【正文】 由資金耗費(fèi)項(xiàng)目上的考慮，就 CNC 機(jī)床刀具而言，為了明確新計(jì)劃是否必要或證明在短期內(nèi)實(shí)現(xiàn)資金回收，一個(gè)公司必須進(jìn)行可行性分析。 計(jì)算機(jī)的體積減小，從而它的生產(chǎn)費(fèi)用也極大的降低。新的控制器的產(chǎn)生便使公司可通過(guò)改變程序改變了一個(gè)工件外形。這是早期情形，是值得欽佩的。用這種方式，自動(dòng)換刀特性使這加工中心高效的加工多種部件，用新刀具代替舊刀具或預(yù)選刀具，使得現(xiàn)今的加工過(guò)程循環(huán)操作。 早期的 NC 機(jī)床，主要的在磨床基礎(chǔ)發(fā)展起來(lái)的，控制的概念主要用于形成，打孔，磨削以及后來(lái)的大量的另外的機(jī)床刀具。作為一個(gè)鉆操作的機(jī)床刀具的點(diǎn)至點(diǎn)移動(dòng)例子，典型的運(yùn)動(dòng)是快速經(jīng)過(guò)在鉆主軸下的工件，鉆空 后，迅速的滑移的運(yùn)動(dòng)可能過(guò)每軸以連續(xù)且獨(dú)立的方式獲得。幾年后，在 USA 與歐洲開始了更深遠(yuǎn)的研究。辛辛那提機(jī)床刀具公司把他們的一個(gè) 28 英寸的“ Hydro— Tel”軍用機(jī)床改裝為三軸自動(dòng)機(jī)床，改變了它們的外部輪廓。通常認(rèn) 為，關(guān)于數(shù)控的研究是 1949 年美國(guó)政府的授權(quán)。 數(shù)控機(jī)床刀具早期的發(fā)展 今天在機(jī)器化大生產(chǎn)領(lǐng)域中千形百態(tài)，結(jié)構(gòu)復(fù)雜的刀具，起源于一些主要的工業(yè)國(guó)，開始很簡(jiǎn)陋。啟動(dòng)機(jī)床之前，確定工作裝置和工件是否安全的固定了 。一些 CAD 和 CAM 程序，如果在相同的計(jì)算機(jī)上下載，可同時(shí)使用一些按鍵、圖紙和程序，使其能相互匹配。程序員仍需準(zhǔn)備一個(gè)工藝卡，含有所用需要的刀具 。若不只一個(gè) CNC 機(jī)床可以來(lái)加工這工件，制作代碼和比較在加工總時(shí)間可以表示一個(gè)機(jī)床是否比另一個(gè)機(jī)床該更有效， CAM/CAD 另一個(gè)確立刀具路徑的方法是借助計(jì)算機(jī)輔助繪圖。當(dāng)代碼發(fā)生器完成時(shí)，加工的計(jì)劃時(shí)間就確定了。運(yùn)行時(shí)，指定機(jī)床的代碼發(fā)生器相當(dāng)于四個(gè)不同的鍵。一個(gè)CAM 系統(tǒng)可讓程序員從不同的角度觀察圖形，比如說(shuō)從頂部、正面、側(cè)面或立體圖。首先，在 CAM 中編譯已加工孔的外部輪廓，再把外部輪廓當(dāng)成粗基準(zhǔn)來(lái)加工內(nèi)孔。 在程序運(yùn)行的任意時(shí)刻，命令 SHOWPATH 會(huì)顯示當(dāng)前的刀具軌跡，也會(huì)顯示刀具在實(shí)際加工時(shí)的使用順序。對(duì)鉆床而言，一旦孔的位置坐標(biāo)和深度被給出，一個(gè)孔就給出現(xiàn)在那點(diǎn)。首先還是工藝卡的建立。點(diǎn)控公司（ POINT CPNTROLL COMPANY）的 SMARTCAM 系統(tǒng)使用接下來(lái)的手段：首先設(shè)計(jì)人員使用一個(gè)金屬零件模型去加工。程序被用來(lái)計(jì)算磨床每次進(jìn)的給量，特別是在微量的光潔度加工中。對(duì)于光潔度的加工，零件在加工中最小進(jìn)給量被選定，接著切削速度直到轉(zhuǎn)速與機(jī)床的最佳轉(zhuǎn)速相等時(shí)才不變。新刀具的信息來(lái)自手冊(cè)或刀具制造商的刀具之資料。這個(gè)加工過(guò)程的程序是吹毛求疵地獲得符合的結(jié)果。 CNC 程序員必須對(duì)這個(gè)即將寫入程序的CNC 機(jī)床的能力和局限有一個(gè)完全的了解。這些改進(jìn)通常包括附加的代碼語(yǔ)句在已有代碼如何工作上的變化。許多CNC 代碼語(yǔ)句可被不同的控制器識(shí)別。在很多情況下，一個(gè) CNC 機(jī)床完成了要建立幾臺(tái)相同傳統(tǒng)機(jī)床才能做的操作。這個(gè)一致性允許很精確地控制加工成本。零件的設(shè)計(jì)變化通過(guò)改變控制機(jī)床的程序而相對(duì)容易實(shí)現(xiàn)?？焖龠M(jìn)給從 60發(fā)展到 200到 400到現(xiàn)在已接近每分 1000英寸了。切削速度和進(jìn)給量要象在其他操作機(jī)床中一樣是正確的。 NC 的優(yōu)勢(shì) 人工操作機(jī)床可能有和 CNC 機(jī)床一樣的物理特性，例如馬力和尺寸，其金屬切削原理也是一樣的。舉幾個(gè)例子，如刳刨機(jī)進(jìn)行木料加工；激光、離子弧、火焰切削、噴水切削鋼板；在制造和裝配中機(jī)器人的控制等。先進(jìn)的機(jī)床控制方法和完全不同的材料成形方法還迫使機(jī)械設(shè)計(jì)人員進(jìn)行前幾年還完全沒(méi)有進(jìn)行的方向（研究）。 this meant that the motions would be sluggish, and sliderways would inevitably suffer from backlash, but more will be said about this topic later in the chapter. The early NC machines were, in the main, based upon a modified milling machine with this concept of control being utilized on turning, punching, grinding and a whole host of other machine tools later. Towards the end of the 1950s,hydrostatic slideways were often incorporated for machine tools of highly precision, which to sonic extent overcame the section problem associated with conventional slideway response, whiles averagingout slideway inaccuracy brought about a much increased preasion in the machine tool and improved their control characteristics allows concept of the machining center was the product of this early work, as it allowed the machine to manufacture a range of ponents using a wide variety of machining processes at a single setup, without transfer of workpieces to other variety