新型制磚用原料拱土機的設計

新型制磚用原料拱土機的設計,新型制磚用原料拱土機的設計,新型,制磚用,原料,拱土機,設計 UNIVERSITY 說明書 題目： 新型制磚用原料拱土機的設計 學 院： 姓 名： 學 號： 專 業(yè)： 機械設計制造及其自動化 年 級： 指導教師： XX 職 稱： 講師 二○一二 年 五 月 摘要 本論文設計是根據(jù)國家對制磚行業(yè)節(jié)能減排的政策而產(chǎn)生新的機械設計課題。在機械自動化大發(fā)展的趨勢下古老的制磚方式必將淘汰出局。機械自動化的革新無論是從勞動力市場、生產(chǎn)成本、生產(chǎn)效率特別生產(chǎn)磚的原料來說都有巨大的優(yōu)勢。本設計機械是機械化制磚流程中的一個起始環(huán)節(jié)也是較重要的一環(huán)節(jié)。論文設計從結構和動力方面對拱土機做了設計并就重要零件的設計進行校核，為機械的安全可靠工作提供了保證。 關鍵詞： 機械自動化 制磚 拱土機設計 Abstract The design is based on the state of the brick industry energy saving and emission reduction policy and generate a new mechanical design issues . In mechanical automation development trend under the ancient brick method will be eliminated. Mechanical Automation innovation either from the labor market，the cost of production，the production efficiency in particular the production of bricks，have tremendous advantages .The design of machinery is mechanized brick making process in a start link also more important link. The paper design from the structure and dynamic of soil arch machine is designed and the important parts of the design verification ，for the safety of machinery and it ensures reliable operation Key: mechanical automation brick oil arch machine design 目錄 摘要 Abstract 1 緒論…………………………………………………………………………1 1.1 制磚行業(yè)現(xiàn)狀…………………………………………………………1 1.2 制磚機械的發(fā)展………………………………………………………1 1.3 設計論文的主要內容…………………………………………………1 2 原料拱土機結構的設計……………………………………………………1 2.1 原料拱土機的作用……………………………………………………1 2.2 原料拱土機的使用要求………………………………………………2 2.3 原料拱土機機構的選擇………………………………………………2 2.3.1 鉸鏈四桿機構分析…………………………………………………2 2.3.2曲柄滑塊機構分析……………………………………………………2 2.3.3導桿機構分析…………………………………………………………3 2.3.4拱土機機構選用分析…………………………………………………4 3 拱土機運動方案的設計………………………………………………………5 3.1 電機的選擇……………………………………………………………5 3.2 傳動裝置的設計………………………………………………………5 3.2.1 各傳動裝置的分析……………………………………………………6 3.2.2 拱土機傳動裝置的選擇………………………………………………7 3.3 拱土機運動參數(shù)的校核計算……………………………………………7 4 拱土機重要零件的設計校核…………………………………………………7 4.1 拱土機工作概述…………………………………………………………7 4.2 v帶傳動的設計校核計算………………………………………………7 4.3 軸的設計校核計算……………………………………………………9 4.4 鍵的設計…………………………………………………………………10 4.4.1 皮帶輪鍵的選擇………………………………………………………10 4.4.2 減速器與搖臂間的鍵的選擇及校核…………………………………11 4.5 軸承座設計………………………………………………………………11 4.6 軸承座端蓋選材，結構設計……………………………………………11 4.7 軸承座聯(lián)接用螺栓的設計計算…………………………………………11 5 拱土機底架的設計……………………………………………………………12 設計小結…………………………………………………………………………13 參考文獻…………………………………………………………………………14 1 緒論 1.1制磚行業(yè)的現(xiàn)狀 磚瓦建材業(yè)是建筑的基礎，特別最近幾年我國房地產(chǎn)市場持續(xù)升溫，高速發(fā)展帶動制磚也的發(fā)展。老式由人工粘泥曬坯的生產(chǎn)方式很難滿足房地產(chǎn)市場及農村大發(fā)展建設的需求。雖然我國磚廠遍布很多但現(xiàn)如今的經(jīng)濟發(fā)展現(xiàn)狀給磚廠的發(fā)展帶來了很多的挑戰(zhàn)，嚴重制約了磚石的生產(chǎn)。主要方面有：一、人口紅利的下降勞動力成本比原來提高了很多加大了磚的生產(chǎn)成本。二、老式的磚廠生產(chǎn)要進行磚的晾曬影響生產(chǎn)進度且很易受天氣的影響。三、燒結磚時燃料不能合理完全的利用造成資源的浪費同時也加大了生產(chǎn)成本。四、制磚用黃泥土是對資源的極大浪費過度的利用影響了生態(tài)環(huán)境的平衡。綜合各方面因素加國家政策對節(jié)能環(huán)保的要求我國的磚石生產(chǎn)企業(yè)將向大型機械化方向發(fā)展。古老式小型磚窯廠將會慢慢被淘汰。 1.2 制磚機械的發(fā)展 磚瓦在我們過度具有較悠久的歷史?，F(xiàn)也因古建筑的漂亮和精致成為旅游景區(qū)的不少。追溯古代人力化生產(chǎn)那也就是將黃泥土和好曬干后幾塊幾塊慢慢的燒制基本全是人力化。到八九十年代在某些規(guī)模稍大型的磚廠能見到有柴油機為動力的和泥簡單機械，但磚廠的生產(chǎn)工人還是熙熙郎朗，做磚、曬磚、拉磚、燒磚、上車等都要大量人手。進入21世紀社會經(jīng)濟提速發(fā)展拉動建材市場的發(fā)展，老式磚石的生產(chǎn)跟不上步伐了。四川成都、西北、西南部的磚廠就慢慢在尋找出路，機械化的進步恰好就為解決磚石生產(chǎn)落后提供了出路。機械和泥、出坯、切坯、碼坯、運輸流水線作業(yè)大大提高了產(chǎn)量和降低了成本。最近幾年隨著國家十一五、十二五政策的出臺實施。國家在節(jié)能環(huán)保提出了要求，制磚原材料的改變加之窯爐方式的創(chuàng)新出現(xiàn)了隧道窯，鋼材機械化在制磚廠上有了大量的需求。巖石的破碎、碾碎、和泥、出坯、切坯、碼坯、窯車的運輸、磚的打包銷售都是機械自動化作業(yè)。在磚機有大量市場的今天機械行業(yè)也有許多廠家進軍其中山西眉山的做的比較早也比較好，四川成都、福建等地磚機生產(chǎn)企業(yè)都做得不錯。我省江西振大機械最近幾年在磚機行業(yè)發(fā)展的也很好。磚機雖然發(fā)展有些年但技術和設計并不是完全成熟還有很大發(fā)展進步空間。相信在國家政策的扶持和引導下在機械同仁的努力下我國磚機將會更加完美實用。 1.3 設計論文的主要任務內容 根據(jù)該機械應完成的功能作用合理設計選擇滿足工作條件的運動機構并選擇合適大小的電機。完成對重要零部件的設計分析和校核。 2 原料拱土機的結構設計 2.1 原料拱土機的作用 在現(xiàn)代機械化磚廠生產(chǎn)磚石過程中包括巖石的取料，巖石的破碎碾成粉末。巖石粉與燃料粉末的配合和泥、擠磚、切磚、碼轉、烘干、燒結等環(huán)節(jié)。其中本設計的原料拱土機是裝載車取巖石后放在拱土機上方的漏斗內。拱土機根據(jù)破碎機工作的情況來回進給運動喂入巖石。拱土機主要是保證破碎機正常工作合理喂入巖石的作用。 