復(fù)讀機后蓋注射模具的設(shè)計【屏蔽罩】【一模兩腔】【側(cè)抽芯】【注塑模具】【說明書+CAD+PROE+仿真】,屏蔽罩,一模兩腔,側(cè)抽芯,注塑模具,說明書+CAD+PROE+仿真,復(fù)讀機后蓋注射模具的設(shè)計【屏蔽罩】【一模兩腔】【側(cè)抽芯】【注塑模具】【說明書+CAD+PROE+仿真】,復(fù)讀機,注射,模具,設(shè)計,屏蔽 本 科 畢 業(yè) 論 文（設(shè) 計） 題目： 復(fù)讀機后蓋注射模的設(shè)計 學(xué) 院： 姓 名： 學(xué) 號： 專 業(yè)： 機械設(shè)計制造及其自動化 年 級： 指導(dǎo)教師： 職 稱：高級實驗師 二○一二 年 五 月 30 摘要 塑料成型制品是以塑料為主要結(jié)構(gòu)材料經(jīng)成型加工獲得的制品，又稱塑料制件，簡稱塑件。塑料成型制品應(yīng)用廣泛，特別是在電子儀表、電器設(shè)備、通信工具、生活用品等方面獲得大量應(yīng)用。如各種受力不大的殼體、支架、機座、結(jié)構(gòu)件、裝飾件等；建筑用各種塑料管材、板材和門窗異型材；塑料中空容器和各種生活用塑料制品等。 塑料制件的主要加工方法是塑料成型加工。塑料成型是將各種形態(tài)的塑料原料（粉狀、粒狀、熔體或分散體）熔融塑化或加熱達到要求的塑性狀態(tài)，在一定壓力下經(jīng)過要求形狀模具或填充到要求模具模腔內(nèi)，待冷卻定型后，獲得要求形狀、尺寸幾性能塑料制件的生產(chǎn)過程。其特點是生產(chǎn)制品形狀尺寸穩(wěn)定，可實現(xiàn)連續(xù)生產(chǎn)，一模多件生產(chǎn)，生產(chǎn)效率高。 常用的塑料成型工藝有注射成型、壓縮成型、中空成型等，注射成型是塑料模塑成型的一種主要成型方法。注射成型技術(shù)出現(xiàn)了許多新的工藝方法，如無流道凝料注射成型、熱固性塑料注射成型、排氣注射成型、反應(yīng)注射成型以及多品種塑料的共注射成型。 關(guān)鍵詞：塑料制件 注塑成型 Repetition machine back injectiong mold Abstract:（Times New Roman） Plastic molding plastic products is the main structural material obtained by forming products, also known as plastic parts, plastic parts for short. Plastic molding products are widely used, especially in the electronic instruments, electrical equipment, communication tools, daily necessities, such as a large number of applications received. such as a large shell, frame, base, structural parts, decorative parts; all kinds of plastic pipe used in construction, sheet metal and profile windows and doors; hollow plastic containers and plastic products such as life. The main processing of plastic parts are made of plastic processing method. Plastic molding is to various types of plastic raw materials (powder, granular, melt or dispersion) plastics melt or heating plastic to meet the requirements of state, to a certain shape under pressure after a request to the requirements of mold or mold-filled cavity, stereotypes to be cooling after it has been requested the shape, size, number of properties of plastic parts of the production process. Characterized by the shape of the production of dimensionally stable