The machining or cutting of metals portion of manufacturing became important around the
time of the industrial revolution. In 1775, John Wilkinson invented a cannon-boring
machine (lathe) in England .He adapted that machine for boring the cylinders for
Boulton & Watt's steam engines. His boring process was the only one of its kind to produce
the smooth, tightly tolerance bores required of the cylinder of a steam engine.
A bit later in the year 1818 Eli Whitney (inventor of the cotton gin) invented a milling
machine in New Haven Connecticut .Prior to the milling machine, a machinist's tools
were primarily files and required a highly skilled operator. The milling machine allowed a
less skilled operator to make the same quality of parts as the skilled operator with the file.
The spindle of Eli Whitney's milling machine was moved from being horizontal to being
vertical. This is commonly seen in the Bridgeport style knee-mill.
In year 1952 John Parsons invented NC (Numeric Control) milling machine. Parsons
worked to attach servomotors to the x and y axis controlling them with a computer that
reads punch cards to give it positioning instructions .The reason for devising such a
system was to machine complex shapes like arcs that can be made into airfoils for
airplanes.
Today, modern machinery are CNC (Computer Numeric Control) milling machines and
lathes. A microprocessor in each machine reads the G-Code program that the user creates
and performs the programmed operations. Personal Computers are used to design the parts
and are also used to write programs by either manual typing of G-Code or using CAM
(Computer Aided Manufacturing) software that outputs G-Code from the users input of
cutters and tool path . CNC can be classified according work as lathes, milling machines,
laser cutters and other industrial tools. The CNC term refers to a large group of these
machines that utilize computer logic to control movements and perform the
metalworking[2].
Lathes are designed for the precise machining of relative hard materials. These rigid
machine tools remove material from a rotating work piece via the (typically linear)
movements of various cutting tools, such as tool bits and drill bits.
Rotating is the way that lathe shapes the material and with a rapid speed, this is done by
pressing a fixed cutting or abrading tool. Now a days, lathes equipped with the CNC to help
fashion tool and products.
The machine is controlled electronically via a computer menu style interface, the program
may be modified and displayed at the machine, along with a simulated view of the process.
The operator needs a high level of skill to perform the process, however the knowledge
base is broader compared to the older production machines where intimate knowledge of
each machine was considered essential. These machines are often set and operated by the
same person, where the operator will supervise a small number of machines (cell)[3].
Milling is the process of cutting away material by feeding a workpiece past a rotating
multiple tooth cutter. The cutting action of the many teeth around the milling cutter
provides a fast method of machining. Milling machines are classified to, peripheral milling,
Another classification of milling according to the movement is the vertical and horizontal
milling. In the vertical mill, the spindle axis is vertically oriented. The horizontal mill has
the same sort of x–y table, but the cutters are mounted on a horizontal arbor across the
table[4].
All CNC machine types share this commonality: They all have two or more programmable
directions of motion called axes. An axis of motion can be linear (along a straight line) or
rotary (along a circular path). One of the first specifications that implies a CNC machine's
complexity is how many axes it has. Generally, the more axes, the more complex the
machine .