2.2 原料拱土機的使用要求 原料拱土機上方應根據(jù)拱土機的安放位置焊個留一口的漏斗。裝載車將巖石倒入拱土機上，拱土機的前后運動要完成將部分巖石喂入破碎機內。其工作原理主要是運用巖石自身的摩擦和慣性隨拱土機前后運動部分掉入破碎機內。拱土機工作時應具有較好的反應能力和較大的承載運動能力。 2.3 原料拱土機機構的選擇 原料拱土機主要完成的是前后往復運動可簡易的看成平面內要實現(xiàn)的運動。在平面機構學中主要有1）鉸鏈四桿機構；2）曲柄滑塊機構；3）導桿機構。 2.3.1 鉸鏈四桿機構 如圖1所示，所有運動副均為轉動副的平面四桿機構稱為鉸鏈四桿機構，它是平面四桿機構的最基本的型式，其他型式的平面四桿機構都可看做是在它的基礎上通過演化而成的。在此機構中，構件四位機架，與機架組成運動副的構件1.3稱為連架桿，不與機架組成運動副的構件2成為連桿。若組成轉動副的兩構件能作整轉相對轉動，則該轉動副稱為整轉副，否則成為擺動副。與機架組成整轉副的連架桿稱為曲柄，與機架組成擺動副的連架桿稱為搖桿。因此根據(jù)兩連架桿為曲柄或搖桿的不同，鉸鏈四桿機構可分為三種基本形式。1）曲柄搖桿機構，其中兩連架桿一為曲柄另一為搖桿，如圖1a所示；2）雙曲并機構，其中兩連架桿均為曲柄，如圖1b所示；3）雙搖桿機構，其中兩連架桿均為搖桿，如圖1C。 圖1 2.3.2 曲柄滑塊機構 曲柄滑塊機構是由曲柄的運動傳遞到滑塊前后運動的過程如圖2所示。 圖2 在此機構中1的整轉運動會帶動C塊的前后往復運動。對其運動形式進行分析。若已知構件1的轉速為W可求出C的速度。因根據(jù)三心定理求構件1.3的相對速度瞬心P13.滑塊3作直線運動，其上各點速度相等。將p13看成是滑塊上的一點，根據(jù)瞬心的定義Vc=Vp13，所以Vc=L1w1 2.3.3 導桿機構 如圖3所示構件1為整軸轉動2在導桿3上來回運動。構件3做左右擺動運動。 圖3 2.3.4 拱土機機構選用分析 根據(jù)上述分析曲柄滑塊機構最簡易也最方便運用實現(xiàn)拱土機的功能，對曲柄滑塊機構進行設計分析。 為便于拱土機行程的調節(jié)和安裝用可調節(jié)的套和螺桿作為2桿的構件。對于原動件（曲柄）作勻速定軸轉動，從動件相對于機架作往復運動（擺動或移動）的連桿機構，從動件正行程和反行程的位移量相同，而所需的時間一般并不相等，因此從動件正反兩個行程的平均速度也就不相等。這種現(xiàn)象稱為機構的急回特性。但也并不是所有的機構都會出現(xiàn)此現(xiàn)象，可以通過調節(jié)導路的偏置大小盡量避免急回特性。如圖4當e=0時θ=0即不存在急回特性故減速器的安裝應與推板齊水平。 圖4 3 拱土機運動方案的設計 機構簡圖 圖5 3.1 電機的選擇 給定拱土機的工作條件：上方漏斗3立方米可載重3000㎏在室內間斷性工作，工作環(huán)境多塵，電源為三相交流，電壓為380V 選擇電動機類型和結構形式，系統(tǒng)無特殊需求，一般選用y系列三相交流異步電動機。選用全封閉自扇冷式籠型，電壓380v。根據(jù)p=fv,F=f=mgчч查表取0.3, v根據(jù)工作情況不應大于0.5m/s,故p=0.5x3000x10x0.3=4500w 查電動機參數(shù)表選取電動機額定功率p=5.5kw。根據(jù)動力源和工作條件電機的轉速選擇常用的兩種同步轉速：1500r/min和1000r/min。選用1000r/min查表選用Y132M1—6型號的電機，其參數(shù)如下 電機型號 額定功率（kw） 同步轉速（r/min) 滿載轉速（r/min） 參考價格元 Y132M1—6 5.5 1000 960 1000 3.2 傳動裝置的設計 傳動裝置是一種在距離間傳遞能量并兼實現(xiàn)某些其他作用的裝置。這些作用是：1）能量的分配；2）轉速的改變；3）運動形式的改變（如回轉運動改變?yōu)橥鶑瓦\動），等等。 機器中所以要采用傳動裝置是因為：1)工作機構所要求的速度、轉矩或力，通常與動力機不一致；2）工作機構常要求改變速度，用調節(jié)動力機速度的方法來達到這一目的往往不很經(jīng)濟；3）動力機的輸出軸一般只做等速回轉運動，而工作機構往往需要多樣的運動，如螺旋運動、直線運動或間歇運動等；4）一個動力機有時要帶動若干個運動形式和速度都不同的工作機構。 在我們機械行業(yè)所涉及的常用傳動中主要包括以下幾種常見的方式1）摩擦輪傳動；2）帶輪傳動；3）齒輪傳動；4）蝸桿傳動；5)鏈傳動；6）減速器等方式 3.2.1 各傳動裝置的分析 a) 摩擦傳動 摩擦輪傳動具有下列優(yōu)點：1）由于摩擦輪輪面沒有輪齒，所以制造簡單，而且工作時不會發(fā)生類似齒輪節(jié)距誤差所引起的周期性沖擊，因而運轉平穩(wěn)，噪聲很?。?）過載時打滑，故能防止機器中重要零件的損壞；3）能無級的改變傳動比等等。它的主要缺點是：1）效率較低；2）當傳遞同樣大的功率時，輪廓尺寸和作用在軸與軸承上的載荷都比齒輪傳動大；3）由于上述兩項原因，所以不宜傳遞很大的功率；4）不能保持準確的傳動比；5）干摩擦時磨損塊、壽命低；6）必須采用壓緊裝置等。應用范圍 摩擦輪傳動在傳遞功率、傳動比和調速幅度、速度、軸間距離等方面都有很大的適用范圍。傳動功率可自幾瓦直到300kw，但多數(shù)不超過20kw。傳遞功率的摩擦輪傳動的傳動比一般可到7，有卸載軸時可到15，在手動儀器中傳動比可達25.調速幅度在直接接觸的傳動中，一般為3~4，在有中間幾件的傳動中，一般可達到8~12.圓周速度可自很低到高達25m/s。 b) 帶傳動 帶傳動是具有中間撓性件的一種傳動，所以：1）能緩和載荷沖擊；2）運行平穩(wěn)，無噪聲；3）制造和安裝精度不像嚙合傳動那樣嚴格；4）過載時將引起帶在帶輪上打滑，因而可防止其他零件的損壞；5）可增加帶長以適應中心距較大的工作條件。 帶傳動和摩擦輪傳動一樣，也有下列缺點：1）有彈性滑動和打滑，使效率降低和不能保持準確的傳動比；2）傳遞同樣大的圓周力時，輪廓尺寸和軸上的壓力都比嚙合傳動大；3）帶的壽命短。 應用范圍 帶傳動的應用范圍很廣。帶的工作速度一般為5m/s~20m/s，使用高速環(huán)形膠帶時可達60m/s；使用錦綸片復合平帶時，可高達80m/s。膠帆布平帶傳遞功率小于500kw，普通v帶傳遞功率小于700kw。 c) 齒輪傳動 和其他機械傳動比較，齒輪傳動的主要優(yōu)點是：工作可靠，使用壽命長；瞬時傳動比為常數(shù)；傳動效率高；結構緊湊；功率和速度適用范圍很廣等。缺點是：齒輪制造需專用機床和設備，成本較高；精度低時，振動和噪聲較大；不宜用于軸間距離大的傳動等。 d) 蝸桿傳動 蝸桿傳動的主要優(yōu)點是結構緊湊、工作平穩(wěn)、無噪聲、沖擊振動小以及能得到很大的單級傳動比。在傳遞動力時，傳動比一般為8~100，常用的為15~50.在機床工作臺中，傳動比可達幾百，甚至到1000.這時，需采用導程角很小的單頭蝸桿，但傳動效率很低，只能用在功率小的場合。在現(xiàn)代機械制造業(yè)中正力求提高蝸桿傳動的效率，多頭蝸桿的傳動效率可達到98%。與多級齒輪傳動相比，蝸桿傳動零件數(shù)目少，結構尺寸小，重量輕。缺點是在制造精度和傳動比相同的條件下，蝸桿傳動的效率比齒輪傳動低，同時蝸桿一般需用貴重的減摩材料制造。 蝸桿傳動多用于減速，以蝸桿為原動件。也可用于增速，齒數(shù)比單級為5~15,但應用很少。 e) 鏈傳動 鏈傳動是在兩個或多于兩個鏈輪之間用鏈作為撓性拉曳元件的一種嚙合傳動，因其經(jīng)濟、可靠，故廣泛用于農業(yè)、采礦、冶金、起重、運輸、石油、化工、紡織等各種機械的動力傳動中。和帶傳動比較，鏈傳動的主要優(yōu)點是：1）沒有滑動；2）工況相同時，傳動尺寸比較緊湊；3）不需要很大的張緊力，作用在軸上的載荷較??；4）效率較高，98%；5）能在溫度較高、濕度較大的環(huán)境中使用等。因鏈傳動具有中間元件，和齒輪、蝸桿傳動比較，需要時軸間距離可以很大。 鏈傳動的缺點是：1）只能用于平行軸間的傳動；2）瞬時速度不均勻，高速運轉時不如帶傳動平穩(wěn) ；3）不宜在載荷變化很大和急促反向的傳動中應用；4）工作時有噪聲；5）制造費用比帶傳動高等。 應用范圍 鏈傳動在傳遞功率、速度、傳動比、中心距等方面都有很廣的應用范圍。目前，最大傳遞功率達到5000kw，最高速度到40m/s，最大傳動比達到15，最大中心距達到8m。由于經(jīng)濟及其他原因，鏈傳動的傳動功率一般小于100kw，速度小于15m/s，傳動比小于8. f) 減速器 減速器是一種由封閉在剛性殼體內的齒輪傳動、蝸桿傳動或齒輪-蝸桿傳動所組成的獨立部件，常用在動力與工作機之間做為減速的傳動裝置；在少數(shù)場合下也用作增速的傳動裝置，這時就稱為增速器。減速器由于結構緊湊、效率較高、傳遞運動準確可靠、使用維護簡單，并可成批生產(chǎn)，故在現(xiàn)代機器中應用很廣。 