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編號(hào)
無(wú)錫太湖學(xué)院
畢業(yè)設(shè)計(jì)（論文）
相關(guān)資料
題目： MKZ84125軋輥磨床軸承
箱體翻轉(zhuǎn)機(jī)構(gòu)設(shè)計(jì)
信機(jī) 系 機(jī)械工程及自動(dòng)化專(zhuān)業(yè)
學(xué) 號(hào)： 0923226
學(xué)生姓名： 吳 佳
指導(dǎo)教師： 尤麗華 （職稱(chēng)：副教授 ）
（職稱(chēng)： ）
2013年5月25日
目 錄
一、畢業(yè)設(shè)計(jì)（論文）開(kāi)題報(bào)告
二、畢業(yè)設(shè)計(jì)（論文）外文資料翻譯及原文
三、學(xué)生“畢業(yè)論文（論文）計(jì)劃、進(jìn)度、檢查及落實(shí)表”
四、實(shí)習(xí)鑒定表
無(wú)錫太湖學(xué)院
畢業(yè)設(shè)計(jì)（論文）
開(kāi)題報(bào)告
題目： MKZ84125軋輥磨床軸承
箱體翻轉(zhuǎn)機(jī)構(gòu)設(shè)計(jì)
機(jī)械 系 機(jī)械工程及自動(dòng)化 專(zhuān)業(yè)
學(xué) 號(hào)： 0923226
學(xué)生姓名： 吳 佳
指導(dǎo)教師： 尤麗華 （職稱(chēng)：副教授 ）
（職稱(chēng)： ）
2012年11月25日
課題來(lái)源
本課題來(lái)自于無(wú)錫上機(jī)磨床有限公司的生產(chǎn)實(shí)際。該公司設(shè)計(jì)生產(chǎn)的自動(dòng)數(shù)控軋輥磨床在磨削工作輥的過(guò)程中，兩端的軸承箱體會(huì)與砂輪架發(fā)生干涉，而頻繁的裝卸軸承箱體則會(huì)使加工過(guò)程變得繁瑣。為了解決這個(gè)問(wèn)題，本課題要設(shè)計(jì)一個(gè)軋輥磨床翻轉(zhuǎn)機(jī)構(gòu)，在磨削工作輥時(shí)將軸承箱體翻轉(zhuǎn)90°，既避免了在加工過(guò)程中軸承箱體和砂輪架干涉，又保證了加工的效率。
科學(xué)依據(jù)（包括課題的科學(xué)意義；國(guó)內(nèi)外研究概況、水平和發(fā)展趨勢(shì)；應(yīng)用前景等）
十八世紀(jì)30年代，為了適應(yīng)鐘表、自行車(chē)、縫紉機(jī)和槍械等零件淬硬后的加工，英國(guó)、德國(guó)和美國(guó)分別研制出使用天然磨料砂輪的磨床。這些磨床是在當(dāng)時(shí)現(xiàn)成的機(jī)床如車(chē)床、刨床等上面加裝磨頭改制而成的，它們結(jié)構(gòu)簡(jiǎn)單，剛度低，磨削時(shí)易產(chǎn)生振動(dòng)，要求操作工人要有很高的技藝才能磨出精密的工件。
1876年在巴黎博覽會(huì)展出的美國(guó)布朗-夏普公司制造的萬(wàn)能外圓磨床，是首次具有現(xiàn)代磨床基本特征的機(jī)械。它的工件頭架和尾座安裝在往復(fù)移動(dòng)的工作臺(tái)上，箱形床身提高了機(jī)床剛度，并帶有內(nèi)圓磨削附件。1883年，這家公司制成磨頭裝在立柱上、工作臺(tái)作往復(fù)移動(dòng)的平面磨床。
1900年前后，人造磨料的發(fā)展和液壓傳動(dòng)的應(yīng)用，對(duì)磨床的發(fā)展有很大的推動(dòng)作用。隨著近代工業(yè)特別是汽車(chē)工業(yè)的發(fā)展，各種不同類(lèi)型的磨床相繼問(wèn)世。例如20世紀(jì)初，先后研制出加工氣缸體的行星內(nèi)圓磨床、曲軸磨床、凸輪軸磨床和帶電磁吸盤(pán)的活塞環(huán)磨床等。
自動(dòng)測(cè)量裝置于1908年開(kāi)始應(yīng)用到磨床上。到了1920年前后，無(wú)心磨床、雙端面磨床、軋輥磨床、導(dǎo)軌磨床，珩磨機(jī)和超精加工機(jī)床等相繼制成使用；50年代又出現(xiàn)了可作鏡面磨削的高精度外圓磨床；60年代末又出現(xiàn)了砂輪線速度達(dá)60～80米/秒的高速磨床和大切深、緩進(jìn)給磨削平面磨床；70年代，采用微處理機(jī)的數(shù)字控制和適應(yīng)控制等技術(shù)在磨床上得到了廣泛的應(yīng)用。
