唧筒注塑模模具設(shè)計(jì)【一模一腔】【說(shuō)明書(shū)+CAD】,一模一腔,說(shuō)明書(shū)+CAD,唧筒注塑模模具設(shè)計(jì)【一模一腔】【說(shuō)明書(shū)+CAD】,唧筒,注塑,模具設(shè)計(jì),說(shuō)明書(shū),仿單,cad 目 錄 目 錄 1 前 言 2 第一章 導(dǎo)滑壓板工作零件結(jié)構(gòu)工藝性分析 5 第一節(jié) 熟悉和分析導(dǎo)滑壓板制定工藝規(guī)程的主要依據(jù) 5 第二節(jié) 導(dǎo)滑壓板零件的結(jié)構(gòu)工藝性分析 7 第二章 設(shè)備與工藝裝備的選擇 10 第一節(jié) 設(shè)備的確定 10 第二節(jié) 機(jī)床的選用 13 第三章 確定毛坯的類型及其制造加工方法 14 第四章 擬定導(dǎo)滑壓板工藝路線 16 第五章 確定導(dǎo)滑壓板工序的加工余量 20 第一節(jié) 確定導(dǎo)滑壓板加工余量的方法 20 第二節(jié) 確定主要工序的技術(shù)要求及檢驗(yàn)方法 21 第三節(jié) 檢驗(yàn) 22 第六章 確定導(dǎo)滑壓板工序的切削用量和時(shí)間定額 22 第七章 導(dǎo)滑壓板加工的技術(shù)文件 23 第八章 參考文獻(xiàn) 25 前 言 本工藝規(guī)程主要將學(xué)生學(xué)到的理論與實(shí)際相結(jié)合，突出模具設(shè)計(jì)基礎(chǔ)的結(jié)合運(yùn)用，以提供更準(zhǔn)確，實(shí)用，方便的計(jì)算方法，正確掌握并運(yùn)用塑模工藝參數(shù)和模具工作部分的幾何形狀和尺寸的綜合應(yīng)用，提高自我的模具設(shè)計(jì)與制造能力的綜合應(yīng)用。 在以后的生產(chǎn)生活中，研究和推廣新工藝，新技術(shù)提高模具在生產(chǎn)生活中的應(yīng)用，并進(jìn)一步提高模具技術(shù)水平。 塑料制件之所以能夠在工業(yè)生產(chǎn)中得到廣泛應(yīng)用，是由于它們本身具有的一系列特殊優(yōu)點(diǎn)所決定的。塑料謎底小，質(zhì)量輕。這就是“以塑代鋼”的明顯優(yōu)點(diǎn)所在。塑料的比強(qiáng)度高，絕緣性能好，介電損耗低，所以塑料是現(xiàn)代電工行業(yè)和電器行業(yè)中不可缺少的原材料。塑料的化學(xué)穩(wěn)定性最高，減磨耐磨性能好。此外，塑料的減振和隔音性能也很好。許多塑料還具有透光性能和絕熱性能以及防水，防透氣和防輻射等特殊性能。因此，塑料已成為各行各業(yè)中不可缺少的一種重要材料。需求量的日益增加，這些產(chǎn)品的更新?lián)Q代的周期愈來(lái)愈短。因此對(duì)塑料的品種，產(chǎn)量和質(zhì)量都提出了越來(lái)越高的要求。 因此，本工藝規(guī)程課程設(shè)計(jì)說(shuō)明書(shū)具有以下的優(yōu)點(diǎn)： 一、本工藝規(guī)程課程設(shè)計(jì)說(shuō)明書(shū)本課程設(shè)計(jì)計(jì)算說(shuō)明書(shū)結(jié)合了塑料模具圖冊(cè)的若干圖列，并突出性和實(shí)用性的對(duì)每一幅模具進(jìn)行詳細(xì)的對(duì)比分析與學(xué)習(xí)，然后再結(jié)合相應(yīng)的實(shí)踐知識(shí)進(jìn)行的設(shè)計(jì)計(jì)算。 二、本工藝規(guī)程設(shè)計(jì)說(shuō)明書(shū)本課程設(shè)計(jì)計(jì)算說(shuō)明書(shū)主要闡述了塑料注射模具注射成形的整個(gè)設(shè)計(jì)計(jì)算過(guò)程，以及每一個(gè)組成部的設(shè)計(jì)計(jì)算，同時(shí)較為嚴(yán)密合理的進(jìn)行相應(yīng)的校核與驗(yàn)證。 三、本工藝規(guī)程課程設(shè)計(jì)說(shuō)明書(shū)本課程設(shè)計(jì)計(jì)算說(shuō)明書(shū)同時(shí)也結(jié)合了模具設(shè)計(jì)與制造專業(yè)所學(xué)的所有知識(shí)，比如塑料模具設(shè)計(jì)與制造、機(jī)械制圖，公差與測(cè)量技術(shù)、模具工藝與工裝等專業(yè)課的知識(shí)。所有的這知識(shí)儲(chǔ)備均體現(xiàn)了本課程設(shè)計(jì)計(jì)算說(shuō)明書(shū)依據(jù)與合理性。 隨著現(xiàn)代工業(yè)的發(fā)展需要塑料制品在工業(yè)、農(nóng)業(yè)、以及日常生活等各個(gè)領(lǐng)域應(yīng)用越來(lái)越廣，質(zhì)量要求也越來(lái)越高。在塑料制品的生產(chǎn)中高質(zhì)量的模具設(shè)計(jì)、先進(jìn)的模具制造設(shè)備、合理的加工工藝、優(yōu)質(zhì)的模具材料和現(xiàn)代化成形設(shè)備等都已成為成形優(yōu)質(zhì)塑件的重前提條件。 因此，本工藝規(guī)程課程設(shè)計(jì)說(shuō)明書(shū)本課程設(shè)計(jì)計(jì)算說(shuō)明說(shuō)書(shū)具有以下的不足之處： 一、由于初步接觸塑料模具設(shè)計(jì)與制造知識(shí)以及共進(jìn)入機(jī)械行業(yè)，因此對(duì)塑料模成型以及成型工藝了得比較浮淺，設(shè)計(jì)時(shí)困難比較大，設(shè)計(jì)也夠準(zhǔn)確。