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花生脫殼機(jī)的設(shè)計(jì) 摘要 本文首先花生脫殼機(jī)的脫殼原理，應(yīng)用現(xiàn)狀及現(xiàn)在市場上應(yīng)用的個(gè)脫殼機(jī)存在的問題進(jìn)行調(diào)研分析，針對(duì)其問題進(jìn)行了分析。根據(jù)設(shè)計(jì)要求及花生脫殼機(jī)的功能要求，確定了花生脫殼機(jī)的總體方案的設(shè)計(jì)，以封閉式滾筒脫殼機(jī)為研究對(duì)象，對(duì)脫殼機(jī)的關(guān)鍵脫殼部件、進(jìn)料機(jī)構(gòu)、振動(dòng)篩分選機(jī)構(gòu)和偏心輪機(jī)構(gòu)等部分進(jìn)行詳細(xì)設(shè)計(jì)與三維建模分析。最后對(duì)本次設(shè)計(jì)心得體會(huì)與成果進(jìn)行的總結(jié)。 關(guān)鍵詞：花生脫殼機(jī)、滾筒、半籠柵、結(jié)構(gòu)設(shè)計(jì) 目錄 摘要 1 目錄 2 1.緒論 4 1.1本課題研究的背景及意義 4 1.2 花生脫殼機(jī)的脫殼原理 4 1.3 花生脫殼機(jī)的應(yīng)用現(xiàn)狀與未來發(fā)展趨勢 5 1.3.1 花生脫殼機(jī)的應(yīng)用現(xiàn)狀介紹 5 1.3.2 未來發(fā)展趨勢 6 2. 花生脫殼機(jī)的整體結(jié)構(gòu)方案與工作原理 8 2.1本設(shè)計(jì)中的脫殼原理 8 2.2花生脫殼機(jī)的總體結(jié)構(gòu) 8 2.3 殼仁分離裝置 10 3. 花生脫殼機(jī)關(guān)鍵部件的結(jié)構(gòu)設(shè)計(jì) 11 3.1脫殼部件的設(shè)計(jì) 11 3.1.1滾筒半徑及轉(zhuǎn)速初定 11 3.1.2脫殼機(jī)所需功率計(jì)算與電機(jī)選型 13 3.1.3傳動(dòng)裝置的傳動(dòng)參數(shù)計(jì)算 14 3.1.4電機(jī)與脫殼轉(zhuǎn)子軸之間的V帶傳動(dòng)設(shè)計(jì) 15 3.1.5滾筒材料的選擇 19 3.2轉(zhuǎn)軸的設(shè)計(jì)與校核 19 3.2.1初步確定軸的最小直徑 19 3.2.2擬定軸上零件的裝配方案與尺寸確定 20 3.2.3.主軸的強(qiáng)度校核 21 3.2.4軸承的校核 23 3.3比重分選篩動(dòng)力系統(tǒng)設(shè)計(jì) 24 3.3.1比重分選篩裝置設(shè)計(jì) 24 3.3.2偏心輪轉(zhuǎn)軸設(shè)計(jì) 25 3.3.3偏心軸的V帶傳動(dòng)設(shè)計(jì) 26 4. 花生脫殼機(jī)的各部件設(shè)計(jì)與三維建模 27 4.1 關(guān)鍵組件的設(shè)計(jì)與三維建模 27 4.1.1半柵籠 27 4.1.2風(fēng)扇組件設(shè)計(jì) 28 4.1.3箱體 28 4.1.4料斗 29 4.1.5振動(dòng)篩的箱體 30 4.1.5篩網(wǎng) 31 4.1.6機(jī)架 31 4.2 脫殼機(jī)的三維建模與裝置檢查 32 圖4.10 脫殼機(jī)三維模型的主視圖 33 5.結(jié)論 34 致謝 35 參考文獻(xiàn) 36 1.緒論 1.1本課題研究的背景及意義 花生是人們生活中重要的實(shí)物及食用油品的來源，花生需求量在增大，花生種植面積與產(chǎn)量也在增加。因此，這就要求對(duì)花生種植、收割及脫殼等機(jī)械裝置的發(fā)展與應(yīng)用滿足其生產(chǎn)需求。目前，采用機(jī)械自動(dòng)脫殼設(shè)備的生產(chǎn)效率是遠(yuǎn)遠(yuǎn)高于人工手動(dòng)效率，且降低農(nóng)民的工作強(qiáng)度，節(jié)省時(shí)間和生產(chǎn)成本[1]。 針對(duì)花生脫殼的質(zhì)量要求，需要綜合分析其各影響因素，如脫殼設(shè)備的轉(zhuǎn)動(dòng)特性、脫殼工藝流程和脫殼加工對(duì)象的形狀、干燥情況等物理特性。常用的脫殼設(shè)備主要由脫殼機(jī)外殼、轉(zhuǎn)子、篩分等部件，這里需要綜合考慮外形結(jié)構(gòu)形式、關(guān)鍵零部件材質(zhì)、幾何特征參數(shù)、各部件之間的配合參數(shù)以及動(dòng)力學(xué)運(yùn)動(dòng)參數(shù)。目前，市場上出現(xiàn)的花生脫殼機(jī)設(shè)備種類型號(hào)繁多，結(jié)構(gòu)功能也是也有特點(diǎn)，但是多數(shù)的花生脫殼機(jī)還是或多或少的存在一些缺點(diǎn)，或不完善，比如脫殼性能不穩(wěn)定、花生的破損率高等問題 [2]。 因此，本課題的研究目的是針對(duì)現(xiàn)有花生脫殼設(shè)備的應(yīng)用與發(fā)展現(xiàn)狀，分析各類脫殼機(jī)的脫殼原理、結(jié)構(gòu)組成及存在的問題進(jìn)行優(yōu)化改進(jìn)。 1.2 花生脫殼機(jī)的脫殼原理 花生脫殼機(jī)的工作原理就是通過高速旋轉(zhuǎn)的沖擊機(jī)體將花生仁與殼進(jìn)行分離，在保證花生仁的完整性前提下，對(duì)花生仁進(jìn)行篩分清。因此，采用最優(yōu)的脫殼原理是解決脫殼機(jī)現(xiàn)存問題?；ㄉ摎C(jī)的種類非常多，常用的脫殼機(jī)工作原理主要有以下幾種： （1）打擊法 打擊法脫殼（離心式脫殼）是利用高速回轉(zhuǎn)的轉(zhuǎn)子部件給花生莢果強(qiáng)大的離心力作用，使得花生殼受到劇烈沖擊力破裂，花生殼受撞擊變形裂開，花生仁就從花生殼裂縫中脫落出來。離心式脫殼機(jī)脫殼方法對(duì)花生莢果的含水率有嚴(yán)格要求，且與脫殼轉(zhuǎn)子的轉(zhuǎn)速及加料量有密切聯(lián)系。 2）擠壓法 擠壓法脫殼工作原理的利用具有一定量間距的兩個(gè)轉(zhuǎn)速相同，方向相反的滾筒擠壓花生莢果，在擠壓力作用下花生被壓破裂與花生仁分離達(dá)到脫殼。通過擠壓原理脫殼的影響因素主要是兩滾筒之間的間隙值，能否使莢果被夾住并順利進(jìn)入間隙達(dá)到擠壓的目的。 （3）碾搓法 碾搓法脫殼的工作原理是利用一個(gè)固定磨片與一個(gè)運(yùn)動(dòng)磨片使得花生莢果在兩者之間通過，在定圓盤和擁有轉(zhuǎn)動(dòng)離心力的動(dòng)圓盤之間碾搓，受到碾搓作用撕碎花生殼，從而實(shí)現(xiàn)花生殼與花生仁分離的目的，如圖1.1所示。影響脫殼機(jī)效果的因素也是花生莢果含水率、圓盤表面幾何結(jié)構(gòu)和其轉(zhuǎn)速等。 圖1.1碾搓法的工作原理 （4）剪切法 剪切法脫殼的工作原理是固定刀架與高速運(yùn)轉(zhuǎn)刀板之間的相對(duì)運(yùn)動(dòng)將花生莢果切裂打開，實(shí)現(xiàn)花生仁與殼分離。為增加脫殼機(jī)的使用范圍，可根據(jù)花生莢果顆粒大小來調(diào)節(jié)刀架與刀板之間的間距，這種脫殼原理設(shè)備脫殼時(shí)與花生莢果接觸面小，漏剝重剝的出現(xiàn)比較小，因此，脫凈率相對(duì)較高。 1.3 花生脫殼機(jī)的應(yīng)用現(xiàn)狀與未來發(fā)展趨勢 1.3.1 花生脫殼機(jī)的應(yīng)用現(xiàn)狀介紹 目前，市場上的花生脫殼設(shè)備的種類繁多，在設(shè)備結(jié)構(gòu)組成、型號(hào)特點(diǎn)、功率大小等都是各具特點(diǎn)的，其采用的脫殼原理也是從單一到多種方式相結(jié)合的，基本上可以滿足各類花生脫殼加工、分選、復(fù)脫、分級(jí)等多種工序。 圖1.2所示為國內(nèi)成熟的兩款花生脫殼機(jī)。 目前，已在使用的花生脫殼機(jī)是各具特色的花生脫殼機(jī)，均是20世紀(jì)七八十年代引進(jìn)、改造出來的產(chǎn)品，也就是具有一定脫殼效率，基本上能夠滿足勞動(dòng)者對(duì)花生脫殼要求。對(duì)于小型家用脫殼機(jī)械多數(shù)的應(yīng)用于廣大農(nóng)村，脫殼機(jī)的脫殼效率較低，性能不是非常穩(wěn)定度，存在花生仁的損傷率大等問題。 （A） （B） 圖1.3典型的花生脫殼機(jī) 對(duì)于那些要求比較的花生種子脫殼，其對(duì)破損率有嚴(yán)格要求，現(xiàn)有的脫殼機(jī)械也比較難滿足的。因此，針對(duì)現(xiàn)有花生脫殼設(shè)備的應(yīng)用與發(fā)展現(xiàn)狀，分析各類脫殼機(jī)的脫殼原理、結(jié)構(gòu)組成及存在的問題進(jìn)行優(yōu)化改進(jìn)。 1.3.2 未來發(fā)展趨勢 進(jìn)入21世紀(jì)，隨著工業(yè)技術(shù)的飛速發(fā)展，我國花生生產(chǎn)加工機(jī)械化進(jìn)入了新發(fā)展階段，為花生種植、收獲、加工、等機(jī)械化提供發(fā)展條件。花生脫殼機(jī)設(shè)備的研發(fā)與優(yōu)化重點(diǎn)集中在如下方面： 1）提高花生脫殼機(jī)械的通用性和兼容性，使用過程中僅僅變換脫殼機(jī)主要的執(zhí)行工作部件，就能滿足不能種類、不同粒度的物料的脫殼加工。 2）即通過對(duì)脫殼機(jī)的脫殼原理與關(guān)鍵部件的結(jié)構(gòu)、材料應(yīng)用進(jìn)行重點(diǎn)攻關(guān)，提高機(jī)械脫殼率，降低破損率。 3） 提高脫殼設(shè)備的脫殼自動(dòng)控制與自動(dòng)化方向。