【正文】 s continuing surge CAE, ComputerAided Engineering, Mar, 1997(5):4548 洛陽(yáng)理工學(xué)院畢業(yè)設(shè)計(jì)論文 37 外文資料翻譯 Application and development Of case based reasoning in fixture design Fixtures are devices that serve as the purpose of holding the workpiece securely and accurately, and maintaining a consistent relationship with respect to the tools while machining. Because the fixture structure depends on the feature of the product and the status of the process planning in the enterprise, its design is the bottleneck during manufacturing, which restrains to improve the efficiency and leadtime. And fixture design is a plicated process, based on experience that needs prehensive qualitative knowledge about a number of design issues including workpiece configuration, manufacturing processes involved, and machining environment. This is also a very time consuming work when using traditional CAD tools (such as Unigraphics, CATIA or Pro/E), which are good at performing detailed design tasks, but provide few benefits for taking advantage of the previous design experience and res ources, which are precisely the key factors in improving the efficiency. The methodology of case based reasoning (CBR) adapts the solution of a previously solved case to build a solution for a new problem with the following four steps: retrieve, reuse, revise, and retain [1]. This is a more useful method than the use of an expert system to simulate human thought because proposing a similar case and applying a few modifications seems to be self explanatory and more intuitive to humans .So various case based design support tools have been developed for numerous areas[24], such as in injection molding and design, architectural design, die casting die design, process planning, and also in fixture design. Sun used six digitals to pose the index code that incl uded workpiece shape, machine portion, bushing, the 1st locating device, the 2nd locating device and 洛陽(yáng)理工學(xué)院畢業(yè)設(shè)計(jì)論文 38 clamping device[5]. But the system cannot be used for other fixture types except for drill fixtures, and cannot solve the problem of storage of the same index code that needs to be retained, which is very important in CBR[6]. 1. Construction of a Case Index and Case Library Case index The case index should be posed of all features of the workpiece, which are distinguished from different fixtures. Using all of them would make the operation in convenient. Because the forms of the parts are diverse, and the technology requirements of manufacture in the enterprise also develop continuously, lots of features used as the case index will make the search rate slow, and the main feature unimportant, for the reason that the relative weight which is allotted to every feature must diminish. And on the other hand, it is hard to include all the features in the case index. Hierarchical form of Case The structure similarity of the fixture is represented as the whole fixture similarity, ponents similarity and ponent similarity. So the whole fixture case library, ponents case library, ponent case library of fixture are formed correspondingly. Usually design information of the whole fixture is posed of workpiece information and workpiece procedure information, which represent the fixture satisfying the specifically designing function demand. The whole fixture case is made up of function ponents, which are described by the function