為此本課程設(shè)計(jì)計(jì)算說(shuō)明說(shuō)書(shū)也有待進(jìn)一步改進(jìn)。 二、社會(huì)實(shí)踐經(jīng)驗(yàn)缺乏，在設(shè)計(jì)時(shí)有這方面原因從而忽略了很多因素，為此設(shè)計(jì)計(jì)算中也有許多不嚴(yán)密之處。 本課程設(shè)計(jì)主要將學(xué)生學(xué)到的理論與實(shí)際醒結(jié)合，突出模具設(shè)計(jì)基礎(chǔ)的結(jié)合運(yùn)用，以提供更準(zhǔn)確，實(shí)用，方便的計(jì)算方法，正確掌握并運(yùn)用沖壓工藝參數(shù)和模具工作部分的幾何形狀和尺寸的綜合應(yīng)用，提高自我的模具設(shè)計(jì)與制造能力的綜合應(yīng)用。 在以后的生產(chǎn)生活中，研究和推廣新工藝，新技術(shù)提高模具在生產(chǎn)生活中的應(yīng)用，并進(jìn)一步提高模具技術(shù)水平。 實(shí)踐證明，理論聯(lián)系實(shí)際的學(xué)習(xí)才是最有效的學(xué)習(xí)方法。因此本設(shè)計(jì)計(jì)算說(shuō)明書(shū)結(jié)合了塑料模具圖冊(cè)、塑料模具設(shè)計(jì)與制造、機(jī)械制圖，公差與測(cè)量技術(shù)、機(jī)械設(shè)計(jì)基礎(chǔ)等專業(yè)課知識(shí)，再結(jié)合實(shí)際生產(chǎn)經(jīng)驗(yàn)而設(shè)計(jì)的。從而充分體現(xiàn)了所學(xué)的專業(yè)知識(shí)實(shí)際生產(chǎn)的應(yīng)用。 第一章 導(dǎo)滑壓板工作零件結(jié)構(gòu)工藝性分析 第一節(jié) 熟悉和分析導(dǎo)滑壓板制定工藝規(guī)程的主要依據(jù) 一 、熟悉和分析導(dǎo)滑壓板制定工藝規(guī)程的主要依據(jù)，確定零件的生產(chǎn)綱領(lǐng)和生產(chǎn)類型，進(jìn)行零件的結(jié)構(gòu)工藝性分析。 1、導(dǎo)滑壓板制訂工藝規(guī)程的主要依據(jù)（既原始資料）。 1〉產(chǎn)品的裝配圖樣和零件圖樣（見(jiàn)圖附頁(yè)） 2〉產(chǎn)品的生產(chǎn)綱領(lǐng) 3〉產(chǎn)品的生產(chǎn)綱領(lǐng) 現(xiàn)有的生產(chǎn)條件和資料，它包括毛坯的生產(chǎn)條件或協(xié)作關(guān)系，工藝裝備及專用設(shè)備的制造能力，有關(guān)機(jī)械加工車間的設(shè)備和工藝裝備的條件，技術(shù)工人的水平以及各 種工藝資料和標(biāo)準(zhǔn)等。 4〉外國(guó)內(nèi)產(chǎn)品的有關(guān)工藝資料等。 2原始資料 1）零件圖樣 如設(shè)計(jì)任務(wù)書(shū)所示的零件圖及尺寸。（見(jiàn)下圖） 零件圖 2）生產(chǎn)綱領(lǐng) 生產(chǎn)綱領(lǐng)是企業(yè)在計(jì)劃期內(nèi)應(yīng)當(dāng)生產(chǎn)的產(chǎn)品質(zhì)量和進(jìn)度計(jì)劃，計(jì)劃期常定為一年，所以生產(chǎn)綱領(lǐng)也稱年產(chǎn)量。該零件是組成滑輪注塑摸的一個(gè)結(jié)構(gòu)零件，一副模具只需要一個(gè)此零件即可，所以初步擬訂其生產(chǎn)綱領(lǐng)為100件。 3）生產(chǎn)類型 生產(chǎn)類型是企業(yè)（或車間，工段，班組，工作地）生產(chǎn)專業(yè)化程度的分類，一般分為大量生產(chǎn)，成批生產(chǎn)和單件生產(chǎn)三 種類型。 根據(jù)生產(chǎn)綱領(lǐng)和產(chǎn)品及零件的特征或工作地每月?lián)?fù)的工序數(shù)，查文獻(xiàn)[1]表1—3生產(chǎn)類型和生產(chǎn)綱領(lǐng)的關(guān)系，確定該零件的生產(chǎn)類型為單件小批量生產(chǎn)。 4）生產(chǎn)組織形式 生產(chǎn)類型不同，零件和產(chǎn)品的生產(chǎn)組織形式，采用的技術(shù)措施和達(dá)到的技術(shù)經(jīng)濟(jì)效果也會(huì)不同，因?yàn)樵摿慵菃渭∨可a(chǎn)，所以其生產(chǎn)組織形式查文獻(xiàn)[1]表1-5的各種生產(chǎn)類型的 二、導(dǎo)滑壓板的工藝特征有其生產(chǎn)組織形式 1零件的互換性：有修配法，鉗工修配，缺乏互換性。 毛坯的制造方法與加工余量，木模手工造型或自由鍛造毛坯精度低，加工余量大。 2機(jī)床設(shè)備及其布置形式：通用機(jī)床，按機(jī)類別采用機(jī)群式布置。 3工藝裝備：大多采用通用夾具，標(biāo)準(zhǔn)附件，通用刀具和萬(wàn)能量具，標(biāo)準(zhǔn)附件，通用刀具和萬(wàn)能量具，靠劃線和試切法達(dá)到精度要求。 4對(duì)工人的技術(shù)要求：需技術(shù)水平較高的工人。 5工藝文件：有工藝路線卡和關(guān)鏈工序工序卡。 6成本：較高。 結(jié)合上述分析對(duì)現(xiàn)有條件作出合理的調(diào)整使得該零件的加工更能體現(xiàn)“質(zhì)優(yōu)價(jià)廉”。 第二節(jié) 導(dǎo)滑壓板零件的結(jié)構(gòu)工藝性分析 一、導(dǎo)滑壓板零件的結(jié)構(gòu)工藝性分析 熟悉導(dǎo)滑壓板零件圖，了解零件的性能，用途，工作條件及其所在模具中的作用。 