隨著高精度、高硬度機(jī)械零件數(shù)量的增加，以及精密鑄造和精密鍛造工藝的發(fā)展，磨床的性能、品種和產(chǎn)量都在不斷的提高和增長(zhǎng)。
磨床是各類(lèi)金屬切削機(jī)床中品種最多的一類(lèi)，主要類(lèi)型有外圓磨床、內(nèi)圓磨床、平面磨床、無(wú)心磨床、工具磨床等。
外圓磨床是使用的最廣泛的，能加工各種圓柱形和圓錐形外表面及軸肩端面的磨床。萬(wàn)能外圓磨床還帶有內(nèi)圓磨削附件，可磨削內(nèi)孔和錐度較大的內(nèi)、外錐面。不過(guò)外圓磨床的自動(dòng)化程度較低，只適用于中小批單件生產(chǎn)和修配工作。
內(nèi)圓磨床的砂輪主軸轉(zhuǎn)速很高，可磨削圓柱、圓錐形內(nèi)孔表面。普通內(nèi)圓磨床僅適于單件、小批生產(chǎn)。自動(dòng)和半自動(dòng)內(nèi)圓磨床除工作循環(huán)自動(dòng)進(jìn)行外，還可在加工中自動(dòng)測(cè)量，大多用于大批量的生產(chǎn)中。
平面磨床的工件一般是夾緊在工作臺(tái)上，或靠電磁吸力固定在電磁工作臺(tái)上，然后用砂輪的周邊或端面磨削工件平面的磨床；無(wú)心磨床通常指無(wú)心外圓磨床，即工件不用頂尖或卡盤(pán)定心和支承，而以工件被磨削外圓面作定位面，工件位于砂輪和導(dǎo)輪之間，由托板支承，這種磨床的生產(chǎn)效率較高，易于實(shí)現(xiàn)自動(dòng)化，多用在大批量生產(chǎn)中。
工具磨床是專(zhuān)門(mén)用于工具制造和刀具刃磨的磨床，有萬(wàn)能工具磨床、鉆頭刃磨床、拉刀刃磨床、工具曲線磨床等，多用于工具制造廠和機(jī)械制造廠的工具車(chē)間。
砂帶磨床是以快速運(yùn)動(dòng)的砂帶作為磨具，工件由輸送帶支承，效率比其他磨床高數(shù)倍，功率消耗僅為其他磨床的幾分之一，主要用于加工大尺寸板材、耐熱難加工材料和大量生產(chǎn)的平面零件等。
專(zhuān)門(mén)化磨床是專(zhuān)門(mén)磨削某一類(lèi)零件，如曲軸、凸輪軸、花鍵軸、導(dǎo)軌、葉片、軸承滾道及齒輪和螺紋等的磨床。除以上幾類(lèi)外，還有珩磨機(jī)、研磨機(jī)、坐標(biāo)磨床和鋼坯磨床等多種類(lèi)型。
由于長(zhǎng)期以來(lái)對(duì)新技術(shù)的應(yīng)用相對(duì)滯后，國(guó)內(nèi)機(jī)床產(chǎn)品的總體技術(shù)水平比之先進(jìn)國(guó)家同類(lèi)型機(jī)床還有著相當(dāng)大的差距，勞動(dòng)生產(chǎn)率低下，在國(guó)際市場(chǎng)中競(jìng)爭(zhēng)力不足，經(jīng)濟(jì)效益不高。在國(guó)外高檔機(jī)床大舉進(jìn)攻中國(guó)市場(chǎng)的情況下，我們只有以積極的姿態(tài)面對(duì)這一嚴(yán)峻的形勢(shì)。盡快應(yīng)用先進(jìn)的設(shè)計(jì)技術(shù)，能快速開(kāi)發(fā)出結(jié)構(gòu)合理、自動(dòng)化水平高、加工精度高、低振動(dòng)、低成本的機(jī)床新產(chǎn)品響應(yīng)市場(chǎng)，我國(guó)的機(jī)床工業(yè)才有出路。為了達(dá)到這一目的，掌握先進(jìn)的機(jī)床設(shè)計(jì)方法就顯得尤為重要。我國(guó)機(jī)床工業(yè)的竟?fàn)幠芰Φ奶岣咭簿腿Q于機(jī)床新品的開(kāi)發(fā)和關(guān)鍵技術(shù)的研究、掌握、應(yīng)用和迅速推廣。隨著我國(guó)加入世界貿(mào)易組織和全球經(jīng)濟(jì)一體化環(huán)境的形成，機(jī)床行業(yè)的市場(chǎng)競(jìng)爭(zhēng)將會(huì)愈演愈烈。目前，國(guó)內(nèi)外機(jī)床產(chǎn)品技術(shù)水平之間的差距仍然很大，主要表現(xiàn)為:產(chǎn)品仿制多，創(chuàng)新少，市場(chǎng)競(jìng)爭(zhēng)力不足，利潤(rùn)低:設(shè)計(jì)方法落后，機(jī)床結(jié)構(gòu)設(shè)計(jì)，尚處于傳統(tǒng)的經(jīng)驗(yàn)、靜態(tài)、類(lèi)比的設(shè)計(jì)階段，很少考慮結(jié)構(gòu)動(dòng)、靜態(tài)特性對(duì)機(jī)床產(chǎn)品性能產(chǎn)生的影響，產(chǎn)品精度低，質(zhì)量難以保證;設(shè)計(jì)周期長(zhǎng)，成功率低，反復(fù)設(shè)計(jì)、試制與修改，產(chǎn)品更新?lián)Q代慢，且成本高。
