1789_汽車前燈罩的沖壓模具設計

1789_汽車前燈罩的沖壓模具設計,汽車,燈罩,沖壓,模具設計 畢業(yè)設計（論文）外文文獻翻譯題目 汽車前燈罩的沖壓模具設計專 業(yè) 名 稱 機械設計制造及其自動化班 級 學 號 078105319學 生 姓 名 聶文軍指 導 教 師 陳為國填 表 日 期 2011 年 05 月 20 日Mould type of numerical control process computer assist the cutter choose and studyForewordNumerical control include cutter production and cutter of orbit choose two key problems process ,. The first problem has been got and studied extensivly and deeply over the past 20 years, a lot of algorithms developed have already got application in commercial CAD/ CAM system. Most CAM systems can produce the cutter orbit automatically after users input relevant parameters at present. Comparatively speaking , it is still not ripe to regard quality , efficiency as the research of choosing the problem of cutter of optimizing the goal correctly, do not have commercial CAM system that can offer the preferred decision support tool of cutter at present, therefore it is difficult to realize the integrating automatically and organically of CAD/ CAM. The cutter is chosen to usually include cutter type and cutter size. Generally speaking , suitable for one processing cutter of target for much kind , one cutter can finish different processing tasks, so it is easier to only consider meeting the cutter that basically processes the requirement and choose, especially to geometirc characteristics of model such as the hole , trough ,etc. But in fact, it is common for cutter to choose and sure optimization goal interrelate, for instance most heavy to cut efficiency , process time , minimum process cost , longest service life ,etc. at least, so the cutter is chosen it is a complicated optimization question. Such as mould type one of parts, because the geometirc form is complicated (usually include curved surface of freedom and island), influence geometry that cutter choose it restrains from to be can explicit to say among CAD model, need to design the corresponding algorithm to draw, therefore choose the cutter specification suitable and cutter association , it is not easy things by improving efficiency and quality processed in numerical control.Mould type generally with preparation method that numerical control mill, usually including rough machining, half finish machining , precise process of processing etc. The principle of rough machining is to spare no effort to remove the surplus metal with high efficiency, therefore hope to choose the larger cutter, but the cutter is oversized, may cause the increase of the crude volume ; Half finish machining of tasks to remove rough machining leave over step that get off mainly; Finish machining mainly guarantees size of the part and surface quality. Consider , go on , select exist , sure by computer difficult automatically totally up till now, therefore assist the cutter to choose in the computer that we developed (Computer Aided Tool Selection , CATS) among the system, base on , provide one aid decision tool for user, rough machining , half finish machining , precise to process etc., the real policy-making power is still left to users, in order to give full play to the advantages of computer and people.1 Basic structure of the system CATS system is CAD model, output for cutter type , cutter specification , mill depth of sharpening , enter the giving amount , rotational speed of main shaft (cut the pace ) and process six parameters such as time (such as Fig. 1), including choosing the aid decision tool in cutter type, rough machining cutter choose aid decision tool, half finish machining cutter choose aid decision tool and finish machining cutter choose aid decision tool ,etc.Given the rough machining in Xingqiang processing of the important position (usually rely time 510 times), rough machining, the system automatically optimize portfolio with cutlery functions to enhance overall processing efficiency. In addition to the decision-making tools, the system also has a detailed look cutlery norms, based on the type and size cutlery recommended processing parameters and assess the function of processing time, the last generation of the overall results of choice cutlery statements (figure 2). All the data and knowledge systems cutlery done by the background database support.2 Key technologies and algorithms2.1Cutlery type choiceAccording to Assistant Xingqiang digital processing practice, Xingqiang Xi state general processing cutlery into milling cutter, milling cutter radius milling cutter and the first three balls. D based cutlery diameter, radius radius r when r=0 for milling cutter, 0RCutlery can be divided into the overall style and embed films ceremony. For inlay film style, the key is to select the materials razor blades, razor blades materials choice depends on three elements : the processing of working materials, machine tools and cutlery jig stability of the state structures. Processing system will be translated into material steel, stainless steel, cast iron, nonferrous metals, materials and hard to cut materials six groups. Machine tool jig stability into good, better and less than three levels. Cutlery investigation into the short and long cantilever structures two, the system automatically reasoning on the basis of the specific circumstances of razor blades materials, decision-making knowledge from Walter cutlery manual system by the users first choice cutlery type in the world. To embed film style cutlery, a rules-based automated reasoning suitable razor blades materials. For example, if the final processing of materials for the steel, machine tool jig for good stability, cutlery cantilever structures for short, razor blades materials for WAP25.Rough machining cutlery portfolio optimizationXingqiang rough machining the aim is to maximize the removal of excess metal normally used milling cutter, take-cutting approach. Thus, 3D mould Xingqiang the rough machining process, is actually a series of 2.5D components Xingqiang processing. Cutlery optimization is to find a group of cutlery portfolio, allowing for maximum efficiency removal of most metals. Cutlery portfolio optimized basic methods as follows :A. To do some long step into knife in the direction of a group of vertical and horizontal search Xingqiang another entity to form a search layer.B. Derive closed to the contours.C. Calculated between Central and outside the island or islands and the distance between the key that affect cutlery choice geometric constraints algorithm flow As shown in figure 3D. According to the principle of the merger (adjacent to the critical distance will be smaller than the difference between the threshold) to search layer merger, graphic processing and identifying viable cutlery sets, a