英文文献 科技类 原文及翻译.docx

本科毕业设计(论文)外文翻译
姓 名: 王文超
学 号： 200715010220
专 业: 电气工程及其自动化
班 级: 电气071502
指导教师:fit, fast change-overs. Since these machines are very easy to setup and run, and since programs can be easily loaded, they allow very short setup time. This is imperative with today’s Just-In-Time product requirements.
1. Motion control-the heart of CNC
The most basic function of any CNC machine is automatic, precise, and consistent motion. Rather than applying completely mechanical devices to cause motion as is required on most conventional machine tools, CNC machines allow motion control in a revolutionary manner. All forms of CNC equipment have two or more directions of motion, called axes. These axes can be precisely and automatically positioned along their lengths of travel. The two most common axis types are linear (driven along a straight path) and rotary (driven along a circular path).
Instead of causing motion by turning cranks and handwheels as is required on conventional machine tools, CNC machines allow motions to be commanded through programmed commands. Generally speaking, the motion type (rapid, linear, and circular), the axes to move, the amount of motion and the motion rate (feedrate) are
programmable with almost all CNC machine tools.
Accurate positioning is accomplished by the operator counting the number of revolutions made on the handwheel plus the graduations on the dial. The drive motor is rotated a corresponding amount, which in turn drives the ball screw, causing linear motion of the axis. A feedback device confirms that the proper amount of ball screw revolutions has occurred.
A CNC command executed within the control (commonly through a program) tells the drive motor to rotate a precise number of times. The rotation of the drive motor in turn rotates the ball screw. And the ball screw causes drives the linear axis. A feedback device at the opposite end of the ball screw allows the control to confirm that the comm