3.2.2 拱土機傳動裝置的選擇 根據(jù)上述分析皮帶輪和減速器的運用在拱土機的設計方面最可行。根據(jù)市場選擇JZQ400型40.17的傳動比比較合理。大小皮帶輪設計傳動比為2.5初步估算能滿足要求。 3.3 拱土機運動參數(shù)的校核計算 根據(jù)所設計要求供土機推板運動速度不得大于0.5m/s。根據(jù)已有設計條件電機選擇為5.5kw,構1為搖臂設計長度為150mm，由運動學分析V.為此時最大V.=V,V=Wr 根據(jù)傳動比 故拱土機能夠合理正常工作 4 拱土機重要零部件的設計與校核 4.1 拱土機工作概述 拱土機為了完成進給原土料需前后往復運動，由電動機用皮帶輪傳動至JZQ400減速器。減速器有左右對稱軸輸出轉動，其后面的工作機構就可簡化成曲柄滑塊機構，亦可如上圖。這幾個緩解中V待傳動的傳動比及V帶根數(shù)和皮帶輪的直徑大小就為比較重要的參數(shù)，故這幾個參數(shù)需校核設計計算。由于減速器輸出軸和搖臂需用鍵連接傳遞轉動，故鍵的設計計算校核也不可少。在推板結構中有軸和滾輪的支撐推動運動，對軸也就要進行校核計算。軸承滾輪座與蓋的連接用標準件螺桿擰緊，需設計計算擰緊林及螺桿的個數(shù)。其他些零部件和結構為常用普通形式故無需特別設計計算校核。 4.2 V帶傳動的設計校核計算 選用普通V帶傳動，動力機為Y系列三相異步電動機，功率P=5.5KW，轉n=960r/min，每天工作16h,中心距小于600mm。 計算項目 計算內容 計算結果 定V帶型號和帶輪直徑 工作情況系數(shù) 由表 計算功率 選帶型號 由圖表 A型 小帶輪直徑 由圖表 取=90mm 大帶輪直徑 為滑動率取=2% 選=224 大帶輪轉速 =378 計算帶長 求Dm 求Δ Δ=67 初取中心距 a=500 帶長 L=1502 基準長度 由機械設計查圖表 求中心距和包角 中心距 a=537.75 小輪包角 求帶根數(shù) 帶速 V=4.52m/s 傳動比 i=2.5 帶跟數(shù) 由表 Z==2.9 Z=3 帶輪結構設計 由于帶速V<30m/s，帶輪用HT250制造。小帶輪采用整體式結構，大帶輪采用輪輻式結構，且D<500mm,輪輻數(shù)目取為4，具體結構見零件圖。 綜上整理帶傳動參數(shù)如表： 小帶輪直徑 大帶輪直徑 傳動比 帶基準長度 根數(shù)z 中心距a 90mm 224mm 2.5 1600 3 537.75mm 4.3 軸的設計校核計算 軸材料選用45鋼調質， 軸的設計計算部棸如下 繪制受力圖和彎矩圖 軸的結構圖 圖6 由彎矩圖知危險截面在中間，對中間截面進行校核計算 已知 d為50mm 長度為1426mm 故按所設計尺寸能滿足工作要求 4.4 鍵的設計 4.4.1 皮帶輪鍵的選擇 因無特殊要求，選用圓頭普通平鍵，鍵14x9,通常 因此，，取L=55mm 校核計算如下: 鍵的接觸長度=L-b=41mm,鍵與轂的接觸高度為4.5，許用擠壓應力，所以鍵連接所能傳遞的轉矩為： >452.64N.m 所以以上選擇的參數(shù)滿足強度要求。合理 4.4.2 減速器與搖臂間的鍵的選擇及校核 因無特殊要求選用圓頭普通平鍵，鍵10x8，通常因此， 取L=50mm 校核計算如下： 鍵的接觸長度=L-b=50-10=40mm，鍵與轂的接觸高度4mm；許用擠壓應力查表取150Mpa，所以鍵連接所能傳遞的轉矩為 >129.68N.m 所以，以上選擇的參數(shù)滿足強度要求。設計合理 4.5 軸承座設計 由于軸承座在使用中同時也具有滾輪的作用但并無較大沖擊載荷，且軸承外徑較大?？紤]節(jié)約成本，故選用灰鑄鐵HT300，，硬度190~240HB 結構設計見零件圖 4.6 軸承座端蓋選材，結構設計 端蓋選用灰鑄鐵HT300。硬度190~240HB，用螺栓與軸承座連接。端蓋用于限制軸承在軸承座內的軸向位移。具體結構見零件圖 4.7 軸承座連接用螺栓的設計計算 螺栓材料選用45鋼，材料的許用拉應力=350Mpa，螺栓直徑d的設計計算; 對于固定軸承座的螺栓預緊力只需滿足： ;Z—螺栓個數(shù)6；——螺栓預緊力；——接觸面間的摩擦系數(shù)0.135；m——結合面數(shù)目1；——考慮摩擦傳動力的可靠系數(shù)取1.3 螺栓直徑=6.16mm 即軸承座選用螺栓M8 5 拱土機底架的設計 底架材料選用型鋼，由型鋼焊接成架，底架的結構設計中主要考慮兩導軌的距離便于滾輪的安裝運動。 參考文獻 [1]邱宣懷、郭可謙、吳宗澤等.機械設計.4版.北京：高等教育出版社.2010. [2]劉混舉、趙河明、王春燕.機械可靠性設計.北京：國防工業(yè)出版社.2010. [3]趙衛(wèi)軍、任金泉、陳鋼.機械設計基礎課程設計.北京：科學出版社.2010. [4]金清肅、范順成、范曉珂.機械設計課程設計.武漢：華中科技大學出版社.2006. [5]王慧、呂宏、王連明.機械設計課程設計.北京：北京大學出版社.2011. [6]于永泗、齊民.機械工程材料.8版.大連：大連理工大學出版社.2010. [7]鄭文緯、吳克堅.機械原理.7版.北京：高等教育出版社.2010. [8]劉鴻文.材料力學.4版.北京：高等教育出版社.2010. [9]哈爾濱工業(yè)大學理論力學教研室.6版.北京：高等教育出版社.2004. [10]陳于萍、周兆元.互換性與測量技術基礎.2版.北京：機械工業(yè)出版社.2009. [11]何銘新、錢可強.機械制圖.5版.北京：高等教育出版社.2008. [12]蔣曉、沈培玉、苗青.AutoCAD2008中文版機械設計標準實例教程.北京：清華大學出版社.2008. 設計總結 經(jīng)過這么幾個月的畢業(yè)設計，回顧溫習了自己大學四年所學的有關專業(yè)方面的知識，是那些知識在腦中不再那么雜亂無章的儲存著，而是有了個系統(tǒng)整體的認識。在設計的過程中既有汗水淚水也有歡笑。有時被一個問題纏住幾天不見天日，也為最后的解決而歡快喜悅。從中感悟獨自一個人要完成一項機械的設計真的要付出很多的努力，即便是簡單的機械也并不是那么的簡單。此次設計讓我感觸較深的是嚴謹仔細認真的習慣態(tài)度對作為一名機制人員是多么重要。機械圖作為我們機制人員交流的語言，對個人的嚴謹仔細認真好習慣要求更高，也完全能體現(xiàn)作為一名機制人員專業(yè)技能和素養(yǎng)。 本次畢業(yè)論文（設計）得到XX老師的諄諄教導和殷切關心，也還有撫州廣昌東勝機械廠的工人師傅的大量幫助和指導，我才能這么順利的完成此次設計，在此一并表示感謝！ 限于個人水平知識和時間的有限，疏漏和不妥之處肯定不少，望各位前輩老師同仁指正。本人將以不吝賜教為感！ 18 THE INDUSTRIAL ENGINEERING REVOLUTION by SAMUEL EILON, Ph.D., M.I.Prod.E. Associate Professor in Industrial Engineering, Israel Institute of Technology. Summary Classical industrial engineering was based on five main foundations: the rule of intuition, the philosophy of the one best way, the deterministic system, the principle of simplification and the classical methods of experimentation. Intuition rarely yields satisfactory results in complicated systems and is giving way to operational research techniques. The philosophy of the one best way has been replaced by the philosophy of the better way, and the deterministic methods by statistical analysis. We are increasingly aware of the inadequacy of the principle of simplification and believe that industrial operations are inherently complex and require a new approach to their study. The Hawthorne experiments demonstrated the effect of observation on the observed system and also emphasized the necessity