A machine tool is a machine that is capable of producing another machine. Before the industrial revolution (1750-1830), products were largely made by hand. Each craftsman produced goods by employing hand tools, visual judgment, some simple patterns, or fixtures and a lot of skill. This method is sufficient if few products are produced. But when number of products to be produced increases, it becomes a problem of productivity. To scale-up production from a few rifles to a few thousand rifles requires specialization. The craftsman can no longer do the entire job. Specialists are needed to perform a small portion of the production over and over again. They need to produce the same part, the same way, the same size each time. For this, there is a need of machine tools. These early machine tools were used to shape metals more accurately than was possible by hand. They allowed manufacturers to consistently produce parts that were nearly identical in size, shape, and form.
Machine tools stayed roughly the same for 100 years. Innovations have changed the machine tools afterwards. Steam power was replaced by electric motors, and the accuracy was improved. Machine tools have adapted various levels of mechanical automation. The development in metallurgy had tripled the productivity of an average machine tool with high speed tool steel. NC and CNC machine tools were later introduced to match the level of productivity gained by CNC machining since the industrial revolution.
The history of numerical control and later computer numerical control parallels the history of electronics technology and computer science. The predecessor to CNC was called Numerical Control (NC). The invention of numerical control has been due to the pioneering works of John T. Parsons in the year 1940, when he tried to generate a curve automatically by milling cutters by providing coordinate motions. In the late 1940s Parsons conceived the method of using punched cards containing coordinate position system to control a machine tool. The machine directed to move in small increments and generate the desired finish. In the year, 1948, Parons demonstrated this concept to the US Air Force, who sponsored the series of project at laboratories of Massachusetts Institute of Technology (MIT). In the early 1952, the Department of Defense commissioned the Massachusetts Institute of Technology to produce the first workable NC machine.
Soon the machine tool manufacturers began their own efforts to introduce commercial NC units in the market. Meanwhile, the research continued as MIT, who were able to discover Automatically Programmed Tools, known as APT language that could be used for programming the NC machines. The main aim of APT language was to provide the means to the programmer by which they can communicate the machining instructions to the machine tools in easier manner using English like statements. The APT language is still used in widely in the manufacturing industry and a number of modern programming languages are based on the concepts of APT.
In the early days, there were electronics, but no computers. The machines were crude and difficult to program. They had no ability to perform contouring cuts or interpolate arcs. Every axis movement had to be programmed with a series of holes punched through paper tape. CNC technology really only matured in the mid-1980s with the development of relatively cheap microprocessors and electronic memory to replace punched tape. In contrast to NC machine tools, today's programs are typically stored on hard disks or other secondary storage devices, and the program can be easily modified directly at the control or at a PC workstation. The terms NC and CNC are used synonymously today, although actual NC machines are
becoming rare in most shops. Regardless of the control type, the code that is used to produce the parts is known as NC code (not CNC code).
Today, manual machine tools have been largely replaced by Computer Numerical Control (CNC) machine tools. The machines still perform essentially the same functions, but movements of the machine tool are controlled electronically rather than by hand. CNC machine tools can produce the same parts over and over again with very little variation. They can run day and night, week after week, without getting tired. These are obvious advantages over manual machine tools, which need a great deal of human interaction in order to do anything. The CNC brought major revolution in the manufacturing industry. The next development has been the combination of computer aided manufacturing (CAM) and computer aided designing (CAD) called as CAD/CAM.