通過機(jī)電一體化技術(shù)的應(yīng)用，開發(fā)設(shè)計(jì)出具有自動(dòng)喂料、自動(dòng)定位脫殼裝置，保證均勻喂料，實(shí)現(xiàn)機(jī)組自動(dòng)化操作，提高作業(yè)精確性和作業(yè)速度。 2. 花生脫殼機(jī)的整體結(jié)構(gòu)方案與工作原理 2.1本設(shè)計(jì)中的脫殼原理 經(jīng)過對(duì)市場上現(xiàn)有的花生脫殼機(jī)進(jìn)行調(diào)研分析，確定本次課題設(shè)計(jì)一款封閉木質(zhì)滾筒式花生剝殼機(jī)。即剝殼部件是在一個(gè)圓筒上鑲上若干齒形筋條，下部與半圓形型柵條式凹板配合，且滾筒外徑與半籠柵圓周進(jìn)行控制在30-38mm，如圖1-1所示。 工作時(shí)，花生莢果在重力作用下，進(jìn)入到脫殼機(jī)構(gòu)箱體內(nèi)，在高速回轉(zhuǎn)滾筒的離心力作用下由進(jìn)口向出口端運(yùn)動(dòng)，此時(shí)，花生莢果在滾筒和柵條凹板的揉搓、擠壓、摩擦綜合效應(yīng)下，完成強(qiáng)制裂縫、脫殼。 圖 2-1 脫殼原理示意圖 在脫殼時(shí)，與柵條縫尺寸相同或小于柵條間隙的花生顆粒就直接從柵縫中分離出來，這就造成一次性脫殼率較低。為保證脫殼率要求，可以通過更換柵條凹板部件來改變滾筒與凹板之間的間隙，或者將半籠型凹板的柵條間隙，針對(duì)與普通花生顆粒，柵條間隙去9mm-13mm。另外，脫殼機(jī)需要配置花生仁和未脫果分離的裝置。 2.2花生脫殼機(jī)的總體結(jié)構(gòu) 根據(jù)前面的剝殼原理可知，花生脫殼的過程是：物料首先從進(jìn)料斗進(jìn)入到剝殼箱之內(nèi)，經(jīng)過滾筒及柵格，從下箱的出口流出，為實(shí)現(xiàn)花生殼與仁的分離，需要設(shè)置比重分選篩裝置，最后花生仁在重力作用下進(jìn)入到收集斗中。 滾筒式脫殼機(jī)構(gòu)是本設(shè)計(jì)中最為重要的機(jī)構(gòu)，我將在本文第三章中重點(diǎn)進(jìn)行設(shè)計(jì)。因花生進(jìn)度到剝殼箱內(nèi)之后，花生經(jīng)過高速回轉(zhuǎn)的滾筒與柵條之間的撞擊和擠壓作用，花生莢果被強(qiáng)制裂縫、剝殼，然后經(jīng)過位于剝殼箱底部的柵格，柵格直接設(shè)計(jì)成一個(gè)側(cè)面封閉的半籠柵，它是通過螺栓固定安裝在剝殼箱的下半箱之內(nèi)。 如果花生在下落過程中沒有與輥筒外圓周的齒輪發(fā)生接觸碰撞，或者是發(fā)生接觸了花生僅出現(xiàn)裂紋但是沒有完全殼、仁分離，此時(shí)，這部分花生將直接落入到半籠柵格上，在下一個(gè)轉(zhuǎn)子旋轉(zhuǎn)周期上輥筒旋轉(zhuǎn)外徑與柵格頂部間的間距因不足以容納一個(gè)完整花生果，因此花生果將再次受到輥筒齒型的擠壓而被壓碎。 圖2-2 滾筒式破碎機(jī)結(jié)構(gòu)組成原理圖 如圖2.2所示，封閉式滾筒脫殼機(jī)主要由進(jìn)料機(jī)構(gòu)、剝殼機(jī)構(gòu)、分選機(jī)構(gòu)和機(jī)架支承機(jī)構(gòu)等部分組成。脫殼機(jī)的驅(qū)動(dòng)源采用一個(gè)電機(jī)提供動(dòng)力，經(jīng)帶傳動(dòng)道滾筒脫殼裝置；比重分選的篩分裝置采用偏心輪機(jī)構(gòu)，動(dòng)力直接由滾筒主軸經(jīng)帶傳動(dòng)到分選篩分裝置主軸。 為保證脫殼整機(jī)的各部件安裝要求，本機(jī)設(shè)計(jì)采用矩形鋼管型材焊接的機(jī)架，起到支承、定位、連接作用，驅(qū)動(dòng)電機(jī)安裝在機(jī)架下部。 2.3 殼仁分離裝置 殼仁分離裝置的實(shí)現(xiàn)分離的基本原理是利用花生殼、花生仁的重量及受力面積的不同，重量稍重的不被風(fēng)吹走，而重量較輕的花生殼將被風(fēng)機(jī)吹來的氣流帶入到花生殼收集通道，用氣流對(duì)其進(jìn)行分離。重量稍重的不被氣流吹走，直接下落到花生仁收集通道，落入比重分選篩上，然后比重分選篩運(yùn)行。 3. 花生脫殼機(jī)關(guān)鍵部件的結(jié)構(gòu)設(shè)計(jì) 3.1脫殼部件的設(shè)計(jì) 3.1.1滾筒半徑及轉(zhuǎn)速初定 本磁設(shè)計(jì)的是封閉式滾筒式脫殼機(jī)構(gòu)，脫殼執(zhí)行裝置由一個(gè)圓筒型滾筒外部設(shè)置了齒輪打擊齒，下部與半圓形柵條凹板配合組成，如圖3.1所示。 1.打擊齒 2.半籠柵 圖3.1 脫殼裝置組成 為保證高速回轉(zhuǎn)的滾筒與半圓柵條的撞擊、擠壓、揉搓作用下實(shí)現(xiàn)對(duì)花生的強(qiáng)制脫殼，這里需要設(shè)置合理的間隙，進(jìn)籠側(cè)入口的間隙值一般取30-50mm，出籠側(cè)出口的間隙一般取10-15mm。 滾筒的幾何形狀、尺寸及結(jié)構(gòu)形式需要與花生的尺寸箱匹配，同時(shí)轉(zhuǎn)子轉(zhuǎn)速和轉(zhuǎn)軸部件的邊界轉(zhuǎn)速需要避免出現(xiàn)頻率相近而使得脫殼機(jī)產(chǎn)生共振，造成脫殼設(shè)備產(chǎn)生附加振動(dòng)及較大的噪音。 滾筒的半徑與轉(zhuǎn)速確定依據(jù)為：滾筒旋轉(zhuǎn)必須確保能將進(jìn)入的花生殼撞碎，經(jīng)過查閱相關(guān)資料，當(dāng)花生莢果與鋼性物體的相對(duì)速度約為3.5時(shí)，可以保證花生殼破碎而且可以保證花生仁的損壞率在98%以下。如圖3-2所示，花生下落點(diǎn)位置在之間，因此最小碰撞半徑為計(jì)算半徑： 整理得： 取半徑R=170mm，則由 因此本次設(shè)計(jì)的脫殼滾筒幾何尺寸與轉(zhuǎn)速初選為：R=170mm，n=395r/min 圖3.2 滾筒截面圖 確定滾筒圓周的齒輪的幾何參數(shù)，如圖3.3所示，經(jīng)過統(tǒng)計(jì)測量數(shù)據(jù)，花生莢果長為39.41mm，寬度尺寸為13.8mm，厚度尺寸為14.5mm。為保證滾筒在高速回轉(zhuǎn)中與半籠柵之間的能順利擠殼花生殼，且不損壞花生仁，這里滾筒齒輪的結(jié)合形狀如圖3.4所示，開口35mm，角度為60度。 圖3.3 花生外形參數(shù) 圖3.4 齒型槽幾何參數(shù) 3.1.2脫殼機(jī)所需功率計(jì)算與電機(jī)選型 根據(jù)功率計(jì)算公式：，需要先計(jì)算滾筒所需的功率； 滾筒在高速回轉(zhuǎn)過程中對(duì)花生做功包含兩部分，動(dòng)能與勢能之和， 上式：：滾筒改變花生的動(dòng)能； ：滾筒改變花生的勢能 上式中 ：花生果的初動(dòng)能（J）； 花生果的末動(dòng)能（J）； 花生果的初速度(m/s)； 花生果地末速度(m/s)； 這里設(shè)定花生脫殼機(jī)的額定單位脫殼產(chǎn)量為30kg/min，折合每秒產(chǎn)量為0.5kg/s?；ㄉ佑|滾筒齒槽板時(shí)的初速度設(shè)為1m/s，方向近似向下，當(dāng)滾筒旋轉(zhuǎn)一定角度后，花生離開滾筒的速度擬定達(dá)到15m/s，方向向左，脫離齒槽板時(shí)相對(duì)初位置高度降低了170mm。 代入計(jì)算得到：P=67W 同時(shí)，需要計(jì)算滾筒與花生在柵格中擠壓所需要的能量，所需功率P遠(yuǎn)小于500W。電機(jī)通過帶傳動(dòng)到滾筒主軸，這里需要確定帶傳動(dòng)與脫殼裝置之間的傳遞總效率。初設(shè)滾動(dòng)軸承效率為、V帶傳動(dòng)的效率為，則可以計(jì)算出總效率為 圖3.5 滾筒轉(zhuǎn)動(dòng)示意圖（理論狀態(tài)下） 考慮到本脫殼機(jī)的風(fēng)扇及重力篩分裝置的偏心輪裝置的動(dòng)力源都是利用主軸驅(qū)動(dòng)電機(jī)，這里需要充分預(yù)留一定功力，因此這里初選電動(dòng)機(jī)的功率為1.5kW。 根據(jù)前面計(jì)算所需的電機(jī)功率及滾筒的轉(zhuǎn)速，可選用的電機(jī)型號(hào)有兩種 ：Y90L-4型和Y100L-6型，他們參數(shù)詳細(xì)見下表。 表3-1 驅(qū)動(dòng)電機(jī)的參數(shù) 方案號(hào) 電機(jī)型號(hào) 額定功率kw 同步轉(zhuǎn)速r/min 滿載轉(zhuǎn)速r/min 總傳動(dòng)比 i 1 Y100L-6 1．5 1000 940 2.38 2 Y90L-4 1．5 1500 1400 3.65 比較上述兩款電機(jī)，方案2傳動(dòng)比稍微大點(diǎn)，但是電機(jī)價(jià)格低，適合于家用機(jī)械設(shè)備。Y90L-4型電機(jī)的中心高H為90mm，外伸軸徑為24mm，軸的外伸長度為50mm。 3.1.3傳動(dòng)裝置的傳動(dòng)參數(shù)計(jì)算 滾筒式花生去殼機(jī)的滾筒轉(zhuǎn)速已確定為，這里直接選用V帶傳動(dòng)，保證傳動(dòng)結(jié)構(gòu)簡單，安裝方案，設(shè)備的制造成本低。下面來計(jì)算系統(tǒng)的傳動(dòng)比： 滾筒軸的轉(zhuǎn)速： 滾筒軸轉(zhuǎn)速為： 傳動(dòng)比： 軸的輸入功率： 軸的轉(zhuǎn)矩： 上式中： 為滾筒軸的轉(zhuǎn)矩(N.m)； 為滾筒軸的輸入功率(kw)； 3.1.4電機(jī)與脫殼轉(zhuǎn)子軸之間的V帶傳動(dòng)設(shè)計(jì) 電機(jī)型號(hào)：Y90L-4 額定功率：1.5kw 電機(jī)轉(zhuǎn)速： 傳動(dòng)比：=3.65 假設(shè)脫殼機(jī)的工作時(shí)間：t<10h/天 1.