機(jī)械外文文獻(xiàn)翻譯-織機(jī)打緯機(jī)構(gòu)的計(jì)算機(jī)輔助分析【中文4000字】【PDF+中文WORD】

機(jī)械外文文獻(xiàn)翻譯-織機(jī)打緯機(jī)構(gòu)的計(jì)算機(jī)輔助分析【中文4000字】【PDF+中文WORD】,中文4000字,PDF+中文WORD,機(jī)械,外文,文獻(xiàn),翻譯,織機(jī),打緯,機(jī)構(gòu),計(jì)算機(jī)輔助,分析,中文,4000,PDF,WORD 【中文4000字】 織機(jī)打緯機(jī)構(gòu)的計(jì)算機(jī)輔助分析 王友江 孫輝 紡織學(xué)院化纖工程，佐治亞理工學(xué)院，亞特蘭大，佐治亞州30332，美國 摘要：分析和設(shè)計(jì)打緯機(jī)構(gòu)對提高織機(jī)性能是極為重要的。計(jì)算機(jī)輔助設(shè)計(jì)和分析工具用于研究不同種類的打緯機(jī)構(gòu)， 包括四連桿和六連桿機(jī)構(gòu)，并且和共軛凸輪機(jī)構(gòu)進(jìn)行比較。從不同的幾何參數(shù)模型可以得到結(jié)果，揭示了合理的操作計(jì)算機(jī)工具是有效的分析和設(shè)計(jì)打緯機(jī)構(gòu)的方法?？梢詫?shí)現(xiàn)低的噪音和振動(dòng)，還有更高的速度。 過去十年，紡織產(chǎn)業(yè)已經(jīng)從勞動(dòng)密集型轉(zhuǎn)變成生產(chǎn)率高的資本密集型產(chǎn)業(yè)。在制造織物時(shí)，對高性能織機(jī)有一個(gè)恒定的要求，它是快速，高效節(jié)能，可靠的，高度自動(dòng)化的，安靜的，耐用，低維修。在過去幾十年中，織機(jī)的生產(chǎn)效率大幅度增加，最大引緯效率從200到超過2000米/分鐘。這樣一個(gè)在性能上的顯著改善是由于技術(shù)的創(chuàng)新（例如，無梭織），使用新技術(shù)（例如，計(jì)算機(jī)和材料），及其更好的機(jī)械設(shè)計(jì)。 無論是哪種織機(jī)，它的技術(shù)狀態(tài)或者是模式要被編織，基本內(nèi)容包括四個(gè)步驟：脫落，采取，打緯，和行動(dòng)/燃放[2]。脫落操作通過形成一個(gè)流束來提高或者降低具體的經(jīng)紗。在采摘步驟，新的緯紗通過棚被插入。開始打緯時(shí)，通過筘座的安裝彈簧片把新插入的填充紗被推到位。最后，整理后的織物被卷成布束。但是更多的經(jīng)紗紗線被彎曲。這四個(gè)步驟會不斷的重復(fù)排列。 打緯對織造過程和產(chǎn)品質(zhì)量非常重要。一個(gè)正常的打緯運(yùn)行會給堅(jiān)固，統(tǒng)一的織物結(jié)構(gòu)。此外，簧片的運(yùn)動(dòng)由筘座帶動(dòng)，通過打緯的完成，對脫落和采摘操作的光滑度有很打的影響。在高速織造中，采取操作的每個(gè)周期相對時(shí)間比上采摘應(yīng)該盡量減少?；善瑧?yīng)該停留盡可能長時(shí)間在后面，就可以留下更多的時(shí)間引緯，然后可以盡快的打新的緯紗。這對現(xiàn)代寬幅織機(jī)是非常重要的。然而，較高的力量和振動(dòng)是和運(yùn)動(dòng)呢相關(guān)的，設(shè)計(jì)協(xié)調(diào)是實(shí)現(xiàn)織機(jī)平衡和平穩(wěn)運(yùn)行所必須的。筘座運(yùn)動(dòng)的動(dòng)態(tài)分析對織布機(jī)的設(shè)計(jì)和制造是十分重要的。 一般有三種基本的打緯機(jī)構(gòu)：四連桿，六連桿和共軛凸輪，如圖1所示。四連桿機(jī)構(gòu)是用的最廣的，比如梭機(jī)，噴氣和劍桿織機(jī)。因?yàn)樗Y(jié)構(gòu)簡單，制造簡單。六連桿機(jī)構(gòu)可以提供更長的停留時(shí)間，主要用在噴氣織機(jī)。在無梭織機(jī)中共軛凸輪機(jī)構(gòu)是應(yīng)用最廣的，是因?yàn)樗芎腕刈目烧{(diào)停留時(shí)間。 圖1 打緯機(jī)構(gòu)類型：四連桿（a） 六連桿（b） 共軛凸輪（c） 打緯機(jī)構(gòu)的設(shè)計(jì)，尤其它們的質(zhì)量分布和幾何，對織機(jī)的性能有顯著的影響。傳統(tǒng)分析這些機(jī)構(gòu)的方法是依據(jù)運(yùn)動(dòng)學(xué)和動(dòng)力學(xué)原理，但是往往涉及長時(shí)間的數(shù)學(xué)推導(dǎo)。計(jì)算機(jī)輔助設(shè)計(jì)和分析工具為分析復(fù)雜的結(jié)構(gòu)的動(dòng)態(tài)相應(yīng)提供了一種簡單的方式。 一個(gè)關(guān)于知識革命的軟件產(chǎn)品[1]-工作模式，結(jié)合了先進(jìn)的運(yùn)動(dòng)仿真技術(shù)與先進(jìn)的編輯能力來提供一個(gè)有用的工具和動(dòng)畫模擬。一個(gè)機(jī)構(gòu)可以轉(zhuǎn)換成一套剛體，在計(jì)算機(jī)上約束建立模型。這個(gè)軟件模擬機(jī)構(gòu)議案，基于集合約束和牛頓力學(xué)原理。工程量定義在模擬量出來之前，在模擬過程的進(jìn)一步分析之中。對象的性能可以調(diào)整通過圖形用戶界面以至形成新的模式和理想的結(jié)果。 在這項(xiàng)研究中，我們首先分析了四連桿機(jī)構(gòu)使用工作模型軟件。一個(gè)參數(shù)的研究探索了筘座運(yùn)動(dòng)的幾何影響。我們還建立一個(gè)六連桿模型來確定能延長在一個(gè)織造循環(huán)中插入時(shí)期的集合配置。最后，我們用不同的打緯機(jī)構(gòu)來比較筘座的運(yùn)動(dòng)。 打緯機(jī)構(gòu) 四連桿機(jī)構(gòu) 圖2顯示了根據(jù)實(shí)際尺寸實(shí)現(xiàn)了具有工作模型的4連桿機(jī)構(gòu)的所有部件所獲得的計(jì)算機(jī)模型;質(zhì)量和連接類型。