Page 692 - Manufacturing Engineering and Technology - Kalpakjian, Serope : Schmid, Steven R.

Section 24.2 Milling and Milling Machines 673

Bed-type Milling Machines. In hed-type ma-
chines, the worktable is mounted directly on the Cutters Cross-rail
bed, which replaces the knee and can move only
Spindle carrier
longitudinally (Fig. 24.16). These machines are Spindle Carrier
not as versatile as other types, but they have
high stiffness and typically are used for high- Workpiece
production work. The spindles may be hori-
zontal or vertical and of duplex or triplex types
(with two or three spindles, respectively), for the
simultaneous machining of two or three Work-
Table Bed
piece surfaces.
Other Types of Milling Machines. Several other FIGURE 24.16 Schematic illustration of a bed-type milling machine.
types of milling machines are available (see also
machining centers, Section 252). Planer-type
milling machines, which are similar to bed-type machines, are equipped with several
heads and cutters to mill different surfaces. They are used for heavy vvorkpieces and
are more efficient than simple planers (Section 24.3) when used for similar purposes.
Rotary-tahle machines are similar to vertical milling machines and are equipped with
one or more heads for face-milling operations.
Milling machines have been rapidly replaced by computer numerical-control
(CNC) machines for all but the lowest production quantities. These machines are
versatile and capable of milling, drilling, boring, and tapping with repetitive accuracy
(Fig. 24.17). Also available are prohle milling machines, which have five axes of

Control panel Head

--- Column
Cutting tool

Worktable

Base

FIGURE 24.11 A computer numerical-control (CNC) vertical-spindle milling machine. This
machine is one of the most versatile machine tools. The original vertical-spindle milling
machine used in job shops is still referred to as a “Bridgeport,” after its manufacturer in
Bridgeport, Connecticut. Source: Courtesy of Bridgeport Machines Division, Textron, Inc.