1）導(dǎo)滑壓板零件的性能：具有較高的強(qiáng)度，硬度和韌性，適用于小型復(fù)雜的塑料模具。 2）導(dǎo)滑壓板零件的用途：固定模具零件，并與它發(fā)生直接聯(lián)系用的零件，在模具打開(kāi)時(shí)帶動(dòng)成型零部件向下移動(dòng)，確保塑件與成型機(jī)構(gòu)的分離，保證模具的順利打開(kāi)和合模。 3） 導(dǎo)滑壓板工作條件：安裝在滑輪注塑模的導(dǎo)滑壓板上，與其他零部件結(jié)合使用，適合滑輪注塑模的工作條件。 4）導(dǎo)滑壓板零件在模具中的作用：該零件在模具中與導(dǎo)滑板，凹模劃塊和彎銷等配合成滑輪的注塑成型機(jī)構(gòu)，起固定和定位作用。 二、了解導(dǎo)滑壓板零件的材料及其力學(xué)性能 1導(dǎo)滑壓板材料 該零件材料為45鋼，它是碳素結(jié)構(gòu)鋼，具有較高的強(qiáng)度和硬度，耐磨性好且熱處理變形小，制品一般用于淬，適用于制品批量生產(chǎn)的熱塑性塑料的成型模具零件。 1材料的力學(xué)性能 查文獻(xiàn)[3]表7-5優(yōu)質(zhì)碳素鋼牌號(hào)，成分及性能（GB699—88）可知45鋼的力學(xué)性能為： бb/MPa бs/MPa δs×100 Ψ×100 Ak/J ≥600 ≥355 ≥16 ≥40 ≥39 推薦的熱處理溫度 正火：830℃ 淬火： 840℃ 回火： 600℃ 硬度： 未處理：229HBS 退火鋼：197HBS 分析：45鋼在退火，正火及調(diào)質(zhì)狀態(tài)下的力學(xué)性能為： 狀態(tài) бb /MPa б5×100 AK/J HBS 退火 650～700 15～20 32～48 ～180 正火 700～800 15～20 40～64 163～220 調(diào)質(zhì) 750～850 20～25 64～96 210～250 正火后鋼的強(qiáng)度，硬度，硬度，韌性都比退火后的高，且塑件也好，操作方便，生產(chǎn)周期短，能量耗費(fèi)少，則在條件允許下，應(yīng)優(yōu)先考慮，采用正火處理，可作為零件的預(yù)先熱處理。 調(diào)質(zhì)處理后鋼的強(qiáng)度較高，而且塑件與韌性更顯著高于正火狀態(tài)，其硬度較低，便于切削加工，并能獲得較低的表面粗造度值，故也可作為表面淬火和化學(xué)熱處理前改善鋼件原始組織狀態(tài)的預(yù)先熱處理。 三、分析選擇該導(dǎo)滑壓板的熱處理為調(diào)質(zhì)。 1導(dǎo)滑壓板結(jié)構(gòu)形狀分析 該零件從形體上分析其總體結(jié)構(gòu)為六面體，上表面有2-Φ15的型芯孔，并且側(cè)面有4-M30螺釘孔，2-Φ21導(dǎo)柱孔擴(kuò)孔為Φ30。因此其結(jié)構(gòu)形狀較為簡(jiǎn)單，屬于加工成形。 故其結(jié)構(gòu)形狀工藝性合理。 2導(dǎo)滑壓板尺寸 該零件的外形尺寸為180mm×300mm×25mm，且一部分孔的加工可在與其配合的零件加工時(shí)保證，因而該零件的加工尺寸較小，減化了加工工序，降低了加工難度，可保證加工質(zhì)量。 故其尺寸工藝性較為合理。 3導(dǎo)滑壓板精度 為了滿足塑件尺寸精度和表面粗造度的要求，根據(jù)塑件精度等級(jí)（精度等級(jí)為IT4～I(xiàn)T5級(jí)）確定模具制造精度為IT6～I(xiàn)T7級(jí)。 4導(dǎo)滑壓板熱處理 為了消除毛坯在加工后的缺陷，改善其工藝性能，且為后續(xù)工序作出組織準(zhǔn)備和提高工件的使用性能及使用壽命采用 調(diào)質(zhì)方式進(jìn)行熱處理。 綜合上述分析可知該零件的加工較容易，可采用先進(jìn)的，高效率的工藝方法進(jìn)行加工制造，但使其加工成本較高，為了降低其加工成本，可適當(dāng)調(diào)整加工設(shè)備采用一般工藝方法進(jìn)行加工 第二章 設(shè)備與工藝裝備的選擇 第一節(jié) 設(shè)備的確定 一、設(shè)備確定 因?yàn)樵摿慵捎媒M織集中工序，所以選擇通用設(shè)備，即：C41—250型空氣錘，加熱爐，銑床，刨床，磨床，鉆床，鉸床，坐標(biāo)磨床等。 二、工藝裝備的選擇 1夾具的選擇 單件小批量生產(chǎn)首先采用各種通用夾具，也可采用組合夾具，結(jié)合實(shí)際生產(chǎn)條件可知該零件選擇四爪卡盤，虎鉗，畫(huà)線平臺(tái)，平行夾頭，火鉗和組合夾具等。 2刀具的選擇 一般優(yōu)先采用標(biāo)準(zhǔn)刀具根據(jù)該零件的工藝性及實(shí)際條件確定其刀具為：剪板機(jī)，平面刨刀，圓柱銑刀；端面銑刀，平行砂輪，劃針，樣沖，立銑刀，鉆頭，絲錐，擴(kuò)刀，砂輪等。 3 量具的選擇 依據(jù)量具的精度必須與加工精度相適應(yīng)，則該零件應(yīng)優(yōu)先采用通用量具，即：鋼尺、游標(biāo)卡尺、直角尺、內(nèi)卡鉗、百分表。 三、擬訂工藝路線 綜合上述分析最終擬訂兩條工藝路線如下： 工藝路線一： 工序號(hào) 工序名稱 0 備料 5 鍛造 10 退火 15 銑（刨）平面 20 磨平面 25 鉗工劃線 30 銑工 35 熱處理 30 鉗工精修 45 磨削 50 檢 驗(yàn) 55 入 庫(kù) 工藝路線二： 工序號(hào) 工序名稱 0 備料 5 鍛造 10 退火 15 銑（刨）平面 20 磨平面加工精基準(zhǔn)面 25 鉗工劃線 30 銑工 35 熱處理 40 鉗工精修 45 磨削 50 檢驗(yàn) 四、工藝路線方案的比較與分析 以上兩種工藝路線方案想比較，第二種方案有以下幾個(gè)優(yōu)點(diǎn)： 1. 