products, can realize continuous production, more than one mode of production, high productivity Common type of plastic molding processes are injection molding, compression molding, Blow Molding and so on, plastic injection molding is a molding method of forming a major. Injection molding technology there are many new technical methods, such as material non-condensate flow injection molding, thermoset plastic injection molding, the exhaust injection molding, reaction injection molding, as well as the total number of varieties of plastic injection molding Key words:（Times New Roman）Plastic parts Injection molding 第一部分 設(shè)計課題及設(shè)計目的 一 設(shè)計內(nèi)容………………………………………………………5 二 設(shè)計目的………………………………………………………5 第二部分 模具設(shè)計 一、產(chǎn)品工藝性分析……………………………………………6 二、注射機的選擇……………………………………………….7 三、確定模具基本結(jié)構(gòu)…………………………………………9 四、模具結(jié)構(gòu)設(shè)計……………………………………………….10 五、模具整體設(shè)計……………………………………………….....25 總結(jié)……………………………………………………………….....27 參考文獻……………………………………………………………28 致謝…………………………………………………………………..29 前 言 模具是工業(yè)生產(chǎn)中使用極為廣泛的重要工藝裝備，采用模具生產(chǎn)制品及零件，具有市場效率高，節(jié)約原材料，成本低廉，保證質(zhì)量等一系列優(yōu)點，是現(xiàn)代工業(yè)生產(chǎn)的重要手段和主要發(fā)展方向。塑料制品已進入到人們生活的各個領(lǐng)域，電器的很大部分都采用塑料制品。塑料以其密度小、機械性能好等優(yōu)點獨領(lǐng)風(fēng)騷，未來的世界必將是塑料的世界，而模具是塑料工業(yè)的基石。 本次畢業(yè)設(shè)計，在老師的精心指導(dǎo)下，通過對復(fù)讀機后蓋注射模的設(shè)計，深入學(xué)習(xí)proe了，掌握了注射模具設(shè)計的一般方法、模具制造的專用設(shè)備及注射機的工作原理，為今后工作打下了堅實的基礎(chǔ)。 本次設(shè)計歷時5周，進程如下：第一周，了解產(chǎn)品的注塑過程和模具的制造方法，初步知道在設(shè)計過程中所需注意的問題；第二周、徹底弄清自己的具體工作，設(shè)計所要達到的要求。計算數(shù)據(jù)，確定每個零件用什么材料、熱處理。第三周、用Proe對產(chǎn)品進行開模，完成三維造型。第四周，對各個零件出工程圖，整理資料并編寫設(shè)計說明書；第五周、交指導(dǎo)教師審閱，并作修改，最后定稿。 最后，由于水平有限，加之經(jīng)驗不足，疏漏和錯誤之處在所難免，懇請各位老師指正。 第一部分 設(shè)計內(nèi)容及設(shè)計目的 本次設(shè)計內(nèi)容：復(fù)讀機后蓋注射模具，對產(chǎn)品（圖1）設(shè)計一副注射模具。 -圖1 本次設(shè)計的目的： 1、掌握注射模設(shè)計的一般方法。 2、了解注射機的工作原理。 3、了解模具加工方法。 4、進一步掌握設(shè)計的一般方法，熟練設(shè)計的一般過程。 5、基本掌握proe和cad機械繪圖軟件。 第二部分 模具設(shè)計 1、產(chǎn)品工藝性分析 1.1、材料性能 所設(shè)計產(chǎn)品采用的材料為ABS，全稱為丙烯腈-丁二烯-苯乙烯共聚物，英文名全稱Acrylonitrile-butadiene-styrene。ABS為熱塑性材料，其密度為1.03～1.07g/cm3 ，抗拉強度30~50Mpa，抗彎強度41~76Mpa，收縮率為0.3～0.8%，常取0.5%。