History of Milling Machines
There is no single inventor or event that led to the modern milling machine. Rather, it developed through a series of innovations, experiments, and improvements over many years.
Early milling machines can be traced to Samuel Rehe around 1783. Later, Simeon North and Robert Johnson contributed to the development of early American milling machines during the 1810s. Eli Whitney is traditionally associated with the milling machine, although his claim as its inventor is disputed.
In 1861, Brown & Sharpe introduced the Universal Milling Machine, an important development in horizontal milling. Finally, Bridgeport's turret mill, introduced in 1938, popularized the highly versatile vertical knee-type milling machine.
Components of a Vertical Milling Machine
A traditional vertical knee-type milling machine has seven main structural components:
Head:
Houses and supports the spindle and its drive mechanism.
Ram:
Supports the head and allows it to move forward and backward.
Column:
Main structural body supporting the knee, ram, and head.
Knee:
Supports the saddle and table and moves vertically along the column.
Table:
Holds the workpiece and provides X-axis movement.
Saddle:
Supports the table and provides Y-axis movement.
Base:
Supports the machine and provides stability and rigidity.
Working Principle of a Milling Machine
A milling machine removes material from a workpiece using a rotating multi-tooth cutting tool. The workpiece is securely held, usually on the machine table, while controlled relative movement between the cutter and workpiece produces the desired shape.
Unlike a lathe, where the workpiece primarily rotates against the cutting tool, in conventional milling the cutting tool rotates; the workpiece is generally held stationary relative to the table and fed along one or more axes.
Each cutting edge removes a small amount of material as it passes through the workpiece. By controlling the cutter speed, feed rate, depth of cut, tool geometry, and relative movement between the cutter and workpiece, a milling machine can accurately produce flat surfaces, slots, pockets, contours, holes, and many other geometries.