of devising new methods for industrial engineering research and study of administrative behaviour. INDUSTRIAL engineering is a comparatively young subject, which grew with the rapid industrial development of Western Europe and America, until in recent years it began to occupy an honourable position in institutions of higher learning. The pioneers in this field endeavoured, at the beginning of the century, to establish it on scientific foundations, to formulate " laws" which would describe and explain phenomena and relations between cause and effect, and to outline principles for procedure and organisation in order to achieve a desirable level of performance. But, with all its “scientific" principles, industrial engineering remained more an art than a science. The success of experts in the field can perhaps be attributed more to a sixth sense based on accumulated experience than to the application of set laws and principles, which are supposed to lead the engineer step by step to the desirable solution. Like many other subjects, industrial engineering has experienced in the past two decades a rapid development, which led to a drastic change in views and outlook. The classical industrial engineering can be said to have been established on the following five foundations: the rule of intuition; the philosophy of the one best way; the deterministic system; the principle of simplification; and the classic methods of experimentation in physics. I shall try to review in this Paper the changes in our understanding of these basic concepts and the way they affect our whole approach to and evaluation of industrial engineering problems. We are now experiencing literally a revolution in this field of engineering, a revolution that will transform it into a completely new engineering science. The rule of intuition When an industrial engineer or a manager is supplied with specific data, on the basis of which he has to take a decision or to outline an engineering plan, what is the conventional method that guides him in his quest for a solution? He tries to digest the facts in his mind; he outlines several logical alternatives for a solution and proceeds to compare them in order to select the best. In this process of comparison, he tries to visualise the possible results that can be expected of each alternative and in this he is guided by his past experience, or by the experience of others, and he mainly uses his sense of intuition to assess these results qualitatively or quantitatively and to relate results of one method or system to those of another. What is intuition? Intuition is a process of thinking, which is difficult to dissect into individual factors or sequences. It is quite often based on the principle of identification of given data of a specific problem with previous experience, and is normally associated with rapid transfer from one sequence to another. This process, however, may be too closely attached to identification with past associations, rather than with the problem at hand. Thus, not all the relevant factors may play a relevant role in the procedure of arriving at a solution, and while intuition sometimes leads to the right answer for the wrong reasons, it should be remembered that an intuitive approach quite often results in a wrong solution, or in a solution which is not the best one. Those instances where the intuitive approach yields wrong answers are usually revealed when undesirable results are obtained. But in most cases, when the suggested solution is neither catastrophic nor the best one, we tend to regard the intuitive solution as a successful one, and if somebody suggests a better solution we usually say that "it is very easy to be clever in retrospect" or that " the conditions have changed in the meantime and we