数控技术应用专业英语教学课件作者刘小芹4.AdvantagesofCNC课件幻灯片.pptVIP

 English on Mechanical Engineering Lesson 3 Advantages of CNC Text Recent studies show that of the amount of time an average part spent in a shop, only a fraction of that time was actually spent in the machining process. Let us assume that a part spent 50 hours from the time it arrived at a plant as a rough casting or bar stock to the time it was a finished product. During this time, it would be on the machine for only 2.5 hours and be cut for only 0.75 hour. The rest of the time would be spent on waiting, moving, setting up, loading, unloading, inspecting the part, setting speeds and feed, and changing cutting tools. CNC( computer numerical control) machines do not necessarily produce components more accurately than NC machines, and are only faster in operation owing to the speed with which the program blocks are transmitted to the control unit. CNC reduces the amount of non-chip-producing time by selecting speeds and feeds, making rapid moves between surfaces to be cut, using automatic fixtures, automatic tool changing, controlling the coolant, in-process gaging, and loading and unloading the part. These factors, plus the fact that it is no longer necessary to train machine operators, have resulted in considerable savings throughout the entire manufacturing process and caused tremendous growth in the use of CNC. Text Some of the major advantages of CNC are as follows: 1.The amount of input information is reduced. 2.There is automatic or semi-automatic operation of machine tools. The degree of automation can be selected as required. 3.Flexible manufacturing of parts is much easier. Only the part programming needs changing to produce another part. 4.Storage space is reduced. Simple work holding fixtures are generally used, reducing the number of jigs or fixtures which must be stored. Text 5.Small part lots can be run economically. Often a single part can be produced more quickly and better b