確定計(jì)算功率 式中 為計(jì)算功率（kw）； 為電機(jī)的額定功率kw； 為工作系數(shù)，由文獻(xiàn)[13]表14.1-12查得； 則 2.選擇V帶帶型： 根據(jù)、查文獻(xiàn)[13]，查帶型參數(shù)，確定帶型為A型； 3.確定帶輪基準(zhǔn)直徑 查文獻(xiàn)[13]，確定帶傳動(dòng)的主動(dòng)輪基準(zhǔn)直徑，取， 計(jì)算得到從動(dòng)輪基準(zhǔn)直徑為： 按文獻(xiàn)[13]將從動(dòng)基準(zhǔn)直徑圓整： 驗(yàn)算傳動(dòng)帶的速度情況： 因此，所選帶的速度合適。 4．確定帶傳動(dòng)的中心距a和傳動(dòng)帶的基準(zhǔn)長度： 則 這里初取中心距： 查文獻(xiàn)[13]由表14.1－7選擇帶的基準(zhǔn)長度 計(jì)算實(shí)際中心距a 5．驗(yàn)算主動(dòng)輪上的包角 計(jì)算主動(dòng)輪包角合適： 上式中 為包角系數(shù)，?。? 為長度系數(shù)，取； 為單根V帶的基本額定功率（KW）；取； 為單根V帶的額定功率的增量（KW），； 代入數(shù)值，計(jì)算： 取z=2 7.計(jì)算預(yù)緊力 查文獻(xiàn)[13]表14.1－14得:： 8．計(jì)算作用在軸上的壓軸力 式中 ——帶的根數(shù)； ——單根帶的預(yù)緊力 N； ——主動(dòng)輪的包角 ( °)； 代入數(shù)值計(jì)算得： 9.V帶輪的結(jié)構(gòu)尺寸計(jì)算及選用 帶輪材料選用HT200； 根據(jù)基準(zhǔn)直徑的大小選用不同的帶輪類型，小徑帶輪采用實(shí)心式，大徑帶輪采用輪輻式，主要結(jié)構(gòu)尺寸如表3-2。 3-2電機(jī)與比重分選篩間傳動(dòng)帶輪參數(shù)表 單位：mm 尺寸類型 小帶輪 大帶輪 90 330 基準(zhǔn)寬度 30 30 基準(zhǔn)線上槽深 3.75 3.75 基準(zhǔn)線下槽深 19 19 槽間距e 15±0.3 15±0.3 第一槽對(duì)稱面至端面距離f 輪緣厚d 12 12 帶輪寬B 60 40 外徑 120 343 輪槽角 極限偏差 孔徑 25 25 輪轂長 50 42 80 輪輻厚 10 20 16 350 具體結(jié)構(gòu)設(shè)計(jì)見零件圖： 圖3.6 小帶輪三維 圖3.7 大帶輪三維 3.1.5滾筒材料的選擇 根據(jù)花生需要的力與花生脫殼機(jī)械轉(zhuǎn)速結(jié)合，減少花生莢果堆積過多時(shí)擠壓力變大將花生仁擠破致其損傷，套筒的形式還可以轉(zhuǎn)動(dòng)，當(dāng)花生莢果堆積或者有雜質(zhì)時(shí)，可以減少花生仁損傷和機(jī)器損傷。 采用木質(zhì)材料作為擊打部件還有硬度大的特點(diǎn)，可以使花生脫殼機(jī)轉(zhuǎn)速無需過大就能使花生殼破裂達(dá)到脫殼的目的；由于其表面較光滑，揉搓力并不明顯。橡膠表面粗糙度相對(duì)較高，對(duì)花生莢果的摩擦力較大，利于花生莢果脫殼。主要運(yùn)用的是擊打、擠壓、碾搓的脫殼原理。 圖3.8 滾筒的三維 3.2轉(zhuǎn)軸的設(shè)計(jì)與校核 3.2.1初步確定軸的最小直徑 根據(jù)前面計(jì)算軸的轉(zhuǎn)速： 轉(zhuǎn)子軸的輸入功率 得 軸的轉(zhuǎn)矩： 上式中： 為滾筒軸的轉(zhuǎn)矩(N.m)； 為滾筒軸的輸入功率(kw)； 先按經(jīng)驗(yàn)公式算出軸的最小直徑，選取軸的材料為45鋼，調(diào)質(zhì)處理。查機(jī)械設(shè)計(jì)手冊選取，得 得 為方便平鍵的設(shè)置，這里選確定軸最小直徑25mm。 圖3.9 轉(zhuǎn)軸結(jié)構(gòu)圖 3.2.2擬定軸上零件的裝配方案與尺寸確定 轉(zhuǎn)軸上各零部件裝配關(guān)系如圖3.10所示： 圖3.10 轉(zhuǎn)軸的裝配示意圖 （1） 軸直徑最小值取，長度30mm，保證V帶輪的軸向定位，1-2軸左端采用軸肩定位，右端采用擋圈加螺母鎖緊定位，擋圈只壓在帶輪上而不壓在軸端面； （2） 第二段為軸承檔位，直徑，長度取為；第三段為滾筒安裝檔位，直徑，長度取為； （3）選擇深溝球軸承 該軸承既可以承受徑向力，也可以承受一定的軸向力，選取深溝球軸承6206；滾動(dòng)軸承與轉(zhuǎn)軸的軸向定位軸肩與軸承座來保證的，本設(shè)計(jì)中軸直徑尺寸公差為。 表3.2 軸承技術(shù)參數(shù) （4）V帶輪與軸的周向定位采用平鍵聯(lián)接； 3.2.3.主軸的強(qiáng)度校核 (1)滾筒軸空間受力如圖3.11所示。 圖3.11 軸空間受力圖 (2)滾筒軸的水平面上的受力分析和彎矩如圖3.12所示。 圖3.12水平面受力圖 作出水平面內(nèi)的彎矩如圖3.13所示： 圖3.13 主軸水平面彎矩圖 (3)垂直平面內(nèi)的受力分析和彎矩如圖3.14。 圖3.14 垂直平面的受力分析 作出垂直平面內(nèi)的彎矩如圖3-12。 圖3.15 主軸垂直面彎矩圖 (4)合成彎矩如圖3-13。 圖3-13 合成彎矩圖 (5)校核軸的強(qiáng)度。 ， ，， ， 由于>23.74MPa,故主軸合格。 3.2.4軸承的校核 滾筒轉(zhuǎn)軸的軸承選擇用深溝球軸承，型號(hào)6206； 由軸的校核可知： ，，， 徑向力 軸向力 ， ， 取沖擊載荷系數(shù) ， 則 由于， 則按軸承2計(jì)算 顯然， ，故軸承壽命很充裕。 3.3比重分選篩動(dòng)力系統(tǒng)設(shè)計(jì) 3.3.1比重分選篩裝置設(shè)計(jì) 本設(shè)計(jì)中采用了平面型振動(dòng)篩，驅(qū)動(dòng)方式采用偏心輪機(jī)構(gòu)直接與振動(dòng)篩下部的橫梁接觸驅(qū)動(dòng)，在重力作用下，振動(dòng)篩向下復(fù)位，其結(jié)構(gòu)如圖3.14所示。 圖3.14 篩選裝置 本設(shè)計(jì)采用大型的平面篩，其與圓筒篩相比，其具有更大的有效篩理面積。通過帶傳動(dòng)將滾筒軸上的動(dòng)能傳遞到偏心輪軸，將回轉(zhuǎn)運(yùn)動(dòng)轉(zhuǎn)變成篩體的往復(fù)振動(dòng)，實(shí)現(xiàn)平面篩在垂直方向上作往復(fù)運(yùn)動(dòng)的振動(dòng)。 此花生脫殼機(jī)中所采用的是偏心輪機(jī)構(gòu)以作為比重分選篩的執(zhí)行機(jī)構(gòu)，篩箱水平全振幅等于偏心距的2倍。 圖3.15比重分選篩原理圖 要求偏心輪的偏心距與兩支點(diǎn)之間的距離之比小于1/10，則可利用均勻旋轉(zhuǎn)的偏心輪促使振動(dòng)篩子上任何一點(diǎn)都按簡諧運(yùn)動(dòng)規(guī)律沿自己的軌跡運(yùn)動(dòng)。 3.3.2偏心輪轉(zhuǎn)軸設(shè)計(jì) 這里輸出動(dòng)力的主動(dòng)輪是滾筒轉(zhuǎn)軸，其轉(zhuǎn)速為； 從動(dòng)軸偏心軸，初步確定其轉(zhuǎn)速為； 軸的輸入功率： 軸的輸入轉(zhuǎn)矩： 1.初步確定軸的最小直徑 選取軸材料為45鋼，調(diào)質(zhì)處理。計(jì)算軸的最小直徑，取， 這里取軸的最小徑為25mm。 圖3.16 偏心輪軸 2.擬定軸上零件的裝配方案 圖3.17 偏心軸裝配方案 3.3.3偏心軸的V帶傳動(dòng)設(shè)計(jì) 對(duì)于滾筒轉(zhuǎn)軸與偏心軸之間的帶傳動(dòng)設(shè)計(jì)，因前面已經(jīng)做 V帶傳動(dòng)的設(shè)計(jì)，這里不做重復(fù)計(jì)算，盡在下表列出相關(guān)參數(shù)。 表3-7偏心軸與滾筒轉(zhuǎn)子軸間的V帶輪參數(shù) 單位：mm 尺寸類型 小帶輪 大帶輪 90 330 基準(zhǔn)寬度 30 30 基準(zhǔn)線上槽深 3.75 3.75 基準(zhǔn)線下槽深 19 19 槽間距e 15±0.3 15±0.3 第一槽對(duì)稱面至端面距離f 輪緣厚d 12 12 帶輪寬B 60 40 外徑 120 343 輪槽角 極限偏差 孔徑 25 25 輪轂長 50 42 80 輪輻厚 10 20 16 350 4. 花生脫殼機(jī)的各部件設(shè)計(jì)與三維建模 4.1 關(guān)鍵組件的設(shè)計(jì)與三維建模 4.1.1半柵籠 半柵籠的主要作用是與滾筒配合，實(shí)現(xiàn)對(duì)進(jìn)入料斗內(nèi)的花生擠壓、撞擊，同時(shí)，柵條可以對(duì)已被剝殼花生與未被剝殼花生進(jìn)行分離，即“小個(gè)通過，大個(gè)不過”。半柵籠的柵條間隙控制在13mm，每個(gè)柵格間隙只能通過一粒花生仁，因此，對(duì)于已被脫殼的花生可以穿過柵格，未被脫殼或已擠裂紋但沒有殼、仁分離花生莢果因?yàn)轶w積太大，無法通過柵格，將被阻擋在剝殼箱內(nèi)，繼續(xù)進(jìn)行剝殼直到其外殼破碎。半籠柵的三維結(jié)構(gòu)如圖4.1所示。 圖4.1 半籠柵的三維 半籠柵兩側(cè)面通過兩塊擋板對(duì)兩端進(jìn)行固定的，組成半圓柵籠，擋板材料為Q235，柵條材料選用20鋼。柵條采用截面圓棒料，長度為635mm，為了防銹處理，需要對(duì)半籠柵表面整體進(jìn)行滲碳處理，熱處理硬度HRC56-62。半柵籠的柵條間隙控制在10mm，每個(gè)柵格間隙只能通過一粒已脫殼的花生仁，而未剝殼的剛不能通過，可以對(duì)半柵籠的安裝采用浮動(dòng)安裝，降低花生仁的破碎率，半柵籠內(nèi)徑為。 4.1.2風(fēng)扇組件設(shè)計(jì) 風(fēng)扇的作用是提高風(fēng)能將花生殼與仁進(jìn)行分離，因?yàn)榛ㄉ鷼?