now have information which we did not have before ". It is true that sometimes changes in the nature of the problem do occur, but the significance of these changes, both qualitatively and quantitatively, is important in the evaluation of the solution. In many cases we can formulate in advance the nature of the changes that may arise, some of them even quantitatively, but the percentage of the cases in which the intuitive method provides a solution that takes such details into account, is almost negligible. How does intuition work and what is the relation between intuition and previous experience? To what extent are intuitive processes in the mind related to past associations and to what extent are they independent of the external world, forming so to speak an isolated system in which the computation yields absolute values? These are complicated problems which provide rich material for research on the structure and performance of the mind and it is not intended to enlarge on them here. But for the purpose of our discussion it is possible to say that every thinking process consists of several elements or steps, each one leading forward in the quest of a solution. The word " forward " is important here, since if the steps do not take us nearer to the target, it is necessary to have more steps from the starting point to get there, and the number of steps is significant in the actual attainment of the goal. Each element is fed with data from the previous element, then an operation based on the data takes place and the output is fed into the next element. Even if we assume that the computational operation itself at each element is free of errors, it is still doubtful whether the input to each element is always identical with the output of the previous one, because each input is accompanied by a suitable re-arrangement of the material and perhaps formulation of the facts in a form easily digestible by the computational operation. Putting the data in a new light or expressing it in different terms may lead to non-identification of input with preceding output. This is a second source of possible errors in the intuitive process, and the accumulated error increases with the number of elements. This is somewhat similar to several toy bricks put on top of each other. If the bricks are accurately located, the structure will be absolutely vertical. A small displacement of one brick in the structure causes a displacement of the top brick, while several displacements of several bricks may lead to an increased displacement of the top from its desirable location. the short cut Another aspect of the intuitive thought is the short cut, i.e., the elimination or combination of several elementary steps in the thinking process, based on an analogy of these elements with other known elements from past experience. This aspect is one of the amazing phenomena associated with the performance of the mind, but from the point of view of error making it has the same pitfalls of unidentical situations and distorted data. The process of analytical thinking is not always as simple as described above. Usually the process is divided into several sub-processes, which have to be carried out simultaneously, which are interconnected and which influence each other. The input to a certain element may not be unidirectional; that is, it may not be obtained from one previous element but from several elements belonging to different processes, and similarly the output may be multidirectional to several elements. Here we have two important aspects: first, the capacity of the mind to carry out assimilation of several inputs to one element without distorting their accuracy and contents; and, secondly, the amount of complexity of simultaneous processes and multidirectional inputs