工序內(nèi)容簡(jiǎn)單，工序連接緊密，有利于組織流水生產(chǎn)。第一種方案中工序之間相互脫節(jié)，造成加工困難，另一面，這樣增加時(shí)間，生產(chǎn)率降低，不夠經(jīng)濟(jì)。 2. 定位基準(zhǔn)的選擇 定位基準(zhǔn)的選擇將直接影響加工精度的高低，同樣作為定位基準(zhǔn)的部位加工質(zhì)量的好壞也影響的定位的準(zhǔn)確性和加工質(zhì)量，使安裝誤差和定位誤差增大，從而對(duì)加工精度有很大影響，零件上的各個(gè)表面間的位置精度，是通過(guò)一系列工序加工后獲得的，這些工序的順序和原始尺寸的大小，標(biāo)注方式和零件圖上的要求直接有關(guān)，第一種方案中，工序45不找正直接加工，易使工件偏斜，位置精度不準(zhǔn)確，給下面的工序的位置精度，定位基準(zhǔn)帶來(lái)一定困難。第二方案中工序之間的采用互為基準(zhǔn)原則的，其作用是加工時(shí)的余量均勻，并使加工后的表面位置度較高，能順利加工。 第二節(jié) 機(jī)床的選用 一、機(jī)床的選用 機(jī)床的選用，主要考慮零件加工的經(jīng)濟(jì)性，應(yīng)該充分運(yùn)用現(xiàn)有設(shè)備，不增加零件的成本。第一套方案中，較多的使用了專用機(jī)床，第二套方案中可使用普通機(jī)床。降低了加工成本，但是精度不能滿足。另外在機(jī)床的選擇上，也必須考慮以下因素： ①機(jī)床的工作精度和工序的加工精度相適應(yīng) ②機(jī)床的工作尺寸應(yīng)和工件的輪廓尺寸或夾具的尺寸相適應(yīng) ③機(jī)床的功率與剛度的性質(zhì)相適應(yīng)，另外，機(jī)床的加工用量范圍應(yīng)和工件要求的合理切削用量相適應(yīng) ④刀具的選擇 刀具的耐用度問(wèn)題也的批量生產(chǎn)中的重要問(wèn)題，刀具耐用度的提高，不僅可以節(jié)約輔助工作時(shí)間，又可降低刀具的費(fèi)用。合理選擇刀具的提高刀具耐用度的關(guān)鍵。第二套方案中，工序30鉆，擴(kuò)φ20孔深19±0.2采用兩把車刀，分別采用合適的幾何角度和材料來(lái)完成粗，精加工，這樣大大減少了刀具的磨損。 二、工藝路線方案確定 經(jīng)過(guò)多方面的分析，第二套工藝路線方案從安排工序依據(jù)的原則，定位基準(zhǔn)的選擇，加工經(jīng)濟(jì)性和刀具的耐用度等方面均比第一套合理，因此用第二套工藝路線作為加工方案。 第三章 確定毛坯的類型及其制造加工方法 一、導(dǎo)滑壓板毛坯的形狀和特征 毛坯的形狀和特征，在很大程度上決定著模具制造過(guò)程中工序的多少，機(jī)械加工的難易程度，材料的大小及模具的質(zhì)量與壽命。 毛坯類型有鑄，鍛，壓制，沖壓，焊接，型材和板材等。 二、導(dǎo)滑壓板毛坯的形狀和特征分析 鍛造后，工件的力學(xué)性能比鑄件好，使零件材料內(nèi)部組織細(xì)密，碳化物分布和流線分布合理，從而提高模具的質(zhì)量和使用壽命，鑄造能夠生產(chǎn)形狀復(fù)雜的毛坯，適應(yīng)性廣，能節(jié)省金屬材料和機(jī)械加工的工作量且成本較低，但鑄造生產(chǎn)存在著工序復(fù)雜，鑄件的力學(xué)性能低于鍛件，勞動(dòng)條件較差；沖壓的生產(chǎn)效率高，易于實(shí)現(xiàn)機(jī)械與自動(dòng)化生產(chǎn)，制品的尺寸精確，互換性好，節(jié)約金屬，操作方便，但是模具制造復(fù)雜成本較高，適用于大量生產(chǎn)，焊接可節(jié)省材料與工時(shí)，減輕結(jié)構(gòu)的質(zhì)量，焊接接頭的致密性好，可以制造密封容器，以及雙金屬結(jié)構(gòu)件，生產(chǎn)效率高，便于機(jī)械化，自動(dòng)化生產(chǎn)，但由于焊接的過(guò)程是局部加熱與冷卻的過(guò)程，容易產(chǎn)生焊接應(yīng)力，變形及焊接缺陷，有些金屬的焊接要求比較復(fù)雜的工藝措施才能保證焊接質(zhì)量。 經(jīng)分析并結(jié)合該零件工藝分析可確定其毛坯為鍛件（即鍛坯）。 毛坯圖 第四章 擬定導(dǎo)滑壓板工藝路線 一確定工藝路線原則 1.制定工藝路線的依據(jù) 應(yīng)使零件的各尺寸精度，位置精度，表面粗糙度和各向技術(shù)要求能得到保證，在一定生產(chǎn)條件下以最快的速度，最少的工作量和最低的成本，安全可靠的加工出符合零件的工作擬定工藝路線一般應(yīng)遵循工藝過(guò)程劃分加工階段的原則。當(dāng)加工質(zhì)量要求不高，工件的剛性足夠，毛坯質(zhì)量高，加工余量小時(shí)可以不劃分加工階段。在數(shù)控機(jī)床上加工零件以及某些運(yùn)輸，裝夾困難的重型零件，也不劃分加工階段，而在一次裝夾下完成全部表面的粗，精加工，對(duì)重型零件可在粗加工之后將夾具松開(kāi)以消除加緊變形，然后再用較小的夾緊力重新夾緊，進(jìn)行精加工，以利于保證重型零件的加工質(zhì)量，對(duì)于精度要求高的重型零件，仍需劃分加工階段，并適時(shí)進(jìn)行時(shí)效處理消除內(nèi)應(yīng)力。該零件的表面質(zhì)量要求較高，且需多次裝夾，所以其工藝路線需劃分加工階段完成。 