油泵齒輪殼鑄造工藝設(shè)計(jì)及模具(芯盒)設(shè)計(jì)【一模四腔】【說明書+CAD+3D】
油泵齒輪殼鑄造工藝設(shè)計(jì)及模具(芯盒)設(shè)計(jì)【一模四腔】【說明書+CAD+3D】,一模四腔,說明書+CAD+3D,油泵齒輪殼鑄造工藝設(shè)計(jì)及模具(芯盒)設(shè)計(jì)【一模四腔】【說明書+CAD+3D】,油泵,齒輪,鑄造,工藝,設(shè)計(jì),模具,芯盒,說明書,CAD
油泵齒輪殼鑄造工藝及模具（芯盒）設(shè)計(jì)
課程設(shè)計(jì)說明書
題 目：油泵齒輪殼鑄造工藝及模具(芯盒)設(shè)計(jì)
院 別：重慶大學(xué)
專 業(yè)：材料成型及控制工程(模具CAD/CAM)
姓 名：
學(xué) 號：
指導(dǎo)教師：
日 期： 2014年01月10日
油泵齒輪殼鑄造工藝及模具(芯盒)設(shè)計(jì)
摘要
對于載重汽車、卡車、消防車、牽引全掛車以及其改裝車型等中型汽車而言，當(dāng)前油泵齒輪殼的需求也越來越大，因此在油泵齒輪殼上也有比較高的要求，然而全國汽車生產(chǎn)量巨大，加上汽車配件量的需求也多，整車維修總量大，東風(fēng)生產(chǎn)的各種油泵齒輪殼的產(chǎn)量僅能維持自身的供給，難以確保對外界的供給。因此本設(shè)計(jì)的目的，是讓中小型企業(yè)擁有對中型貨車油泵齒輪殼自行制造的能力，并且能以較低的設(shè)備成本投入，通過改善提高工藝性能的方案和控制模具（芯盒）精度等方式，來獲取精度要求能與原廠生產(chǎn)油泵齒輪殼媲美的油泵齒輪殼。
關(guān)鍵詞：中型貨車；東風(fēng)汽車公司；油泵齒輪殼；工藝；模具；芯盒
目 錄
1、零件及加工分析 1
1.1.零件分析 1
1.2.零件加工方案分析 1
2、鑄造方案的類型和確定 2
2.1.鑄造方式： 2
2.2.制型方案： 2
2.3.模腔數(shù)量 3
2.4.砂型、砂芯材料選擇： 4
2.5.模樣及芯盒材料： 4
2.6.澆注系統(tǒng)形式選型： 5
3、鑄造工藝設(shè)計(jì) 6
3.1.工藝設(shè)計(jì)參數(shù)： 6
3.2.澆注位置： 7
3.3.鑄造分型面： 8
3.4.砂型（型腔）上下模確定： 9
3.5.砂芯設(shè)計(jì)： 9
4、澆注系統(tǒng)設(shè)計(jì) 10
4.1.澆注時(shí)間的確定 10
4.2.阻流截面面積的確定 11
4.3.內(nèi)澆道設(shè)計(jì) 13
4.4.橫澆道設(shè)計(jì) 13
4.5.直澆道設(shè)計(jì) 14
4.6.澆注系統(tǒng)的分布 14
5、芯盒設(shè)計(jì) 15
5.1.芯盒的總體布局 15
5.2.芯盒的主要結(jié)構(gòu)設(shè)計(jì) 15
5.3.芯盒的附具設(shè)計(jì) 15
6、芯盒工裝設(shè)計(jì) 16
參考文獻(xiàn) 17
致 謝 18
1、零件及加工分析
1.1.零件分析
1.1.1.零件主要結(jié)構(gòu)分析：
圖1 油泵齒輪殼箱體
汽車公司生產(chǎn)零件油泵齒輪殼箱體的零件圖如圖1所示，該油泵齒輪殼箱體是為一軸式結(jié)構(gòu)，安裝輸出軸，是本箱體最為核心的部位。箱體左右兩端平整，用以與其他零件相安裝連接。
1.1.2.制造工藝要求：
根據(jù)實(shí)際生產(chǎn)中的要求，總體歸納為以下4點(diǎn)：
1）工藝的實(shí)踐性要強(qiáng)，操作要輕便；
2）模具結(jié)構(gòu)簡單，制造容易；
3）工藝和模具的經(jīng)濟(jì)性好；
4）方便清砂。
由此，本設(shè)計(jì)的設(shè)計(jì)原則必須遵循以上提及的4個(gè)總體要求。
1.2.零件加工方案分析
根據(jù)零件的結(jié)構(gòu)性以及尺寸形位公差的要求，本設(shè)計(jì)箱體的總體制造方案分為兩步：第一步為鑄造；第二步進(jìn)行各有加工要求的部位以鏜、銑等基本的機(jī)械加工手段進(jìn)行加工，最終達(dá)到圖紙所要求的精度。
2、鑄造方案的類型和確定
2.1.鑄造方式：
鑄造方式多種多樣，而在這些方式里面，較為普遍的而且實(shí)用性較高的方式主要為以下幾種：砂型鑄造、消失模鑄造以及壓鑄。
2.1.1.砂型鑄造：
砂型鑄造成本很低，制作方便，能通過人工、機(jī)械造型，能滿足一般鑄件需求。但是一次鑄造成型砂型必須重新制作，需要另設(shè)造型設(shè)備，不能鑄造直徑小于30mm以下的孔類部位。
2.1.2.消失模鑄造：
鑄造精度較高，能制作各種小孔類型的部位，適應(yīng)于制作形狀較為復(fù)雜的鑄件，由于模樣的高溫融化，所以取件不須考慮型芯或型腔因結(jié)構(gòu)復(fù)雜而造成取模障礙等問題。然而一次模樣也是只能使用一次（因?yàn)樵诟邷罔T造過程中模樣會融化消失），消失模自身的力學(xué)性能較差，容易變形。
2.1.3.壓鑄：
壓鑄的精度非常高，在高壓下能輕松鑄造至每一個(gè)精細(xì)的部位、角落和小孔等，能鑄出結(jié)構(gòu)復(fù)雜的工件。不過設(shè)備成本非常高，對鑄造材料很有要求，鑄鐵類等材料均不宜進(jìn)行壓鑄。
方案確定：如上比較分析，本設(shè)計(jì)由于箱體鑄件材料正好是鑄鐵，因此不能使用壓鑄方式；由于該箱體壁厚7-10毫米，消失模強(qiáng)度不足，在鑄造操作過程中會變形，最終很可能導(dǎo)致鑄件變形量超差。因此本設(shè)計(jì)選擇砂型鑄造。
2.2.制型方案：
本設(shè)計(jì)在2.1的鑄造方式里已經(jīng)確定為砂型鑄造，因此型砂和型芯的制型方式也需要確定下來，普遍的制型方式主要有兩種：手工造型和機(jī)械造型。
2.2.1.手工造型：
不用額外購買造型設(shè)備，在單件小批量生產(chǎn)中成本低。不過勞動強(qiáng)度高，操作人員數(shù)量大，制型精度難以得到保證，造型生產(chǎn)周期長。
2.2.2.機(jī)械造型：
造型速度快，造型精度高，適應(yīng)于中、大批量生產(chǎn)。需要額外投入經(jīng)費(fèi)購買造型機(jī)，根據(jù)不同型號的造型機(jī)價(jià)格有所不一。
方案確定：綜合比較分析后，根據(jù)本設(shè)計(jì)生產(chǎn)實(shí)際需要，砂型精度要求比較高，手工造型無法滿足這種要求，而且本設(shè)計(jì)規(guī)模為中、大批量生產(chǎn)，手工造型會導(dǎo)致工人勞動強(qiáng)度過大，需要操作人員也多，加上生產(chǎn)周期長，到最后成本還會過高。因此選擇為機(jī)械造型，一次投資購買造型機(jī)，而造型機(jī)中,主要型號有Z145A Z148B Z230B其中Z145A適用的砂箱較小,制型數(shù)量有限，不能滿足批量生產(chǎn)要求,Z230B造型機(jī)過大，用砂量大以及較耗費(fèi)人力是主要缺陷，而型號Z148B造型機(jī)則能綜合滿足以上要求，能滿足本設(shè)計(jì)箱體的生產(chǎn)規(guī)模，同時(shí)也能節(jié)省用砂量。因此造型機(jī)選為Z148B。
2.3.模腔數(shù)量
模腔數(shù)量是指一套鑄型在一次裝配并進(jìn)行鑄造后，所獲得的鑄件數(shù)量，這個(gè)參數(shù)直接影響到型腔和澆注系統(tǒng)的布局以及用以制造砂型的砂箱的大小的設(shè)計(jì)，因此此項(xiàng)選擇不容缺失。
2.3.1.一型一腔：
一型一腔最大的特點(diǎn)就是鑄件的空間所占用砂箱空間少，易于鑄件及澆注系統(tǒng)在其內(nèi)的布局。但是部分方向的吃砂量只為單一個(gè)鑄型而設(shè)置，在本設(shè)計(jì)已確定的Z148B造型機(jī)中，這種布局會造成用砂量巨大浪費(fèi)，而且單腔生產(chǎn)數(shù)量的難以滿足較大生產(chǎn)規(guī)模的要求。
2.3.2.一型四腔：
較一型一腔式等批量生產(chǎn)更為節(jié)省用砂量，生產(chǎn)規(guī)模較大。然而由于要考慮砂芯和芯盒所要騰出的芯頭尺寸的空間，有可能會因此而使得所選用的砂箱較大，因此澆注系統(tǒng)以及鑄件擺放的方位需要有比較精細(xì)的安排，而且對鑄造工裝的裝配精度要求較高。
方案確定：由于本課題選擇購買的造型機(jī)型號為Z148B，從用砂量的節(jié)省角度以及生產(chǎn)規(guī)模需求角度考慮，更適合于一型四腔。因此本設(shè)計(jì)選定一型四腔。
2.4.砂型、砂芯材料選擇：
同一套砂型和砂芯雖然是鑄造同一個(gè)鑄件，然而各自負(fù)責(zé)成型部位不一樣，工作的環(huán)境和工藝性能也有所不一，對材料的依賴性很高，因此合理地對砂型和砂芯的型砂材料的選擇是提高鑄造工藝性以及經(jīng)濟(jì)性的重要環(huán)節(jié)之一。
常用的砂芯材料有：水玻璃砂，冷硬樹脂砂，粘土砂，潮模煤粉砂
方案確定：在本設(shè)計(jì)中，鑄件外表面需要有較高表面質(zhì)量，不應(yīng)機(jī)械粘砂，因此外模砂選用潮模煤粉砂。
