SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING In order to obtain higher machining efficiency, several simple operation elements are sometimes combined into one complex operation element. In a complex operation element, several cutting tools are simultaneously used to machine different workpiece surfaces. Fig. 6.2(a) shows the machining of two plane sur faces using two milling cutters Fig. 6.2(b)illustrates the machining of a workpiece on a lathe equipped with a turret. This has been commonly used in 转塔一 many turret lathes, automatic lathes, and numerically controlled turning centers for increased productivity. When it is necessary to remove a thick layer of material from the workpiece and it cannot be done in a single cut, an operation element can be divided into several passes (or cuts). A pass or cut, is a single cutting motion of the cutting tool in the direction of the feed along the machined surface, without changing the set-up of the tool or the cutting speed or feedSCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING In order to obtain higher machining efficiency, several simple operation elements are sometimes combined into one complex operation element. In a complex operation element, several cutting tools are simultaneously used to machine different workpiece surfaces. Fig.6.2 (a) shows the machining of two plane surfaces using two milling cutters. Fig.6.2 (b) illustrates the machining of a workpiece on a lathe equipped with a turret. This has been commonly used in many turret lathes, automatic lathes, and numerically controlled turning centers for increased productivity. When it is necessary to remove a thick layer of material from the workpiece and it cannot be done in a single cut, an operation element can be divided into several passes (or cuts). A pass, or cut, is a single cutting motion of the cutting tool in the direction of the feed along the machined surface, without changing the set-up of the tool or the cutting speed or feed. 转 塔