【正文】 中，零件程序可直接輸入到控制數(shù)控機(jī)床的計(jì)算機(jī)及檢驗(yàn)站中。CAD/CAM系統(tǒng)中的主要構(gòu)想是生成可用于所有設(shè)計(jì)及加工動作的通用數(shù)據(jù)庫。這其中包括：產(chǎn)品的規(guī)格化、設(shè)計(jì)構(gòu)想、最終設(shè)計(jì)、繪圖、加工及檢驗(yàn)。在次過程中的每一個階段，數(shù)據(jù)都可以添加、修改、使用以及分配給工作站的終端和計(jì)算機(jī)中。單個數(shù)據(jù)庫從實(shí)質(zhì)上減少了認(rèn)為誤差，極大的縮短了從產(chǎn)品設(shè)計(jì)構(gòu)想到制造出最終產(chǎn)品所需的時間。所需計(jì)算機(jī)系統(tǒng)的大小及容量取決于產(chǎn)品的復(fù)雜程度。在航空航天工業(yè)中，要用CAD/CAM處理器完成航天器設(shè)計(jì)，系統(tǒng)必須能夠容納從不同用戶處得到的新的數(shù)據(jù)以及對數(shù)據(jù)的修改。因此，它們所用的系統(tǒng)必須有強(qiáng)大的數(shù)據(jù)處理能力。與之相對，如果公司設(shè)計(jì)的產(chǎn)品簡單，所需的CAD/CAM只需一個計(jì)算機(jī)終端即可。如今CAD/CAM系統(tǒng)的主要用戶是航天工業(yè)及汽車工業(yè)。但是隨著CAD/CAM系統(tǒng)價格的降低，也增加了其他方面用戶的數(shù)量。先進(jìn)的CAD/CAM系統(tǒng)除了有線框方式圖形外還包括固體幾何模塊功能。當(dāng)CAM系統(tǒng)中涉及數(shù)控檢驗(yàn)程序以及加工時要求同時觀測零件的變化狀況時，固體幾何模塊描述就很重要。最近幾年CAD/CAM技術(shù)已經(jīng)提高了工業(yè)生產(chǎn)率。CAD/CAM技術(shù)是朝向未來工廠設(shè)計(jì)方向邁出的重要一步。有限元優(yōu)化的應(yīng)用在結(jié)構(gòu)日益復(fù)雜的情況下，當(dāng)工程師們工作時，他們需要合理的、可靠的、快速而經(jīng)濟(jì)的設(shè)計(jì)工具。過去二十多年里，有限元分析法已經(jīng)成為判別和解決涉及這些復(fù)雜設(shè)計(jì)課題時的最常用方法。因?yàn)楣こ讨械拇蠖鄶?shù)設(shè)計(jì)任務(wù)都是可定量的，所以實(shí)踐上，為了快速找到一些可供選擇的設(shè)計(jì)方案。計(jì)算機(jī)令繁瑣的重復(fù)設(shè)計(jì)過程發(fā)生了深刻的變革。但是，即使是現(xiàn)在，許多工程師仍然使用人工的試湊法。這樣一種方法使得即使是很簡單的設(shè)計(jì)任務(wù)也變的困難，因?yàn)橥ǔＫǜL的時間，需要廣泛的人一機(jī)交互配合，且偏于用設(shè)計(jì)組的經(jīng)驗(yàn)來設(shè)計(jì)。優(yōu)化設(shè)計(jì)是以理論數(shù)學(xué)的方法為基礎(chǔ)，改進(jìn)那些對于工程師來說過于復(fù)雜的設(shè)計(jì)，使其設(shè)計(jì)過程自動化。如果在一部臺式計(jì)算機(jī)平臺上能實(shí)現(xiàn)自動優(yōu)化設(shè)計(jì)，那就可以節(jié)省大量的時間和金錢。優(yōu)化設(shè)計(jì)的目的就是要將對象極大化或極小化，例如，重量或基頻，主要受到頻響和設(shè)計(jì)參數(shù)方向的約束。尺寸和結(jié)構(gòu)形狀決定著優(yōu)化設(shè)計(jì)的方法。觀察一下作為零件優(yōu)化設(shè)計(jì)過程，使它變的更容易理解。第一步，包括預(yù)處理分析和后處理分析，正像慣常使用的有限元分析（FEA）和計(jì)算機(jī)輔助設(shè)計(jì)（CAD）程序應(yīng)用。（CAD的特點(diǎn)在于根據(jù)設(shè)計(jì)參數(shù)建立了課題的幾何圖形）。第二步，定義優(yōu)化目標(biāo)和響應(yīng)約束。而最后一步，反復(fù)自動調(diào)節(jié)設(shè)計(jì)作業(yè)。優(yōu)化設(shè)計(jì)程序?qū)⒃试S工程師們監(jiān)督該設(shè)計(jì)步驟和進(jìn)度，必要時停止設(shè)計(jì)，改變設(shè)計(jì)條件和重新開始。一項(xiàng)優(yōu)化設(shè)計(jì)程序的功力取決于有效的預(yù)處理和分析能力。二維和三維設(shè)計(jì)的應(yīng)用既需要自動進(jìn)行也需要設(shè)計(jì)參數(shù)的結(jié)網(wǎng)性能。因?yàn)樵趦?yōu)化循環(huán)過程中，課題的幾何條件和網(wǎng)格會改變，所以優(yōu)化程序必須包含誤差估計(jì)和自適應(yīng)控制。 修改、重配網(wǎng)格和重新估算模式以期獲得特定目標(biāo)的實(shí)現(xiàn)是以輸入初始設(shè)計(jì)數(shù)據(jù)開始的。接著，是規(guī)定合格的公差并形成約束條件以獲得最優(yōu)結(jié)果，或最后改進(jìn)設(shè)計(jì)，解決問題。為了使產(chǎn)品從簡單輪廓圖形到三維實(shí)體模型系統(tǒng)化、系列化，設(shè)計(jì)者必須廣泛接觸設(shè)計(jì)目標(biāo)和特性約束條件。為了易于確定而利用下列參數(shù)作為約束和 目標(biāo)函數(shù)的附加特性條件，也將是需要的：重量、體積、位移、應(yīng)力、應(yīng)變、頻率、翹曲安全系數(shù)、溫度、溫度梯度和熱通量。