2制定導(dǎo)滑壓板工藝規(guī)程時(shí)應(yīng)注意的問(wèn)題 1)技術(shù)的先進(jìn)性 2)經(jīng)濟(jì)上的合理性 3)使用上的安全性由于該零件生產(chǎn)綱領(lǐng)確定了成批生產(chǎn)，因此采用工序集中原則使，用普通 3導(dǎo)滑壓板加工順序由以下原則確定 機(jī)床配以專用夾具，可降低生產(chǎn)成本，以獲得好的經(jīng)濟(jì)效益加工順序由以下原則確定： 先粗加工，后精加工，先加工基準(zhǔn)面，后加工其他面，先加工主要面，后加工次要面，后加工孔，并且應(yīng)遵基準(zhǔn)重合原則，基準(zhǔn)統(tǒng)一原則，自為基準(zhǔn)原則，互為基準(zhǔn)原則。 1)擬定工藝路線一般應(yīng)遵循工藝過(guò)程劃分加工階段的原則 當(dāng)加工質(zhì)量要求不高，工件的剛性足夠，毛坯質(zhì)量高，加工余量小時(shí)可以不劃分加工階段。在數(shù)控機(jī)床上加工零件以及某些運(yùn)輸，裝夾困難的重型零件，也不劃分加工階段，而在一次裝夾下完成全部表面的粗，精加工，對(duì)重型零件可在粗加工之后將夾具松開(kāi)以消除加緊變形，然后再用較小的夾緊力重新夾緊，進(jìn)行精加工，以利于保證重型零件的加工質(zhì)量，對(duì)于精度要求高的重型零件，仍需劃分加工階段，并適時(shí)進(jìn)行時(shí)效處理消除內(nèi)應(yīng)力。該零件的表面質(zhì)量要求較高，且需多次裝夾，所以其工藝路線需劃分加工階段完成。 2) 導(dǎo)滑壓板面加工方法的選擇 當(dāng)模具零件的表面加工精度要求較高時(shí)，可根據(jù)不同工藝方法所能達(dá)到的加工經(jīng)濟(jì)精度和表面粗糙度等因素。首先確定被加工表面的最終加工方法，然后再選定最終加工方法，然后再選定最終加工方法之前的一系列準(zhǔn)備工序的加工方法和順序，以便通過(guò)逐次加工達(dá)到設(shè)計(jì)要求。 二、導(dǎo)滑壓板平面加工方法確定各表面的加工方法 選擇加工方法時(shí)常常根據(jù)經(jīng)驗(yàn)或查表法來(lái)確定，在根據(jù)實(shí)際情況或通過(guò)工藝是試驗(yàn)進(jìn)行修改。依據(jù)各表面加工要求和各加工 要求和各個(gè)加工方法能達(dá)到的經(jīng)濟(jì)精度查文獻(xiàn)[1]表1—11孔的加工方法和表1-12平面加工方法確定各表面的加工方法如下要求和各個(gè)加工方法能達(dá)到的經(jīng)濟(jì)精度查文獻(xiàn)[1]表1—11孔的加工方法和表1-12平面加工方法確定各表面的加工方法如下： 通過(guò)零件分析可分為以下幾部分。 ①：2個(gè)φ21和2個(gè)φ30的階梯孔。銑——半精銑——精銑； ②：4個(gè)M30的螺紋孔，銑——半精銑——精銑； ③：2個(gè)φ9和2個(gè)φ15的階梯孔。銑——半精銑——精銑； 三、零件的外輪廓表面 零件的外輪廓表面： 粗銑——半精銑——磨削。 1導(dǎo)滑壓板工藝階段的劃分 工藝路線按工序性質(zhì)一般分為粗加工階段，半精加工階段和精加工階段。對(duì)于那些加工精度和表面質(zhì)量要求特別高的表面在工藝過(guò)程中還應(yīng)安排光整加工階段。 具體的工藝階段劃分祥見(jiàn)該零件的工藝規(guī)程卡片中各工序的介紹。 2導(dǎo)滑壓板工序的劃分 根據(jù)所選定的表面加工方法和各加工階段中表面的加工要求，可以將同一階段中各表面的加工組合成不同的工序，在劃分工序時(shí)可以采用工序集中或分散的原則。 由于模具加工精度要求高，且多屬于單件或小批量生產(chǎn)，為了簡(jiǎn)化生產(chǎn)組織工作，則多采用組織集中劃分工序 3加工順序的安排 四、導(dǎo)滑壓板加工工序的安排 1導(dǎo)滑壓板切削加工的安排 模具零件的被加工表面切削加工應(yīng)遵循 ① 先粗后精； ② 先基準(zhǔn)后其他 ③ 先主要后次要 ④ 先平面后內(nèi)孔 ⑤內(nèi)外交叉，具體祥見(jiàn)加工工藝規(guī)程路線表卡片。 2導(dǎo)滑壓板熱處理工序的安排 熱處理工序在工藝路線中的安排，主要取決于零件熱處理的目的為了改善金屬組織和便于加工則必須使該零件在粗加工前安排調(diào)質(zhì)熱處理。 為了提高零件硬度和耐磨性，則必須在該零件光整的工序前安排淬火熱處理。 3導(dǎo)滑壓板輔助工序的安排 為了保證該零件質(zhì)量和及時(shí)去除廢品，防止工時(shí)浪費(fèi)，并使責(zé)任分明，則必須在該零件重要工序加工前后和零件加工結(jié)束安排檢驗(yàn)工序。 綜合上述分析：該零件機(jī)械加工的順序是：加工精基準(zhǔn)面——粗加工主要面——精加工主要面——光整加工主要面。 第五章 確定導(dǎo)滑壓板工序的加工余量 第一節(jié) 確定導(dǎo)滑壓板加工余量的方法 一、常用加工余量的方法 確定加工余量的方法有三種：查表法、分析計(jì)算法、經(jīng)驗(yàn)估計(jì)法。 1查表法是根據(jù)個(gè)工廠的生產(chǎn)實(shí)踐和試驗(yàn)研究積累的數(shù)據(jù)，先制成各種表格，再匯集成手冊(cè)確定加工余量是查閱這些手冊(cè)，再結(jié)合工廠的實(shí)際情況進(jìn)行適當(dāng)修改后確定。經(jīng)驗(yàn)估計(jì)法是根據(jù)實(shí)際經(jīng)驗(yàn)確定加工余量。一般情況下，為防止因余量過(guò)小而產(chǎn)生廢品，經(jīng)驗(yàn)估計(jì)的數(shù)值總是偏大。因此其法常用于單件小批量生產(chǎn)。 2分析計(jì)算法是根據(jù)確定加工余量的相關(guān)公式和一定的試驗(yàn)資料，對(duì)影響加工余量的各項(xiàng)因素進(jìn)行分析，并計(jì)算確定加工余量。這種方法比較合理，但必須有比較全面和可靠的試驗(yàn)資料。