該材料綜合性能好，沖擊強度高，尺寸穩(wěn)定，易于成型，耐熱和耐腐蝕性能也較好，并有良好的耐寒性。 1.2、結(jié)構(gòu)工藝性 零件壁厚基本均勻，所有壁厚均大于塑件的最小壁厚1.7mm，根據(jù)pro/e模擬分析，注射成型時不會發(fā)生填充不足現(xiàn)象。 1.3、成型特性 1)其吸濕性強，塑料在成型前必須充分預(yù)熱干燥，其含水量應(yīng)小于0.3%。 2)流動性中等，溢邊值0.05mm。 3）塑料的加熱溫度讀塑件的質(zhì)量影響較大，溫度過高易于分解（分解溫度為250℃）。成型是宜采用較高的加熱溫度（模溫50～80℃）和較高的注射壓力。 1.4、ABS成型條件 注射機類型：柱塞式、螺桿均可 密度 ：1.03~1.05g/cm3 收縮率 ：0.003~0.008 預(yù)熱 ：80~85°C 料筒溫度：前段 150~170°C 中段 165~180°C 后段 180~200°C 噴嘴溫度：170~180°C 模具溫度：50~80°C 注射壓力：60~100Mpa 成型時間：注射時間 ： 20~90s 高壓時間 ： 0~5s 冷卻時間 ： 20~120s 總周期 ： 50~220s 2、注射機的選擇 一個產(chǎn)品的質(zhì)量為21克,根據(jù)以下公式，選擇注射機的最大注射量： K G公≥NG件+G廢 式中 K=0.8 N為型腔數(shù)量 G公為注射機公稱注射量 G件為產(chǎn)品重量 G廢為各部分冷料的質(zhì)量 由于根據(jù)設(shè)計要求和加工的經(jīng)濟性取N=1，通過proe得到G廢=5.628g G公≥（21+5.628）×1.25 =33.285（g） 也就是說注射機的注射量要大于33.285克。參照《模具設(shè)計與制造簡明手冊》選擇公稱注射量為60㎝3的注射機，機型為XZ-60/40，也就是說這臺注射機的公稱注射量為大約為60克。 XZ-60/40注射機參數(shù)如下： 螺桿直徑： 30㎜ 理論注塑容量：60㎝3 注射壓力：180Mpa 鎖模力：400KN 模板行程：250mm 模具厚度： 最大250㎜ 最小 80㎜ 頂出行程：70㎜ 噴嘴： 球半徑R10 孔直徑D3 定位孔直徑：D800+0.06 頂出（中心孔）直徑：D50 下面校核各部分參數(shù)： 2.1、注射量 KG公 =0.8×60 =48(g) NG件+G廢=1×21+5.628 =33.285(g) 很明顯 KG公>N G件+G廢，符合條件 2.2、注射壓力校核 P公=180MPa 產(chǎn)品要求注射壓力P注在70~100MPa之間 2.3、鎖模力校核 F≥K PmA 式中 F——注射機額定鎖模力（KN） Pm——型腔的平均計算壓力（MPa） K——安全系數(shù),取1.1~1.2 A——塑件及澆注系統(tǒng)等在分型面上的投影面積C㎡ 通過計算得A =9492mm2≈94.8 C㎡ F =400KN K PmA =1.2×35×106×9492×106=398664N 所以F >K PmA，符合條件 2.4、模板安裝尺寸 320×320的最大安裝尺寸完全可以安裝250×250的模具 2.5、模具厚度 所設(shè)計的模具厚度為245㎜，小于模具的最大厚度250mm。 3、確定模具基本結(jié)構(gòu) 經(jīng)分析，該零件為外殼類零件，要求外表面光滑，無明細痕跡，可選用的澆口形式有重疊式澆口、點澆口和潛伏式澆口。點澆口去除澆口留下的痕跡在制品外表面，產(chǎn)品為后蓋可以接受。因此必須采用雙分型面注射模，又稱為三板式注射模具，它增加了一個可移動的中間板（又名澆口板）。在開模時由于定距拉環(huán)的限制，中間板與定模座板做定距離的分開，以便取出這兩塊板之間流道內(nèi)的凝料，而利用推桿將型芯上的塑件脫出。 綜上，選擇一模二穴,單分型面,點澆口進料,推桿一次定出的注塑模具。 4、模具結(jié)構(gòu)設(shè)計 4.1、確定型腔數(shù)目及配置 本產(chǎn)品從最大注射量和經(jīng)濟性考慮，宜采用雙型腔。該產(chǎn)品成型面積較大，形狀簡單，為了使產(chǎn)品每個部分得到穩(wěn)定相同的壓力，因此應(yīng)該讓型腔與流道之間的距離盡可能短，使塑料熔體快速均勻充滿每個部分，使模具整體達到平衡穩(wěn)定。 4.2、選擇分型面 為了塑件及澆注系統(tǒng)凝料的托模和安放插件的需要,將模具適當(dāng)?shù)胤椒殖蓛蓚€或多個部分,這些可以分離部分的接觸表面稱之為分型面。為了便于脫模，分型面應(yīng)該設(shè)在塑件斷面尺寸最大的地方，盡量不影響制品的外觀。根據(jù)該塑件的結(jié)構(gòu)特征，主分型面設(shè)在塑件的下表面，垂直于開模方向。模具采用的是點澆口，具體情況見總裝圖。 