【正文】 y at the machine. A punched tape used to be the popular media of the past but has virtually disappeared from machine shops.* DisadvantagesThere are some disadvantages associated with manual programming. Perhaps the most mon is the length of time required to actually develop a fully functioning CNC program. The manual calculation, verification and other related activities in manual programming are very time consuming. Other disadvantages, also very high on the list, are a large percentage of errors, a lack of tool path verification, the difficulty is making changes to a program, and many others.* AdvantagesOn the positive side, manual part programming does have quite a few unmatched qualities. Manual programming is so intense that it requires the total involvement of the CNC programmer and yet offers virtually unlimited freedom in the development of the program structure. Programming manually does have some disadvantages, but it teaches a tight discipline and organization in program development. It forces the programmer to understand programming techniques to the last detail. In fact, many useful skill learned in manual programming are directly applied to CAD/CAM programming. Programmer has to know what is happening at all times and why it is happening. Very important is the indepth understanding of every detail during the program development.Contrary to many beliefs, a thorough knowledge of manual programming methods is absolutely essential for efficient management of CAD/CAM programming.CAD/CAM AND CNCThe need for important improved efficiency and accuracy in CNC programming has been the major reason for development of a variety of methods that use a puter to prepare part programs. Computer assisted CNC programming has been around for many years. First, in the form of language based programming, such as APT? or Compact Ⅱ?. Since the late 1970’s, CAD/CAM has played a significant role by adding the visual aspect to the programming process. The acronym CAD/CAM means Computer Aided Design and Computer Aided Manufacturing. The first three letters (CAD) cover the area of engineering design and drafting. The second three letters (CAM), covers the area of puterize manufacturing, where CNC programming is only a small part. The whole subject of CAD/CAM covers much more than just design, drafting and programming. It is a part of modern technology also known as CIM – Computer Integrated Manufacturing.In the area of numerical control, puters have played a major role for a long time. Machine controls have bee more sophisticated, incorporating the latest techniques of data processing, storage, tool path graphics, machining cycles, etc. Programs can now be prepared with the use of inexpensive puters, using graphical interface. Cost is no longer an issue。這個過程的起點就是所需工件的工程圖。但還是有一些基本的步驟可供參考：l 初始信息、機床的加工特性l 工件的復雜程度l 手工編程、電腦編程l 典型的編程工藝l 工件圖紙、工程數(shù)據(jù)l 處理表、材料規(guī)格l 加工工序l 刀具選擇l 工件的夾裝l 技術(shù)要求l 工程草圖和計算l 編程要達到的質(zhì)量要求這些建議只是提供了一點基本的方向。對于工件來說最主要的信息就是工程圖和原材料數(shù)據(jù)，在這基礎(chǔ)上程序才得于建立。機床加工特性如果CNC不能適合某個作業(yè)的話再多的初始信息也沒有用。在通常的情況下，CNC設(shè)備已經(jīng)在工廠設(shè)置好了，很少有公司為了適應(yīng)某個特殊的作業(yè)而購置新的CNC機床，這種情況非常罕見，除非這樣做符合經(jīng)濟意義。l 控制系統(tǒng)控制系統(tǒng)是CNC機床的心臟。程序反映出了編程員對CNC機床運行知識的理解程度。排除個人偏好，沒有人喜歡一個設(shè)計有缺陷的程序。困難或復雜的作業(yè)得益于計算機編程系統(tǒng)。有幾種編程系統(tǒng)在不同計算機上都可以使用，可以處理任何作業(yè)。新型的CNC控制器可以提供固定循環(huán)、多種類型的編程、刀具運動的圖型模擬、標準的數(shù)學輸入以及其它節(jié)省時間的特性，這使得手工編程比以前簡單了許多。更簡短的程序可以通過機床的鍵盤直接輸入。手工計算、核對等等工作都很費時間。程序的手工編制肯定會有弊端，但對于養(yǎng)成良好的編程習慣和提高程序結(jié)構(gòu)組織能力非常有益。對每個細節(jié)深度的理解，這對于編程非常重要。最初都是基于語句的編程，例如APT?和Compact Ⅱ?。CAM涵蓋了計算機自動化加工，CNC編程只是其中的一小部分。程序可以在并不昂貴的使用圖形界面的計算機上準備好。同臺計算機還可以完成CNC程序的上傳和下載。使用CAD/CAM軟件重要原則之一就是“一件事不能做兩次”。典型的轉(zhuǎn)換是DXF和IGES格式之間的轉(zhuǎn)換。l 手工編程的未來手工編程好像看起來用得越來越少。為各種功能更強大的硬件和應(yīng)用軟件的發(fā)展提供了可能。另外還要決定要達到預期的目標采用什么合理的方法。這種順序針對具體的情況和工作習慣而改變，一些條款可能會省略，一些可能會重疊。