研究?jī)?nèi)容
軋輥磨床為金屬切削機(jī)床，由床身、頭架、尾架、托架、縱橫拖板、磨頭、測(cè)量架及電氣數(shù)控系統(tǒng)組成，分為承載系統(tǒng)、驅(qū)動(dòng)系統(tǒng)、磨削系統(tǒng)、測(cè)量系統(tǒng)和控制系統(tǒng)五個(gè)子系統(tǒng)。工件由頭架、尾架和托架支撐，并由頭架驅(qū)動(dòng)旋轉(zhuǎn)。數(shù)控系統(tǒng)根據(jù)軋輥表面母線的數(shù)學(xué)模型，控制機(jī)床作多軸復(fù)合運(yùn)動(dòng)，在運(yùn)動(dòng)過(guò)程中實(shí)現(xiàn)砂輪對(duì)輥面金屬的磨削。在線測(cè)量系統(tǒng)實(shí)時(shí)地將測(cè)量數(shù)據(jù)反饋給磨床控制系統(tǒng)，并由控制系統(tǒng)對(duì)機(jī)床出閉環(huán)控制，從而完成對(duì)工件的精密加工。
床身：采用砂輪床身與工件床身分離的結(jié)構(gòu)。床身調(diào)整墊鐵間距短，剛性強(qiáng)，床身精度不易變化。砂輪床身為大約為1200mm導(dǎo)軌間距的寬體床身，配備的伸縮式不銹鋼防護(hù)罩保證永不生銹，安裝在砂輪床身內(nèi)的精密滾珠絲桿，用于驅(qū)動(dòng)大拖板(Z軸)。
頭架：采用三級(jí)三角皮帶傳動(dòng)保證了傳動(dòng)的平穩(wěn)和精度；使用交流主軸電機(jī)驅(qū)動(dòng)能使頭架實(shí)現(xiàn)正向和反向旋轉(zhuǎn)；頭架的位置控制功能，可實(shí)現(xiàn)撥盤(pán)角度自動(dòng)定位，方便軋輥的吊裝，減少輔助時(shí)間。頭架潤(rùn)滑系統(tǒng)選用了油脂泵，可實(shí)現(xiàn)自動(dòng)定時(shí)給油。
尾架：移動(dòng)采用電動(dòng)驅(qū)動(dòng)方式，液壓自動(dòng)鎖緊。尾架配備大行程(1000mm)液壓套筒。
砂輪主軸系統(tǒng)：前后徑后軸承均采用高精度動(dòng)靜壓軸承，主軸軸向采用高精度推力軸承。另外，在后軸承設(shè)計(jì)中增強(qiáng)了工作腔動(dòng)靜壓軸承的靜態(tài)壓力效果，以克服較大皮帶拉力對(duì)軸瓦造成的損傷。主軸動(dòng)靜壓軸承具有回轉(zhuǎn)精度高，穩(wěn)定性好，動(dòng)態(tài)剛性強(qiáng)，不易振動(dòng)等特點(diǎn)。
磨架及其進(jìn)給機(jī)構(gòu)：磨架采用單層整體結(jié)構(gòu)，具有很高的剛性，磨架導(dǎo)軌為貼塑靜壓導(dǎo)軌，磨架進(jìn)給機(jī)構(gòu)由帶減速裝置的西門(mén)子交流伺服電機(jī)和經(jīng)過(guò)精確預(yù)拉伸的精密滾珠絲桿副組成，具有很高的進(jìn)給精度和靈敏度。
拖板(Z軸)：拖板采用V-平形形式的貼塑靜壓導(dǎo)軌，拖板進(jìn)給機(jī)構(gòu)由帶減速裝置的西門(mén)子交流伺服電機(jī)和經(jīng)過(guò)精確預(yù)拉伸精密滾珠絲桿副組成，由數(shù)控系統(tǒng)通過(guò)交流伺服電機(jī)和圓光柵實(shí)現(xiàn)拖板的閉環(huán)位置控制。拖板采用滾珠絲桿傳動(dòng)，與國(guó)內(nèi)外同類(lèi)磨床所采用的傳統(tǒng)齒輪齒條傳動(dòng)相比，具有機(jī)械傳動(dòng)鏈短、運(yùn)動(dòng)平穩(wěn)、傳動(dòng)精度高、間隙小等優(yōu)點(diǎn)。