、花生仁的重量不同，且花生殼的受力面積大，通過風(fēng)扇作用，可以將重量較輕的花生殼將被風(fēng)機(jī)吹來的氣流帶入到花生殼收集處，用氣流對(duì)其進(jìn)行分離。重量稍重的不被氣流吹走，直接下落到花生仁收集通道，落入比重分選篩上，然后比重分選篩運(yùn)行。 如圖4.2、4.3所示，風(fēng)扇組件由軸承座、帶輪、風(fēng)扇葉片及外罩組成。 圖4.2 風(fēng)扇轉(zhuǎn)子三維 圖4.3 風(fēng)扇外罩三維 4.1.3箱體 箱體構(gòu)成一個(gè)封閉的剝殼環(huán)境，它對(duì)滾筒轉(zhuǎn)子及半籠柵等構(gòu)起到支承。箱體尺寸直接根據(jù)滾筒轉(zhuǎn)軸部件的尺寸來決定的，如圖4.4所示，下箱體的三維模型圖，側(cè)面通過四個(gè)側(cè)耳與機(jī)架進(jìn)行固定連接 。 為了便于脫殼機(jī)滾筒部件的安裝和拆卸，這里將箱體做成剖分式的，分為上箱蓋和下箱體兩部分組成，剖分面設(shè)置在轉(zhuǎn)軸所在的中心線所在平面。上箱蓋和下箱體采用四個(gè)螺栓聯(lián)接，用圓錐銷定位。箱體材料選用Q235，焊接而成。 圖4.4 下箱體的三維 4.1.4料斗 漏斗采用斜錐式漏斗，漏斗直接與上箱體焊接為一體，三維結(jié)構(gòu)如圖4.5所示。前面已估算當(dāng)喂料速率在30kg/min 時(shí)，這樣可以保證留在脫殼箱體的花生莢果較，莢果進(jìn)入箱體之內(nèi)的阻滯作用??；使得莢果與滾筒的擠壓得以充分脫殼，花生莢果與旋轉(zhuǎn)滾筒齒型槽的接觸機(jī)會(huì)多，脫殼效率也高。 如果進(jìn)一步增加喂入量，則直接造成脫殼箱體內(nèi)的物料量增加，花生莢果之間的擠壓摩擦也增大，因脫殼室內(nèi)存留物料過多，花生仁、殼在阻礙作用下 ，不能及時(shí)排出脫殼室 ，導(dǎo)致果仁破碎率和損傷率增加 。 圖4.5 料斗三維 4.1.5振動(dòng)篩的箱體 振動(dòng)篩的箱體是振動(dòng)篩分的框架部件，它與篩網(wǎng)配合，將篩選出的花生仁收集。箱體下部橫梁直接與偏心輪接觸，通過帶傳動(dòng)將滾筒軸上的動(dòng)能傳遞到偏心輪軸，將回轉(zhuǎn)運(yùn)動(dòng)轉(zhuǎn)變成篩體的往復(fù)振動(dòng)，實(shí)現(xiàn)平面篩在垂直方向上作往復(fù)運(yùn)動(dòng)的振動(dòng)。振動(dòng)篩箱體與機(jī)架通過銷釘相聯(lián)，通過偏心輪與機(jī)架相聯(lián)從而產(chǎn)生比重分選篩的振動(dòng)效果。箱體的材料選用Q235，板材焊接成型。具體結(jié)構(gòu)如圖4.6所示。 圖4.6 振動(dòng)篩箱體 4.1.5篩網(wǎng) 本設(shè)計(jì)采用大型的平面篩，其與圓筒篩相比，其具有更大的有效篩理面積。通過帶傳動(dòng)將滾筒軸上的動(dòng)能傳遞到偏心輪軸，將回轉(zhuǎn)運(yùn)動(dòng)轉(zhuǎn)變成篩體的往復(fù)振動(dòng)，實(shí)現(xiàn)平面篩在垂直方向上作往復(fù)運(yùn)動(dòng)的振動(dòng)。 根據(jù)粒度的不同，篩面的材料和安裝方式也是存在差異的。針對(duì)花生仁粒度小于15 mm，篩面直接選擇中等硬度的篩面。軟質(zhì)篩網(wǎng)的安裝多采用張緊鉤式的，篩網(wǎng)的兩端固定有張緊鉤。 篩網(wǎng)的材料為鋼絲編織篩網(wǎng)，篩分效果最好，花生因自重較小故對(duì)它的損壞較小，使用壽命較長。篩網(wǎng)部件如圖4.7所示。 圖4.7 篩網(wǎng) 4.1.6機(jī)架 花生脫殼機(jī)的機(jī)架采用截面為50*50mm矩形鋼管焊接而成，機(jī)架的作用的支承與定位滾筒部件，連接箱體、料斗、偏心輪軸等部件的作用，并將電機(jī)安裝在機(jī)架里面，各部件的聯(lián)接采用普通螺栓聯(lián)接。如圖4.8所示。 圖4.8 脫殼機(jī)的機(jī)架三維 4.2 脫殼機(jī)的三維建模與裝置檢查 滾筒式花生脫殼機(jī)的三維裝配圖如圖4.9所示。 圖4.9 滾筒式花生脫殼機(jī)的三維裝配 花生脫殼機(jī)的設(shè)計(jì)采用自下而上的建模設(shè)計(jì)方案，首先根據(jù)脫殼產(chǎn)量初步確定滾筒直徑及長度，確定滾筒轉(zhuǎn)速，在此基礎(chǔ)上對(duì)各關(guān)鍵的轉(zhuǎn)軸部件、 半籠柵、箱體、機(jī)架和風(fēng)機(jī)等部件單獨(dú)建模設(shè)計(jì)，然后在對(duì)各組件裝配起來。 圖4.10為脫殼機(jī)三維模型的主視圖，將完成虛擬裝配的三維模型進(jìn)行干涉檢查分析，平面剖切分析，分析各零部件中不合理結(jié)構(gòu)，通過干涉檢查發(fā)現(xiàn)各零部件尺寸不正確的地方。另外，也可以通過運(yùn)動(dòng)仿真分析，演示脫殼機(jī)各部件的動(dòng)態(tài)過程。 圖4.10 脫殼機(jī)三維模型的主視圖 5.結(jié)論 本文首先花生脫殼機(jī)的脫殼原理，應(yīng)用現(xiàn)狀及現(xiàn)在市場上應(yīng)用的個(gè)脫殼機(jī)存在的問題進(jìn)行調(diào)研分析，針對(duì)其問題進(jìn)行了分析。根據(jù)設(shè)計(jì)要求及花生脫殼機(jī)的功能要求，確定了花生脫殼機(jī)的總體方案的設(shè)計(jì)，以封閉式滾筒脫殼機(jī)為研究對(duì)象，對(duì)脫殼機(jī)的關(guān)鍵脫殼部件、進(jìn)料機(jī)構(gòu)、振動(dòng)篩分選機(jī)構(gòu)和偏心輪機(jī)構(gòu)等部分進(jìn)行詳細(xì)設(shè)計(jì)與三維建模分析。最后對(duì)本次設(shè)計(jì)心得體會(huì)與成果進(jìn)行的總結(jié)。 在設(shè)計(jì)過程中，從分析課題，搜集相關(guān)材料，閱讀并綜述相關(guān)資料以及設(shè)計(jì)計(jì)算等過程有了清晰的思路。我通過查閱大量有關(guān)資料，與同學(xué)交流經(jīng)驗(yàn)，向老師請(qǐng)教，使自己培養(yǎng)了我獨(dú)立工作的能力，樹立了對(duì)自己工作能力的信心，相信會(huì)對(duì)今后的學(xué)習(xí)工作生活有非常重要的影響。 致謝 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Masood · B. Abbas · E. Shayan · A. Kara An investigation into design and manufacturing of mechanical conveyors systems for food processing Received: 29 March 2003 / Accepted: 21 June 2003 / Published online: 23 June 2004 ? Springer-Verlag London Limited 2004 Abstract This paper presents the results of a research investi- gation undertaken to develop methodologies and techniques that will reduce the cost and time of the design, manufacturing and assembly of mechanical conveyor systems used in the food and beverage industry. The improved methodology for design and production of conveyor components is based on the minimisa- tion of materials, parts and costs, using the rules of design for manufacture and design for assembly. Results obtained on a test conveyor system verify the bene?ts of using the improved tech- niques. The overall material cost was reduced by 19% and the overall assembly cost was reduced by 20% compared to conven- tional methods. Keywords Assembly · Cost reduction · Design · DFA · DFM · Mechanical conveyor 1 Introduction Conveyor systems used in the food and beverage industry are highly automated custom made structures consisting of a large number of parts and designed to carry products such as food cartons, drink bottles and cans in fast production and assembly lines. Most of the processing and packaging of food and drink in- volve continuous operations where cartons, bottles or cans are