而由于本設(shè)計(jì)中，油泵齒輪殼內(nèi)部結(jié)構(gòu)有內(nèi)凸部位，如果用水玻璃砂或者粘土砂這些較硬的芯砂，將必須經(jīng)過敲擊才能逐步取芯，特別是粘土砂，如果粘在內(nèi)部的內(nèi)壁上，在敲擊的過程中稍有不慎很容易會傷及鑄件本體，加上該設(shè)計(jì)的油泵齒輪殼最薄的壁厚僅有7毫米，如此的敲擊很容易會對其進(jìn)行損害，所以水玻璃砂和粘土砂不大可取，然而冷硬樹脂砂在鑄造的冷卻過程中，金屬會逐步收縮包緊型芯，利用冷硬樹脂砂與鐵水接觸表面的樹脂砂層強(qiáng)度的喪失，相互之間的距離會收縮，從而減少鑄件的收縮阻力，降低了鑄件的內(nèi)應(yīng)力及日后工作過程中開裂的傾向。因此本設(shè)計(jì)中砂芯選用冷硬樹脂砂。
2.5.模樣及芯盒材料：
模樣是用來對型腔成型的必要工具，芯盒是用于制作砂芯的母體。而這兩者的材料各種各樣，木制、塑膠、金屬，各自的使用性能、制造成本、加工工藝以及加工難度也各不一樣，正確的選擇模樣和芯盒的材料同樣是直接影響零件最終制造成本的關(guān)鍵因素之一。
芯盒材料分三種，木材，塑料和金屬，其中金屬是三者中最為昂貴的材料，加工難度也因模樣或芯盒的外形尺寸而變化，有的可以通過壓鑄直接獲得所需的成品，有的需要鑄造后進(jìn)行后機(jī)械加工或者熱處理或者電鍍加工等等方可投入使用。但金屬耐磨性是三者中最高的，而且強(qiáng)度很高，在高壓力的噴砂、壓砂和振砂的工作條件下依然能保持結(jié)實(shí)的狀態(tài)，盡管在批量生產(chǎn)工作后出現(xiàn)的小部分破損或者磨損，也能通過電焊的方式進(jìn)行填補(bǔ)修復(fù)工作，通過電鍍后在此進(jìn)行機(jī)械加工也能恢復(fù)表面質(zhì)量，因此維修效率和性價(jià)比都高。
方案確定：結(jié)合本設(shè)計(jì)需求和對表格內(nèi)容的分析，生產(chǎn)規(guī)模較大，如果用塑料和木材作為模樣的話，長期進(jìn)行造型工作中導(dǎo)致變形和失效。而選用金屬的話將能滿足長時(shí)間砂型造型工作而不被磨損和變形的要求。因此本設(shè)計(jì)選擇金屬作為模樣材料，為了防銹需要，具體選擇鑄鋁合金，牌號為ZL-106，而芯盒的材料牌號選定為ZL-108。
2.6.澆注系統(tǒng)形式選型：
澆注系統(tǒng)是整個(gè)鑄造系統(tǒng)中重要的組成部分，不同形式的澆注系統(tǒng)會影響到灰鐵金屬液體澆注的流動狀況以及和卷氣情況，最終決定了鑄件密度和內(nèi)部質(zhì)量。
澆注系統(tǒng)分：全封閉式，半封閉式，開放式，三種。
方案確定：由于本設(shè)計(jì)對鑄件的鑄造精度和表面質(zhì)量有比較高的要求，因此不允許出現(xiàn)斷續(xù)澆注的情況，而且澆注均勻，不卷氣，而且沖刷力應(yīng)足夠大，因此應(yīng)選擇全封閉式澆注系統(tǒng)。即直流道橫截面積必須大于橫澆道橫截總面積之和，橫澆道橫截面積之和必須大于內(nèi)澆道總面積之和。而且在直流道底部必須設(shè)有直流道窩，在橫澆道頂部要設(shè)有燕尾式斜角。
3、鑄造工藝設(shè)計(jì)
在所有的工程設(shè)計(jì)中，工藝設(shè)計(jì)必不可少，而鑄造工藝，主要就是根據(jù)鑄造零件的結(jié)構(gòu)特點(diǎn)、技術(shù)要求、生產(chǎn)批量和生產(chǎn)條件等，確定鑄造工藝方案和工藝參數(shù)，繪制鑄造工藝圖，編織工藝卡等技術(shù)文件。鑄造工藝設(shè)計(jì)的好壞，對鑄件品質(zhì)、生產(chǎn)率和成本起著重要作用，而鑄造工藝設(shè)計(jì)也是本設(shè)計(jì)中的工作重點(diǎn)。
3.1.工藝設(shè)計(jì)參數(shù)：
3.1.1.鑄件尺寸公差：
本設(shè)計(jì)中得鑄件尺寸公差，是從通過資料[2] P39表2-12中獲得的，根據(jù)實(shí)際生產(chǎn)的要求以及生產(chǎn)規(guī)模，鑄件的公差定為CT11級，在此表格中具體每一個(gè)尺寸范圍都有對應(yīng)的公差值，單位為mm。而本設(shè)計(jì)的主要對象是芯盒，主要加工結(jié)構(gòu)為內(nèi)腔結(jié)構(gòu)，在批量生產(chǎn)中，長期與型砂的摩擦和接觸，都會帶來一定的磨損。因此為了保留磨損余量，盡可能提高芯盒耐用度，特選擇尺寸公差值為負(fù)偏差。
3.1.2.鑄件重量公差：
本設(shè)計(jì)給定兩個(gè)鑄件加上澆注系統(tǒng)的總公稱重量，范圍在40~100kg內(nèi)，從資料[2] P40表2-13中本設(shè)計(jì)取得鑄件重量公差為12%。
3.1.3.機(jī)械加工余量：
通過資料中，結(jié)合P41表2-14 表2-15及P42表2-16的綜合查選，根據(jù)最大尺寸100~250mm范圍內(nèi)所對應(yīng)的G級選擇加工余量為2.0mm，為確保安全，特預(yù)為機(jī)械加工工人預(yù)留略多些的余量，取為2.5mm。
3.1.4.鑄件收縮率（模樣、芯盒放大率）：
本設(shè)計(jì)的鑄件收縮率是通過 資料 P43表2-17中獲得的，此表格中有兩個(gè)可供參考的欄目，分別是中國機(jī)械工程學(xué)會資料和美國鑄造學(xué)會資料，兩者略有不一，而本設(shè)計(jì)根據(jù)這是提供國內(nèi)中小型企業(yè)的生產(chǎn)設(shè)計(jì)，應(yīng)更趨于使用中國標(biāo)準(zhǔn)，因此參考表2-17中左欄的參數(shù)，條件為中小型件，受阻收縮，因此收縮率為0.7-0.9%。
3.1.5.最小鑄出孔槽：
根據(jù)灰鑄鐵的材料特性以及現(xiàn)有實(shí)際生產(chǎn)經(jīng)驗(yàn)，在本設(shè)計(jì)中，設(shè)定為鑄出的孔直徑不能小于，而由于本油泵齒輪殼箱體的倒檔齒輪的卡槽為內(nèi)部的盲槽，對日后機(jī)械加工不方便，因此該2個(gè)槽皆應(yīng)直接在鑄造時(shí)鑄出。
根據(jù)工藝參數(shù)，本設(shè)計(jì)的鑄件圖如圖2所示，詳見原CAD圖或圖紙。
圖2 油泵齒輪殼箱體鑄件圖
3.2.澆注位置：
鑄件的澆注位置是指澆注時(shí)鑄件在鑄型中的位置，澆注位置需要考慮以下的原則：
1）鑄件的重要部位、重要加工面應(yīng)該朝下或者呈直立狀態(tài)；
2）使鑄件的大平面應(yīng)該朝下；
3）應(yīng)保證鑄件能充滿；
4）應(yīng)有利于鑄件的補(bǔ)縮；
5）盡可能避免吊砂、吊芯或者單邊懸臂式砂芯，便于下芯、合箱以及檢驗(yàn)。
經(jīng)過綜合的考慮，選擇為圖3的澆注位置，中注式。
圖3 中注式澆注位置
3.3.鑄造分型面：
分型面是指兩半鑄型相互接觸的表面，本設(shè)計(jì)中有以下方案
如圖4-A所示，分型面是則能大大提高模底板的通用性以及分型面的簡易程度，分型面的平直意味著對模底板的通用性提高，只要是平直的底板即可使用，而且還會在兩個(gè)大軸圓邊上出現(xiàn)不可避免的工藝角，但由于其工藝角厚度非常小，能在鑄造完畢后通過清理修配方式進(jìn)行簡單的處理即可達(dá)到要求。
圖4-A 分（模）型面
3.4.砂型（型腔）上下模確定：
由于澆注系統(tǒng)往往是設(shè)置在上砂型（型腔）中，砂型（型腔）上下模會因?yàn)殍T件所占的高度不一而使得澆注系統(tǒng)占用的空間體積不一，再者靜壓力是否足夠也是個(gè)需要考慮的要素。具體如圖5-A
圖5-A
3.5.砂芯設(shè)計(jì)：
根據(jù)工藝參數(shù)的要求，砂芯的設(shè)計(jì)主要是隨形成型。
3.5.1.芯頭形狀設(shè)計(jì)：
本設(shè)計(jì)中的芯頭有2個(gè)，用以成型2個(gè)主軸孔的水平芯頭，2個(gè)水平芯頭皆為圓柱延伸體，頂部垂直芯頭為垂直方向往上延伸的隨形延伸體。
3.5.2.芯頭尺寸設(shè)計(jì)：
由于砂芯長度最大尺寸接近200mm，高度最大尺寸也超過100mm，因此為了讓砂芯擁有足夠的強(qiáng)度，2個(gè)水平芯頭皆設(shè)定為40mm，直徑與圖紙?jiān)庸げ课恢睆揭恢?，頂部砂芯高度也?0mm。
4、澆注系統(tǒng)設(shè)計(jì)
4.1.澆注時(shí)間的確定
計(jì)算體積，單個(gè)鑄件（機(jī)械加工余量已經(jīng)算入）約為5.2kg 澆注系統(tǒng)給定重量為4.5kg，拋灑系數(shù)1.02
得本設(shè)計(jì)中鑄造總重量約為W澆=（5.2kg4件+4.5kg）x1.02=25.806kg
4.1.1.澆注時(shí)間計(jì)算：
通過查 資料[1] P136表3-2查得適用公式為
其中鑄件厚度為7.0mm，所以S取1.95，而G則是鑄造總重量（即4個(gè)鑄件重量+澆注系統(tǒng)重量），G為25.806kg。
代入運(yùn)算
4.1.2.澆注時(shí)間校核：
通過 資料[1] P136式3-1
式中v——液面上升速度（mm/s）；
h——鑄件澆注時(shí)的高度，此處為150mm；
t——澆注時(shí)間，已算出9.9s。
代入運(yùn)算