machine tools. A machining center differed conceptually in its design from that of a milling machine, In that the cutting tools could be changed automatically by the transfer machanism, or selector, from the magazine to spindle, or vice this ductively and the automatic tool changing feature enabled the machining center to productively and efficiently machine a range of ponents, by replacing old tools for new, or reselecting the next cutter whilst the current machining process is in cycle. In the mid 1960s,a UK pany, Molins, introduced their unique System 24 which was meant represent the ability of a system to machine for 24 hours per day. It could be thought of as a machining plex which allowed a series of NC single purpose machine tools to be linked by a puterized conveyor system. This conveyor allowed the work pieces to be palletized and then directed to as machine tool as necessary. This was an early, but admirable, attempt at a form of Flexible manufacturing System concept, but was unfortunately doomed to failure. Its principal weakness was that only a small proportion of ponent varieties could be machine at any instant and that even fewer work pieces required the same operations to be performed on them. These factors meant that the utilization level was low, coupled to the fact that the machine tools were expensive and allowed frequent production bottlenecks of workinprogress to arise, which further slowed down the whole operation. The early to mid1970s was a time of revolutionary in the area of machine tool controller development, when the term puterized numerical control (CNC) became a reality. This new breed of controllers gave a pany the ability to change work piece geometries, together with programs, easily with the minimum of development and lead time, allowing it to be economically viable to machine small batches, or even oneoff successfully. The dream of allowing a puterized numerical controller the flexibility and ease of program editing in a production environment became a reality when two ralated factors were:the development of integrated circuits, which reduces electronics circuit size, giving better maintenance and allowing more standardization of desing。s contribution to this numerical control development. A major problem occurred just after the Second World War, in that progress in all areas of military and mercial development had been so rapid that the levels of automation and accuracy required by the modern industrialized world could not be attained from the lab our intensive machines in use at that time. The question was how to overe the disadvantages of conventional plant and current manning levels. It is generally ackonwledged that the earliest work into numerical control was the study missioned in 1947 by the US government. The study39。s maximum horsepower for roughing cuts. For a finishing cut, the smallest diameter of the part being machined is selected and then the cutting speed varied until the RPM is equal to the maximum RPM of the machine. This helps in maximizing machining efficiency. Knowing the horsepower requirement for a cut is critical if more than one tool is cutting at the same time. Software for a machining center application would be Ingersoll Tool Company39。 parts can be machined as needs .In conven