Early machine tools were designed so that the operator was standing in front of the machine while operating the controls. This design is no longer necessary, since in CNC the operator no longer controls the machine tool movements. On conventional machine tools, only about 20 percent of the time was spent removing material. With the addition of electronic controls, actual time spent removing metal has increased to 80 percent and even
higher. It has also reduced the amount of time required to bring the cutting tool into each machining position.
Machine Types Lathe
The engine lathe, one of the most productive machine tools, has
always been an efficient means of producing round parts Most lathes are programmed on two axes.
• The X axis controls the cross motion of the cutting tool Negative X (X-) moves the tool towards the spindle
centerline; positive X moves the tool away from the spindle centerline.
• The Z axis controls the carriage travel toward or away from the headstock.
The milling machine has always been one of the most versatile machine tools used in industry (Fig. 5). Operations such as milling, contouring, gear cutting, drilling, boring, and reaming are only a few of the many operations which can be performed on a milling machine. The milling machine can be programmed on
• The X axis controls the table movement left or right.
• The Y axis controls the table movement toward or away from
• The Z axis controls the vertical (up or down) movement of
the knee or spindle.