頭架控制系統(tǒng)：頭架采用西門(mén)子1PH7型交流主軸電機(jī)驅(qū)動(dòng)，內(nèi)裝西門(mén)子Sine/Cos1Vpp，2048 S/R光電編碼器，完成頭架速度及位置的閉環(huán)控制。頭架可實(shí)現(xiàn)正向和反向旋轉(zhuǎn)以及撥盤(pán)角度自動(dòng)定位。交流主軸電機(jī)的采用使頭架電機(jī)的維護(hù)工作量大大減少。針對(duì)軋輥驅(qū)動(dòng)的特點(diǎn)頭架采用了低額定轉(zhuǎn)速、大啟動(dòng)扭矩的交流主軸電機(jī)，在保證重型軋輥啟動(dòng)需要的同時(shí)節(jié)約寶貴的能源。
砂輪控制系統(tǒng)：砂輪采用西門(mén)子1PH7型交流主軸電機(jī)驅(qū)動(dòng)，內(nèi)裝西門(mén)子Sine/Cos1Vpp,2048 S/R光電編碼器，完成砂輪速度及位置的閉環(huán)控制。砂輪可實(shí)現(xiàn)正向和反向旋轉(zhuǎn)以及角度自動(dòng)定位。另外，交流主軸電機(jī)的采用極大地方便了砂輪電機(jī)的維護(hù)。砂輪采用了高達(dá)100KW的交流主軸電機(jī)，保證了磨床具有強(qiáng)力磨削能力，滿(mǎn)足用戶(hù)的軋輥快速大負(fù)荷加工要求。
電氣控制柜及柜內(nèi)配電系統(tǒng)和控制元件：為保證磨床電氣系統(tǒng)的整體可靠性，從電氣控制柜箱殼到柜內(nèi)的配電系統(tǒng)以及保護(hù)元件、開(kāi)關(guān)元件、控制元件全部采用進(jìn)口的國(guó)際名牌產(chǎn)品(西門(mén)子、威圖)。
擬采取的研究方法、技術(shù)路線、實(shí)驗(yàn)方案及可行性分析
通過(guò)對(duì)MKZ84125自動(dòng)數(shù)控軋輥磨床實(shí)地考察，總結(jié)得出該磨床的基本結(jié)構(gòu)，工作方式與原理，然后根據(jù)考察的結(jié)果，再查閱相關(guān)書(shū)籍后對(duì)其進(jìn)行整體設(shè)計(jì)的基礎(chǔ)，再根據(jù)上機(jī)磨床廠給定的關(guān)于機(jī)床的尺寸參數(shù)，翻箱動(dòng)作的具體要求以及大連重工集團(tuán)有限公司設(shè)計(jì)的待加工工作輥的相關(guān)資料，對(duì)在MKZ84125自動(dòng)數(shù)控軋輥磨床上使用的翻箱機(jī)構(gòu)進(jìn)行設(shè)計(jì)，進(jìn)行初步設(shè)計(jì)。交由指導(dǎo)老師檢查，修改。完成后，再對(duì)主要載荷部件進(jìn)行校核。最后出主要零件的零件圖，編寫(xiě)設(shè)計(jì)說(shuō)明書(shū)。
可行性分析：軋輥磨床通常是用來(lái)磨削工作輥的。由于工作輥在使用過(guò)程中磨損較快，平均兩到三個(gè)小時(shí)就要進(jìn)行修整磨削，否則將達(dá)不到所要求的加工精度，所以軋輥磨床除用于在加工工作輥時(shí)來(lái)磨削工作輥外，還需要在生產(chǎn)中用于對(duì)工作輥進(jìn)行頻繁的修磨。當(dāng)軋輥磨床用于加工工作輥時(shí)，工作輥是在沒(méi)有和其兩端的軸承箱體進(jìn)行裝配的情況下，單獨(dú)在磨床上進(jìn)行磨削的。而工作輥在使用中兩端會(huì)裝配有軸承箱體，如果對(duì)工作輥進(jìn)行帶箱磨削，則由于軸承箱體的結(jié)構(gòu)和存在一定的偏心，在重力作用下擺放的自然位置會(huì)和砂輪架發(fā)生干涉，使工作輥的工作表面不能得到完整的修磨。因此對(duì)工作輥進(jìn)行修磨前要將軸承箱體拆卸下來(lái)，需要耗費(fèi)大量的時(shí)間和人力。由此可見(jiàn)，該課題方案切實(shí)可行。
研究計(jì)劃
對(duì)于本課題,初步確定按以下步驟進(jìn)行：
（1）應(yīng)先通過(guò)查找文獻(xiàn)了解機(jī)床的基本結(jié)構(gòu)，熟悉機(jī)床的具體工作原理；
（2）完成整機(jī)的總體布局設(shè)計(jì)，并繪制相應(yīng)的二維圖紙；
（3）完成翻箱機(jī)構(gòu)的設(shè)計(jì)，繪制相應(yīng)的二維裝配圖；
（4）完成部分零件圖設(shè)計(jì)。
預(yù)期成果
由于工作輥在使用過(guò)程中磨損較快，平均兩到三個(gè)小時(shí)就要進(jìn)行修整磨削，否則將達(dá)不到所要求的加工精度，所以軋輥磨床除用于在加工工作輥時(shí)來(lái)磨削工作輥外，還需要在生產(chǎn)中用于對(duì)工作輥進(jìn)行頻繁的修磨。