然后查 資料[1] P136表3-3校驗(yàn)，正好大于所要求最小液面上升速度15mm/s，所以澆注時(shí)間計(jì)算合理。
4.2.阻流截面面積的確定
阻流截面面積，通過 資料[1] P137式3-2
式中 ——阻流截面面積（cm）；
G ——澆注系統(tǒng)（kg）；
——流量系數(shù)
t——澆注時(shí)間（s）；
HP——作用于內(nèi)澆道的金屬液靜壓頭，一般取平均壓頭（cm）。
4.2.1.鑄件重量：
澆注重量G為單個(gè)鑄件重量+澆注系統(tǒng),即=（5.2kg+1.1kg）x1.02=6.426kg
4.2.2.流量系數(shù)的計(jì)算：
先通過 資料[2] P138表3-6取值，干型，結(jié)構(gòu)相對簡單，阻力取中等，因此取得0.48。
然后在表3-7進(jìn)行細(xì)分修正：
1）從1280°起每50°C則+0.025，本設(shè)計(jì)澆注溫度選為1400°C，所以+0.05；
2）本設(shè)計(jì)不設(shè)有冒口，此處不修正；
3）根據(jù)設(shè)計(jì)從 資料[2] P65表3-6查得薄壁灰鑄件砂型鑄造的澆注系統(tǒng)面積比例為，則不符合，所以此處不修正；
4）阻流后澆注系統(tǒng)的截面面積比較均勻，沒有明顯的擴(kuò)大，此處不修正；
5）本設(shè)計(jì)單個(gè)鑄件設(shè)有2個(gè)內(nèi)澆道，-0.05；
6）雖然本設(shè)計(jì)不設(shè)有冒口，但型砂特別是砂芯的型砂為自硬樹脂砂，通氣性較好，此處不修正；
7）本設(shè)計(jì)為中間注入式，此處不作修正
最終得出=0.48。
4.2.3.平均壓頭Hp計(jì)算計(jì)算：
通過 資料[1] P138式3-3查得
式中C——澆注時(shí)鑄件高度，此處為43.5cm；
P——內(nèi)澆道以上的鑄件高度，此處，即為21.75cm；
Ho——內(nèi)澆道以上的金屬液壓頭，等于內(nèi)澆道到澆口盆液面的高度（cm）。為確定Ho，需要先計(jì)算壓力角。
給定鑄件與內(nèi)澆道接觸邊緣至直澆道中心線距離為35mm，經(jīng)過計(jì)算，L為150mm
給定單個(gè)砂型的澆注高度為83mm，上下砂型相同。
則有，則算出=28.8°
通過 資料[3] P131表3-13查得高于要求值10°，所以壓力角符合要求，設(shè)計(jì)合理，得Hm剩余壓頭高度為40mm，Ho=83mm=8.3cm。
最后代入公式
由上面已完全確定的 G、、Hp以及t，則可以代入原式計(jì)算
即阻流截面面積為2.58cm。
4.3.內(nèi)澆道設(shè)計(jì)
4.3.1.內(nèi)澆道形狀設(shè)計(jì)：
由 資料[2] P55圖3-11，參考（a）方案，扁平梯形，因?yàn)楸驹O(shè)計(jì)的鑄件最小壁厚只有7mm，根據(jù)鑄造的澆注系統(tǒng)設(shè)計(jì)原則，內(nèi)澆道高度應(yīng)該小于鑄件的最小壁厚，而且本設(shè)計(jì)為中間注入式澆注，所以方梯形，高梯形，圓形內(nèi)澆道均不適合。給定內(nèi)澆道高度為12毫米，斜度約為2°，在橫截面中上下底長度近乎一致，為簡化計(jì)算和模樣加工，所以直接取為相等，即本設(shè)計(jì)的內(nèi)澆道橫街面積定為矩形。
4.3.2.內(nèi)澆道尺寸設(shè)計(jì)：
考慮到應(yīng)安全系數(shù)，阻流截面面積應(yīng)該放大，取值為=258mm，即單個(gè)內(nèi)澆道的截面面積為，即=129mm。又因h=12mm，所以b=35mm。長度視橫澆道的尺寸而定。
4.4.橫澆道設(shè)計(jì)
4.4.1.橫澆道形狀設(shè)計(jì)：
橫澆道橫截面形狀為等腰梯形，為阻擋最先進(jìn)入澆道而且溫度相對低的金屬液體不進(jìn)入型腔，因此本設(shè)計(jì)橫澆道設(shè)有為傾斜末端。
4.4.2.橫澆道尺寸設(shè)計(jì)：
根據(jù)設(shè)計(jì)從 資料[2] P65表3-6查得澆注系統(tǒng)各澆道橫截面面積比例為
則
（注：為兩個(gè)鑄件所有內(nèi)澆道的面積代數(shù)和）
則一邊的橫澆道橫截面積為。
由于本設(shè)計(jì)橫澆道梯形為等腰梯形，設(shè)水平中線長度b，高度h=1.4b，得面積，即可求出b=20mm ，h=12mm。上下底分別相對中線，則上底長16mm，下底長20mm，高度取整12mm。
4.4.3.橫澆道長度設(shè)計(jì)：
考慮到先到達(dá)液體應(yīng)進(jìn)入橫澆道的末端，所以從內(nèi)澆道之外延伸30mm，兩內(nèi)澆道之間間隔為80mm，則總長度為150mm。
4.5.直澆道設(shè)計(jì)
4.5.1.直澆道形狀設(shè)計(jì)：
本設(shè)計(jì)的直澆道為直通型的圓柱體形狀，從砂型的頂部直接開通連接到橫澆道上的形式。
4.5.2.直澆道尺寸設(shè)計(jì)：
同上橫澆道設(shè)計(jì)，根據(jù)
則可求出半徑R為13.53mm，取整為13.5mm。即直澆道為。
長度因?yàn)槭侵蓖ㄊ?，所以設(shè)計(jì)為250mm。
為避免在澆注過程中發(fā)生反沖紊流現(xiàn)象，在直澆道的底部，即下砂型的頂部開設(shè)半球型的直澆道窩，尺寸為SR13.5。
4.6.澆注系統(tǒng)的分布
內(nèi)澆道分布設(shè)計(jì)，兩內(nèi)澆道應(yīng)該正好與鑄件的邊緣接觸。詳細(xì)請見CAD鑄造工藝圖所示。直澆道分布在兩個(gè)內(nèi)澆道距離上的正中央，直澆道的外圓邊緣與內(nèi)澆道之間的距離已超過了1.5倍橫澆道的高度，因此擁有足夠的浮渣行程。
5、芯盒設(shè)計(jì)
5.1.芯盒的總體布局
芯盒是用來制作砂芯的主要部件，在本設(shè)計(jì)中芯盒選為對開式芯盒，分為兩大部分，上芯盒和下芯盒，直接靠雙芯盒的分型。
5.2.芯盒的主要結(jié)構(gòu)設(shè)計(jì)
5.2.1.芯盒分模面設(shè)計(jì)：
芯盒的分模面可選與鑄造的分模面一樣，都可選擇平面分型面和曲面分型面，然而由于芯盒要制作的砂芯部位包括了芯頭，如果依然采用平線過渡的話，將會浪費(fèi)型砂，由于砂芯的型砂是自硬砂，價(jià)格相對很昂貴，因此為了盡可能的讓型砂都充分利用，分型面會隨著芯頭圓心所在的位置而發(fā)生變化。
5.2.2.壁厚設(shè)計(jì)：
根據(jù) 資料[1] P275圖6-19，經(jīng)過計(jì)算，本設(shè)計(jì)芯盒的平均輪廓尺寸為約200mm，則芯盒壁厚取為10mm。
5.2.3芯盒本體加強(qiáng)筋設(shè)計(jì)：
芯盒本體加強(qiáng)筋取為與芯盒壁厚相當(dāng)，為6mm，布置在芯盒急拐角、容易變形以及應(yīng)力集中的部位。
5.2.4.耐磨片設(shè)計(jì)：
本設(shè)計(jì)的芯盒刮砂面頂端設(shè)有2根3mm厚的條形防刮窄片，使用錐沉頭螺釘進(jìn)行固定，以保證在不影響刮砂前提下又能緊固防刮片。
5.3.芯盒的附具設(shè)計(jì)
5.3.1.芯盒導(dǎo)向機(jī)構(gòu)：
本設(shè)計(jì)的芯盒是以定位銷和定位套進(jìn)行定位，采用的是自行設(shè)計(jì)的可換導(dǎo)套座及可換銷座，該2個(gè)可換座的尺寸和裝配關(guān)系詳細(xì)請見可換套座的零件圖以及芯盒裝配圖。
6、芯盒工裝設(shè)計(jì)
芯盒工裝設(shè)計(jì)重點(diǎn)在于夾緊裝置，芯盒在合模之后，充砂之前，施加夾緊力是必不可少的。在實(shí)際生產(chǎn)中，轉(zhuǎn)動對開式芯盒的夾緊手段以活節(jié)螺栓與蝶形螺母為主，有的企業(yè)甚至為了獲得更大的夾緊力，采用渦輪蝸桿機(jī)械式鎖緊，甚至氣壓液壓式夾緊裝置。而本設(shè)計(jì)由于鑄件屬于中小型尺寸，用砂量相對少，充砂漲型不大，因此不必采用渦輪蝸桿或者氣液壓夾緊裝置，出于本芯盒外形結(jié)構(gòu)特征，并非轉(zhuǎn)動對開式芯盒，因此本設(shè)計(jì)的夾緊裝置為一種自行設(shè)計(jì)加工的緊固套。此緊固套工作原理是以緊固套內(nèi)壁在垂直方向7°的斜面對本芯盒特設(shè)置的垂直方向7°加強(qiáng)筋進(jìn)行接觸，角度為7°所提供的自鎖力足夠承受兩芯盒在水平方向的漲型力，能在不需施加任何外力的前提下確保緊固套本體不會往上反彈?？梢妶D17 緊固套裝配示意圖，詳細(xì)尺寸請見緊固套CAD零件圖。
參考文獻(xiàn)
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[12]Mistler.casting practice.America:American Ceramic Society, 2000 致 謝
本設(shè)計(jì)是在我的指導(dǎo)老師的親切關(guān)懷和悉心指導(dǎo)下完成的。他嚴(yán)肅的科學(xué)態(tài)度，嚴(yán)謹(jǐn)?shù)闹螌W(xué)精神，精益求精的工作作風(fēng)，深深地感染和激勵著我。從題目的選擇到最終完成，老師都始終給予我細(xì)心的指導(dǎo)和不懈的支持。