在模擬期間測量和記錄的數(shù)量包括筘座（X）的位移，筘座的速度（V），筘座的加速度（A）和作用在劍pin上的力（F）。為了驗(yàn)證工作模型，我們比較了工作模型模擬和運(yùn)動(dòng)學(xué)分析的結(jié)果，發(fā)現(xiàn)沒有明顯的差異。 對于參數(shù)研究，我們使用梭織機(jī)（圖一a）中的機(jī)器部件的實(shí)際尺寸 - 曲軸長度r = 6厘米，連桿長度s = 32厘米，長度L = 72.11厘米。這種幾何配置是與其他型號的性能比較的參考。我們總結(jié)說，織機(jī)速度是200 rpm。觀察不同比例的slr對運(yùn)動(dòng)的影響連桿長度從17至102厘米不等，而r和L保持不變。我們評估了s / r比為2.83到17的elevem模型。 ? 從工作模型模擬數(shù)據(jù)，我們獲得了每個(gè)模型的筘速V，加速度A和連桿F中的力的最大值。結(jié)果如圖3所示，相對于參考模型也沒有發(fā)現(xiàn)。因?yàn)閟 / r從2變化到8，所以V，A和F的最大值顯著降低。然而。隨著slr進(jìn)一步增加，Vmax，Amj，F(xiàn)max幾乎沒有變化。為了確保通過梭口順利地填充紗線，在灌裝過程中棚棚應(yīng)該保持足夠大。棚子的大小由兩片山藥的高度和筘座的位置決定。在編織周期中，填充紗線只能在襪帶靠近時(shí)插入。 ;后退位置和棚口開放是足夠的。因此，對于快速織機(jī)的操作，大部分時(shí)間的襪子應(yīng)該在填充插入時(shí)保持向后，然后快速移動(dòng)以進(jìn)行跳動(dòng)。允許填充插入的筘座位置的確切范圍取決于織機(jī)的關(guān)節(jié)設(shè)計(jì)。在這個(gè)分析中，我們假設(shè)填充插入在“s”位于“后區(qū)”期間完成。在其原始（最后退）位置和其最大位移的一半之間（圖4）。相應(yīng)的期間稱為插入期。從關(guān)于筘座位移的模擬數(shù)據(jù)可以看出，根據(jù)4連桿機(jī)構(gòu)的幾何形狀，我們可以看出，在不同的曲柄旋轉(zhuǎn)角度下，筘座的最大位移量達(dá)到了其一半，如表I所示。隨著增加s / r，短褲在較短的時(shí)間內(nèi)保持在最靠后的位置，留下更少的時(shí)間將填充物插入織機(jī)。 無論討論什么機(jī)制，較低的Amax表示更平穩(wěn)的運(yùn)動(dòng)，較高的A ,,,,,,導(dǎo)致一個(gè)動(dòng)作。特別是對于織機(jī)而言，絲杠的移動(dòng)會影響打嗝的效率。然而，對于不同的織物，需要不同的打擊動(dòng)作[2]。細(xì)微的織物不應(yīng)粗略處理，而粗紗線可能需要清醒的毆打才能有效。因此，對于諸如絲綢和細(xì)棉的輕質(zhì)織物，僅需要非常溫和的打漿，并且適合大的細(xì)度（例如> 6）。對于中等織物如密度棉，需要平滑打漿，而且比率應(yīng)該是中等的（例如3到6之間）。對于諸如牛仔褲或工業(yè)材料的重型織物，需要一種沖動(dòng)，干燥的打嗝，并且較小的比率更適合（例如，<3）。對于需要長時(shí)間填充的寬織機(jī)，應(yīng)選擇較低的slr比率。相比之下，更高的slr 比對于窄織機(jī)來說是足夠的，這對于填充插入需要很短的時(shí)間。通過組合幾何.s / r比對襪帶運(yùn)動(dòng)和插入周期的影響，獲得了圖5所示的性能圖。水平軸是作用在連桿和筘座的銷接頭上的最大力?？v向軸線是由打漿機(jī)構(gòu)的幾何形狀允許的插入時(shí)間。從該圖可以看出，由于較長的插入周期和較小的力，左上角的性能是可取的，而右下角則是不希望的，因?yàn)椴迦胩畛涞臅r(shí)間較短和較大的力。如前所述，對于精細(xì)織物，需要較高的s / r值來保證在編織過程中紗線的破損率低。然而，不可避免地，高slr的另一個(gè)效果是短的插入期。因此，當(dāng)織造寬細(xì)的織物時(shí)，必須在力和插入時(shí)間之間作出妥協(xié)。 圖2 四連桿打緯機(jī)構(gòu)電腦模型 圖3.幾何比率.s / r對襪帶運(yùn)動(dòng)特性的影響。 圖4.幾何比率先生對筘座位移曲線的影響。 圖5. 4鏈路機(jī)制的性能圖。 六連桿打緯機(jī)構(gòu) 我們已經(jīng)開發(fā)了一個(gè)基于Picanol PGW4-R / Z織機(jī)采用6連桿驅(qū)動(dòng)的筘座的實(shí)際機(jī)理的模型，如圖6所示。我們試圖通過將一些幾何參數(shù)，經(jīng)過一系列試驗(yàn)，我們得到了修改后的模型。也顯示在 圖6.兩個(gè)模型之間的角位移的比較如圖7所示。這里，標(biāo)記筘座的最大位移的二分之一的時(shí)刻，并且移位的時(shí)間間隔至少為1 - 指出兩種型號的最大值的一半。很明顯，在mod- 如果是型號，則短褲在后面區(qū)域比原始配置更長的時(shí)間段。通過修改，插入周期從編織周期的199°或55％的時(shí)間段增加到240°或67％的時(shí)間段。這對于高速運(yùn)行是有幫助的。 一個(gè)6連桿驅(qū)動(dòng)的sley，如圖6所示。我們試圖通過調(diào)整一些幾何參數(shù)來增加填充插入時(shí)間，經(jīng)過一系列試驗(yàn)，我們得到了修改后的模型。也顯示在 圖6.兩個(gè)模型之間的角位移的比較如圖7所示。這里，標(biāo)記筘座的最大位移的二分之一的時(shí)刻，并且移位的時(shí)間間隔至少為1 - 指出兩種型號的最大值的一半。很明顯，如果是型號，則短褲在后面區(qū)域比原始配置更長的時(shí)間段。通過修改，插入周期從編織周期的199°或55％的時(shí)間段增加到240°或67％的時(shí)間段。這對于高速運(yùn)行是有幫助的 圖3 六連桿機(jī)構(gòu)的電腦模型：原來的配置（左），修改后的配置（右） 圖4 六連桿角位移的比較 在不用的機(jī)構(gòu)中比較筘座的運(yùn)動(dòng)特性 為了比較筘座在不同機(jī)構(gòu)中的運(yùn)動(dòng)，我們制定了一個(gè)共軛凸輪打緯機(jī)構(gòu)的模型[3]。這里，我們比較共軛凸輪引，四連桿和六連桿機(jī)構(gòu)筘座的運(yùn)動(dòng)特性。