此外，工程師們應(yīng)該能夠通過多學(xué)科的不同類型的優(yōu)化分析使多種約束條件結(jié)合起來。例如設(shè)計(jì)者為了應(yīng)力分析，可以進(jìn)行熱力分析和加熱以變更溫度，也可將多種約束條件，諸如最高溫度、最大應(yīng)力和變形聯(lián)系在一起進(jìn)行研究，然后規(guī)定一個所希望的基本頻率范圍。目標(biāo)函數(shù)代表著整體模式或部分模式。甚至更重要的是通過說明重量或者成本應(yīng)因素，就應(yīng)該能反映該模式的各個部分的重要性。計(jì)算機(jī)輔助繪圖的好處 用計(jì)算機(jī)完成繪圖及設(shè)計(jì)任務(wù)的好處是令人難忘的：提高速度、提高準(zhǔn)確性、減少硬拷貝存儲空間及易于恢復(fù)信息、加強(qiáng)信息傳遞能力、改善傳輸質(zhì)量和便于修改。 速度 工業(yè)用計(jì)算機(jī)能以平均每秒3300萬次完成一項(xiàng)任務(wù)；更新的計(jì)算機(jī)起速度更快。用計(jì)算機(jī)計(jì)算零件的變形量是一個重要功績。當(dāng)理論上的載荷力加到零件上時、通過計(jì)算機(jī)進(jìn)行有限元分析或者在監(jiān)視器上顯示一個城市的整體規(guī)劃時，這兩者都是既費(fèi)時又計(jì)算最大的任務(wù)。AutoCAD軟件可根據(jù)需要多次復(fù)制所需模型的形狀和幾何尺寸，快速自動地進(jìn)行剖面填充及尺寸標(biāo)注。準(zhǔn)確AutoCAD程序依靠操作系統(tǒng)及計(jì)算機(jī)平臺每點(diǎn)具有14位的精度。這在用數(shù)字計(jì)算諸如一個圓的線段數(shù)、程序必須圓整線段數(shù)時是十分重要的。存儲計(jì)算機(jī)能夠在物理中存儲上千幅圖，這空間能夠存儲上百幅手工圖。而且計(jì)算機(jī)能夠很容易地搜索和找到一幅圖，只要操作者擁有正確的文件名。傳輸由于計(jì)算機(jī)的數(shù)據(jù)是以電子形式存儲，它能被送到各個位置。最明顯的位置是監(jiān)視器。計(jì)算機(jī)可以在屏幕上以不同方式顯示數(shù)據(jù)，如圖形，并能方便地將數(shù)據(jù)轉(zhuǎn)換成可讀圖形。這些數(shù)據(jù)也可被傳送給繪圖機(jī)，打印出常見的圖紙，通過直接連接到計(jì)算機(jī)輔助制造機(jī)床或電話線傳到地球的任何地方。你可以不再冒損壞或丟失的危險去郵寄圖紙，現(xiàn)在圖紙可以通過電信網(wǎng)立即發(fā)送到目的地。質(zhì)量計(jì)算機(jī)總是從最初生成的數(shù)據(jù)形式保存數(shù)據(jù)。它可以不顧疲勞的不斷地重復(fù)同一個數(shù)據(jù)輸出。線型將總是鮮明和清晰的，具有一致的線寬，而文本也總是清晰明了的。計(jì)算機(jī)不會改變輸出質(zhì)量，因?yàn)橛?jì)算機(jī)不會像人那樣因周末的郊游或深夜觀看娛樂節(jié)目而疲勞。修改計(jì)算機(jī)以某種便于修改的形式存儲數(shù)據(jù)并且不斷地提供反饋給用戶。某些圖形一旦畫成，它就不必再畫，因?yàn)槲矬w可以被復(fù)制、延伸、改變尺寸并且在不重畫的情況下，可以多種形式加以修改。除了最初購買CAD工作站的花費(fèi)，CAD的唯一缺點(diǎn)是它是一個小軟件，而它能容易被克服。由于圖形是以電子格式存儲而不是圖紙格式，所以有可能會容易地刪除繪圖文件。這就是為什么強(qiáng)調(diào)要培養(yǎng)自己一個好的繪圖習(xí)慣以避免意外地刪除繪圖文件。一盎司的保護(hù)等于一磅的治療。如果你按照正確的順序操作，則有很多種成功恢復(fù)文件的方式。如此輕松！ComputerAided Design (CAD)A CAD system is basically a design tool in which the puter is used to analyze various aspects of a designed product. The CAD system supports the design process at all levels—conceptual, preliminary, and final design. The design can then test the product in various environmental conditions, such as temperature changes, or under different mechanical stress.Although CAD systems do not necessarily involve puter graphics, the display of the designed object on a screen is one of the most valuable features of CAD systems. The picture of the object is usually displayed on the surface of cathoderay tube (CRT).Computer graphics enables the designer to study the object by rotating it on the puter screen, separating it into segments, enlarging a specific portion of the object in order to observe it in detail, and studying the motion of mechanisms with the aid of programs.Most