4.3、澆注系統(tǒng)設(shè)計 4.3.1,主流道是澆注系統(tǒng)中從注射機噴嘴與模具相接觸的部位開始，到分流道為止的塑料熔體的流道通道。由于選的是臥式注塑機，主流道垂直于分型面。大頭并為倒錐形，錐角為3°，澆口套內(nèi)為錐形，其錐角為2°。 CAD Proe圖 4.3.2,澆口設(shè)計 澆口亦稱進料口，是指連接料流入型腔前的最狹窄部分,也是澆注系統(tǒng)中最短的一段,其尺寸狹小且短.目的是使料流入型腔前加速,便于充滿型腔,且利于封閉型腔口,防止熔體倒流,也便于成型后冷料于塑件分離.連接主流道與型腔的通道，根據(jù)該產(chǎn)品的結(jié)構(gòu)特點，采用點澆口。 如圖3所示為點進料結(jié)構(gòu)形式，又稱點澆口。適用于成型腔殼類零件，點澆口一般設(shè)在型腔底部這樣排氣順暢，成型良好。由于進料口小，故去澆口后殘留余量小，塑件上不易留有痕跡。 圖3 為了塑件熔體能快速地充滿型腔，澆口表面粗糙度很小，一般為Ra0.4以下,現(xiàn)取Ra0.4作為澆口的表面粗糙度。這樣不致產(chǎn)生較大的摩擦阻力，有利于充型。 4.3.3,冷料穴 在每個注塑成型周期開始時,最前端的料接觸低溫模具后會將溫,變硬被稱為冷料 . 4.3.4,定位圈:為保證模具主流道中心線與注塑機噴嘴中心線重合,注塑機固定模板上設(shè)有定位孔,模具的定模座板上應(yīng)設(shè)有凸起的定位圈,兩者按H9/h9間隙配合，對于其高度，去5mm CAD圖 PROE圖 4.3.4、排溢系統(tǒng)設(shè)計 排溢是指排出充模冷料中的前鋒冷料和模具內(nèi)的氣體等。廣義的注射模排溢系統(tǒng)應(yīng)包括澆注系統(tǒng)部分的排溢和成型部分的排溢。通常指的排溢是指成型部分的排溢。 模具充型過程程中，除了型腔內(nèi)原有的空氣外，還有塑料受熱或凝固而產(chǎn)生的低分子揮發(fā)氣體，尤其是在高速注射成型時，必須考慮如何將多余的氣體排出模外，否則被壓縮的氣體產(chǎn)生高溫引起塑件局部炭化，或使塑件產(chǎn)生氣泡的工藝缺陷。因此必要時可開設(shè)排氣槽等辦法.但是對于ABS這種材料,排氣間隙不得高于0.0 5㎜。 該零件為小型零件，所以利用分型面間隙以及推桿之間的縫隙排氣即可，不必單獨考慮排氣方式。 4.3. 5、確定型腔、型芯的結(jié)構(gòu)及固定方式 4.3. 5.1,型芯、型腔的結(jié)構(gòu)設(shè)計 為了便于熱處理和節(jié)約優(yōu)質(zhì)鋼材，型芯和型腔都采用整體鑲塊式結(jié)構(gòu)；另外，為便于制造，局部還采用鑲拼式結(jié)構(gòu)，型腔的四根吊桿，型芯的兩個吊塊，以及電池盒的吊塊。 4.3. 5.2,固定方式 型芯采用螺釘固定方式固定，型芯固定在支承板上，型腔固定在定模固定板上，兩者采用過盈配合。 型芯采用過盈配合 型腔與支撐板靠螺釘連接 4.3.6、確定頂出機構(gòu)類型 頂出機構(gòu)的結(jié)構(gòu)的基本要求是使塑件在頂出過程中不會損壞變形，本模具選用一次頂出機構(gòu)。 4.3.6.1,推桿數(shù)量及結(jié)構(gòu)形式 根據(jù)推桿布置許可空間，制品設(shè)16根推桿，推桿采用A型推桿，其公稱直徑為2mm。 4.3.6.2,復(fù)位裝置設(shè)計 頂出機構(gòu)在完成塑件的頂出動作后，為了進行下一步循環(huán)必須回到其初始位置。所以必須設(shè)置復(fù)位裝置，此處選用自動復(fù)位機構(gòu)。 4.3.6.3,頂出機構(gòu)的導(dǎo)向 推桿一般裝配在推板和頂桿固定板之間，為了防止推桿變形或折斷，必須在動模座板和支承板之間設(shè)置導(dǎo)向機構(gòu)。頂出機構(gòu)的導(dǎo)向裝置選用推板導(dǎo)柱和導(dǎo)套導(dǎo)向，導(dǎo)柱、導(dǎo)套的公稱直徑為16mm。 4.3.6.4,拉料桿 如前面澆注系統(tǒng)所示，采用凹槽型拉料桿，公稱直徑為4mm。 4.3.6.5,頂出距離 為了確保側(cè)抽芯和頂出時塑件能完全脫離動模，頂出距離不小于45mm。 4.3.6.7 型芯和型腔具體結(jié)構(gòu)設(shè)計 4.3.6.7.1型芯設(shè)計 1）、型芯的尺寸計算 a)、型芯的尺寸按以下公式計算 D=〈〔1+〕d+xΔ〉 式中D—型芯外徑尺寸 d—塑件內(nèi)形尺寸 Δ—塑件公差 —塑料平均收縮率 —成形零件制造公差,取Δ/2。 4.3.6.7.2 型腔設(shè)計 1）、型腔徑向尺寸按以下公式計算 D=〈〔1+〕d－xΔ〉 式中D—型腔的內(nèi)形尺寸 d—塑件外形基本尺寸 Δ— 塑件公差 —塑料平均收縮率 —成形零件制造公差,取Δ/2。 