【正文】 instructions, it was necessary to interrupt machining operations and make a new tape. It was also still necessary to run the tape through the reader as many times as there were parts to be produced. Fortunately, puter technology became a reality and soon solved the problems of NC associated with punched paper and plastic tape. The development of a concept known as direct numerical control (DNC) solved the paper and plastic tape problems associated with numerical control by simply eliminating tape as the medium for carrying the programmed instructions. In direct numerical control, machine tools are tied, via a data transmission link, to a host puter. Programs for operating the machine tools are stored in the host puter and fed to the machine tool an needed via the data transmission linkage. Direct numerical control represented a major step forward over punched tape and plastic tape. However, it is subject to the same limitations as all technologies that depend on a host puter. When the host puter goes down, the machine tools also experience downtime. This problem led to the development of puter numerical control. 3 Turning The engine lathe, one of the oldest metal removal machines, has a number of useful and highly desirable attributes. Today these lathes are used primarily in small shops where smaller quantities rather than large production runs are encountered. The engine lathe has been replaced in today’s production shops by a wide variety of automatic lathes such as automatic of singlepoint tooling for maximum metal removal, and 5 the use of form tools for finish on a par with the fastest processing equipment on the scene today. Tolerances for the engine lathe depend primarily on the skill of the operator. The design engineer must be careful in using tolerances of an experimental part that has been produced on the engine lathe by a skilled operator. In redesigning an experimental part for production, economical tolerances should be used. Turret Lathes Production machining equipment must be evaluated now, more than ever before, this criterion for establishing the production qualification of a specific method, the turret lathe merits a high rating. In designing for low quantities such as 100 or 200 parts, it is most economical to use the turret lathe. In achieving the optimum tolerances possible on the turrets lathe, the designer should strive for a minimum of operations. Automatic Screw Machines Generally, automatic screw machines fall into several categories。因此，在生產(chǎn)中使用的各種車床比任何其他種類的機床都多。它是一個堅固的剛性框架，所有其他基本部件都安裝在床身上。為了抵抗磨損和擦傷，大多數(shù)現(xiàn)代機床的導軌是經(jīng)過表面淬硬的，但是在操作時還應該小心，以避免損傷導軌。它基本上由一個安裝在精密軸承中的空心主軸和一系列變速齒輪(類似于卡車變速箱 )所 組成。一種正在不斷增長的趨勢是通過電氣的或者機械的裝置進行無級變速。 尾座組件主要由三部分組成。尾座的第三個組成部分是尾座套筒。第一個稱為車床的床面上最大加工直徑。車床床面上最大加工直徑表示在車床上能夠車削的最大工件直徑，而兩頂尖之間的最大距離則表示在兩個頂尖之間能夠安裝的工件的最大長度。這些車床大部分都有切屑盤和一個安裝在 內(nèi)部的冷卻液循環(huán)系統(tǒng)。此外，需要技術(shù)熟練的工人來操作普通車床，這種工人的工資高而且很難雇到。在數(shù)控技術(shù)出現(xiàn)之前，所有的機床都是由人工操縱和控制的。 數(shù)字控制意味著采用預先錄制的、存儲的符號指令來控制機床和其他制造系統(tǒng)。數(shù)字控制的機器比人工操縱的機器精度更高、生產(chǎn)出零件的一致性更好、生產(chǎn)速度更快、而且長期的工藝裝備成本更低。 同許多先進技術(shù)一樣，數(shù)控誕生于麻省理工學院的實驗室中。構(gòu)成臺階的每一個線段越短，曲線就越光滑。 APT 語言的研究和發(fā)展是在數(shù)控技術(shù)進一步發(fā)展過程中的一大進步。所有這些共同構(gòu)成了機床數(shù)字控制方面的巨大進步。在機床上每加工一個零件，都需要將載有編程指令的紙帶放入閱讀機中重新運行一次。 這就導致了一種專門的塑料磁帶的研制。 其中最重要的 一個問題是，對輸入到帶中指令進行修改是非常困難的，或者是根本不可能的。 在形成了直接數(shù)字控制（ DNC）這個概念之后，可以不再采用紙帶或塑料帶作為編程指令的載體，這樣就解決了與之有關(guān)的問題。直接數(shù)字控制是在穿孔紙帶和塑料帶基礎(chǔ)上的一大進步。 微處理器的發(fā)展為可編程邏輯控制器和微型計算機的發(fā)展做好了準備。它還可以在機床以外編制程序，并將其下載到每臺機床中。 普通車床作為最早的金屬切削機床的一種，目前仍然有許多有用的和為人要的特性和為人們所需的特性。這種加工方法的生產(chǎn)速度與現(xiàn)在工廠中使用的最快的加工設(shè)備的速度相等。 六角車床 對生產(chǎn)加工設(shè)備來說，目前比過去更注重評價其是否具有精確的和快速的重復加工能力。 自動螺絲車床自動螺絲車床通被分為以下幾種類型：單軸自動、多軸自動和自動夾