因此當(dāng)前只在材料十分貴重以及軍工生產(chǎn)或少數(shù)大量生產(chǎn)的工廠中采用。 3模具加工中常用經(jīng)驗(yàn)估計(jì)法確定加工余量。則該零件的加工余量確定，由查表法和經(jīng)驗(yàn)估計(jì)法結(jié)合確定。其相關(guān)加工余量查文獻(xiàn)［6］表8－27有平面第一次粗加工余量為：1.5mm～2.5mm; 表8－28有平面粗刨后精銑加工余量為：0.7mm～0.9 mm; 表8－29有銑平面的加工余量為；1.2mm;表8－30有磨平面的加工余量為0.3mm;表8－31有銑及磨平面的厚度公差為：粗銑（IT12～I(xiàn)T13），－0.21mm～0.33mm；半精銑－0.13mm（IT11），精磨（IT8～I(xiàn)T9），－0.033 mm～－0.062mm；表8－33有凹模的加工余量及公差為：寬度余量①粗銑后半精銑4.0mm；②半精銑后磨1.0mm；寬度公差①粗銑（IT12～I(xiàn)T13）+0.35mm～+0.54mm , ②半精銑（IT11）+0.22mm；表8－34研磨平面的加工余量為：0.024mm ～0.030mm;表8－35磨孔和鉸孔的加工余量為：磨孔時(shí)，粗：0.2mm,精0.1mm, 熱處理（粗）0.5mm ,熱處理（半精）0.4 mm；鉸孔時(shí)0.15mm. 二、確定導(dǎo)滑壓板加工余量 綜上分析本模具采用經(jīng)驗(yàn)估計(jì)法確定加工余量。 第二節(jié) 確定主要工序的技術(shù)要求及檢驗(yàn)方法 1零件圖中未注公差尺寸的極限偏差按GB／T1804－2000《公差與配合 未注公差尺寸的極限偏差》。 2零件圖中未注形為公差按GB／T1184－1996《形狀和位置公差 未注公差的規(guī)定》，其中直線度、平面度、同軸度的公差等級(jí)均按C級(jí)。 3板類零件的棱邊均須倒鈍。 4零件圖中螺紋的基本尺寸按GB196－1981《普通螺紋基本尺寸（直徑1～600mm）》的規(guī)定，其偏差按GB197－1981《普通螺紋公差與配合》（直徑1～355mm）的3級(jí)。 5零件圖中砂輪越程槽的尺寸按JB／T3－1959《砂輪越程槽》的規(guī)定。 6零件材料允許代用，但代用材料的機(jī)械性能不得低于規(guī)定材料的要求。 7零件表面經(jīng)目測(cè)不允許有銹斑裂紋，夾雜物、凹坑氧化斑點(diǎn)和影響使用的劃痕等缺陷。 8零件的材料和熱處理硬度按GB／T699－1999《模具設(shè)計(jì)指導(dǎo) 模具成型零件材料及硬度》的規(guī)定選取。 9模具零件的幾何形狀、尺寸精度、表面粗糙度等應(yīng)符合圖樣要求。 10如對(duì)零件有其他技術(shù)要求，可依據(jù)實(shí)際條件協(xié)調(diào)決定。 第三節(jié) 檢驗(yàn) 一、 檢驗(yàn)方法： 1利用卡鉗和鋼尺配合使用測(cè)量零件孔的具體數(shù)據(jù)，保證零件表面質(zhì)量。 2利用游標(biāo)卡尺直接測(cè)量工件的內(nèi)表面、外表面和深度，確保其個(gè)表面精度。 3利用分厘卡尺測(cè)量孔外徑、內(nèi)徑、深度、螺紋孔的尺寸精度。 4利用百分表檢驗(yàn)工件的形狀誤差、位置誤差和安裝工件與刀具時(shí)的精密找正，其測(cè)量精度為0.01 mm。 第六章 確定導(dǎo)滑壓板工序的切削用量和時(shí)間定額 因?yàn)樵摿慵閱渭∨可a(chǎn)，所以在工藝文件上一般不規(guī)定切削用量，而由工作者根據(jù)實(shí)際情況自行決定。 一、時(shí)間定額 時(shí)間定額是在一定的生產(chǎn)條件下，規(guī)定生產(chǎn)一件產(chǎn)品或完成一道工序所需消耗的時(shí)間合理的時(shí)間定額能調(diào)動(dòng)生產(chǎn)者的積極性，促進(jìn)生產(chǎn)者技術(shù)水平的提高。制定時(shí)間定額應(yīng)注意調(diào)查研究，有效利用生產(chǎn)設(shè)備和工具，以提高生產(chǎn)效率和產(chǎn)品質(zhì)量。 二、時(shí)間定額計(jì)算 時(shí)間定額計(jì)算公式為： T c=Ta+Tb+Ts+Tr+Te／n在大量生產(chǎn)中，由于n的數(shù)值很大， 即Te／n=0,可忽略不計(jì)。 式中： Tc：該零件的時(shí)間定額。 T b ：基本時(shí)間 。 Ta : 輔助時(shí)間。 Ts: 布置工作地時(shí)間。 Tr： 休息與生理需要時(shí)間。 Te: 準(zhǔn)備與終結(jié)時(shí)間。 N： 生產(chǎn)批量（個(gè)）。 具體數(shù)值可查閱相關(guān)資料代入上式計(jì)算即可確定出確切時(shí)間定額時(shí)間。 第七章 導(dǎo)滑壓板加工的技術(shù)文件 一、進(jìn)行技術(shù)經(jīng)濟(jì)分析，選擇最佳方案。 因?yàn)樵摿慵賳渭∨可a(chǎn)，所以對(duì)其可不進(jìn)行技術(shù)分析。依據(jù)現(xiàn)有條件及工人工作經(jīng)驗(yàn)做適當(dāng)調(diào)整即可。 二、填寫(xiě)工藝文件。 因?yàn)樵摿慵賳渭∨可a(chǎn)，所以一般只填寫(xiě)機(jī)械加工工藝過(guò)程卡片。根據(jù)設(shè)計(jì)任務(wù)要求該零件還需填寫(xiě)機(jī)械加工工序卡片。 機(jī)械加工工藝過(guò)程卡片以工序?yàn)閱挝缓?jiǎn)要說(shuō)明產(chǎn)品活 或零件、部件加工（裝配）過(guò)程，它以工序?yàn)閱挝涣谐隽肆慵庸さ墓に嚶肪€，（包括毛坯，機(jī)械加工和熱處理等）。 