and outputs that the intuitive mind can carry out, without unwarrantably eliminating complete processes in order to achieve simplicity. Both aspects can become sources of appreciable errors. The intuitive processes have been mentioned at some length in order to point out the reasons for either their missing the target altogether, or for incurring accumulated errors of such a magnitude as to render the proposed solution unsatisfactory. The very fact that different intuitive minds give different solutions to the same problem, and that the solutions are usually not equivalent (i.e., it is possible to say that one solution should be preferred to another) would indicate the necessity of analysing methods that would yield a solution independent of intuitive faculties, and would therefore be free from the mistakes which might be attributed to them. New methods in analysis of situations and systems are provided by operational research techniques, which facilitate the study of intricate and complex systems when any intuitive attempt to a solution is doomed to failure for two reasons: first, many systems of this kind have specific characteristics and it is difficult or impossible to draw conclusions about their nature from previous experience of other systems; secondly, the complexity of the systems and the large number of variables on which they depend, make it impossible for the human mind to achieve an effective absorbtion of all the facts and the intricate relationship between them. The tools of operational research can be used for a systematic analysis and quantitative evaluation of the characteristics of the system, and though intuition can always be of some help, just as it is helpful in the solution of mathematical problems, the autocratic rule of intuition in the solution of classical industrial engineering problems is coming to an end. The first critical steps in the evaluation of industrial operations are the definition of the problem, the definition of the objective and the definition of criteria for measurement. It is often said that the definition of the problem is half-way to its solution ,and this is probably quite true, as the definition of the problem inevitably entails gathering of adequate and relevant information and precise understanding of the characteristics of the factors involved. The definitions of the objective and the criteria for measurement have undoubtedly been one of the major stumbling blocks of critical operational analysis in the past. Not only has there been a lack of agreement as to what objective is desirable; many managements have been trying to achieve several objectives at the same time, and quite often these objectives are not compatible with each other. It has often been asserted that the definition of objective is a matter for higher management and the task of the industrial engineer begins after that. In view of the confusion on this score in the past, and the different and sometimes conflicting criteria which have been applied in the study of operations, it would seem that a meticulous study of industrial objectives and criteria is warranted, if operational research methods are to be fully exploited. The philosophy of the one best way At the beginning of the century the pioneers in industrial engineering had already recognised the fact that there are large variations between different workers, between their methods of work and between their outputs. Frederick Taylor came to the conclusion that it is necessary to outline scientific methods in order to enable objective measurements with the aid of a clearly defined criterion. He asserted that the desirable maximum efficiency would be achieved if tasks in industry were undertaken by people trained for them. He wanted to solve the problem of existing