當(dāng)軋輥磨床用于加工工作輥時(shí)，工作輥是在沒(méi)有和其兩端的軸承箱體進(jìn)行裝配的情況下，單獨(dú)在磨床上進(jìn)行磨削的。而工作輥在使用中兩端會(huì)裝配有軸承箱體，如果對(duì)工作輥進(jìn)行帶箱磨削，則由于軸承箱體的結(jié)構(gòu)和存在一定的偏心，在重力作用下擺放的自然位置會(huì)和砂輪架發(fā)生干涉，使工作輥的工作表面不能得到完整的修磨。因此對(duì)工作輥進(jìn)行修磨前要將軸承箱體拆卸下來(lái)，需要耗費(fèi)大量的時(shí)間和人力。
通過(guò)對(duì)該自動(dòng)數(shù)控軋輥磨床上使用的翻箱機(jī)構(gòu)進(jìn)行設(shè)計(jì)，實(shí)現(xiàn)在磨削前將軸承箱體從自然位置翻轉(zhuǎn)一定的角度，使其在磨削過(guò)程中不再和砂輪架發(fā)生干涉，從而實(shí)現(xiàn)帶箱磨削，可大大提高用戶(hù)在生產(chǎn)中的效率。
已具備的條件和尚需解決的問(wèn)題
① 設(shè)計(jì)過(guò)程中所需要的各種軟硬件資源和相關(guān)產(chǎn)品實(shí)物照片。
② 相關(guān)文獻(xiàn)資料的缺乏，對(duì)一些結(jié)構(gòu)設(shè)計(jì)部分的具體設(shè)計(jì)指導(dǎo)，以及一些裝配尺寸的確定。
指導(dǎo)教師意見(jiàn)
指導(dǎo)老師簽名：
年 月 日
教研室（學(xué)科組、研究所）意見(jiàn)
教研室主任簽名：
年 月 日
系意見(jiàn)
教研室主任簽名：
年 月 日
Fundamentals of Mechanical Design
Mechanical design means the design of things and systems of a mechanical nature—machines, products, structures, devices, and instruments. For the most part mechanical design utilizes mathematics, the materials sciences, and the engineering-mechanics sciences.
The total design process is of interest to us. How does it begin? Does the engineer simply sit down at his desk with a blank sheet of paper? And, as he jots down some ideas, what happens next? What factors influence or control the decisions which have to be made? Finally, then, how does this design process end?
Sometimes, but not always, design begins when an engineer recognizes a need and decides to do something about it. Recognition of the need and phrasing it in so many words often constitute a highly creative act because the need may be only a vague discontent, a feeling of uneasiness, of a sensing that something is not right.
The need is usually not evident at all. For example, the need to do something about a food-packaging machine may be indicated by the noise level, by the variations in package weight, and by slight but perceptible variations in the quality of the packaging or wrap.
There is a distinct difference between the statement of the need and the identification of the problem. Which follows this statement? The problem is more specific. If the need is for cleaner air, the problem might be that of reducing the dust discharge from power-plant stacks, or reducing the quantity of irritants from automotive exhausts.
Definition of the problem must include all the specifications for the thing that is to be designed. The specifications are the input and output quantities, the characteristics of the space the thing must occupy and all the limitations on these quantities. We can regard the thing to be designed as something in a black box. In this case we must specify the inputs and outputs of the box together with their characteristics and limitations. The specifications define the cost, the number to be manufactured, the expected life, the range, the operating temperature, and the reliability.
There are many implied specifications which result either from the designer's particular environment or from the nature of the problem itself. The manufacturing processes which are available, together with the facilities of a certain plant, constitute restrictions on a designer's freedom, and hence are a part of the implied specifications. A small plant, for instance, may not own cold-working machinery. Knowing this, the designer selects other metal-processing methods which can be performed in the plant. The labor skills available and the competitive situation also constitute implied specifications.
After the problem has been defined and a set of written and implied specifications has been obtained, the next step in design is the synthesis of an optimum solution. Now synthesis cannot take place without both analysis and optimization because the system under design must be analyzed to determine whether the performance complies with the specifications.
