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Types of Milling Machines



There are several different types of milling machines available which are suitable for a variety of machining applications. Beyond classification based solely on either machine configuration or the number of axes of motion, milling machines are further classified based on the combination of their specific characteristics. Some of the most common types of milling machines include:

Knee-type
Ram-type
Bed-type (or manufacturing-type)

Planer-type

Knee-type: Knee-type milling machines employ a fixed spindle and vertically adjustable worktable which rests on the saddle supported by the knee. The knee can be lowered and raised on the column depending on the position of the machine tool. Some examples of knee-type milling machines include floor-mounted and bench-type plain horizontal milling machines.

Ram-type: Ram-type milling machines employ a spindle affixed to a movable housing (i.e., ram) on the column, which allows the machine tool to move along the XY axes. Two of the most common ram-type milling machines include floor-mounted universal horizontal and swivel cutter head milling machines.  

Bed-type: Bed-type milling machines employ worktables affixed directly to the machine bed, which prevents the workpiece from moving along both the Y-axis and Z-axis. The workpiece is positioned beneath the cutting tool, which, depending on the machine, is capable of moving along the XYZ axes. Some of the bed-type milling machines available include simplex, duplex, and triplex milling machines. While simplex machines employ one spindle which moves along either the X-axis or Y-axis, duplex machines employ two spindles, and triplex machines employ three spindles (two horizontal and one vertical) for machining along the XY and XYZ axes, respectively.

Planer-type: Planer-type milling machines are similar to bed-type milling machines in that they have worktables fixed along the Y-axis and Z-axis and spindles capable of moving along the XYZ axes. However, planer-type machines can support multiple machine tools (typically up to four) simultaneously, which reduces the lead time for complex parts.

Some of the specialized types of milling machines available include rotary table, drum, and planetary milling machines. Rotary table milling machines have circular worktables which rotate around the vertical axis and employ machine tools positioned at varying heights for roughing and finishing operations. Drum milling machines are similar to rotary table machines, except the worktable is referred to as a “drum” and it rotates around the horizontal axis. In planetary machines, the worktable is stationary, and the workpiece is cylindrical. The rotating machine tool moves across the surface of the workpiece cutting internal and external features, such as threads. 

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