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CNC MACHINING CENTERS

CNC machining centers evolved from the need to be able to perform a variety of different operations and machining sequences on a workpiece on a single machine in one setup. In the past, many parts that required machining on several machines could spend weeks on the shop floor waiting and moving from machine to machine. A workpiece may spend only 5% of its time in the shop on a machine, and only about 30% of that 5%, or 1.5%, in actual machining time greatly reducing manufacturing productivity, Fig. 7-1. Operations such as milling, contouring, drilling, counterboring, boring, spotfacing, and tapping can be performed on CNC machining centers in any sequence and require only one setup. Machining centers equipped with automatic-tool changers, rotary tables, and rotary work heads make the maching center a very versatile machine while reducing the operator intervention during the cutting cycle.

Figure 7-1: A distribution of time a part spends in a conventional shop shows only a small percentage of time is actually spent machining the part. (Cincinnati Machine, A UNOVA Co.)

Since the introduction of the first NC controlled machining centers in the late 1950s they have developed over the years into the highly-productive CNC machining centers of today. A major factor in this development was the introduction of computer controls in...