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163 9 NUMERICAL CONTROL OF MACHINE TOOLS CHAPTER CONTENTS Defnitions Numerical Control (NC) refers to the method of controlling the manufacturing operation by means of directly inserted coded numerical instructions into the machine tool. It is important to realize that NC is not a machining method, rather, it is a concept of machine control. Although the most popular applications of NC are in machining, NC can be applied to many other operations, including welding, sheet metalworking, riveting, etc. Because of the introductory character of this chapter, we will restrict our discussion only to two- dimensional machining operations (e.g. turning), which are among the most simple applications of NC. Nevertheless, most of the principles and conclusions here are also valid for more advanced NC applications. The major advantages of NC over conventional methods of machine control are as follows: v higher precision : NC machine tool are capable of machining at very close tolerances, in some operations as small as 0.005 mm; v machining of complex three-dimensional shapes : this is discussed in Section 6.2 in connec- tion with the problem of milling of complex shapes; v better quality : NC systems are capable of maintaining constant working conditions for all parts in a batch thus ensuring less spread of quality characteristics; v higher productivity : NC machine tools reduce drastically the non machining time. Adjusting the machine tool for a different product is
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This note was uploaded on 12/11/2010 for the course MECH 364 at Cornell.

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