问题描述：
The History of NC and CNC Development
Numerical Control (NC) is any machining process in which the operations are executed automatically in sequences as specified by the program that contains the information for the tool movements. The NC concept was proposed in the late 1940s by John Parsons of Traverse City, Michigan. Parsons recommended a method of automatic machine control that would guide a milling cutter to produce a "thru-axis curve" in order to generate smooth profiles on work pieces.
when Numerical Control is performed under computer supervision, it is called Computer Numerical Control (CNC). Computers are the control units of CNC machines, they are built in or linked to the machines via communications channels. when a programmer input some information in the program by tape and so on, the computer calculates all necessary data to get the job done.
On the first Numerically Controlled (NC) machines were controlled by tape, and because of that the NC systems were known as tape-controlled machines. They were able to control a single operation entered into the machine by punched or magnetic tape. There was no possibility of editing the program on the machine. To change the program, a new tape had to be made.
Today's systems have computers to control data; they are called Computer Numerically Controlled (CNC) machines. For both NC and CNC systems, work principles are the same. Only the way in which the execution is controlled is different. Normally, new systems are faster, more powerful, and more versatile.
The Applications of NC/CNC
Since its introduction, NC technology has found many applications, including lathes and turning centers, milling machines and machining centers, punches, electrical discharge machines (EDM), flame cutters, grinder, and testing and inspection equipment. The most complex CNC machine tools are the turning center, shown in Fig.4-1 (A modem turning center with a ten-station turret that accepts quick-change tools. Each tool can be positioned in Seconds with the press of a button). And the machining center shown in Fig.4-2 (Vertical machining center, the tool magazine is on the left of the machine. The control panel on the right can be swiveled by the operator) and Fig.4-3 (Horizontal machining center, equipped with an automatic tool changer. Tool magazines can store 200 cutting tools).
问题解答：
The History of NC and CNC Development
Numerical Control (NC) is any machining process in which the operations are executed automatically in sequences as specified by the program that contains the information for the tool movements. The NC concept was proposed in the late 1940s by John Parsons of Traverse City, Michigan. Parsons recommended a method of automatic machine control that would guide a milling cutter to produce a "thru-axis curve" in order to generate smooth profiles on work pieces.
when Numerical Control is performed under computer supervision, it is called Computer Numerical Control (CNC). Computers are the control units of CNC machines, they are built in or linked to the machines via communications channels. when a programmer input some information in the program by tape and so on, the computer calculates all necessary data to get the job done.
On the first Numerically Controlled (NC) machines were controlled by tape, and because of that the NC systems were known as tape-controlled machines. They were able to control a single operation entered into the machine by punched or magnetic tape. There was no possibility of editing the program on the machine. To change the program, a new tape had to be made.
Today's systems have computers to control data; they are called Computer Numerically Controlled (CNC) machines. For both NC and CNC systems, work principles are the same. Only the way in which the execution is controlled is different. Normally, new systems are faster, more powerful, and more versatile.
The Applications of NC/CNC
Since its introduction, NC technology has found many applications, including lathes and turning centers, milling machines and machining centers, punches, electrical discharge machines (EDM), flame cutters, grinder, and testing and inspection equipment. The most complex CNC machine tools are the turning center, shown in Fig.4-1 (A modem turning center with a ten-station turret that accepts quick-change tools. Each tool can be positioned in Seconds with the press of a button). And the machining center shown in Fig.4-2 (Vertical machining center, the tool magazine is on the left of the machine. The control panel on the right can be swiveled by the operator) and Fig.4-3 (Horizontal machining center, equipped with an automatic tool changer. Tool magazines can store 200 cutting tools).
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