The design is an iterative process in which we proceed through several steps, evaluate the results, and then return to an earlier phase of the procedure. Thus we may synthesize several components of a system, analyze and optimize them, and return to synthesis to see what effect this has on the remaining parts of the system. Both analysis and optimization require that we construct or devise abstract models of the system which will admit some form of mathematical analysis. We call these models mathematical models. In creating them it is our hope that we can find one which will simulate the real physical system very well.
Evaluation is a significant phase of the total design process. Evaluation is the final proof of a successful design, which usually involves the testing of a prototype in the laboratory. Here we wish to discover if the design really satisfies the need or needs. Is it reliable? Will it compete successfully with similar products? Is it economical to manufacture and to use? Is it easily maintained and adjusted? Can a profit be made from its sale or use?
Communicating the design to others is the final, vital step in the design process. Undoubtedly many great designs, inventions, and creative works have been lost to mankind simply because the originators were unable or unwilling to explain their accomplishments to others. Presentation is a selling job. The engineer, when presenting a new solution to administrative, management, or supervisory persons, is attempting to sell or to prove to them that this solution is a better one. Unless this can be done successfully, the time and effort spent on obtaining the solution have been largely wasted.
Basically, there are only three means of communication available to us. There are the written, the oral, and the graphical forms. Therefore the successful engineer will be technically competent and versatile in all three forms of communication. A technically competent person who lacks ability in any one of these forms is severely handicapped. If ability in all three forms is lacking, no one will ever know how competent that person is!
The competent engineer should not be afraid of the possibility of not succeeding in a presentation. In fact, occasional failure should be expected because failure or criticism seems to accompany every really creative idea. There is a great to be learned from a failure, and the greatest gains are obtained by those willing to risk defeat. In the find analysis, the real failure would lie in deciding not to make the presentation at all.
Introduction to Machine Design
Machine design is the application of science and technology to devise new or improved products for the purpose of satisfying human needs. It is a vast field of engineering technology which not only concerns itself with the original conception of the product in terms of its size, shape and construction details, but also considers the various factors involved in the manufacture, marketing and use of the product.
People who perform the various functions of machine design are typically called designers, or design engineers. Machine design is basically a creative activity. However, in addition to being innovative, a design engineer must also have a solid background in the areas of mechanical drawing, kinematics, dynamics, materials engineering, strength of materials and manufacturing processes.
As stated previously, the purpose of machine design is to produce a product which will serve a need for man. Inventions, discoveries and scientific knowledge by themselves do not necessarily benefit people; only if they are incorporated into a designed product will a benefit be derived. It should be recognized, therefore, that a human need must be identified before a particular product is designed.
Machine design should be considered to be an opportunity to use innovative talents to envision a design of a product is to be manufactured. It is important to understand the fundamentals of engineering rather than memorize mere facts and equations. There are no facts or equations which alone can be used to provide all the correct decisions to produce a good design. On the other hand, any calculations made must be done with the utmost care and precision. For example, if a decimal point is misplaced, an otherwise acceptable design may not function.
Good designs require trying new ideas and being willing to take a certain amount of risk, knowing that is the new idea does not work the existing method can be reinstated. Thus a designer must have patience, since there is no assurance of success for the time and effort expended. Creating a completely new design generally requires that many old and well-established methods be thrust aside. This is not easy since many people cling to familiar ideas, techniques and attitudes. A design engineer should constantly search for ways to improve an existing product and must decide what old, proven concepts should be used and what new, untried ideas should be incorporated.
New designs generally have “bugs” or unforeseen problems which must be worked out before the superior characteristics of the new designs can be enjoyed. Thus there is a chance for a superior product, but only at higher risk. It should be emphasized that if a design does not warrant radical new methods, such methods should not be applied merely for the sake of change.
During the beginning stages of design, creativity should be allowed to flourish without a great number of constraints. Even though many impractical ideas may arise, it is usually easy to eliminate them in the early stages of design before firm details are required by manufacturing. In this way, innovative ideas are not inhibited. Quite often, more than one design is developed, up to the point where they can be compared against each other. It is entirely possible that the design which ultimately accepted will use ideas existing in one of the rejected designs that did not show as much overall promise.