ponents’ names and numbers. The ponents case represents the members. (function ponent and other structure ponents ， main driven parameter, the number, and their constrain relations.) The ponent case (the lowest layer of the fixture) is the structure of function ponent and other ponents. In the modern fixture design there are lots of parametric standard parts and mon non standard parts. So the ponent case library should record the specification parame ter and the way in which it keeps them. 2. Strategy of Case Retrieval 洛陽(yáng)理工學(xué)院畢業(yè)設(shè)計(jì)論文 39 In the case based design of fixtures ,the m。 最后， 深深地感謝支持、理解和關(guān)心我的同學(xué)們，讓我圓滿完成了畢業(yè)設(shè)計(jì)所 要求 的 所有 任務(wù)。 再次，也非常感謝學(xué)校能給我這次機(jī)會(huì)來(lái)進(jìn)行我的畢業(yè)設(shè)計(jì)，讓我把書本上的知識(shí)運(yùn)用的實(shí)踐中去，讓我深刻的體會(huì)到了 “ 學(xué)以致用 ” 的道理。 洛陽(yáng)理工學(xué)院畢業(yè)設(shè)計(jì)論文 34 謝 辭 本 次 畢業(yè)設(shè)計(jì)是在 楊 老師的指導(dǎo)下完成的，衷心感謝 楊 老師的悉心指導(dǎo)以及在 知識(shí)層面 上給予的 指點(diǎn)， 對(duì)我的設(shè)計(jì)提出了許多改進(jìn)的建議，并且對(duì)我的設(shè)計(jì)方案，圖形繪制等提出了許多寶貴的建議。但也有很多地方還有 待進(jìn)一步的改進(jìn) 。在本次 畢業(yè) 設(shè)計(jì)中， 能 熟練 運(yùn)用 大學(xué)四年 所學(xué) 的 基本理論知識(shí)，正確解決工件在加工時(shí)的定位和夾緊問題，選擇合理的 設(shè)計(jì) 方案 ，進(jìn)行必要的 定位誤差和夾緊力的 計(jì)算，根據(jù) 課 題設(shè)計(jì)出符合 要求 、 優(yōu)質(zhì)、高效、低成本的夾具。在設(shè)計(jì)的過程中，我們綜合運(yùn)用了系統(tǒng)的設(shè)計(jì)方法和相關(guān)設(shè)計(jì)軟件（如AutoCAD），且應(yīng)用熟悉相關(guān)設(shè)計(jì)資料（包括手冊(cè)、標(biāo)準(zhǔn)和規(guī)范等）以及進(jìn)行經(jīng)驗(yàn)估算等方面有了一定程度的提高，深刻的感受到計(jì)算機(jī)和工具書及手冊(cè)在設(shè)計(jì)中帶來(lái)的便利和幫助。設(shè)計(jì)中的很多 地方 參照 了 工廠 中現(xiàn)行使用的夾具 結(jié)構(gòu)。指導(dǎo)老師親自帶我們?cè)啻紊钊?洛陽(yáng)一拖進(jìn)行實(shí)地考察。 在設(shè)計(jì)過程中，通過各種方式收集、查閱相關(guān)資料。 支桿的左半部分開有螺紋孔，它用來(lái)與頂頭相連支撐壓板，支桿的右端開有 T 形槽， 它用來(lái)與夾具體連接緊固支桿，其凸出部分切掉一部分，是為了避免與支撐板 在位置上 發(fā)生干涉 。 導(dǎo)桿上方開有斜槽，其斜度并不完全一樣，當(dāng)導(dǎo)桿運(yùn)動(dòng)到大斜度處時(shí)，由于其 斜度較大，它可以起到快速釋放工件的作用，從而可以減少裝卸工件的時(shí)間。 頂桿的結(jié)構(gòu)設(shè)計(jì) 頂桿的結(jié)構(gòu)見圖 42 所示 洛陽(yáng)理工學(xué)院畢業(yè)設(shè)計(jì)（論文） 29 圖 42 頂桿的結(jié)構(gòu)圖 套筒的結(jié)構(gòu)設(shè)計(jì) 其結(jié)構(gòu)見圖 43 所示 圖 43 套筒的結(jié)構(gòu)設(shè)計(jì) 洛陽(yáng)理工學(xué)院畢業(yè)設(shè)計(jì)（論文） 30 導(dǎo)桿的結(jié)構(gòu)設(shè)計(jì) 導(dǎo)桿 是連接頂桿與支柱的中間環(huán)節(jié)，其實(shí)際起到的作用就是一個(gè)斜楔機(jī)構(gòu)，它將由氣缸所帶動(dòng)產(chǎn)生的水平運(yùn)動(dòng)轉(zhuǎn)化為豎直運(yùn)動(dòng)，是運(yùn)動(dòng)轉(zhuǎn)化的中間環(huán)節(jié)，其結(jié)構(gòu)見圖 44 所示 圖 44 導(dǎo)桿的結(jié)構(gòu)圖 由導(dǎo)桿的結(jié)構(gòu)圖，其左端的前端面開由通孔，其作用可以方便頂桿的頭部從側(cè)面裝入，導(dǎo)桿的右端實(shí)際上就是一個(gè)斜楔機(jī)構(gòu)，它通過其下端面與滾輪接觸，從而拉下支柱 壓緊工件。 活 塞的邊沿上 開 有徑向槽，槽內(nèi)裝入 擋氣環(huán)，可以防止氣體的泄漏，減少不必要的能量損失。 (6)聯(lián)動(dòng)夾 緊機(jī)構(gòu) 工件裝夾所使用的夾具，有的需要同時(shí)有幾個(gè)點(diǎn)對(duì)工作的工件進(jìn)行夾緊，而有的則需要同時(shí)夾緊幾個(gè)工件，為了提高效率，減少裝夾時(shí)間，可采用聯(lián)動(dòng)夾緊機(jī)構(gòu)。 (4)鉸鏈夾緊機(jī)構(gòu) 因鉸鏈夾緊機(jī)構(gòu)的結(jié)構(gòu)簡(jiǎn)單，擴(kuò)力比大，適用于洛陽(yáng)理工學(xué)院畢業(yè)設(shè)計(jì)（論文） 28 多點(diǎn)或多件夾緊，在氣動(dòng)或者液動(dòng)夾具中廣泛應(yīng)用。 (2) 螺旋夾緊機(jī)構(gòu) 利用螺桿直接夾緊工件，或者與其他元件組成復(fù)合夾緊機(jī)構(gòu) 夾緊工件，是應(yīng)用較廣泛的一種夾緊機(jī)構(gòu)，由于螺旋夾緊機(jī)構(gòu)具有結(jié)構(gòu)簡(jiǎn)單，容易制造，夾緊可靠，擴(kuò)力比大和夾緊行程不受限制等特點(diǎn)，所以在手動(dòng)夾緊裝置中被廣泛應(yīng)用，在夾具中除采用螺桿直接夾緊工件外，經(jīng)常采用螺旋壓板夾緊機(jī)構(gòu)。 在夾緊的組成中可以看出，不論采用何種動(dòng)力源（手動(dòng)或機(jī)動(dòng)），外加的原始作用力要轉(zhuǎn)化為夾緊力，都必須通過夾緊機(jī)構(gòu)。夾緊機(jī)構(gòu)是接受和傳遞原始作用力，使其變?yōu)閵A緊力 并執(zhí)行夾緊任務(wù)的部分，包括中間傳遞力機(jī)構(gòu)和夾緊元件。 洛陽(yáng)理工學(xué)院畢業(yè)設(shè)計(jì)（論文） 27 4. 2 夾具中的夾緊機(jī)構(gòu) 夾緊機(jī)構(gòu)的組成 夾具中的夾緊 裝置 一般是由動(dòng)力源 和夾緊機(jī)構(gòu)兩個(gè)部分組成。 (2)電磁夾緊 如平面磨床上的電磁吸盤，當(dāng)線圈中通上直流電后，其鐵