TABLE OF CONTENTS In many applications for a CNC machining center, the material has to be removed from the inside of a certain area, bounded by a contour and a flat bottom. This process is generally known as pocketing. To have a true pocket, the contour that defines the pocket boundary must be closed. However, there are many other applications, where the material has to be removed from an open area, with only a partial contour defined. An open slot is a good example of this type. This chapter looks at applications of closed pockets, partial pockets, slots and various programming techniques for internal material removal.
A continuous contour on which the start point and the end point is in a different location, is called an open contour. Continuous contour defined in the program that starts and ends at the same point location, is called a closed contour. From the machining point of view, the major difference between an open and closed contour is how the cutting tool reaches the contour depth.
An open boundary is not a true pocket, but belongs to a related category. Machining of this kind of a contour is quite flexible, as the tool can reach the required depth in an open space. Any good quality end mill in different varieties can be used to machine an open boundary.
The excessive material within a closed boundary can be removed in two ways, depending on the cutting operation.