re- quired to move at a controlled speed for ?lling or assembly oper- ations. Their operations require highly ef?cient and reliable me- chanical conveyors, which range from overhead types to ?oor- mounted types of chain, roller or belt driven conveyor systems. In recent years, immense pressure from clients for low cost but ef?cient mechanical conveyor systems has pushed con- veyor manufacturers to review their current design and assembly methods and look at an alternative means to manufacture more economical and reliable conveyors for their clients. At present, S.H. Masood (u) · B. Abbas · E. Shayan · A. Kara Industrial Research Institute Swinburne, Swinburne University of Technology, Hawthorn, Melbourne 3122, Australia E-mail: smasood@swin.edu.au  most material handling devices, both hardware and software, are highly specialised, in?exible and costly to con?gure, install and maintain [1]. Conveyors are ?xed in terms of their locations and the conveyor belts according to their synchronised speeds, mak- ing any changeover of the conveyor system very dif?cult and ex- pensive. In today’s radically changing industrial markets, there is a need to implement a new manufacturing strategy, a new system operational concept and a new system control software and hard- ware development concept, that can be applied to the design of a new generation of open, ?exible material handling systems [2]. Ho and Ranky [3] proposed a new modular and recon?gurable 2D and 3D conveyor system, which encompasses an open re- con?gurable software architecture based on the CIM-OSA (open system architecture) model. It is noted that the research in the area of improvement of conveyor systems used in beverage in- dustry is very limited. Most of the published research is directed towards improving the operations of conveyor systems and inte- gration of system to highly sophisticated software and hardware. This paper presents a research investigation aimed at im- proving the current techniques and practices used in the de- sign, manufacturing and assembly of ?oor mounted type chain driven mechanical conveyors in order to reduce the manufactur- ing lead time and cost for such conveyors. Applying the con- cept of concurrent engineering and the principles of design for manufacturing and design for assembly [4, 5], several critical conveyor parts were investigated for their functionality, material suitability, strength criterion, cost and ease of assembly in the overall conveyor system. The critical parts were modi?ed and redesigned with new shape and geometry, and some with new materials. The improved design methods and the functionality of new conveyor parts were veri?ed and tested on a new test con- veyor system designed, manufactured and assembled using the new improved parts. 2 Design for manufacturing and assembly (DFMA) In recent years, research in the area of design for manufacturing and assembly has become very useful for industries that are con- 552 sidering improving their facilities and manufacturing methodol- ogy. However, there has not been enough work done in the area of design for conveyor components, especially related to the is- sue of increasing numbers of drawing data and re-engineering of the process of conveyor design based on traditional methods. · · · · ·  Emphasise standardisation Use the simplest possible operations Use operations of known capability Minimise setups and interventions Undertake engineering changes in batches A vast amount of papers have been published that have investi- gated issues related to DFMA and applied to various methodolo- gies to achieve results that proved economical, ef?cient and cost effective for the companies under investigation. The main classi?cations of DFMA knowledge can be iden- ti?ed as (1) General guidelines, (2) Company-speci?c best prac- tice or (3) Process and or resource-speci?c constraints. General guidelines refer to generally applicable rules-of-thumb, relat- ing to a manufacturing domain of which the designer should be aware. The following list has been compiled for DFM guidelines [6]. These design guidelines should be thought of as “optimal suggestions”. They typically will result in a high-quality, low- cost, and manufacturable design. Occasionally compromises must be made, of course. In these cases, if a guideline goes against a