圖5顯示了筘座在三個(gè)不同驅(qū)動(dòng)機(jī)構(gòu)下的角位移和加速度。 圖5 不同機(jī)構(gòu)下的筘座運(yùn)動(dòng)比較：（a）角位移 （b）角加速度 在圖5中，我們看到凸輪筘座完成它的運(yùn)動(dòng)在130°的回升周期。駐留（保持靜止）在后面的位置230°（確切時(shí)間取決具體的設(shè)計(jì)）。相對四連桿和六連桿，驅(qū)動(dòng)筘座經(jīng)常移動(dòng)在整個(gè)挑選周期(0°-360°)。連桿機(jī)構(gòu)驅(qū)動(dòng)筘座與共軛凸輪機(jī)構(gòu)比，一個(gè)類似棚大小緯線，線束要取消/降低到更大距離。因?yàn)楣曹椡馆喸试S填充的紗線插入附近的線束。在較高的織機(jī)速度或者較寬的引緯比率時(shí)，緯線必須穿越棚在更短的時(shí)間內(nèi)。共軛凸輪筘座預(yù)留更長的時(shí)間，大于200°在一個(gè)插入循環(huán)中，使引緯更容易，也能允許提高織機(jī)速度，縮短線束升降距離，降低經(jīng)紗張力。 另一方面，我們很清晰從圖5中看到，凸輪驅(qū)動(dòng)的筘座加速度遠(yuǎn)遠(yuǎn)高于那些連桿驅(qū)動(dòng)的。因?yàn)橥馆嗱?qū)動(dòng)的筘座已經(jīng)完成向前和向后運(yùn)動(dòng)，在驅(qū)動(dòng)筘座不到一半的時(shí)間內(nèi)（130°對凸輪驅(qū)動(dòng)系統(tǒng)而360°對連桿驅(qū)動(dòng)系統(tǒng)）。高加速度可以適用于凸輪驅(qū)動(dòng)筘座，這可以更小更輕比那些連桿驅(qū)動(dòng)的。用超高的剛度和超輕復(fù)合材料，筘座機(jī)構(gòu)的慣性質(zhì)量可以進(jìn)一步減少，一提高織機(jī)的速度。 總結(jié) 高速織機(jī)有一個(gè)快速緯線插入和快速脫落和打緯動(dòng)作。一個(gè)關(guān)于織機(jī)系統(tǒng)的復(fù)雜工程設(shè)計(jì)是需要快速.平滑和有效的織機(jī)操作。計(jì)算機(jī)輔助設(shè)計(jì)工具提供了一個(gè)快速和可靠的方法研究機(jī)床動(dòng)態(tài)特性的機(jī)制。在本文中，我們使用這模型軟件來分析四連桿和六連桿打緯機(jī)構(gòu)。通過分析筘座運(yùn)動(dòng)特性的幾何參數(shù)的影響，我們論證在計(jì)算機(jī)模型上調(diào)整某些幾何參數(shù)。在一個(gè)織造循環(huán)中，該系統(tǒng)可以很容易的做到調(diào)整來允許一個(gè)相對較長時(shí)間的填充插入。我們還可以比較連桿機(jī)構(gòu)和共軛凸輪驅(qū)動(dòng)機(jī)構(gòu)的運(yùn)動(dòng)特性。 引用文獻(xiàn) [1] Knowledge Revolution. Working Model User’s Manual.1992 [2] Lord, P. R. and Mohamed, M. H. "Weaving: Conversion of Yarn to Fabric," 2nd ed. Merrow Publishing Co. Ltd.1982 [3] Sun, H. Computer Aided Design and Analysis of Loom Beat-ing-up Mechanisms, Masters thesis, School of Textile & Fiber Engineering, Georgia Institute of Technology, 1997. http:/ Research Journal http:/ online version of this article can be found at:DOI:10.1177/004051759806800902 1998 68:630Textile Research JournalYoujiang Wang and Hui SunComputer Aided Analysis of Loom Beating-up Mechanisms Published by:http:/ can be found at:Textile Research JournalAdditional services and information for http:/ Alerts:http:/ is This?-Sep 1,1998Version of Record Downloaded from 630Computer Aided Analysis of Loom Beating-up MechanismsYOUJIANG WANG AND HUI SUN School of Textile&Fiber Engineering,Georgia Institute of Technology,Atlanta,Georgia 30332,U.S.A.ABSTRACTAnalysis and design of the beating-up mechanism is of great importance for im-proving loom performance.Computer aided design and analysis tools are used to studydifferent kinds of beating-up mechanisms,including the 4-link and 6-link systems,andtheir characteristics are compared with those of the conjugate-cam mechanism.Resultsfrom models with varying geometric parameters are presented,revealing that the com-puter tools are effective and useful in analyzing and designing beating-up mechanisms