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ORIGINAL ARTICLEFast collision detection approach to facilitate interactivemodular fixture assembly design in a virtual environmentGaoliang Peng&Xin Hou&Chong Wu&Tianguo Jin&Xutang ZhangReceived: 27 May 2008 /Accepted: 21 April 2009 /Published online: 9 May 2009#Springer-Verlag London Limited 2009Abstract Collision detection is a fundamental componentto simulate realistic and natural object behaviors in virtualreality-based system. In this paper, a hybrid method ofspace decomposition and bounding volume approach ispresented to assist modular fixture assembly design in avirtual environment. Based on characteristics of modularfixture, a novel space decomposition methodology at objectlevel is proposed, which is achieved by automaticallypartitioning the checking space into cells according to theoriented bounding boxes of assembled elements after theinitial approximate collision detection using the intersectionchecking method based on separation plane-based bound-ing box. Then the pairs of candidate objects are determinedfor narrow phase exact polygons overlap tests. Results fromseveral performance tests on modular fixture design systemshow that an important advantage of this proposed methodcompared with other universal algorithms is its simpleinformation representation and low preprocessing cost.Keywords Collisiondetection.Virtualassembly.Modularfixture.Spacedecomposition.Boundingvolume1 IntroductionVirtual reality (VR) became a very common mean duringthe development of the industrial products. The aidprovided by VR is noticeable, since the user can interactwith the virtual prototype in a very natural way 13. VRholds great potential in manufacturing applications to solveproblems before fatal mistakes occur in practical manufac-turing so that great costs are prevented. VR applicationshave gained increasing attention internationally.Fixture design takes a significant part of the total time(cost) necessary for technical and technological productionpreparation. The design of a fixture is a highly complex andintuitive process, which requires knowledge and experience4. Modular fixtures are one of the important aspects ofmanufacturing. Proper fixture design is crucial to productquality with regard to the precision, accuracy, and finish ofthe machined part. Modular fixture is a system ofinterchangeable and highly standardized componentsdesigned to securely and accurately position, hold, andsupport the workpiece throughout the machining process5. Traditionally, fixture designers rely on experiences oruse trial-and-error methods to determine an appropriatefixture scheme.Since the potentially high degree of “reality” experi-enced in a virtual environment (VE), the VR-based modularfixture design has the advantages of designing a fixture in anatural and instructive manner, providing better match tothe working conditions, reducing lead-time, and generallyproviding a significant enhancement to fixture productivityand economy 6. In order to achieve this goal, the VRsystem must be able to simulate realistic and natural objectbehaviors. First of all, as a basic requirement of fixturedesign, there should be no collision between fixture,component and machine tool 7, 8; the objects notInt J Adv Manuf Technol (2010) 46:315328DOI 10.1007/s00170-009-2073-0G. Peng (*):X. Hou:T. Jin:X. ZhangSchool of Mechanical and Electrical Engineering,Harbin Institute of Technology,Harbin, Chinae-mail: C. WuSchool of Management, Harbin Institute of Technology,Harbin, Chinapenetrating into others must be guaranteed. Therefore, a fastinteractive collision detection (CD) algorithm is fundamen-tal in such a VR system.However, collision checking for a complex VE iscomputationally intensive. Researchers have addressedsome “universal” algorithms to reduce the computationalcosts. But these algorithms often need auxiliary datastructures and require intensive preprocessing time cost.In addition, the implementation of such