機(jī)械加工工序卡片具有工藝簡(jiǎn)圖，和該工序的每個(gè)工步的加工（或裝配）內(nèi)容，工藝參數(shù)，操作要求以及所用設(shè)備和工藝裝備等具體見(jiàn)該零件的工藝文件。 三、導(dǎo)滑壓板加工工藝規(guī)程 見(jiàn)下工藝卡片 第八章 參考文獻(xiàn) ⒈ 鄭修本主編，機(jī)械制造工藝學(xué)，北京.機(jī)械工業(yè)出版社.1999-5. 2. 張龍勛主編，機(jī)械制造工藝學(xué)課程設(shè)計(jì)指導(dǎo)書(shū)及習(xí)題.北京.機(jī)械工業(yè)出版社.1999—11。 3. 王運(yùn)炎. 葉尚川主編，機(jī)械工程材料.北京.機(jī)械工業(yè)出版社.2000-5.2版. 4. 王孝達(dá)主編，金屬工藝學(xué).北京.高等教育出版社.1997. 5. 侯維芝.樣金風(fēng)主編.北京高等教育出版社.2005—7. 6. 張耀良主編，機(jī)械加工工藝設(shè)計(jì)手冊(cè).北京.航空工業(yè)出版社出版.1987—12第2版. 7. 李永增主編，金工實(shí)習(xí).北京.高等教育出版社.1995. 8. 史鐵梁主編，模具設(shè)計(jì)指導(dǎo).北京.機(jī)械工業(yè)出版社.2003-8. 25 Int J Adv Manuf Technol (2000) 16:739747 2000 Springer-Verlag London Limited Automated Assembly Modelling for Plastic Injection Moulds X. G. Ye, J. Y. H. Fuh and K. S. Lee Department of Mechanical and Production Engineering, National University of Singapore, Singapore 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-oriented 1. Introduction Injection moulding is the most important process for manufac- turing plastic moulded products. The necessary equipment con- sists 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 Correspondence and offprint requests to: Dr Jerry Y. H. Fuh, Depart- ment of Mechanical and Production Engineering, National University of Singapore (NUS), 10 Kent Ridge Crescent, Singapore 119260. E-mail: mpefuhyhKnus.edu.sg 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 of tasks 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 geo- metrical 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. The Mould Mouldbase Cool Fill Layout Plug Socket Cav_1 Cav_2 CA-plate Guild-bush TCP-plate Bep-plate Cb-plate Ea-plate Eb-plate Guid-pin Ip-plate Ret-pin Slider body guide Stop-blk Heel-blk head Core Cavity Product-independent part Product-dependent part Move-half Fixed-half Fig. 1. Assembly structure of an injection mould. 740 X. G. Ye et al. automatic 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 difficult- ies 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 follow- ing two key issues for automatic assembly modelling: rep- resenting 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 sym- bolic method is proposed to determine the position and orien- tation of a part in the mould assembly. An example of auto- matic 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 model- ling. 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 compo- nents. 