Psychologists frequently talk about trying to fit people to the machines they operate. It is essentially the responsibility of the design engineer to strive to fit machines to people. This is not an easy task, since there is really no average person for which certain operating dimensions and procedures are optimum.
Another important point which should be recognized is that a design engineer must be able to communicate ideas to other people if they are to be incorporated. Initially the designer must communicate a preliminary design to get management approval. This is usually done by verbal discussions in conjunction with drawing layouts and written material. To communicate effectively, the following questions must be answered:
(1) Does the design really serve a human need?
(2) Will it be competitive with existing products of rival companies?
(3) Is it economical to produce?
(4) Can it be readily maintained?
(5) Will it sell and make a profit?
Only time will provide the true answers to the preceding questions, but the product should be designed, manufactured and marketed only with initial affirmative answers. The design engineer also must communicate the finalized design to manufacturing through the use of detail and assembly drawings.
Quite often, a problem well occur during the manufacturing cycle. It may be that a change is required in the dimensioning or telegramming of a part so that it can be more readily produced. This falls in the category of engineering changes which must be approved by the design engineer so that the product function will not be adversely affected. In other cases, a deficiency in the design may appear during assembly or testing just prior to shipping. These realities simply bear out the fact that design is a living process. There is always a better way to do it and the designer should constantly strive towards finding that better way.
Machining
Turning The engine lathe, one of the oldest metal removal machines, has a number of useful and highly desirable attributes. Today these lathes are used primarily in small shops where smaller quantities rather than large production runs are encountered.
The engine lathe has been replaced in today's production shops by a wide variety of automatic lathes such as automatic of single-point tooling for maximum metal removal, and the use of form tools for finish and accuracy, are now at the designer's fingertips with production speeds on a par with the fastest processing equipment on the scene today.
Tolerances for the engine lathe depend primarily on the skill of the operator. The design engineer must be careful in using tolerances of an experimental part that has been produced on the engine lathe by a skilled operator. In redesigning an experimental part for production, economical tolerances should be used.
Turret Lathes Production machining equipment must be evaluated now, more than ever before, in terms of ability to repeat accurately and rapidly. Applying this criterion for establishing the production qualification of a specific method, the turret lathe merits a high rating.
In designing for low quantities such as 100 or 200 parts, it is most economical to use the turret lathe. In achieving the optimum tolerances possible on the turret lathe, the designer should strive for a minimum of operations.
Automatic Screw Machines Generally, automatic screw machines fall into several categories; single-spindle automatics, multiple-spindle automatics and automatic chucking machines. Originally designed for rapid, automatic production of screws and similar threaded parts, the automatic screw machine has long since exceeded the confines of this narrow field, and today plays a vital role in the mass production of a variety of precision parts. Quantities play an important part in the economy of the parts machined on the automatic to set up on the turret lathe than on the automatic screw machine. Quantities less than 1000 parts may be more economical to set up on the turret lathe than on the automatic screw machine. The cost of the parts machined can be reduced if the minimum economical lot size is calculated and the proper machine is selected for these quantities.
Automatic Tracer Lathes Since surface roughness depends greatly upon material turned, tooling, and fees and speeds employed, minimum tolerances that can be held on automatic tracer lathes are not necessarily the most economical tolerances.
Is some case, tolerances of ±0.05mm are held in continuous production using but one cut. Groove width can be held to ±0.125mm on some parts. Bores and single-point finishes can be held to ±0.0125mm. On high-production runs where maximum output is desirable, a minimum tolerance of ±0.125mm is economical on both diameter and length of turn.
Milling With the exceptions of turning and drilling, milling is undoubtedly the most widely used method of removing metal. Well suited and readily adapted to the economical production of any quantity of parts, the almost unlimited versatility of the milling process merits the attention and consideration of designers seriously concerned with the manufacture of their product.
As in any other process, parts that have to be milled should be designed with economical tolerances that can be achieved in production milling. If the part is designed with tolerances finer than necessary, additional operations will have to be added to achieve these tolerances——and this wi