marketing or performance requirement, the next best alternative should be selected [7]. Company-speci?c best practice refers to the in-house design rules a company develops, usually over a long period of time, and which the designer is expected to adhere to. These design rules are identi?ed by the company as contributing to improved quality and ef?ciency by recognising the overall relationships between · · · · · · · · · · · · · · · · ·  Design for a minimum number of parts Develop a modular design Minimise part variations Design parts to be multifunctional Design parts for multiuse Design parts for ease of fabrication Avoid separate fasteners Maximise compliance: design for ease of assembly Minimise handling: design for handling presentation Evaluate assembly methods Eliminate adjustments Avoid ?exible components: they are dif?cult to handle Use parts of known capability Allow for maximum intolerance of parts Use known and proven vendors and suppliers Use parts at derated values with no marginal overstress Minimise subassemblies particular processes and design decisions. Companies use such guidelines as part of the training given to designers of products requiring signi?cant amounts of manual assembly or mainte- nance. Note that most of the methodologies are good at either being quick and easy to start or being more formal and quanti- tative. For example, guidelines by Boothroyd and Dewhurst [8] on DFA are considered as being quantitative and systematic. Whereas the DFM guidelines, which are merely rules of thumb derived from experienced professionals, are more qualitative and less formal [9]. 3 Conventional conveyor system design Design and manufacturing of conveyor systems is a very com- plex and time-consuming process. As every conveyor system is a custom-made product, each project varies from every other project in terms of size, product and layout. The system design Fig. 1. Layout of conveyor sys- tem for labelling plasic bottles 553 is based on client requirements and product speci?cations. More- over, the system layout has to ?t in the space provided by the company. The process of designing a layout for a conveyor sys- tem involve revisions and could take from days to months or in some instances years. One with the minimum cost and maximum client suitability is most likely to get approval. Figure 1 shows a schematic layout of a typical conveyor system installed in a production line used for labelling of plastic bottles. Different sections of the conveyor system are identi?ed by speci?c technical names, which are commonly used in similar industrial application. The “singlizer” sec- tion enables the product to form into one lane from multiple lanes. The “slowdown table” reduces the speed of product once it exits from ?ller, labeller, etc. The “mass ?ow” sec- tion is used to keep up with high-speed process, e.g., ?ller, labeller, etc. The “transfer table” transfers the direction of prod- uct ?ow. The purpose of these different conveyor sections is thus to control the product ?ow through different processing machines. A typical mechanical conveyor system used in food and bev- erage applications consists of over two hundred mechanical and electrical parts depending on the size of the system. Some of the common but essential components that could be standard- ised and accumulated into families of the conveyor system are side frames, spacer bars, end plates, cover plates, inside bend plates, outside bend plates, bend tracks and shafts (drive, tail and slave). The size and quantity of these parts vary according to the length of conveyor sections and number of tracks correspond- ing to the width and types of chains required. The problems and shortcomings in the current design, manufacturing and assembly of mechanical conveyors are varied, but include:  4 Areas of improvement In order to identify the areas of cost reduction in material and labour, a cost analysis of all main conveyor parts was conducted to estimate the percentage of cost of each part in relation to the total cost of all such parts. The purpose of this analysis was to identify the critical parts, which are mainly responsible for in- creasing the cost of the conveyor and thereby investigate means for reducing the cost of such parts. Table 1 shows the cost analysis of a 50-section conveyor sys- tem. The