一部分是凹模的冷卻，一部分是型芯的冷卻。凹模冷卻回路形式采用直流式冷卻回路，該回路是由定模板上的四條直徑為10mm的冷卻水道。如下圖5： 模溫調(diào)節(jié)系統(tǒng)圖5定模板板冷卻回路形式采用隔板式管道冷卻回路。3.8確定排氣方式利用分型面間隙排氣就可以4.選擇成型設(shè)備并校核有關(guān)參數(shù)4.1計(jì)算塑件的體積 V=3026.4034.2計(jì)算塑件的質(zhì)量 計(jì)算塑件的質(zhì)量是為了選擇注塑機(jī)及確定模具型腔數(shù)。根據(jù)有關(guān)手冊(cè)查的=1.05g/3所以，塑件的質(zhì)量為 W= V =3026.401.0510-3=3.18g4.3有關(guān)參數(shù)根據(jù)塑件形狀及尺寸采用一模四件的模具結(jié)構(gòu)，考慮外形尺寸、對(duì)塑件原材料的分析及注射是所需的壓力情況，參考模具設(shè)計(jì)手冊(cè)柱塞式注射機(jī)：SZSZ630/3500 其有關(guān)參數(shù)如下最大注射量 634/cm3注射壓力 150MP鎖模力 3500/KN最大模具厚度 500/mm移模行程式 490/mm拉桿內(nèi)間距 545mmX485mm噴嘴球半徑 18mm噴嘴口孔徑 4mm 該模具外形尺寸為300mm*500mm*450mm,小于注射機(jī)拉桿間距和最大模具厚度，可以方便安裝在注射機(jī)上。經(jīng)校核注射機(jī)的最大注射量、注射壓力、鎖模力和開(kāi)模行程等參數(shù)均能滿足使用要求，故可用。5.模具設(shè)計(jì)的有關(guān)計(jì)算5.1成型零件工作尺寸的計(jì)算取ABS的平均收縮率0.6%，塑件未注公差按照MT5級(jí)精度公差選取，因而各尺寸為：15-00.38 3+0.230400.1 11 -00.74 3.50.01 90.025.1.1型腔內(nèi)形尺寸： DM=D+DS-/2-Z/2 0+zDM1=15+15*0.6-0.38/2-0.38/6 0+0.38/6 =12.990+0.06DM1=3+3*0.6-0.5/2-0.5/6 0+0.5/6 =4.470+0.085.1.2型芯外形尺寸的計(jì)算 dM=d+ds+/2+Z/2 0dM=11+11*0.6+0.1+0.05 -00.05 =17.75-00.05dM2=3+3*0.6+0.25+0.25/3 -00.08 =4.97 -00.085.1.3型腔深度尺寸計(jì)算： HM1=H+HS-/2-Z/2 0+zHM1=9+9*0.6-0.38/2-0.38/6 0+z =14.150+0.06HM1=3.5+3.5*0.6-0.64/2-0.64/6 0+z =4.170+0.105.1.4型芯高度尺寸計(jì)算 hm=h+hs+/2+Z/2 0hm=4+4*0.6+0.38/2+0.38/6 -0.10 =6.65-00.065.1.5型腔中心尺寸：LM=L+LSZ/2LM=20+20*0.60.05 =32 0.056.模具的試模與修模試模中所獲得的樣件是對(duì)模具整體質(zhì)量的一個(gè)全面反映。以檢驗(yàn)樣件來(lái)修正和驗(yàn)收模具，是塑料模具這種特殊產(chǎn)品的特殊性。首先，在初次試模中我們最常遇到的問(wèn)題是根本得不到完整的樣件。常因塑件被粘附于模腔內(nèi)，或型芯上，甚至因流道粘著制品被損壞。這是試模首先應(yīng)當(dāng)解決的問(wèn)題。6.1塑件粘著模腔制品粘著在模腔上，是指塑件在模具開(kāi)啟后，與設(shè)計(jì)意圖相反，離開(kāi)型芯一側(cè)，滯留于模腔內(nèi)，致使脫模機(jī)構(gòu)失效，制品無(wú)法取出的一種反常現(xiàn)象。其主要原因是：1） 注射壓力過(guò)高，或者注射保壓壓力過(guò)高。2） 注射保壓和注射高壓時(shí)間過(guò)長(zhǎng)，造成過(guò)量充模。3） 冷卻時(shí)間過(guò)短，物料未能固化。4) 檢查工件的加工精度是否達(dá)標(biāo)或增加脫模試劑6.2粘著模芯1） 注射壓力和保壓壓力過(guò)高或時(shí)間過(guò)長(zhǎng)而造成過(guò)量充模，尤其成型芯上有加強(qiáng)筋槽的制品，情況更為明顯。2） 冷卻時(shí)間過(guò)長(zhǎng)，制件在模芯上收縮量過(guò)大。3） 模腔溫度過(guò)高，使制件在設(shè)定溫度內(nèi)不能充分固化。4) 檢查脫模斜度是否夠用5) 排氣槽是否通暢6) 塑件工藝性差，及時(shí)改進(jìn)塑件工藝性6.3 粘著主流道1） 閉模時(shí)間太短，使主流道物料來(lái)不及充分收縮。2） 料道徑向尺寸相對(duì)制品壁厚過(guò)大，冷卻時(shí)間內(nèi)無(wú)法完成料道物料的固化。3） 主流道襯套區(qū)域溫度過(guò)高，無(wú)冷卻控制，不允許物料充分收縮。一旦發(fā)生上述情況，首先要設(shè)法將制品取出模腔（芯），不惜破壞制件，保護(hù)模具成型部位不受損傷。仔細(xì)查找不合理粘模發(fā)生的原因，一方面要對(duì)注射工藝進(jìn)行合理調(diào)整；另一方面要對(duì)模具成型部位進(jìn)行現(xiàn)場(chǎng)修正，直到認(rèn)為達(dá)到要求，方可進(jìn)行二次注射。6.4成型缺陷當(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(jiàn)的成型制品主要缺陷及其改進(jìn)的措施進(jìn)行分析。6.4.1 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(jiàn)。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。6.4.2溢邊（毛刺、飛邊、拼鋒）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. 注射壓力大，及時(shí)調(diào)整注射壓力6.4.3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(chēng)尺寸。 c. 加料量過(guò)多或過(guò)少采用定量加料總結(jié)當(dāng)老師出題的那天，就開(kāi)始在想，這模具怎么辦，心里沒(méi)有一點(diǎn)兒底，一片空白，經(jīng)過(guò)大量的查閱資料，與動(dòng)手畫(huà)圖后，才找到點(diǎn)信心。幾次給老師的查閱，和聊天中，了解了設(shè)計(jì)的流程，怎么樣去完成任務(wù)書(shū)，和在設(shè)計(jì)中要注意的問(wèn)題與解決方案，比如，成型零件的結(jié)構(gòu)設(shè)計(jì)中，凹模采用組合式可以簡(jiǎn)化復(fù)雜的機(jī)加工藝，有利于模具成型零件的熱處理和模具的修復(fù)；圖紙的明細(xì)表中應(yīng)有零件的材料、規(guī)格、數(shù)量、備注等一些內(nèi)容；開(kāi)模次序的確定,并采用相應(yīng)機(jī)構(gòu)來(lái)確保這種開(kāi)模次序的實(shí)現(xiàn)。回過(guò)頭來(lái)看我的設(shè)計(jì)，唉，真的是如此的簡(jiǎn)單，如果要在工作崗位上，相信這些就不值得一提了，人生只有在慢慢的進(jìn)步過(guò)程中才會(huì)長(zhǎng)大，假如你不做這個(gè)設(shè)計(jì)，從而現(xiàn)在收獲還是從零開(kāi)始，或許哪天自己真真踏上這設(shè)計(jì)的旅程，肯定來(lái)不急后悔。在這我忠心感謝老師現(xiàn)場(chǎng)的指導(dǎo)與遠(yuǎn)程協(xié)助。致謝首先向我的指導(dǎo)老師杜偉致謝，他仔細(xì)審閱了本文的全部?jī)?nèi)容并對(duì)我的畢業(yè)設(shè)計(jì)思路提出了許多改進(jìn)性的建議。杜偉老師扎實(shí)的知識(shí)，誠(chéng)懇的為人，對(duì)工作認(rèn)真負(fù)責(zé)的態(tài)度，讓我永難忘記。設(shè)計(jì)中對(duì)我嚴(yán)格的要求，自我認(rèn)為甚至是苛刻的要求。雖然讓我很頭痛但使我受益匪淺，真的感激他。感謝母校河南機(jī)電高等專(zhuān)科學(xué)校，感謝諸位恩師的的辛勤培育之恩！感謝材料工程系給我提供的良好學(xué)習(xí)及實(shí)踐環(huán)境，使我學(xué)到了許多新的知識(shí)，掌握了一定的操作技能。感謝和我在一起進(jìn)行畢業(yè)設(shè)計(jì)研究的同窗翁坤同學(xué)，我們做的是同一個(gè)制件但用的卻是不同的方案和他在一起討論、研究使我受益非淺。也認(rèn)識(shí)到了自己的差距和不足。寫(xiě)到最后，我非常慶幸在三年的的學(xué)習(xí)和生活中認(rèn)識(shí)了很多可欽可敬的老師和可愛(ài)的的同學(xué)，并感激師友的教誨和幫助！