variations by carefully selecting personnel, suitable in skill and aptitude for each particular job, and he called these people " first class men ", a definition that aroused severe criticism at the time. Frank Gilbreth put the emphasis on the work method. He said that for the attainment of maximum efficiency there exists one method for the execution of each job which is " the best way ", the acquisition of which should be the objective of operators' training. Gilbreth was prepared to admit that the existing variations between operators may cause deviations from the best method, even after the operators have been trained to use it, and he was prepared to allow such deviations, provided the output attained by the best method was not affected. This philosophy of Gilbreth was enlarged upon by Alford, who said that this view was identical with the philosophy of the engineering standard. The one best way should be regarded as a relative engineering concept, which describes the best method that can be found under the given circumstances. " It is not an ultimate best way but is in the line of progress, and may be changed or modified as soon as a better way is discovered. The new way then becomes the best way until it is superseded by something better. To the one who accepts and applies this philosophy comes the grace and rhythm and perfection of motion of him who knows, and knows that he knows, and does what he knows, no matter what his work may be." 1 This is quite a liberal interpretation of the philosophy of the one best way, but at the beginning of the century this philosophy was rigid, deterministic and static. Rigid, in that it implied that there exists only one method which is the best. Deterministic, in that it said that the method can be defined after suitable study and research. Static, in that it made the work system dependent on fixed parameters. But we are now beginning to understand that the three assumptions of this philosophy are unfounded. First, we are no longer confident that to every problem there is only one best solution, even when we overcome the obstacle of defining the criterion by means of which the solution should be evaluated. Many problems have several equivalent solutions and in the design of machinery and equipment, for instance, this phenomenon is well known. Secondly, we are now convinced that the deterministic outlook has no foundation either in theory or in practice. Theoretically, as we shall see later, we cannot be sure that the proposed method will really prove to be up to the mark, as hoped in advance, since the feeding of the method into the system may lead to some unexpected results. From the practical point of view, the classical assertion is that it is possible to find the method " after suitable study and research ", i.e., the search is a function of time and money, and these are not always available in abundance. And, lastly, no work system is static. It cannot be defined in static terms but by statistical parameters. It changes with time and with the many variables on which it depends. Its characteristics change fundamentally with changes of methods, with changes of processes or even with changes of views. Perhaps it is permissible to say that for the philosophy of the one best way has now been substituted the philosophy of the better way. The philosophy of the best way recognises one absolute idealistic method, a super target to be aimed at by every worker or engineer seeking perfection. The philosophy of the better way is the philosophy of reality. It asserts that every process of development is unlimited. In this process we are moving along an indefinite spiral which continuously transfers us into a new space and with each step the system is faced with new problems demanding their