with smoother operation,lower noise and vibration,and higher speeds.The last decade has witnessed the transformation of,the textile industry from a labor intensive one into ahigh productivity,capital intensive industry.In manu-facturing woven fabrics,there is a constant desire forhigh performance looms that are fast,energy efficient,reliable,highly automated,quiet,durable,and lowmaintenance.Over the last few decades,the production rate of looms has increased tremendously,with maxi-mum weft insertion rates moving from about 200.towell over 2000 m/min.Such a significant improvementin performance is a result of technological innovations(e.g.,shuttleless weaving),employment of new tech-nologies(e.R.,computers and materials),and bettermachinery designs.Regardless of the kind of loom,its technologicalstate,or the pattern to be woven,the basic weavingoperations consists of four steps:shedding,picking,beating-up,and taking-up/letting-off 2 J.The shed-.ding operation raises and lowers specific warp yarns bymeans of harnesses to form a shed.During the pickingstep,the new filling yam is inserted through the shed.Beating-up occurs when the newly inserted filling yarnis pushed firmly in place by means of the reed mountedon the sley.Finally,the finished fabric is wound on the;cloth beam.while more warp yarn is released from the:warp beam.These four operations are performed in a.constantly repeated sequence.Beating-up is of great importance to the weavingprocess and the quality of the product.A normal beat-ing-up operation will give a firm,uniform fabric struc-ture.In addition,the movement of the reed carried bythe sley,through which beating-up is achieved,has animportant effect on the.smoothness of shedding andpicking operations.In high speed weaving,the relativetime per cycle taken by operations other than pickingshould be minimized.It is desirable that the reed dwell;as long as possible at the rear to leave more time forweft insertion,and then move swittly to beat up thenew filling yarn.This is especially crucial for modernwide-width looms.However,higher forces and vibra-tions are associated with jerky movements,and designcompromise is necessary to achieve a balance betweenloom speed and smooth operation.Dynamic analysisof the motion of the sley(reed)is therefore importantfor loom designers and manufacturers.In general,there are three basic kinds of beating-upmechanisms:4-link.6-link,and conjugate-carn,asshown in Figure 1.The 4-link mechanism is used mostwidely on shuttle,air-jet,and rapier looms.since it hasa simple structure and is easy to manufacture.The 6-link mechanism,which may provide a longer dwell pe-riod,is mainly used in air-jet looms.The conjugate-cam mechanism is being