寫(xiě)到這里突然有一種離別的傷痛，我想說(shuō)一聲老師我們畢業(yè)了，我們也會(huì)努力地。同學(xué)們海闊憑魚(yú)躍，天高任鳥(niǎo)飛，鳥(niǎo)不飛天高在哪里？同學(xué)們讓我們展翅高飛吧！參考文獻(xiàn)：1.楊占堯，塑料注射模結(jié)構(gòu)與設(shè)計(jì)，高等教育出版社，20082.蔣繼宏,王效岳編繪.注塑模具典型結(jié)構(gòu)100例. 北京: 化學(xué)工業(yè)出版社,20003.屈華昌主編. 塑料成型工藝與模具設(shè)計(jì), 北京: 機(jī)械工業(yè)出版社, 19984.賈潤(rùn)禮, 程志遠(yuǎn)主編. 實(shí)用注塑模設(shè)計(jì)手冊(cè). 北京: 中國(guó)輕工業(yè)出版社,20005.付宏生, 劉京華編著. 注塑制品與注塑模具設(shè)計(jì). 北京: 化學(xué)工業(yè)出版社, 20036.黃虹主編. 塑料成型加工與模具. 北京; 化學(xué)工業(yè)出版社,20027.許發(fā)樾主編.模具常用機(jī)構(gòu)設(shè)計(jì). 北京; 機(jī)械工業(yè)出版社20038.許鶴峰,陳言秋編著. 注塑模具設(shè)計(jì)要點(diǎn)與圖例, 北京 :化學(xué)工業(yè)出版社,1999第 21 頁(yè) 共 21 頁(yè)第 22 頁(yè) 共 23 頁(yè) 桂林電子科技大學(xué)畢業(yè)設(shè)計(jì)用紙 Automated Assembly Modelling for Plastic Injection Moulds An injection mould is a mechanical assembly that consists of product-dependent parts and product-independent parts. This paper addresses the two key issues of assembly modelling for injection moulds, namely, representing an injection mould assembly in a computer and determining the position and orientation of a product-independent part in an assembly. A feature-based and object-oriented representation is proposed to represent the hierarchical assembly of injection moulds. This representation requires and permits a designer to think beyond the mere shape of a part and state explicitly what portions of a part are important and why. Thus, it provides an opportunity for designers to design for assembly (DFA). A simplified symbolic geometric approach is also presented to infer the configurations of assembly objects in an assembly according to the mating conditions. Based on the proposed representation and the simplified symbolic geometric approach, automatic assembly modelling is further discussed.Keywords: Assembly modelling; Feature-based; Injection moulds; Object-oriented1. Introduction Injection moulding is the most important process for manufacturing plastic moulded products. The necessary equipment consists of two main elements, the injection moulding machine and the injection mould. The injection moulding machines used today are so-called universal machines, onto which various moulds for plastic parts with different geometries can be mounted, within certain dimension limits, but the injection mould design has to change with plastic products. For different moulding geometries, different mould configurations are usually necessary. The primary task of an injection mould is to shape the molten material into the final shape of the plastic product. This task is fulfilled by the cavity system that consists of core, cavity, inserts, and slider/lifter heads. The geometrical shapes and sizes of a cavity system are determined directly by the plastic moulded product, so all components of a cavity system are called product-dependent parts. (Hereinafter, product refers to a plastic moulded product, part refers to the component of an injection mould.) Besides the primary task of shaping the product, an injection mould has also to fulfil a number oftasks such as the distribution of melt, cooling the molten material, ejection of the moulded product, transmitting motion, guiding, and aligning the mould halves. The functional parts to fulfil these tasks are usually similar in structure and geometrical shape for different injection moulds. Their structures and geometrical shapes are independent of the plastic moulded products, but their sizes can be changed according to the plastic products. Therefore, it can be concluded that an injection mould is actually a mechanical assembly that consists of product-dependent parts and product-independent parts. Figure 1 shows the assembly structure of an injection mould. The design of a product-dependent part is based on extracting the geometry from the plastic product. In recent years, CAD/CAM technology has been successfully used to help mould designers to design the product-dependent parts. TheFig. 