2)、型腔深度尺寸按以下公式計算 = 式中—型腔深度 —塑件外形高度尺寸 Δ— 塑件公差 —塑料平均收縮率 —成形零件制造公差,取 4.3.6.7.3 由于該產(chǎn)品不是透明的，所以型芯的表面粗糙度要求不需那么高。一般取Ra1.6,在機床上加工就可以直接投入使用，不需要經(jīng)過其它的特殊加工?？紤]模具的修模以及型芯的磨損，在精度范圍內(nèi)，型芯尺寸盡量取大值。而型腔則取大值，型腔的表面粗糟將決定產(chǎn)品的外觀，因此型腔的表面粗糙度則要求較高，一般取Ra0.8～0.4。在本次設(shè)計中，型腔取Ra0.8。 4.X——綜合修正系數(shù)（考慮塑料收縮率的偏差和波動，成型零件的磨損等因素），塑件精度低、批量較小時，X取1/2；塑件精度高、批量比較大，X取3/4，根據(jù)設(shè)計要求取X為0.5。 4.3.6. 8 型腔、型芯工作尺寸的計算 要計算型芯、型腔的工作尺寸，必先確定塑件的公差及模具的制造公差。根據(jù)要求塑件精度取五級精度。根據(jù)塑料制件公差數(shù)值表（SJ1372—78）塑件在五級精度下，基本尺寸對應(yīng)的尺寸公差如下： 基本尺寸㎜ 公差㎜ 基本尺寸㎜ 公差㎜ ＜3 0.16 3~6 0.18 6~10 0.20 10~14 0.22 14~18 0.24 18~24 0.28 24~30 0.32 30~40 0.36 40~50 0.40 50~65 0.46 65~80 0.52 80~100 0.60 100~120 0.68 4.3.6. 8.1 型腔：寬度方向d=47.7；取=0.5%（以下收縮率都取0.5%） D=[（1+0.005）×47.7－0.5×0.60]=47.6835 長度方向 d2’=55; D2’=[（1+0.005）×55－0.5×0.68]=54.935 4.3.6. 8. 2 型腔深度：H=40.2 ; X=0.4 H=[(1+0.005) ×40.2+0.4×0.18]=41.12 4.3.6. 8.3 型芯： 1）寬度方向d=47.7 D=[（1+0.005）×47.7+0.5×0.60]=48.2385 2）長度方向d=55 D=[（1+0.005）×55+0.5×0.68]=55.615 4.3.6. 9、型腔壁厚計算 4.3.6. 9.1.型腔的強度及剛度要求 塑料模具型腔的側(cè)壁和底壁厚度計算是模具設(shè)計中經(jīng)常遇到的問題，尤其對大型模具更為突出。目前常用的計算方法有按強度條件計算和按剛度條件計算兩類，但塑料模具要求既不許因強度不足而發(fā)生明顯變形，甚至破壞，也不許剛度不足而變形過大的情況，因此要求對強度和剛度加以考慮。對于型腔主要受到的力是塑料熔體的壓力，在塑料熔體的壓力作用下，型腔將產(chǎn)生內(nèi)應(yīng)力及變形。如果型腔側(cè)壁和底壁厚度不夠。當(dāng)型腔中產(chǎn)生的內(nèi)應(yīng)力超過材料的許用應(yīng)力時，型腔發(fā)生強度破壞，與此同時，剛度不足則發(fā)生彈性變形，從而產(chǎn)生溢料現(xiàn)象，將影響塑件成型質(zhì)量，所以模具對強度和剛度都有要求。 但是，實踐證明，模具對強度和剛度的要求并非同時兼顧，對大型腔，按剛度條件，對小型腔則按強度條件計算即可。（在本設(shè)計中按強度條件來計算） 1） 對長方形型腔壁厚和底板厚度的計算 a、型腔底板厚度： 式中——型腔內(nèi)塑料熔體的壓力（MPa），一般取25~45MPa L——型腔側(cè)壁邊長（mm） b——型腔寬度（mm） B——凹模寬度（mm） [σ]——材料的許用應(yīng)力，一般取100Mpa ——型腔側(cè)壁長邊尺寸（mm） =23.65mm 由于根據(jù)標(biāo)準模架查得定模板的厚度為25mm，綜合各方面考慮，現(xiàn)確定定模板厚為25mm，可以滿足型腔的強度要求。 b、確定型腔的壁厚 型腔寬度 鑲拼式腔壁厚 40 9 ＞40～50 9～10 ＞50～60 10～11 ＞60～70 11～12 ＞70～80 12～13 ＞80～90 13～14 ＞90～100 14～15 ＞100～120 15～17 ＞120～140 17～19 ＞140～160 19～21 4.3.6. 10、導(dǎo)向機構(gòu)的設(shè)計 注射模的導(dǎo)向機構(gòu)與定位機構(gòu)，主要用來保證動模與定模兩大部分或模內(nèi)其它零件之間的準確配合和可靠地分開，以避免模內(nèi)各零件發(fā)生碰撞和干涉，并確保塑件的形狀和尺寸精度。導(dǎo)向零件應(yīng)合理地均勻分布在模具的周圍或靠近邊緣的部位，其中心至模具邊緣應(yīng)有足夠的距離，以保證模具的強度，防止壓入導(dǎo)柱和導(dǎo)套后發(fā)生變形。根據(jù)模具的形狀和大小，一副模具 一般使用4根導(dǎo)柱。