algorithm is verycomplicated. Therefore, based on the well study of modularfixture characteristics and practical requirements, wedevelop a “special” CD algorithm to keep the associatedcosts as low as possible for VR-based modular fixtureassembly design.The paper is organized as follows. A review of relatedwork of the existing CD algorithms is presented inSection 2. Section 3 gives an overview of our proposedalgorithm. In Section 4, we describe the space subdivisionmodel used in our algorithm. Section 5 provides the detailsabout the broad phase of our proposed algorithm, in whichirrelevant objects are discarded and a set of objects that canpossibly collide are determined. The narrow phase for exactpolygon based overlap tests is described in Section 6.Section 7 presents some experimental results of ouralgorithm, and finally, in Section 8, we give concludingremarks and outline directions for future extensions of thiswork.2 Related workDuring the past few years, a great deal of effort has beenmade to solve the CD problem for various types ofinteractive 3D graphics and scenarios. For a workspacefilled with n objects, the most obvious problem is the O(n2)problem of detecting collisions between all objects, whichis time consuming and not bearable if the number n is large.Thus, some necessary techniques are needed to reduce thecomputational costs. Generally, a CD algorithm consists oftwo main steps, namely broad phase and narrow phase 9.The first phase aims to filter out pairs of objects which areimpossible to interact and determine which objects in theentire workspace potentially interact. The second phase isto perform a more accurate test to identify collisionbetween those selected object parts in the first phase,moreover if necessary, to find the pairs of contactingprimitive geometric elements (polygons), and to calculatethe overlapping distance.For a CD algorithm, it is critical to reduce the number ofpairs of objects or primitives that need to be checked.Therefore, a number of different techniques have been usedto make coarse grain detection, among which spacedecomposition and bounding volumes is most popular.In space decomposition methods, the environment issubdivided into space grids using hierarchical spacesubdivision. Objects in the environment are clusteredhierarchically according to the regions that they fall into.These objects are then checked for intersection by testingfor overlapping grid cells exploiting spatial partitioningmethods like Octrees 10, 11, BSP-trees 12, k-d trees13, etc. Using such decompositions in a hierarchicalmanner can further speed up the collision detection processbut leads to extremely high storage requirements.Bounding volume (BV) approach is used in previouscomputer graphics algorithms to speed up computation andrendering process. The BVof a geometric object is a simplevolume enclosing the object. Typically, BV types are axis-aligned boxes (AABBs) 14, spheres 15, and orientedbounding boxes (OBB) 16.Since AABBs method is simple to compute and allowsefficient overlap queries, it is often used in hierarchy, but italso may be a particularly poor approximation of the setthat they bound, leaving large “empty corners.” Thesystems utilizing AABBS include I-COLLIDE 17, Q-COLLIDE 18, and SOLID 19, etc.Bounding sphere is another natural choice to approxi-mate an object as it is particularly simple to test pairs foroverlap, and the update for a moving object is trivial.However, spheres are similar to AABBs as they can be poorapproximations to the convex hull of contained objects.In comparison, an OBB is a rectangular bounding box atarbitrary orientations in 3D space. In an ideal case, theOBB can be repositioned such that it is able to enclose anobject as tightly as possible. In other words, the OBB is thesmallest possible bounding box of arbitrary orientation thatcan enclose the geometry in question. This approach is verygood at performing fast rejection tests. A system calledRAPID 20 for interference detection based on OBB hasbeen built, which