1. Assembly structure of an injection mouldautomatic generation of the geometrical shape for a product-dependent part from the plastic product has also attracted a lot of research interest 1,2. However, little work has been carried out on the assembly modelling of injection moulds, although it is as important as the design of product-dependent parts. The mould industry is facing the following two difficulties when use a CAD system to design product-independent parts and the whole assembly of an injection mould. First, there are usually around one hundred product-independent parts in a mould set, and these parts are associated with each other with different kinds of constraints. It is time-consuming for the designer to orient and position the components in an assembly. Secondly, while mould designers, most of the time, think on the level of real-world objects, such as screws, plates, and pins, the CAD system uses a totally different level of geometrical objects. As a result, high-level object-oriented ideas have to be translated to low-level CAD entities such as lines, surfaces, or solids. Therefore, it is necessary to develop an automatic assembly modelling system for injection moulds to solve these two problems. In this paper, we address the following two key issues for automatic assembly modelling: representing a product-independent part and a mould assembly in a computer; and determining the position and orientation of a component part in an assembly.This paper gives a brief review of related research in assembly modelling, and presents an integrated representation for the injection mould assembly. A simplified geometric symbolic method is proposed to determine the position and orientation of a part in the mould assembly. An example of automatic assembly modelling of an injection mould is illustrated.2. Related Research Assembly modelling has been the subject of research in diverse fields, such as, kinematics, AI, and geometric modelling. Lib-ardi et al. 3 compiled a research review of assembly modelling. They reported that many researchers had used graph structures to model assembly topology. In this graph scheme, the components are represented by nodes, and transformation matrices are attached to arcs. However, the transformation matrices are not coupled together, which seriously affects the transformation procedure, i.e. if a subassembly is moved, all its constituent parts do not move correspondingly. Lee and Gossard 4 developed a system that supported a hierarchical assembly data structure containing more basic information about assemblies such as “mating feature” between the components. The transformation matrices are derived automatically from the associations of virtual links, but this hierarchical topology model represents only “part-of” relations effectively.Automatically inferring the configuration of components in an assembly means that designers can avoid specifying the transformation matrices directly. Moreover, the position of a component will change whenever the size and position of its reference component are modified. There exist three techniques to infer the position and orientation of a component in the assembly: iterative numerical technique, symbolic algebraic technique, and symbolic geometric technique. Lee and Gossard 5 proposed an iterative numerical technique to compute the location and orientation of each component from the spatial relationships. Their method consists of three steps: generation of the constraint equations, reducing the number of equations, and solving the equations. There are 16 equations for “against” condition, 18 equations for “fit” condition, 6 property equations for each matrix, and 2 additional equations for a rotational part. Usually the number of equations exceeds the number of variables, so a method must be devised to remove the redundant equations. The NewtonRaphson iteration algorithm is used to solve the equations. This technique has two disadvantages: first, the solution is heavily dependent on the initial