在此設(shè)計中采用了8根導(dǎo)柱，4根在定模部分，四根在定模部分，由于模具的凸模與凹模在裝配時有方位要求，在設(shè)計時采用等直徑不對稱結(jié)構(gòu)。 加工定模部分的4個導(dǎo)柱、導(dǎo)套孔時，應(yīng)將定模板、推流道板、動模板合在一起，一次性加工出來，以保證孔的同心度，然后再在定模座板上加工沉頭孔，動模部分導(dǎo)柱同理。 本模具采用有導(dǎo)柱導(dǎo)套配合要求的導(dǎo)向機構(gòu)，且在導(dǎo)柱導(dǎo)套上設(shè)有油槽，便于潤滑，使用壽命長。 4.3.6. 11.支承板 支撐板是墊在固定板后面的模板,他的作用是防止型芯或凸模.型腔,導(dǎo)柱,導(dǎo)套等零件突出,增強這些零件的穩(wěn)定性并承受型芯和型腔等傳來的成型壓力. 支撐板因具有足夠的強度和剛度,以承受成型壓力,他的強度和剛度計算與型腔底板的計算方法相似. 支撐板與固定板的連接方式; 4.3.6. 12.墊塊 墊塊的作用是使動模支撐板與動模座板間形成推出機構(gòu)運動的空間,或調(diào)接模具總高度以適應(yīng)成型設(shè)備上磨具安裝空間對模具總高度的要求 CAD圖 Proe圖 所有墊塊的高度應(yīng)一致,否著由于負荷不均勻而造成動模板損壞. 4.3.6. 13、冷卻系統(tǒng)設(shè)計 因塑料的加熱溫度對塑件的質(zhì)量影響較大，溫度過高容易分解，成型時要控制模溫在50~80℃?？紤]到模具的具體結(jié)構(gòu)，安裝冷卻水通道是一個既實惠又簡單的解決方法。 本模具比較復(fù)雜，零件較多，定模板已無空間放置冷卻水管，因此冷卻回路從定模直通型腔，在定模和型腔的配合部位加入防漏圈，裝配時應(yīng)該注意。 5、模具整體設(shè)計 模具的整體設(shè)計也就是模具的綜合設(shè)計，依據(jù)塑件的性能要求，綜合設(shè)計模具，以達到低成本、高效率、高效益的目的。而標(biāo)準化設(shè)計可降低成本，根據(jù)塑料注射模中小型模架GB/T 1255.6~12556.2━1990,選取定模板、動模板、定模座板、動模座板、墊塊、頂桿固定板、推板、導(dǎo)柱、導(dǎo)套、復(fù)位桿、澆口套、導(dǎo)柱、導(dǎo)套、頂桿、水嘴、定位銷等標(biāo)準件。 塑件在脫模后應(yīng)進行調(diào)濕處理，調(diào)濕處理是將剛脫模的制品放在熱水中（60～75℃），不僅可以隔絕空氣進行防止氧化的退火處理，同時還可以加快達到吸濕平衡，一般處理16～20min。 該模具的總體結(jié)構(gòu)如下圖6所示 圖6 其中定模座板、動模座板厚度為25mm，及定模板厚度都為40mm，而動模板厚度取20mm，動模支撐板10mm，推板取20mm，推桿固定板取16mm，支承板厚度取30mm，墊塊的高度取80mm，可以保證產(chǎn)品能順利的脫模。 根據(jù)以上選取，模具的厚度H==246mm＜250mm，符合要求。 總 結(jié) 經(jīng)過這次畢業(yè)設(shè)計，我覺得自己學(xué)到了不少東西。歸納起來，主要有以下幾點： ????1、大學(xué)四年的時間都是在學(xué)習(xí)機械理論基礎(chǔ)知識，并未真正地去應(yīng)用和實踐。平時很少接觸設(shè)計，加工，生產(chǎn)。但是在這次畢業(yè)設(shè)計，我在指導(dǎo)老師的帶領(lǐng)下多次深入工廠了解產(chǎn)品的注塑方法和模具的加工過程。在參觀學(xué)習(xí)中，發(fā)現(xiàn)了自己很多不足之處。我還體會到了所學(xué)理論知識的重要性：知識掌握得越多，設(shè)計得就更全面、更順利、更好。 2、了解進行一項設(shè)計必不可少的幾個階段。畢業(yè)設(shè)計能夠從理論設(shè)計和工程實踐相結(jié)合、鞏固基礎(chǔ)知識與培養(yǎng)創(chuàng)新意識相結(jié)合、個人作用和集體協(xié)作相結(jié)合等方面全面的培養(yǎng)學(xué)生的全面素質(zhì)。我經(jīng)過這次系統(tǒng)的畢業(yè)設(shè)計，熟悉了對模具進行設(shè)計、生產(chǎn)的詳細過程。這些對我在將來的工作和學(xué)習(xí)當(dāng)中都會有很大的幫助和啟發(fā)。 ?3、學(xué)會了怎樣查閱資料和利用工具書。平時課堂上所學(xué)習(xí)的知識不夠全面，作為機械專業(yè)的學(xué)生，由于專業(yè)特點自己更要積極查閱資料吸取別的在設(shè)計，加工中的寶貴經(jīng)驗。