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Numerical Control Tool Programmers


One of the earliest attempts to automate machinery occurred in the early 1700s, when a system of punched cards was used to control knitting machines in England. Holes in punched cards controlled mechanical linkages, which directed yarn colors and allowed various patterns to be woven into a piece of material. Automated machinery did not progress much further, though, until the computer was developed in the late 1940s.

The first use of numerical control (NC) was in 1947. John Parsons, owner of a helicopter rotor blade manufacturing company, experimented with regulating milling machinery through numerical control. He discovered that parts made through automated control were more accurate than those made manually. The U.S. Air Force, which had a need for uniquely shaped machined parts, contracted with Parsons and the Massachusetts Institute of Technology to develop a machine tool that could be programmed to make contoured parts automatically. In 1952, they built the first numerically controlled machine tool. Shortly afterward, Giddings and Lewis, a large machine tool builder, built an NC profiling mill.

By 1958, other companies followed with NC machine tools of their own. Early NC tools used paper tapes to program machines. Machine commands were standardized and assigned numerical codes. These codes were then sequenced in the order in which the machine was to perform various operations. After these codes were punched onto a paper tape, a machine operator loaded the tape into a tape reader, loaded raw material, and started the machine, which ran automatically. As numerical control technology evolved, plastic tapes replaced paper, and magnetic spots rather than holes were used to represent codes. Unfortunately, this form of numerical control did not handle changes well; a whole new tape had to be created when process modifications were required. This was a slow and tedious process.

By the 1980s, computer numerical control (CNC) began to replace older NC methods. CNC programmers write computer programs to sequence the various steps a machine needs to complete. Many machines now have computers or microprocessors built into them. Programmers can easily revise the sequence of operations or other elements. In addition, these programs can store information about the machine tool operation (such as number and dimensions of parts made), request additional raw materials, and record maintenance requirements.

Another advancement in numerical control is direct numerical control, a process in which several machines are controlled by a central computer. This eliminates the need for individual machine control units and gives programmers more flexibility for modification and control.

The use of CNC machine tools has grown steadily during the last decade and is expected to increase in the future. New applications, such as versatile machining centers, are being developed that allow machines to provide multiple capabilities. Engineers and researchers continue to explore ways to improve the speed, precision, and versatility of machine processes through the use of numerical control and other automated processes.

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