solution; secondly, the iterative numerical technique cannot distinguish between different roots in the solution space. Therefore, it is possible, in a purely spatial relationship problem, that amathematically valid, but physically unfeasible, solution can be obtained.Ambler and Popplestone 6 suggested a method of computing the required rotation and translation for each component to satisfy the spatial relationships between the components in an assembly. Six variables (three translations and three rotations) for each component are solved to be consistent with the spatial relationships. This method requires a vast amount of programming and computation to rewrite related equations in a solvable format. Also, it does not guarantee a solution every time, especially when the equation cannot be rewritten in solvable forms. Kramer 7 developed a symbolic geometric approach for determining the positions and orientations of rigid bodies that satisfy a set of geometric constraints. Reasoning about the geometric bodies is performed symbolically by generating a sequence of actions to satisfy each constraint incrementally, which results in the reduction of the objects available degrees of freedom (DOF). The fundamental reference entity used by Kramer is called a “marker”, that is a point and two orthogonal axes. Seven constraints (coincident, in-line, in-plane, parallelFz, offsetFz, offsetFx and helical) between markers are defined. For a problem involving a single object and constraints between markers on that body, and markers which have invariant attributes, action analysis 7 is used to obtain a solution. Actionanalysis decides the final configuration of a geometric object, step by step. At each step in solving the object configuration, degrees of freedom analysis decides what action will satisfy one of the bodys as yet unsatisfied constraints, given the available degrees of freedom. It then calculates how that action further reduces the bodys degrees of freedom. At the end of each step, one appropriate action is added to the metaphorical assembly plan. According to Shah and Rogers 8, Kramers work represents the most significant development for assembly modelling. This symbolic geometric approach can locate all solutions to constraint conditions, and is computationally attractive compared to an iterative technique, but to implement this method, a large amount of programming is required. Although many researchers have been actively involved in assembly modelling, little literature has been reported on feature based assembly modelling for injection mould design.Kruth et al. 9 developed a design support system for an injection mould. Their system supported the assembly design for injection moulds through high-level functional mould objects (components and features). Because their system was based on AutoCAD, it could only accommodate wire-frame and simple solid models.3. Representation of Injection Mould Assemblies The two key issues of automated assembly modelling for injection moulds are, representing a mould assembly in com- puters, and determining the position and orientation of a product-independent part in the assembly. In this section, we present an object-oriented and feature-based representation for assemblies of injection moulds. The representation of assemblies in a computer involves structural and spatial relationships between individual parts. Such a representation must support the construction of an assembly from all the given parts, changes in the relative positioning of parts, and manipulation of the assembly as a whole. Moreover, the representations of assemblies must meet the following requirements from designers: 1. It should be possible to have high-level objects ready to use while mould designers think on the level of real-world objects. 