approximates geometry better thanAABBs. The shortcomings of OBB-tree against sphere treelie in its slowness to update and orientation sensitive 9.Most CD-related researches are involved in “universal”algorithms, and few literatures are found to develop CDapproach in a special application like virtual assembly.Actually, a fast and interactive collision detection algorithmis fundamental to a virtual assembly environment, whichallows designers to move parts or components to performassembly and disassembly operations.Figueiredo 21 presented a faster algorithm for thebroad and narrow phases of the collision detectionalgorithm of determining precise collisions between surfa-ces of 3D assembly models in virtual prototype environ-ments. The algorithm used the overlapping AABB and theR-tree data structure to improve performance in both thebroad and narrow phases of the collision detection. Thisapproach is for such a VE with objects dispersed in the316Int J Adv Manuf Technol (2010) 46:315328space. In addition, the R-tree data structure is very memoryintensive.Stephane 22 worked on continuous collision detectionmethods and constraints to deal with rigid polyhedralobjects for desktop virtual prototyping. Whereas such a4D method is only useful for handling the path of knownmoving objects. Especially, the algorithm is so computa-tionally intensive that it has to run on high-end computers.Collision detection is a critical problem in multi-axisnumerical control (NC) machining with complex machiningenvironments. There has been much previous work oninterference detection and avoidance in NC machiningsimulation. Wang 23 developed a graphics-assistedcollision detection approach for multi-axis NC machining.In this method, a combination of machining environmentculling and a two-phase collision detection strategy wasused.Researches surveyed above provided various efficienttechniques to carry out collision detection for polygonalmodels. However, these popular algorithms aimed atgeneral polygonal models, most of which need expensivepretreatments or large system memory or both of them inorder to improve the performance and meet real-timerequirements. Therefore, when these algorithms are utilizedin desktop VR application system such as modular fixturedesign, the requirement of real time cannot be wellguaranteed.Few CD researches can be found in the area ofcomputer-aided fixture design. Hu 24 presented analgorithm of fast interference checking between themachining tool and fixture units, as well as between fixtureunits, to replace the visually checked method. Moreover, inKumars work 25, in order to automate interference-freemodular fixture assembly design, the machining interferencedetection is accomplished through the use of cutter-sweptsolid based on cutter-swept volume approach. However,these algorithms are only capable of static interferencechecking and applied in CAD software packages.The research presented in this paper makes a solution tothese issues by addressing a “special” collision detectionalgorithm for VR-based modular fixture design. Theproposed algorithm uses the hybrid approach of spacedecomposition and bounding volume method to get highperformance.3 Algorithm overview3.1 Requirements for proposed algorithmWe aimed to develop a desktop VR-based modular fixtureassembly design system, in which the designer can selectsuitable fixture elements and put them together to generatea fixture structure, like “building blocks.” Without physicalfixture elements, he/she can test different structure schemesand finally design a feasible fixture configuration that meetsthe fixturing function requirements. In order to retain highdegree of “reality” in engineering application, there arethree main requirements for a CD algorithm to performmodular fixture configuration design:1.Precise and fast: During the simulation of assemblyand disassembly operations, finding precise collisionsis an important task for achieving realistic behavior26. When the user interactively assembles a part