used more and more widelyin shuttleless looms due to its precise and adjustabledwell period of the sley.The design of beating-up mechanism;,particularlytheir mass distribution and geometry,has a significanteffect on the performance of the loom.Traditionalmethods for analyzing these mechanisms based on ki-nematic and dynamic principles are well established,but often involve lengthy mathematical derivations.Computer aided design and analysis tools provide asimpler way of analyzing the dynamic responses ofcomplex structures.Working Model,a software product of KnowledgeRevolution,Ibines advanced motion sim-ulation technology with sophisticated editing abilitiesto provide a useful tool for engineering and animationsimulation.A mechanism can be converted into a setof rigid bodies and constraints to build the model onthe computer.This software simulates the motion ofthe mechanism based on geometric constraints andNewtonian mechanics.principles.Quantities definedbefore the simulation can be exported during the sim-Downloaded from 631FIGURE 1.Typical beating-up mechanisms:(a)4-link,(b)6-J.ink.and(c)conjugate-camulating process for further analysis.The properties ofobjects can be adjusted with its graphic user interfaceto form new models with desirable results.In this study,we first analyze the 4-link mechanismusing the Working Model software.A parametric studyexplores the effect of geometry on the sleys motion.We also build models for the 6-link mechanism to iden-tify geometric configurations that can lead to a longinsertion period in a weaving cycle.Finally,we com-pare the sleys motion for different beating-up mech-anisms.Beating-up MechanismsFOUR-LINK MECHANISMFigure 2 shows the computer model obtained dafterimplementing all parts of a 4-link mechanism withWorking Model,according to the actual size;mass,andconnection type.Quantities measured and recordedduring the simulation include the displacement of thesley(X),the velocity of sley(V),the acceleration ofsley(A),and the force(F)acting on the swordpin.Tovalidate Working Model,we have compared the resultsfrom the Working Model simulation and kinematicsanalysis and found no noticeable differences.For parametric studies,we have used the actual di-mensions of machine parts in a shuttle loom(FigureI a)-crankshaft length r=6 cm,connecting rodlength s=32 cm,and sley length L=72.11 cm.Thisgeometric configuration is the reference for the perfor-mance comparison with other models.We have as-sumed that the loom speed is 200 rpm.To observe theinfluence of different ratios of slr on the motion of thesley,the connecting rod length varies from 17 to 102cm,while r and L are kept constant.We have evaluatedelevem models with s/r ratios from 2.83 to 