processing layer.E. Determine the use of each processing layer cutlery, cutlery Xingqiang processing portfolio. F. According cutlery recommended processing parameters (cutting speed, depth and into Xianxiao to speed), the calculation of material removal. G. According to the actual removal of the volume processing layer, the processing time for each processing layer. H. Xingqiang calculating the total processing time and residual volume.I. The overall portfolio of the Group cutlery processing efficiency assessment. J . Repeat ai until derive optimal mix of cutlery. If time is the goal, called for the entire processing time t Xingqiang shortest portfolio to optimize cutlery.2.2 Semi-finished cutlery choiceThe main purpose is to remove semi-finished rough machining residual contours of the new warrants. To completely remove height, depth must be greater than Xianxiao parts of each level to the surface distance x. Its algorithm steps are as follows :Step 1:entity models from parts of two adjacent to the cross section of the surface contours and the corresponding length;Step 2: The average length of contours;Step 3:calculate its width;Step 4 : calculating height floor to the surface of parts to the law distance x;Step 5 : steps 1 repeat steps 4, each level of decision Xianxiao depth;Step 6 : calculate cutlery diameter D, by or under cutlery experience D=x/0.6 manual recommended;steps7 : choose Xianxiao x depth than the smallest cutlery.2.3 fine cutlery choiceFine cutlery choice is the basic principle : cutlery parts surface radius smaller than the smallest size R curve radius r, the general admission R= (0.80.9) r. Its algorithm steps are as follows :Step 1 : from the smallest curve radius calculation model parts entities; Step 2 : From cutlery database search radius of less than a cutlery calculated radius of the curve all cutlery; Step 3 : select the best cutlery meet the above requirements; Step 4 : If all cutlery than the smallest curve radius, the smallest chosen as a recommended cutlery.3 summary and discussionMould type of craft of processing plan , need high technology and experience very usually, prepare NC time of data nearly and process time to be large. So person who produce of craft of processing plan and NC process demand of the order right away seem further more urgent automatically.This text system research mould type of craft cutter plan , choose problem, put forward mould of rough machining , half finish machining , finish machining principle and method that cutter chooses, the realization algorithm with corresponding structure , and has carried on the realization of preliminary programming under the environment of UG/OPEN API, have developed CATS prototype system. In cutter type and on the foundation that the specification is fixed, system also can recommend parameter of processing according to cutter manual (cut pace , mill , sharpen depth , enter person who give ,etc.), evaluate corresponding processing time. Final purpose its to realize integration of CAD/CAM really , produce through aftertreatment numerical control process the order.Need to point out , should improve the mould type totality of and process efficiency, need it from the rough machining , half finish machining , consideration on the whole of finish machining , make up and optimize many targets, this will be work that we want to carry on next .