CNC Machining Part 2

The machining or cutting of metals portion of manufacturing became important around the time of the industrial revolution. In 1775, John Wilkinson invents a cannon-boring machine (lathe) in England. He immediately adapted this machine for boring the cylinders for Boulton & Watt's steam engines. This boring process was the only one of it's 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) invents 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. This milling machine found use making rifles for the government.

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. The knee-mill is a vertical spindle milling machine that can move the workpiece in the x, y, and z directions by increments of 0.001" by turning the appropriate hand crank.

The year 1952 brought Mr. John Parsons NC (Numeric Control) milling machine. Parsons worked to attach servomotors to the x and y axis controlling them with a computer that reads punches 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. This was not a trivial task to attempt with a manual milling machine, so the NC milling machine was born.

Today modern machinery is 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.