CAD systems are using interactive graphics system. Interactive graphics allows the user to interact directly with the puter in order to generate manipulate, and modify graphic displays. Interactive graphics has bee a valuable tool, if not a necessary prerequisite, of CAD system.The end products of many CAD systems are drawing generated on a plotter interfaced with the puter. One of the most difficult problems in CAD drawing is the elimination of hidden lines. The puter produces the drawing as wire frame diagram. Since the puter defines the object without regard to one’s perspective, it will display all the object’s surfaces, regardless of whether they are located on the side facing the viewer or on the back, which normally the eye cannot see.Various methods are used to generate the drawing of the part on the puter screen. One method is to use a geometric modeling approach, in which fundamental shapes and basic elements are used to build the drawing. The lengths and radii of the elements can be modified. For example, a cylinder is a basic element, the subtraction of a cylinder with a specific radius and length will create hole in the displayed part. Each variation, however, maintains the overall geometry of the part.Other CAD systems use group technology in the design of parts. Group technology is a method of coding and grouping parts on the basis of similarities in function or structure or in the ways they are produced. Application of group technology can enable a pany to reduce the number of parts in use and to make the production of parts and their movement in the plant efficient.Recently CAD systems are using the finiteelement method (FEM) of stress analysis. By this approach the object to be analyzed is represented by a model consisting of small elements, each of which has stress and deflection characteristics. The analysis requires the simultaneous solution of many equations。 a task which is performed by the puter, the deflections of the object can be displayed on the puter screen by generating animation of the model.With any of these methods, or other which are used, the CAD system generates at the design stage a single geometric data base which can be used in all phases of the design and later in the manufacturing, assemble, and inspection processes.CAD/CAM SystemsComputeraided design (CAD) means the use of a puter to assist in the design of an individual part or a system, such as an aircraft. The design process usually involves puter graphics.Computeraided manufacturi