外文翻译车床刀具早期的发展

1、.：.；The Early Development Of Numerically Controlled Machine Tools The highly sophisticated CNC machine tools of today, in the vast and diverse range found throughout the field of manufacturing processing, started from very humble beginnings in a number of the major industrialized countries. Some of

2、the earliest research and development work in this field was completed in USA and a mention will be made of the UKs 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 commercial development had b

3、een 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 overcome the disadvantages of conventional plant and current manning levels. It is generally acko

4、nwledged that the earliest work into numerical control was the study commissioned in 1947 by the US government. The studys 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 dire

5、ct 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 sub-contracted into this research and development by the Parsons

6、Corporation, during the period 1949-1951,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 Hydro- milling machines or a three-axis automatic milling made use of a se

7、rvo-mechanism 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, cross-slide and spindle head. The machine cab be classified as the first truly three axis continuous path machine tool and it was able t

8、o generate a required shape, or 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 19

9、56.Over 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 complex geometric shapes such as airframe components and turbine blades. In parallel with th

10、is development of sophisticated control systems for aerospace requirements, a point-to-point controller was developed for more general machining applications. These less sophisticated point-to-point machines were considerably cheaper than their more complex continuous path cousins and were used when

11、 only positional accuracy was necessary. As an example of point-to-point motion on a machine tool for drilling operations, the typical movement might be fast traverse of the work piece under the drills position-after drilling the hole, anther rapid move takes place to the next holes position-after r

12、etraction of the drill. Of course, the rapid motion of the slideways 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

13、 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 point-to-point machines usually did not use recalculating ball screws; this meant that the motions would be sluggish, a

14、nd 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 machin

15、e 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 averaging-out slideway inaccuracy brought about a much increased

16、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 components using a wide variety of machining processes at a single set-up, without transfer of workpi

17、eces 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 versa.In this ductively and the automatic

18、 tool changing feature enabled the machining center to productively and efficiently machine a range of components, 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 company, Molins, introduced their unique System 24

19、 which was meant represent the ability of a system to machine for 24 hours per day. It could be thought of as a machining complex which allowed a series of NC single purpose machine tools to be linked by a computerized conveyor system. This conveyor allowed the work pieces to be palletized and then

20、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 component varieties could be machine at any instant and that eve

21、n 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 work-in-progress to arise, which further slowed down the whole op

22、eration. The early to mid-1970s was a time of revolutionary in the area of machine tool controller development, when the term computerized numerical control (CNC) became a reality. This new breed of controllers gave a company the ability to change work piece geometries, together with programs, easil

23、y with the minimum of development and lead time, allowing it to be economically viable to machine small batches, or even one-off successfully. The dream of allowing a computerized numerical controller the flexibility and ease of program editing in a production environment became a reality when two r

24、alated factors occurred.These were:the development of integrated circuits, which reduces electronics circuit size, giving better maintenance and allowing more standardization of desing; that general purpose computers were reduced in size coupled to the fact that their cost of production had fallen c

25、onsiderably. The multipie benefits of cheaper electorics with greater reliability have result in the CNC fitted to the machine tools today, with the power and sophistication progtessing considerably in the last few years, allowing an almost artificial intelligence(AI) to the latest systems. Over the

26、 years, the machine tools builders have produced a large diversity in the range of applications of CNC and just some of those development will be reviewed in Volume 。 With any capital cost item, such as a CNC machine tool, it is necessary for a company to undergo a feasibility study in order to asce

27、rtain whether the purchase of new plant is necessary and can be justified over a relatively short pay-back period. These thoughts and other circial decisions will be the subject of the next section which is concerned with the economic justification for CNC.车床刀具早期的开展今天在机器化大消费领域中千形百态，构造复杂的刀具，来源于一些主要的工

28、业国，开场很简陋。这个领域中，最早的一些研讨和开展完成于美国，并记载了UK关于开展方面的奉献。第二次世界大战后的一个主要问题是，商业和军队迅速开展，在劳动力密集的加工中，现代工业界所需的自动化与准确度不可获得。问题是怎样样来抑制常规的加工方法和手工制造的缺乏。通常以为，关于的研讨是1949年美国政府的授权。结论就是致使美国空军与Parsons公司签约，让他们找到一种灵敏的、有力的制造系统，它能扩展消费。麻省理工大学开场进入研讨，而Parsons公司使之开展起来。在19491951期间，他们结合发明了一种可适宜多种刀具的第一个系统。辛辛那提车床刀具公司把他们的一个28英寸的“Hydro军用车床改

29、装为三轴自动车床，改动了它们的外部轮廓。在控制桌面位置，典型的车床是三轴延续曲线的车床刀具，它能产生一个所需求的外形或曲线，能够的话，经过一个延续的滑移实现。与美国车床刀具控制开展的同时，UK中的ALIFRED Herber产生了第一台NC车床。1956年更可靠的曲线途径控制系统开场运用。几年后，在USA与欧洲开场了更深远的研讨。早期的开展主要为了航空业，它需求切削加工复杂的几何外形，如机件部件与涡轮机叶片。在航空所需求的复杂的控制系统开展的同时，点与点控制器开展起来，更广泛的用于加工当中。较简单的点与点车床比复杂的延续途径的同类产品廉价一些，并在用于需求准确定位的加工中。作为一个钻操作的车床刀具的点至点挪动例子，典型的运动是快速经过在钻主轴下的工件，钻空后，迅速的滑移的运动能够过每轴以延续且独立的方式获得。分开的控制可由每轴完成，在早期的点到点车床中，选取途径不很重要，但它必需防止在获得多需求精度中所产生的冲击。所以，趋势下一点的方向必需是一样的。最早的这些点到点车床长循环