or acomponent, the “flying” object may collide with staticmodels, thus the system must find out the “colliding”event immediately. The interval between two checkingpoints should be near enough to achieve betterperformance. Otherwise, when objects move very fast,they may appear before checking, which will reduce theimmersive feelings. Therefore, the proposed systemcarries out a CD checking task in each rendering loopof VE. In addition, in modular fixture assembly designprocess, the designer selects elements and assemblesthem to right position or disassembles them to changethe fixture configuration. Once an element is assembledor disassembled, the “static” environment models areupdated. Accordingly, the CD checking model needsrestructure. So the preprocess should not take too long;otherwise, the performance of proposed system will beimpaired severely for certain “smooth feel” cannot beachieved.2.Low system requirements: Finding collisions in a 3Denvironment is time-consuming. In some cases, it caneasily consume up to 50% of the total run time 21.However, in modular fixture design workspace, thereare some other time-consuming tasks, such as designprocess control and reasoning, automatic geometricconstraints recognition and solving, etc. In spite of thecomplexity of the 3D virtual prototypes due tothousands of polygons, the designed CD checkingprocedure must be done in real time with relativelylow system resource demands.3.Low hardware cost: In order to achieve wider engi-neering applications, the proposed modular fixtureassembly system is designed to run on common PClike popular CAD commercial software. Althoughmuch research has engaged in developing hardware-accelerated CD algorithms, which utilize special graph-ic hardware, like graphics processing unit, to deal withthe computing collisions, thus the systems CPU can befreed. Nevertheless, we did not plan to adopt this kindof method and optimize performance only fromsoftware implementation. The objective of this researchis to develop a CD algorithmInt J Adv Manuf Technol (2010) 46:315328317Taking into account all above requirements, unfortunate-ly, these objectives usually are in conflict. To meet theprecise demand, we must increase checking frequencywhich will enormously increase the computational com-plexity and the memory bandwidth requirement. So, howcan a balance be reached with regard to these? In otherwords, how can the utilization of system resources beminimized yet the performance optimized without the helpof extra hardware? It is the start point of our algorithm.3.2 Modular fixture analysisThe objective of this research is to develop a CD algorithmfor assisting in modular fixture assembly design operationsin VE. To simplify the algorithm and to gain highperformance, the characteristics of modular fixture shouldbe well studied.1.Process of modular fixture assembly design: The tasksof modular fixture assembly design are to select theproper fixture elements and assemble them to aconfiguration one by one according to the designedfixturing plan. Thus, the CD problem in VR-basedmodular fixture assembly design can be stated as: theintersection checking between one moving object(assembling element or unit) with the static environ-ment objects (assembled elements) at discrete time.2.Fixture element shape: Modular fixture elements withregular shape can be classified into three types, namely,block, cylinder, and block-cylinder 27. Other compli-cated assembly units can be regarded as compositionsof these three meta-elements. It is well known that theOBB is tighter than the AABB and sphere. Moreover,when an object changes its position and orientation inVE, its OBB does not need to rebuild. Therefore, wecan construct OBBs of modular fixture elements off-line and store them as attributes of element models.During the assembly design process, such attributes canbe retrieved directly; thus, complex work for construct-ing bounding volume in run time can be avoided.3.Fixture element layout: A modular fixture system oftenconsists of supporting units, locating units, and clamp-ing units. These units lie out on the base plate andprovide corresponding functions at certain positions. AsFig. 