solution. In the search for a better method with limited facilities, it is of course possible to find several solutions, some of which will be better than others, and this is where the real test of the engineer lies. The average engineer, without imagination and initiative, will be satisfied with any better solution, with the pretext that there is no need to make any special effort because we are not after a final and absolute method. A good engineer will try to achieve the maximum with the facilities at his disposal, will not be deterred by the infinite process of development and will not be drawn into apathy, but will regard it as a constant challenge, a source of interest, vitality and action. And is this phenomenon not typical of what happens in other fields of human endeavour ? determinism and probability The first steps of industrial engineering were naturally based on the deterministic outlook and this view, to a certain extent, formed the background to the philosophy of the one best way. The deterministic approach was coupled with the belief that if a set of defined operations is followed, a certain result is obtained, and this same result can be expected to recur again and again from the same set. This view is reminiscent of a set of experiments in classical physics shown by a teacher to his students. He takes, for instance, a metal sphere, slightly smaller in diameter than the internal diameter of a ring at room temperature. He warms the sphere over a Bunsen burner and tries to push the hot sphere through the ring, exhibiting in this way the phenomenon of metal expansion with temperature. Each time it is sufficiently warmed, the teacher expects the sphere not to pass through the ring and he would be extremely surprised, and perhaps worried, if after proceeding with identical sets of operations the sphere would sometimes pass through the ring and sometimes not, and he would undoubtedly express the view that something had gone wrong in the structure or nature of the experimental apparatus. In fabrication processes it has been well known for some time that the result is not deterministic in this sense, i.e., that after a recurring set of operations, a large variation in results is obtained. This is the basis for specifications of tolerances in the design of machinery parts. But although this phenomenon of variation has been known for some time, the study and method of specifying tolerances has been a subject for intuitive decision for many years, until new methods based on statistical analysis were established. It is surprising that the process of recognising the fact that most industrial engineering operations, and not only manufacturing operations, are not deterministic, took such a long time, since many industrial operations are associated with very wide variations, because of their being dependent on or related to human factors, and in biology and medicine it is well known that many characteristics and phenomena are subject to wide variations. The results of fabrication processes are usually related to comparatively small statistical variations, and perhaps their qualitative and quantitative analysis, before other statistical phenomena in industrial engineering, can be attributed to the fact that they were easier to understand and to attack. The principle of simplification Another phenomenon connected with industrial operations is the large number of factors and variables affecting them. In many fields of physics we can carry out experiments by isolating the system. We disconnect the system from other phenomena and proceed with the experiment in a closed system unaffected by the outside, and usually the factors which we cut off have such a small influence, that we may draw conclusions from the experiment about the behavio