模具型腔數(shù)控加工計算機輔助刀具選擇和研究引言 數(shù)控加工中包括刀具軌跡的產(chǎn)生和刀具選擇兩個關鍵問題。前一問題在過去的20 年里得到了廣泛而深入地研究， 發(fā)展的許多算法已在商用 CAD/ CAM 系統(tǒng)中得到應用。目前大多數(shù) CAM 系統(tǒng)能夠在用戶輸入相關參數(shù)后自動產(chǎn)生刀具軌跡。比較而言，對以質(zhì)量、效率為優(yōu)化目標的刀具選擇問題的研究還遠未成熟，當前還沒有商用 CAM 系統(tǒng)能夠提供刀具優(yōu)選的決策支持工具，因而難以實現(xiàn) CAD/ CAM 的自動有機集成。刀具選擇通常包括刀具類型和刀具尺寸。一般來說，適合一個加工對象的刀具通常有多種，一種刀具又可完成不同的加工任務，所以僅考慮滿足基本加工要求的刀具選擇是較容易的，尤其對孔、槽等典型幾何特征。但實際上，刀具選擇通常和一定的優(yōu)化目標相聯(lián)系，如最大切削效率、最少加工時間、最低加工成本、最長使用壽命等，因此刀具選擇又是一個復雜的優(yōu)化問題。比如模具型腔類零件，由于幾何形狀復雜(通常包含自由曲面及島) ，影響刀具選擇的幾何約束在 CAD 模型中不能顯式表示，需要設計相應的算法進行提取，因而選擇合適的刀具規(guī)格及其刀具組合，以提高數(shù)控加工的效率與質(zhì)量并非易事。 模具型腔一般用數(shù)控銑的加工方法，通常包括粗加工、半精加工、精加工等工序。粗加工的原則就是盡最大可能高效率地去除多余的金屬，因而希望選擇大尺寸的刀具，但刀具尺寸過大，可能導致未加工體積的增多;半精加工的任務主要是去除粗加工遺留下來的臺階;精加工則主要保證零件的尺寸及表面質(zhì)量?？紤]到目前完全由計算機進行自動選刀還存在一定困難，因而在我們開發(fā)的計算機輔助刀具選擇(Computer Aided Tool Selection ，CATS)系統(tǒng)中，立足于給用戶提供一個輔助決策工具，即粗加工、半精加工、精加工等，真正的決策權仍留給用戶，以充分發(fā)揮計算機和人的優(yōu)勢。 1 系統(tǒng)基本結(jié)構 CATS 系統(tǒng)的輸入為 CAD 模型，輸出為刀具類型、刀具規(guī)格、銑削深度、進給量、主軸轉(zhuǎn)速(切削速度) 和加工時間等六個參數(shù)(如圖 1) ，包括刀具類型選擇輔助決策工具、粗加工刀具選擇輔助決策工具、半精加工刀具選擇輔助決策工具及精加工刀具選擇輔助決策工具等鑒于粗加工在型腔加工中的重要地位(通常為精加工時間的 510 倍) ，粗加工時系統(tǒng)具有刀具自動優(yōu)化組合的功能，以提高整體加工的效率。除了上述決策工具外，系統(tǒng)還具有查看刀具詳細規(guī)范、根據(jù)刀具類型和尺寸推薦加工參數(shù)及評估加工時間等功能，最后生成總的刀具選擇結(jié)果報表。系統(tǒng)所有的刀具數(shù)據(jù)及知識均由后臺數(shù)據(jù)庫做支持。 2 關鍵技術及算法 2.1 刀具類型選擇 根據(jù)模具型腔數(shù)控加工實踐，型腔銑加工的刀具一般分為平頭銑刀、圓角銑刀及球頭銑刀三種。設刀具直徑為 D，圓角半徑為 r ，當 r=0 時為平頭銑刀，0R刀具又可分為整體式和鑲片式。對于鑲片式，關鍵是選取刀片的材質(zhì)，刀片材質(zhì)的選擇取決于三個要素：被加工工件的材料、機床夾具的穩(wěn)定性以及刀具的懸臂狀態(tài)。系統(tǒng)將被加工工件的材料分為鋼、不銹鋼、鑄鐵、有色金屬、難切削材料和硬材料等六組。機床夾具的穩(wěn)定性分為很好、好、不足三個等級。刀具懸臂分為短懸臂和長懸臂兩種，系統(tǒng)根據(jù)具體情況自動推理出刀片材質(zhì)，決策知識來源于WALTER 刀具手冊，系統(tǒng)由用戶首先交互選擇刀具類型。對鑲片式刀具，基于規(guī)則自動推理出合適的刀片材質(zhì)。例如，如果被加工工件的材料為“鋼” ，機床夾具的穩(wěn)定性為很好，刀具懸臂為短懸臂，則刀片材質(zhì)應為 WAP25 。 粗加工刀具組合優(yōu)化 型腔粗加工的目的就是最大化地去除多余的金屬，通常使用平頭銑刀，采取層切的方法。因此，3D 模具型腔的粗加工過程，實際上就是對一系列 2.5D 模具型腔的加工。刀具優(yōu)化的目的就是要尋找一組刀具組合，使其能夠以最高的效率切除最多的金屬。刀具組合優(yōu)化的基本方法如下： A. 以一定的步長做一組垂直于進刀方向的搜索平面與型腔實體相交，形成若干搜索層。 B. 求出截交輪廓。 C. 計算內(nèi)外環(huán)之間或島與島之間的關鍵距離，即影響刀具選擇的幾何約束. D. 根據(jù)合并原則(相鄰關鍵距離相差小于給定閾值) 對搜索層進行合并，確定加工平面和可行刀具集，形成加工層。 E. 確定每一加工層使用的刀具，即型腔加工的刀具組合。 F. 根據(jù)刀具推薦的加工參數(shù)(切削速度、銑削深度和進給速度) ，計算材料去除率。G. 根據(jù)加工層實際切除的體積，計算每一加工層的加工時間。 H. 計算型腔總的加工時間和殘余體積。 I. 對該組刀具組合的總體加工效率進行評估。 J. 重復 ai，直至求出最優(yōu)的刀具組合。如以時間為目標，即要求以整個型腔的加工時間 t 最短來優(yōu)化刀具組合。 2.2 半精加工刀具選擇 半精加工的主要目的是去除粗加工殘留下的臺階狀輪廓。為完全去除臺階，銑削深度必須大于每一臺階到零件表面的距離 x。其算法步驟如下： 步驟 1 由零件實體模型獲得兩個相鄰截面的表面積以及相應的輪廓長度; 步驟 2 計算平均輪廓長度; 步驟 3 計算臺階寬度; 步驟 4 計算臺階拐角到零件表面的法向距離 x ; 步驟 5 重復步驟 1步驟 4 ，決定每一臺階的銑削深度; 步驟 6 計算刀具直徑 D， 按經(jīng)驗 D=x/0.6 或根據(jù)刀具手冊推薦; 步驟 7 選擇銑削深度大于 x 的最小刀具。 2.3 精加工刀具選擇 精加工刀具選擇的基本原則是：刀具半徑尺寸 R 小于零件表面最小的曲率半徑 r，一般取 R=(0.80.9)r。其算法步驟如下： 步驟 1: 從零件實體模型計算最小曲率半徑; 步驟 2: 從刀具庫中檢索出刀具半徑小于計算所得的曲率半徑的所有刀具; 步驟 3: 選出滿足上述要求的最大刀具; 步驟 4: 如果所有刀具大于最小的曲率半徑，選擇最小的作為推薦刀具。 3 小結(jié)與討論 模具型腔加工的工藝規(guī)劃通常需要很高的技術與經(jīng)驗，準備 NC 數(shù)據(jù)的時間幾乎和加工時間一樣多。因此，自動產(chǎn)生型腔加工的工藝計劃及 NC 加工指令的需求就顯得愈加迫切。 本文系統(tǒng)研究了模具型腔工藝規(guī)劃中的刀具選擇問題，提出了模具型腔粗加工、半精加工、精加工刀具選擇的原則和方法，構造了相應的實現(xiàn)算法，并在 UG/OPEN API 環(huán)境下進行了初步編程實現(xiàn)，開發(fā)了 CATS 原型系統(tǒng)。在刀具類型和規(guī)格確定的基礎上，系統(tǒng)還可根據(jù)刀具手冊推薦加工參數(shù)(切削速度、銑削深度、進給量等) ，對相應的加工時間進行評估。其最終目的是真正實現(xiàn) CAD/CAM 的集成，繼而通過后處理產(chǎn)生數(shù)控加工指令。目前 CATS 系統(tǒng)的界面還是獨立于 UG 的 CAM 界面，CATS 的決策結(jié)果還需要用戶重新輸入到 CAM。 需要指出的是，要提高模具型腔的總體加工效率，需要從粗加工、半精加工、精加工的整體上考慮，進行多目標組合優(yōu)化，這將是我們下一步要進行的工作。