一個人不可能什么都學(xué)過，什么都懂，因此，當(dāng)你在設(shè)計過程中需要用一些不曾學(xué)過的東西時，就要去有針對性地查找資料，然后加以吸收利用，以提高自己應(yīng)用的能力，而且還能增長自己見識，補充最新的專業(yè)知識。???? 4、畢業(yè)設(shè)計對以前學(xué)過的理論知識起到了回顧作用，并對其加以進一步的消化和鞏固，對機械也有了整體性的認識。???? 5、畢業(yè)設(shè)計培養(yǎng)了嚴肅認真和實事求是的科學(xué)態(tài)度，而且培養(yǎng)了吃苦耐勞的精神以及相對應(yīng)的工程意識，同學(xué)之間的友誼互助也充分的在畢業(yè)設(shè)計當(dāng)中體現(xiàn)出來了，使我培養(yǎng)了強烈的團隊合作意識。 參考文獻： 1、譚志玉編著 塑料擠塑模與注塑模優(yōu)化設(shè)計，機械工業(yè)出版社，2000年第二版。 2、彭建生 吳成明 編著 簡明模具工實用技術(shù)手冊 ，機械工業(yè)出版社 ，2003年第二版。 3、彭建生編著 模具設(shè)計與加工速查手冊 機械工業(yè)出版社，2005年第二版。 4、黃小龍 高宏編著 Auto CAD2006 機械制圖 ，人民郵電出版社，2006。 5、龍馬工作室編 Pro/E完全自學(xué)手冊，，人民郵電出版社，2006 6 林慧國主編 模具材料應(yīng)用手冊 機械工業(yè)出版社，2004年。 7、楊占堯 編 注塑模具典型結(jié)構(gòu)圖例 化學(xué)工業(yè)出版社，2005年第一版； 8、譚建榮 張樹有 陸國棟 編 圖學(xué)基礎(chǔ)教程，高等教育出版社，1999年第一版。 9、寇世瑤主編 機械制圖，航空工業(yè)出版社，2001。 10、關(guān)興舉、杜智敏編 Pro/ENGINEER塑料模具設(shè)計，人民郵電出版社，2007。 11、金滌塵、宋放之主編 現(xiàn)代模具制造技術(shù)，機械工業(yè)出版社，2001。 12、楊明忠、朱家誠主編 機械設(shè)計，武漢理工大學(xué)出版社，2006。 13、曾志新主編 機械制造基礎(chǔ)，武漢理工大學(xué)出版社，2007。 14、彭建生 秦曉剛 模具技術(shù)問答，機械工業(yè)出版社，2003年第二版。 15、劉彩英編 塑料模設(shè)計手冊，機械工業(yè)出版社，2000年第二版。 16、王勻主編 Pro/e Wildfire模具設(shè)計，機械工業(yè)出版社，2005。 17、齊曉杰主編 塑料成型工藝與模具設(shè)計，機械工業(yè)出版社，2005。 致謝 這次畢業(yè)設(shè)計是在老師的精心指導(dǎo)下完成的，在整個學(xué)習(xí)和做論文的過程中，蔣老師對我們悉心指導(dǎo)和嚴格要求，為我們創(chuàng)造了良好的學(xué)習(xí)氛圍；他嚴謹?shù)闹螌W(xué)態(tài)度、高尚的敬業(yè)精神和淵博的學(xué)識，給我留下了深刻的印象，對我產(chǎn)生了巨大的影響，使我不僅掌握了更多的理論知識，而且在分析問題、解決問題的能力上有了很大的提高。 在設(shè)計過程中，一方面我深感自己知識的貧乏和平時鍛煉的重要性，深刻領(lǐng)會到實踐與理論的差異性；另一方面，通過這次獨立的設(shè)計，深深體會到理論與實踐的有機結(jié)合是學(xué)習(xí)和掌握知識的重要途徑，面對工作我們應(yīng)該有強大的學(xué)習(xí)努力，大學(xué)只是我們一個學(xué)習(xí)的一個天堂。在整個畢業(yè)設(shè)計過程中，使我提高了獨立思考問題和解決實際問題的能力。我通過各種方式收集、查找相關(guān)資料，發(fā)現(xiàn)了自己很多地方的不足，提高了對模具設(shè)計的興趣，更加堅定了自己的選擇。在此過程中我刻苦努力，虛心請教，不放過任何難點與疑問。設(shè)計中的很多問題都親自前往車間看產(chǎn)品相關(guān)設(shè)備和工人的實踐操作。這使我忘不了指導(dǎo)老師對我的多層次的認真的技術(shù)指導(dǎo)和真誠幫助。在此，我再次向他致以我最真誠的敬意和衷心的感謝。 與此同時，班集體給了我極大的幫助，與人交流與人分享其樂無窮，在這次設(shè)計中，和同學(xué)們互相學(xué)習(xí)共同提高，在此我要向班上的每一位同學(xué)致謝，是你們給了我學(xué)習(xí)的動力和探索的興趣。 最后，我要感謝機械行業(yè)的前輩們，是你們不斷的摸索和高超的智慧總結(jié)出來的經(jīng)驗給我夯實了學(xué)習(xí)的基礎(chǔ)，在此表示忠心的感謝。 