【導讀】加工手段得到了普遍應用。這已經(jīng)成為近幾年機床加工的發(fā)展趨勢。具有超過絕大多數(shù)經(jīng)驗豐富的機械師所具有的加工能力。在這個部分我們來看數(shù)控機床切削使用的工具。CNC控制器能被用來驅動和控。制多種機床和機構。切削、噴水切削鋼板；在制造和裝配中機器人的控制等。本書的這個部分僅是一。般介紹而不能作為專業(yè)機床的設計手冊。由于計算機能力和容量的巨大增長，機。CNC機床的最大優(yōu)勢來自無錯的和快速的可能運動的控制。這樣高的進給率對在機床工作區(qū)的任何人構成了安全威脅。CNC機床不需要額外的時間和特別的預防就可生產(chǎn)高精度的嚴格公差的零件。CNC使機床不需要復雜的夾具，這使零件很快被加工從而節(jié)約了時間。在很多情況下，一個CNC機床完成了要建立幾臺。自從手工CNC機床被一大批廠家生產(chǎn)以來，許多不同的CNC控制單元就。每個制造商在不斷地提高和更新其CNC控制。CAM系統(tǒng)允許CNC程序員在高效的加工過。CNC程序員必須對這個即將寫入程序的CNC機床的能力。誤也可立即被糾正。

　　

【正文】 and current manni ng levels. It is generally acknowledged that the earliest work into numerical control was the study missioned in 1947 by the US government. The study39。s conclusion was that the metal cutting industry throughout the entire country could not copy with the demands of the American Air Force, let alone the rest of industry! As a direct result of the survey, the US Air Force contracted the Persons Corporation to see if they could develop a flexible, dynamic, manufacturing system which would maximize productivity. The Massachusetts Institute of Technology (MIT) was subcontracted into this research and development by the Parsons Corporation, during the period 19491951,and jointly they developed the first control system which could be adapted to a wide range of machine tools. The Cincinnati Machine Tool Company converted one of their standard 28 inch HydroTel milling machines or a threeaxis automatic milling made use of a servomechanism for the drive system on the axes. This machine made use of a servomechanism for the drive system on the axes, which controlled the table positioning, crossslide and spindle head. The machine cab be classified as the first truly three axis continuous path machine tool and it was able to generate a required shape, or 11 curve, by simultaneous slide way motions, if necessary. At about the same times as these American advances in machine tool control were taking Place, Alfred Herbert Limited in the United Kingdom had their first Mutinous path control system which became available in the next few years in both the USA and Europe, further development work occurred. These early numerical control developments were principally for the aerospace industry, where it was necessary to cut plex geometric shapes such as airframe ponents and turbine blades. In parallel with this development of sophisticated control systems for aerospace requirements, a pointtopoint controller was developed for more general machining applications. These less sophisticated pointtopoint machines were considerably cheaper than their more plex continuous path cousins and were used when only positional accuracy was necessary. As an example of pointtopoint motion on a machine tool for drilling operations, the typical movement might be fast traverse of the work piece under the drill39。s positionafter drilling the hole, anther rapid move takes place to the next hole39。s positionafter retraction of the drill. Of course, the rapid motion of the sideways could be achieved by each axis in a sequential and independent manner, or simultaneously. If a separate control was utilisec for each axis, the former method of table travel was less essential to avoid any backlash in the system to obtain the required degree of positional accuracy and so it was necessary that the approach direction to the next point was always the same. The earliest examples of these cheaper pointtopoint machines usually did not use recalculating ball screws。 this meant that the motions would be sluggish, and sideways 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 sideways were often incorporated for machine tools of highly precision, which to sonic extent overcame the section problem associated with conventional sideway response, whiles averagingout sideway 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 12 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) beca