17.FIGURE 2.Computer model of 4-link beating-up mechanism.From the Working Model simulation data,we haveobtained the maximum values of sley velocity V,ac-celeration A,and the force in the connecting rod F,foreach model.The results are shown in Figure 3,nor-malized with respect to the reference model.Becauses/r varies from 2 to 8,the maximum values of V,A.and F decrease significantly.However.there is littlechange in Vmax,Amj,and Fmax as slr increases further.To ensure smooth filling yam insertion through theshed,the shed should be kept large enough during thefilling traverse.The size of the shed is determined bythe height between the two sheets of yams and the po-Downloaded from 632FIGURE 3.Effect of geometric ra-tio.s/r on sleys motion character-istics.sition of the sley.During a weaving cycle,the fillingyam can only be inserted when the sley stays close to.;the backward position and the shed opening is suffi-cient.Thus,for fast loom operation,the sley shouldstay backward most of the time for filling insertion,andthen move rapidly for beating-up.The exact range ofsley positions allowing filling insertion depends on theparticular design of a loom.In this analysis,we haveassumed that the filling insertion is completed duringthe period when the sley is in the&dquo;back zone&dquo;betweenits original(most backward)position and one-half of.its maximum displacement(Figure 4).The corre-:.sponding period is refered to as the insertion period.From the simulation data on the displacement of the.sley.,we see that the sley reaches one half its maximum.displacement at different degrees of the crank rotation,depending on the geometry of the 4-link mechanism,.as summarized in Table I.With increased s/r,the sleystays near its most backward position for a shorterFIGURE 4.Effect of geometric ratio sir on thedisplacement profile of the sley.TABLE 1.Insertion periods for different 4-link models.amount of time,leaving less time for the filling to beinserted across the loom.No matter what mechanism is discussed,a lower Amaxindicates a smoother movement and a higher A,leadsto a jerky action.For a loom in particular,the move-ment of the sley affects the efficiency of beating-up.For different fabrics,however,different actions of beat-ing-up are desired 2.A fine,delicate fabric shouldnot be handled roughly,whereas a coarse staple yammay require sharp beating-up to be effective.There-fore,for light fabrics such as silk and fine cotton,onlyvery gentle beating-up is required and a large sli-valueis suitable(e.g.,6).For medium fabrics such as me-dium density cotton,a smooth beat-up is needed,andthe slr ratio should be medium(e.g.,between 3 and6).For heavy fabrics such as jeans or industrial ma-terials,an