analysis reveals that 12 out of 15 parts constitute 79% of the total material cost of the conveyor system, where further improvements in design to reduce the cost is possible. Out of these, seven parts were identi?ed as critical parts (shown by an asterisk in Table 1) constituting maximum number of compo- nents in quantity and comprising over 71% of overall material cost. Among these, three components (leg set, side frame and support channel) were found to account for 50% of the total conveyor material cost. A detailed analysis of each of these 12 parts was carried out considering the principles of concurrent en- gineering, design for manufacture and design for assembly, and a new improved design was developed for each case [10]. De- tails of design improvement of some selected major component are presented below. 5 Redesign of leg set assembly In a conveyor system, the legs are mounted on the side frame to keep the entire conveyor system off the ?oor. The existing design of conveyor legs work, but they are costly to manufacture, they · · · · Over design of some parts High cost of some components Long hours involved in assembly/maintenance Use of non-standard parts have stability problems, and cause delays in deliveries. The delay is usually caused by some of the parts not arriving from over- seas suppliers on time. The most critical speci?cations required for the conveyor legs are: Table 1. Conveyor critical parts based on parts cost analysis Product description Leg set? Side frame? Support channel? Bend tracks Rt. roller shaft? Tail shaft Spacer bar? Support wear strip? Support side wear strip? End plate Cover plate Bend plates Torque arm bracket Slot cover Inside bend plate  Qty 68 80 400 8 139 39 135 400 132 39 39 8 18 97 8  Material used Plastic leg + SS tube 2.5 mm SS C channel SS Plastic 20 dia. SS shaft 35 dia. Stainless steel 50X50X6 SS 40 × 10 mm plastic Plastic 2.5 mm/SS 1.6 mm S/S 2.5 mm/SS 6 mm S/S plate Stainless steel 2.5 mm/SS  Cost (%) 20.22 16.07 15.00 14.36 6.70 6.27 5.43 5.36 3.01 1.88 1.57 1.29 1.21 0.97 0.66  Improvement possible (Yes/No) Yes Yes Yes No Yes No Yes Yes Yes Yes No Yes Yes Yes Yes Total ?Critical  parts 100.00 554 · · · ·  Strength to carry conveyor load Stability Ease of assembly Ease of ?exibility (for adjusting height)  1 and part 3 in Fig. 2) was not rigid enough. The connections for these parts are only a single 6 mm bolt. At times, when the conveyor system was carrying full product loads, it was observed that the conveyor legs were unstable and caused mechanical vi- bration. One of the main reasons for this was due to a single bolt Figure 2 indicates all the parts for the existing design of the conveyor leg. The indicated numbers are the part numbers described in Table 2, which also shows a breakdown of cost an- alysis complete with the labour time required to assemble a com- plete set of legs. The existing leg setup consists of plastic leg brackets ordered from overseas, stainless steel leg tubes, which are cut into speci?ed sizes, leg tube plastic adjustments, which are clipped onto the leg tube at the bottom as shown in Fig. 2. Lugs, which are cut in square sizes, drilled and welded to the leg tube to bolt the angle cross bracing and backing plate to support leg brackets bolts. The # of parts in Table 2 signi?es the number of components in each part number and the quantity is the con- sumption of each part in the leg design. Companies have used this design for many years but one of the common complaints reported by the clients was of the instability of legs. From an initial investigation, it became clear that the connec- tion between the stainless steel tube and plastic legs bracket (part Fig. 2. Existing leg design assembly with part names shown in Table 1 Table 2. Cost analysis for old leg design assembly connection at each end of the lugs in part 3 and part 7. The sta- bility of the conveyor is considered critical matter and requires recti?cation immediately to satisfy customer expectations. Considering the problems of the existing conveyor leg de- sign and the client’s preferences, a new design for the conveyor leg was developed. Generally the stability and the strength of the legs were considered as the primary criteria for improve- ment in the new design proposal but other considerations were the simplicity