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 a mathematically valid, but physically unfeasible, solution can be obtained. Ambler and Popplestone 6 suggested a method of comput- ing 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 attri- butes, action analysis 7 is used to obtain a solution. Action analysis 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 fea- ture 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 Automated Assembly Modelling 741 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 pro- duct-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 oper- ational 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 con- cepts. 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 represen- tation 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 3.2. 3.1 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, tc 1 , tc 2 , %, tc n , 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 tc i (i Fig. 2. Feature-based, object-oriented hierarchical representation. 742 X. G. Ye et al. = 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. Table 1. Definition of an assembly object-ejector. Object Oid ejector-pinF1 Instance-of EjectorFpin Derived from ejector class A Purpose “ejecting moulding” Type string Material “nitrided steel” Type string CatalogFno “THX” Type string M CheckFinterference Check interference (coolFobj) between ejectors and cooling lines PocketFplate() Make a hole on plate to accommodate ejector pins R Part-of ejectorFsys SR align with EB plate DOF Tx, Ty 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 (FF 2 ) is placed with reference to the block feature FF 1 , using their local coordinates F 2 and F 1 , respectively. Equations (2) (5) show the spatial relationships between the counter-bore hole (FF 2 ) and the block feature (FF 1 ). 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: SR(FF 2 ,FF 1 ): F 2i =- F 1i (2) F 2j =- F 1j (3) Fig. 3. Assembly relationships. Automated Assembly Modelling 743 F 2k = F 1k (4) r 2F = r 1F + b 22 *F 1j + A F1 *F 1i (5) DOF: ObjFhasF1FRDOF(FF 2 , F 2j ) The counter-bore feature can rotate about axis F 2j . LTs(FF 2 , FF 1 ): A F1 , b 11 - 0.5*b 21 (6) Fit (FF 2 , FF 1 ): b 22 = b 12 (7) Where F and r are the orientation and position vectors of fea- tures. F 1 = (F 1i , F 1j , F 1k ), F 2 = (F 2i , F 2j , F 2k ). b ij is the dimension of form features, Subscript i is feature number, j is dimension number. A F1 is the dimension between form features. Equations (2)(7) present the relationships between the form feature FF 1 and F