2. The representation of assemblies should encapsulate operational functions to automate routine processes such as pocketing and interference checks. To meet these requirements, a feature-based and object-oriented hierarchical model is proposed to represent injection moulds. An assembly may be divided into subassemblies, which in turn consists of subassemblies and/or individual components. Thus, a hierarchical model is most appropriate for representing the structural relations between components. A hierarchy implies a definite assembly sequence. In addition, a hierarchical model can provide an explicit representation of the dependency of the position of one part on another. Feature-based design 10 allows designers to work at a somewhat higher level of abstraction than that possible with the direct use of solid modellers. Geometric features are instanced, sized, and located quickly by the user by specifying a minimum set of parameters, while the feature modeller works out the details. Also, it is easy to make design changes because of the associativities between geometric entities maintained in the data structure of feature modellers. Without features, designers have to be concerned with all the details of geometric construction procedures required by solid modellers, and design changes have to be strictly specified for every entity affected by the change. Moreover, the feature-based representation will provide high-level assembly objects for designers to use. For example, while mould designers think on the level of a real- world object, e.g. a counterbore hole, a feature object of a counterbore hole will be ready in the computer for use. Object-oriented modelling 11,12 is a new way of thinking about problems using models organised around real-world concepts. The fundamental entity is the object, which combines both data structures and behaviour in a single entity. Object-oriented models are useful for understanding problems and designing programs and databases. In addition, the object- oriented representation of assemblies makes it easy for a“child” object to inherit information from its “parent”. Figure 2 shows the feature-based and object-oriented hier- archical representation of an injection mould. The representation is a hierarchical structure at multiple levels of abstraction, from low-level geometric entities (form feature) to high-level subassemblies. The items enclosed in the boxes represent “assembly objects” (SUBFAs, PARTs and FFs); the solid lines represent “part-of” relation; and the dashed lines represent other relationships. Subassembly (SUBFA) consists of parts (PARTs). A part can be thought of as an “assembly” of form features (FFs). The representation combines the strengths of a feature-based geometric model with those of object-oriented models. It not only contains the “part-of” relations between the parent object and the child object, but also includes a richer set of structural relations and a group of operational functions for assembly objects. In Section 3.1, there is further discussion on the definition of an assembly object, and detailed relations between assembly objects are presented in Section 3.2Fig. 2. Feature-based, object-oriented hierarchical representation3.1 Definition of Assembly Objects In our work, an assembly object, O, is defined as a unique, identifiable entity in the following form: O = (Oid, A, M, R) (1)Where: Oid is a unique identifier of an assembly object (O). A is a set of three-tuples, (t, a, v). Each a is called an attribute of O, associated with each attribute is a type,t, and a value, v. M is a set of tuples, (m, tc1, tc2, %, tcn, tc). Each element of M is a function that uniquely identifies a method. The symbol m represents a method name; and methods define operations on objects. The symbol tci(i= 1, 2, %, n) specifies the argument type and tc specifies the returned value type. R is a set of relationships among O and other assembly objects. There are six types of basic relationships between assembly objects, i.e. Part-of, SR, SC, DOF, Lts, and Fit.Table 1 shows an assembly object of injection moulds, e.g. ejector. The