of design, minimisation of overseas parts and ease of assembly at the point of commissioning. Figure 3 shows, the new design of the conveyor’s leg assembly, and Table 3 gives a description and the cost of each part. Figure 3 shows that the new design consists of only ?ve main parts for the conveyor’s leg compared to eight main parts in the old design. In the old design, the plastic leg bracket, the leg tube plastic adjustment and the leg tube were the most expensive items accounting for 72% of the cost of leg assembly. In the new Part no. 1 5, 6 4 7 2 3 8  Part description Plastic leg bracket Leg tube plastic adjustment Lug Angle cross bracing Backing plate Leg tube Bolts  # of parts 2 4 2 1 2 2 6  Qty 2 2 2 1 2 2 6  Cost $ 30.00 $ 28.00 $ 4.00 $ 5.00 $ 4.00 $ 25.00 $ 3.00  Source Overseas Overseas In-house In-house In-house In-house In-house Total assembly cost (welding) $ 15.00 In-house Total 19 17 $ 114.00 555 Fig. 3. New design for leg assembly with part names in Table 3 Table 3. Cost analysis for new design leg assembly Part no. 1 3 4 5 2  Part description Stainless steel angle (50 × 50 × 3 mm) Leg plastic adjustment Cross brassing Bolts Backing plate  # of parts 2 2 1 8 2  Qty 2 2 1 4 2  Cost $ 24.00 $ 10.00 $ 7.00 $ 4.00 $ 4.00  Source In-house Overseas In-house In-house In-house Total assembly cost $ 10.00 In-house Total design, those parts have been replaced by a stainless steel angle and a new plastic leg adjustment reducing the cost of leg assem- bly by almost 50%. Thus the total numbers of parts in the leg have been reduced from 19 to 15 and the total cost per leg setup 15 · · · · 11 Size of side frame (depth) Strength of the material Ease for assembly Ease for manufacturing $ 59.00 has been reduced by $ 55 in the new design. The new conveyor leg design, when tested, was found to be more secure and stable than the old design. The elimination of part number 1 and 5 from old conveyor design has made the new design more stable and rigid. In addition, the width of the cross bracing has also been increased with two bolts mount instead of one in old design. This has provided the entire conveyor leg setup an additional strength. 6 Redesign of the side frames The side frame is the primary support of a conveyor system that provides physical strength to conveyors and almost all the parts are mounted on it. The side frame is also expected to have a rigid strength to provide support to all the loads carried on the conveyor. It also accommodates all the associated conveyor components for the assembly. The critical considerations of side frame design are: Figure 4 shows the side frame dimension and parameters. The side frame used in existing design appears to be of rea- sonable depth in size (dimension H in Fig. 4). From the initial investigation, it was found that the distance between spacer bar holes and return shaft (dimensions G and F in Fig. 4) could be reduced, as there was some unnecessary gap between those two components. The important point to check before rede?ning the design parameters was to make sure that after bringing those two closer, the return chains would not catch the spacer bar while the conveyor is running. The model of the new side frame design was drawn on CAD to ensure all the speci?cations are sound and the parts are placed in the position to check the clearances and the ?ts. Using the principle of design for manufacturing the new side frame design was made symmetrical so that it applies to all types of side frames. This change is expected to reduce the size of side frame signi?cantly for all sizes of chains. Table 4 shows a comparison of dimensions in the old design and the new design of side frames for the same chain type. It 556 Fig. 4. Side frame dimensions Table 4. New and old side frame dimension parameters Old design Chain type 3.25 LF/SS  STR/LBP/MAG A 31 B 92 C 71 D 196 E 65 F 105 G 211 H 241 I 136 J 58 K 85 L 196 TAB 22 83 62 187 56 96 202 232 127 New design Chain type 3.25 LF/SS  STR/LBP/MAG/TAB A 31 B 100 C 73 D 173 E 67 F 107 G 167 H 199 I 92 J 58 K 85 L 152 is noted that the overall size (depth) of the conveyor has been reduced from 241 mm to 199 mm (dimension H), which gives a saving of 42 mm of stainless steel on every side frame manu- factured. Thus, from a stainless steel sheet 1500 × 3000 mm, the old design parameter