工學(xué)院機制081 嚴維焱 2012年5月10日 編 號 20080986 江西農(nóng)業(yè)大學(xué) 工學(xué)院 畢業(yè)設(shè)計材料 題 目 專 業(yè) 機械設(shè)計制造及其自動化 學(xué)生姓名 材 料 目 錄 序號 附 件 名 稱 數(shù)量 備注 1 畢業(yè)設(shè)計論文 2 總裝配圖 3 零件圖 4 任務(wù)書 二〇一二 年 五 月 復(fù)讀機后蓋注射模設(shè)計姓名：嚴維焱 班級：機制081學(xué)號：20080986指導(dǎo)老師：蔣育華摘要摘要產(chǎn)品分析注塑機的選擇模具成型零件設(shè)計模具整體設(shè)計工作過程模具的特點一、產(chǎn)品分析一、產(chǎn)品分析1.1.復(fù)讀機后蓋產(chǎn)品復(fù)讀機后蓋產(chǎn)品2.2.塑件的材料及性能塑件的材料及性能1 1：所設(shè)計的塑件的材料為ABS，該材料綜合性能 好，沖擊強度高，尺寸穩(wěn)定，易于成型。2 2：成型性能成型性能 吸濕大,必須充分干燥,模溫宜取60-80度，脫模后應(yīng)進行調(diào)濕處理。3.3.產(chǎn)品要求產(chǎn)品要求1.1.1.1.要有較高的強度，在成型過程中應(yīng)無熔接痕。要有較高的強度，在成型過程中應(yīng)無熔接痕。2.2.2.2.要保證產(chǎn)品性能、尺寸精度以及互換性。要保證產(chǎn)品性能、尺寸精度以及互換性。4.4.解決方案解決方案1.由于是后蓋制品，有一定的外觀要求，因此選用點澆口。2.由于該塑件的質(zhì)量不大，采用一模兩腔，由此保證產(chǎn)品的制造精度。三、模具成型零件設(shè)計模具成型零件設(shè)計根據(jù)產(chǎn)品尺寸規(guī)格初選標(biāo)準模架為270X280mm1.1.型芯設(shè)計型芯設(shè)計（1）型芯采用整體式 優(yōu)點：加工效率高 減少裝配難度 可節(jié)約優(yōu)質(zhì)鋼材 減少加工量2.2.型腔設(shè)計型腔設(shè)計（1）型腔采用鑲拼組合式 優(yōu)點：加工難度小 加工成本低 易于保證型腔精度 方便更換四、模具的整體設(shè)計四、模具的整體設(shè)計根據(jù)GB/T12556.11990并結(jié)合塑件的具體情況選取其它結(jié)構(gòu)零件，最后得到如圖所示的模具。按注塑機的方向放置按注塑機的方向放置五、工作過程五、工作過程 1 1.模具的定模座板和動模座板通過四個壓鐵分別裝在注塑機的定模板和動模板上。2.模具閉模后,注塑機將塑料原料加熱到200左右，再通過噴嘴注入模具型腔中。動畫演示六、該模具的特點六、該模具的特點1 1.該模具采用電火花和線切割加工成型零件，從而能保證精度要求。2 2.能很好地解決成型時產(chǎn)生熔接痕造成產(chǎn)品強度不高的問題。謝謝各位老師謝謝各位老師第 22 頁 共 23 頁 桂林電子科技大學(xué)畢業(yè)設(shè)計用紙 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-oriented 1. 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. The Fig. 1. Assembly structure of an injection mould 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 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 Newton–Raphson 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 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 object’s 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 body’s as yet unsatisfied constraints, given the available degrees of freedom. It then calculates how that action further reduces the body’s 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], Kramer’s 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 3.2 Fig. 2. Feature-based, object-oriented hierarchical representation 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, 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