ejector in Table 1 is formally specified as: (ejector-pinF1, (string, purpose, ejecting moulding), (string, material, nitride steel), (string, catalogFno, THX), (checkFinterference(), boolean), (pocketFplate(), boolean), (part-of ejectionFsys), (SR Align EBFplate), (DOF Tx, Ty). In this example, purpose, material and catalogFno are attributes with a data type of string; checkFinterference and pocketFplate are member functions; and Part-of, SR and DOF are relationships.3.2 Assembly Relationships There are six types of basic relationships between assembly objects, Part-of, SR, SC, DOF, Lts, and Fit. Part-of An assembly object belongs to its ancestor object.SR Spatial relations: explicitly specify the positions and orientations of assembly objects in an assembly. For a component part, its spatial relationship is derived from spatial constraints (SC).SC Spatial constraints: implicitly locate a component part with respect to the other parts.DOF Degrees of freedom: are allowable translational/ rotational directions of motion after assembly, with or without limits.Lts Motion limits: because of obstructions/interferences, the DOF may have unilateral or bilateral limits.Fit Size constraint: is applied to dimensions, in order to maintain a given class of fit. Among all the elements of an assembly object, the relation-ships are most important for assembly design. The relationships between assembly objects will not only determine the position of objects in an assembly, but also maintain the associativities between assembly objects. In the following sub-sections, we will illustrate the relationships at the same assembly level with the help of examples.3.2.1 Relationships Between Form Features Mould design, in essence, is a mental process; mould designers most of the time think on the level of real-world objects such as plates, screws, grooves, chamfers, and counter-bore holes. Therefore, it is necessary to build the geometric models of all product-independent parts from form features. The mould designer can easily change the size and shape of a part, because of the relations between form features maintained in the part representation. Figure 3(a) shows a plate with a counter-bore hole. This part is defined by two form features, i.e. a block and a counter-bore hole. The counter-bore hole (FF2) is placed with reference to the block feature FF1, using their local coordinates F2and F1, respectively. Equations (2)(5) show the spatial relationships between the counter-bore hole (FF2) and the block feature (FF1). For form features, there is no spatial constraint between them, so the spatial relationships are specified directly by the designer. The detailed assembly relationships between two form features are defined as follows: Fig. 3. Assembly relationships. F2k= F1k (4) r2F= r1F+ b22*F1j+ AF1*F1i (5) DOF: ObjFhasF1FRDOF(FF2, F2j) The counter-bore feature can rotate about axis F2j. LTs(FF2, FF1): AF1, b11 0.5*b21 (6) Fit (FF2, FF1): b22= b12 (7)Where F and r are the orientation and position vectors of features. F1= (F1i, F1j, F1k), F2= (F2i, F2j, F2k). bij is the dimension of form features, Subscript i ifeature number, j is dimension number. AF1is the dimension between form features.Equations (2)(7) present the relationships between the form feature FF1 and FF2. These relationships thus determine the position and orientation of a form feature in the part. Taking the part as an assembly, the form feature can be considered as “components” of the assembly. The choice of form features is based on the shape characteristics of product-independent parts. Because the form features provided by the Unigraphics CAD/CAM system 13 can meet the shape requirements of parts for injection moulds and the spatial relationships between form features are also maintained, we choose them to build the required part models. In addition to the spatial relationships, we must record LTs, Fits relationships for form features, which are essential to c