impulsive,jerky sort of beat-up is necessary,and a small slr ratio is more appropriate(e.g.,3).For a wide loom,which needs a long time for the fillingto be inserted,a lower slr ratio should be chosen.Incontrast,a higher slr ratio is sufficient for a narrowloom,which requires a short time for filling insertion.The performance map shown in Figure 5 is obtainedby combining the effects of the geometric.s/r ratio onthe sleys motion and insertion period.The horizontalaxis is the maximum force acting on the pin joint ofthe connecting rod and the sley.The longitudinal Downloaded from 633FIGURE 5.Performance map for the 4-link mechanism.is the insertion period allowed by the geometry of thebeating-up mechanism.It is obvious from this figurethat the performance in the top left comer is desirabledue to longer insertion period and lower force,whilethe bottom right comer is undesirable because of lesstime allowed to insert filling and higher force.As men-tioned earlier,for fine fabrics,a higher value of s/r isnecessary to guarantee a low yam breakage rate duringweaving.However,inevitably,another effect of highslr is a short insertion period.Therefore,when a wide,fine fabric is to be woven,some compromise has to bemade between force and insertion period.SIX-LINK MECHANISMWe have developed a model based on the actualmechanism of a Picanol PGW4-R/Z loom employinga 6-link driven sley,as shown in Figure 6.We at-tempted to increase the filling insertion period by ad-justing some of the geometric parameters,and after aset of trials,we got the modified model.also shown inFigure 6.A comparison of the angular displacementbetween the two models is shown in.Figure 7.Here,the moments when the sley is at one-half its maximumdisplacement are marked,and the periods during whichthe displacement is at least one-half the maximum forboth models are indicated.It is obvious that in the mod-ified model,the sley stays in the back zone for a longerperiod of time than in the original configuration.Withthe modification,the insertion period increases from199,or 55%of the time period in a weaving cycle,to240,or 67%of the time period.This is helpful for ahigh speed operation.COMPARISON OI SLEY S MOTION CHARACTERISTICS INVARIOUS MECHANISMSTo compare the motion of sleys driven by differentmechanisms,we have also developed a model for theconjugate-cam beating-up mechanism(Figure lc)r 3 J.Here we compare the characteristics of the sleys motionfor the conjugate-cam,4-link.and 6-link mechanisms.Figure 8 shows the angular displacement and accelerationof the sley for the three different driving mechanisms.In Figure 8,we see that the cam-driven sley com-pletes its movement in 130 of the pick cycle,anddwells(remains stationary)at