数字控制外文文献翻译、中英文翻译

Numerical controlNumerical control of machine tools may be defined as a method of automation in which various functions of machine tools are controlled by letters, numbers and symbols. Basically a NC machine runs on a program fed to it. The program consists of precise instructions about the manufacturing methodology as well as the movements. Fox example, what tool is to be used, at what speed, at what feed and to move from which point to which point in what path, all these instructions are given. Since the program is the controlling point for product manufacture, the machine becomes versatile and can be used for any part. All the functions of an NC machine tool are therefore controlled electronically, hydraulically or pneumatically. In NC machine tools one or more of the following functions may be automatic:(i) Starting and stopping of the machine tool spindle.(ii) Controlling the spindle speed.(iii) Positioning the tool tip at desired locations and guiding it along. Desired paths by automatic control of the motion of slides.(iv) Controlling the rate of movement of tool tip.(v) Changing of tools in the spindle. Initially the need of NC machines was felt for machining complex shaped small batch components as those belonging to an aircraft. However, this spectrum currently encompasses practically all activities of manufacturing, in particular capital goods and white goods. Thus the range covered is very wide. Besides machining with which we are concerned, NC has been used in a variety of manufacturing situations. The majority of applications of NC are in metal cutting machine tools such as milling machines, lathes, drilling machines, grinding machines and gear generating machines. Besides a number of metal forming machine tools such as presses, flame cutting machines, pipe bending and forming machines, folding and shearing machines also use NC for their program control. The inspection machines called Co-ordinate Measuring (CMM) are also based on NC. Lastly the robots basically may be material handling units, but their control principles are very close to the NC. Besides these applications listed for manufacturing, other applications such as filament winding or assembly machines based on the NC principles can also be seen in the industry. NC machines have been found suitable for the following:(i) Parts having complex contours, that cannot be manufactured by conventional machine tools.(ii) Small lot production, often for even single (one off) job production, such as for prototyping, tool manufacturing, etc.(iii) Jobs requiring very high accuracy and repeatability.(iv) Jobs requiring many set-ups and/or when the set-ups are expensive.(v) Parts that are subjected to frequent design changes and consequently require more expensive manufacturing methods.(vi) The inspection cost, which is a significant portion of the total manufacturing cost. One or more of the above considerations would justify the processing of a part by an NC machine tool. Numerical Control is superior to conventional manufacturing in a number of ways. The superiority comes because of the programmability. These are as follows:(i) Parts can be produced in less time and therefore are likely to be less expensive. The idle (non-cutting) time is reduced to minimum. This of course depends on the way the part program for the part is written. The endeavour of the machine tool builder is to provide a facility whereby the non-cutting time can be brought to the minimum. It is possible to reduce the non-productive time in NC machine tools in the following ways:(a) by reducing the number of set-ups(b) by reducing set-up time(c) by reducing workpiece-handling time(d) by reducing tool-changing time.These make machines highly productive.(ii) Parts can be produced more accurately even for smaller batches. In conventional machine tools, precision is largely determined by human skill, NC machines, because of automation and the absence of interrelated human factors, provide much higher precision and thereby promise a product of consistent quality for the entire batch.(iii) The operator involvement in part manufacture is reduced to a minimum and as a result less scrap is generated due to operator errors. No operator skill is needed, except in setting up of the tools and the work. Even here, the set-up has been simplified to a great extent.(iv) Since the part program takes care of the geometry generated, the need for expensive jigs and fixtures is reduced or eliminated, depending upon the part geometry. Even when a fixture is to be used, it is very simple compared to a conventional machine tool. It is far easier to make and store part program (tapes).(v) Inspection time is reduced, since all the parts in a batch are identical, provided proper care is taken about tool compensations and tool wear in part program preparation and operation. With the use of inspection probes in the case of some advanced CNC controllers, the measurement function also becomes part of the program.(vi) The need for certain types of form tools is completely eliminated in NC machines. This is because the profile generated can be programmed, even if it involves three dimensions.(vii) Lead times needed before the job can be put on the machine tool are reduced to a great extent, depending upon the complexity of the job. More complex jobs may require fixtures or templates if they are to be machined in conventional machine tools, which can be reduced to a large extent.(viii) CNC machining centers can perform a variety of machining operations that have to be carried out on several conventional machine tools, thus reducing the number of the machine tools on the shop floor. This would save floor space and result in less lead-time in manufacture. This would also result in an overall reduction in production costs.(ix) The set-up times are reduced, since the set-up involves simple location of the datum surface and position. Further, the number of the set-ups needed can also be reduced. All this translates into lower processing times. A component can be fully machined in a single machining center or turning center, each of which having wider machining capabilities. In conventional manufacture if the part has to be processed through a number of machine tools which are located in different departments, the time involved in completion and the resultant in process inventory would be large. This would be greatly eliminated by the use of NC machine tools.数字控制机床数字控制是一种由数字和符号控制完成机床各种功能的自动化方法。基本上NC机床是通过程序控制来工作的。程序包含了制造工艺运动的精确命令，比如说，用什么样的刀具，什么样的切削速度，什么样的进给量，从这点移动到那点走过什么样的路径，所有这些都已给出指示命令。自从加工产品的程序被控制运用，这种机器变得用途广泛的。NC机床的所有功能也因此由电力，液压或者是气压带动实现的。在NC机床下列功能中由一种或者更多的可能是自动的：（一） 机床主轴的启动和停止。（二） 控制主轴转速。（三） 确定刀尖位置和导向，自动控制滑台的运动路径。（四） 控制刀具的运动速率。（五） 刀具的转换。最初NC机床是用来探索飞机一小批机制合成物成分的。但是这种光谱涵盖目前几乎所有制造业的活动，尤其是资本货物和白色家电。因此这个范围是非常广泛的。除了我们所关心的机制以外，NC被用在很多制造情形中。NV被多数应用在金属切削机床中，比如铣床，车床，钻床，磨床和插齿机。此外一些金属成型机床像压床，火焰切断机，弯管成型机，折叠式剪切机都用NC的程序控制。统筹测量机也是基于NC而工作的。最后机器人基本上具有物料装卸装置，但是他们控制的原则是非常接近NC的。除了这些申请上市的制造业以外，其他如缠绕或装备机器基于数控原则也是经常可以看到的。数控机床有以下用途： (一) 部分有复杂的轮廓线，这是传统机床不能制造的。(二) 小批量生产，往往连单次（一次性）生产，如原型制作，刀具制作等。(三) 准确度和可重复性要求很高的加工。(四) 要求很多设备或者设备很贵的加工。(五) 零部件经常需要更改设计的，因此需要更昂贵的制造方法。(六) 检测费用，占总制造成本很大比例。 一个或更多的上述因素足以证明数控机床可以处理很多问题。 数控机床在一系列的加工方式中明显优于传统的制造业。优势在于数控程序可控的。优势如下：(一) 零件加工时间短，因此可能会很便宜。非