1 shows, in the projection view parallel to the baseplate, the units are arranged in some kind of “regions.”In addition, to meet the height requirement of fixturingpoint, a unit often utilizes a number of supportingelements severed as blocking up objects. Therefore, atthe direction perpendicular to the baseplate, theelements lay out hierarchically. Accordingly, we candecompose the space with regard to elements layoutfeature.3.3 Algorithm flowchartAccording to the above characteristics of modular fixture,the proposed algorithm is designed to decrease thecomplexity and meet the requirements of VR-basedmodular fixture assembly design. As Fig. 2 shows, at thepreprocessing stage, once an element or component isassembled or disassembled, the Layer-based ProjectionModel (LPM) is established in terms of OBBs of thoseassembled elements. Such an LPM is used for the CDchecking when a new object is assembled.Just like the traditional CD method, proposed algorithmconsists of two steps, namely, broad phase and narrowphase. The broad phase is responsible for filtering pairs ofobjects that cannot intersect. At this stage, it determinespairs of objects in the same subspace, whose silhouettes inLPM overlap and their OBBs intersect. These pairs ofobjects are candidates for exact polygon-based collisiontests in the next narrow phase. During the broad phase, the(a)default view(b)downtown view Fig. 1 Modular fixture structure318Int J Adv Manuf Technol (2010) 46:315328test may cease at any time if no intersection is found, whichhelps to reject many noncollision or trivial collision cases.In the narrow phase, the collision detection algorithm willcalculate detailed intersection between geometrical meshesof the objects. If no intersection polygons are found, thecollide will not occur, and the active object can keep onmoving. Otherwise, whenever overlaps are detected, relatedreactions (for proposed system, it highlights objects anddoes back-tracking) may arise.4 Space decomposition for identifyingneighboring objectsConsidering the fact that most regions of the “universe” areoccupied by only a few objects or left empty, it means thatcollision only happens among objects that are close enough.So we can use this phenomenon to filter out most of “far-away” objects. Space decomposition is the commonapproach to be used for this intention. It first splits the“universe” into cells and then does further collision tests forobjects in the same cell. In order to keep generality, most ofexisting space subdivision approaches are based on a set ofpolygons. Such a “polygon-oriented” approach is socomputationally intensive to deal with large number ofpolygons. Since standard components are almost withrelatively regular shapes, we plan to develop an “object-oriented” space decomposition method.4.1 Space decomposition modelAfter the baseplate is arranged, the remaining work is toassemble the fixture elements or units onto the baseplate.As the assembling elements or units move to the assembledposition, collisions may happen between active object andthe assembled elements that have been fixed in the spacearound the baseplate. Hence, the CD checking processneeds start-up only after the active object enters into thisspace. Firstly, as Fig. 3a shows, we define a valid collisionspace noted as , which is a cuboid whose bottom face isdecided by the baseplate, and its height would change alongwith the assembling operation. The top of is determinedby the vertex coordinates of OBBs. is defined toguarantee that all the assembled elements are inside.After the checking space is identified, we need todecompose the space into a number of cells. How can weorganize these cells into proper structure and represent therelevant information to facilitate interaction checking? Inliterature, some
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