the back position for230(exact periods depend on specific design)The 4-link and 6-link driven sleys.on the other had.moveFIGURE 6.Computer models of 6-link mechanisms:original configuration(left),and modified configuration(right)Downloaded from 634.FIGURE 7.Comparison of angular displacementa linkage-driven sley than with a conjugate-cam mech-anism,because the conjugate-cam allows the fillingyarn to be inserted near the harnesses.At higher loomspeeds or higher weft-insertion rates,the weft carriermust cross the shed in a shorter period.Thus the link-driven sleys restrict the weft insertion interval and be-come an obstacle to increasing loom speed and weft-insertion rate.The cam-driven sley leaves a muchlonger time,more than 200 of the pick cycle,availablefor weft insertion,which permits a higher loom speed,shorter harness lift distance,and lower warp tension.On the other hand,it is clear from Figure 8 that theacceleration of the cam-driven sley is much higher thanthose of the link-driven sley,because the cam-drivensley has to complete the forward and backward move-ments within less than half the time used in a link-driven sley(130 for the cam-driven system versus360 for the link-driven system).The high accelerationmay be acceptable for cam-driven sleys,which aresmaller and lighter than those driven by linkage.Withultra high stiffness,ultra light composites,the mass in-ertia for the sley mechanisms can be further reduced,promising even higher loom speeds.ConclusionsA high speed loom speed calls for a swift weft insertionand fast shedding and beating-up actions.A sophisticatedengineering design of the loom system is required for fast,smooth,efficient operation of the loom.Computer aideddesign tools provide a rapid and reliable means of studyingthe dynamic characteristics of machine mechanisms.In thispaper,we use the Working Model software to analyze the4-link and 6-link beating-up mechanisms.We analyzed theeffect of geometric parameters on the motion characteris-tics of the sley,and we demonstrate that by adjusting cer-tain geometric parameters in the computer model,the sys-tem can be easily fine tuned to allow for a relatively longerfilling insertion period in a weaving cycle.We also com-pare the motion characteristics of the linkage mechanismswith that of a conjugate-cam driven mechanism.Literature Cited1.Knowledge Revolution.Working Model Users Manual,1992.2.Lord,P.R.,and Mohamed,M.H.,Weaving:Conversionof Yarn to Fabric,2nd ed.,Merrow Publishing Co.Ltd.,1982.3.Sun,H.,Computer Aided Design and Analysis of Loom Beat-ing-up Mechanisms,Masters thesis,School of Textile&FiberEngineering,Georgia Institute of Technology,1997.AMtMrrf/MrfOfh/trf72/./997;f/.Sfw/7/.#o,/WDownloaded from