数控专业外文翻译--数控机床的组成部分.doc

附录 英文原文 N/C Machine Tool Elements ———From《English for Machinery》 N/C machine tool elements consist of dimensioning systems, control systems, servomechanisms and open-or closed-loop systems. It is important to understand each element prior to actual programming of a numerically controlled port. The term measuring system in N/C refers to the method a machine tool uses to move a part from a reference point to a target point. A target point may be a certain locating for drilling a hole, milling a slot, or other machine operation. The two measuring systems used on N/C machines are the absolute and incremental. The absolute measuring system uses a fixed reference point. It is on this point that all positional information is based. In other words, all the locations to which a part will be moved must be given dimensions relating to that original fixed reference point. Figure shows an absolute measuring system with X and Y dimensions, each based on the origin. The incremental measuring system has a floating coordinating system. With the incremental system, the time the part is moved. Figure 16.2 show X and Y values using an incremental measuring system. Notice that with this system, each new location bases its values in X and Y from the preceding location. One disadvantage to this system is that any errors made will be repeated throughout the entire program, if not detected and corrected. There are two types of control systems commonly used on N/C equipment: point-to-point and continuous path. A point-to-point controlled N/C machine tool, sometimes referred to as a positioning control type, has the capability of moving only along a straight line. However, when two axes are programmed simultaneously with equal values a 45 angle will be generated. Point-to-point systems are generally found on drilling and simple milling machine where hole location and straight milling jobs are performed. Point-to-point systems can be utilized to genetate arcs and angles by progra