中英翻译

NC and CNC

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.When NC is performed under computer supervision,it is called Computer Numerical Control(CNC).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,andmore versatile.

1.Machines Using NC

Early machine tools were operated by craftsmen who decided many variables such as speeds, feeds, and depth of cut, etc. With the development of science and technology, a new term, Numerical Control (NC) appeared. Controlling a machine tool using a punched tape or stored program is known as Numerical Control. NC has been defined by the Electronic Industries Association (EIA) as “A system in which actions are controlled by the direct insertion of numerical data at some point. The system must automatically interpret at least some portion of this data.”

In the past, machine tools were kept as simple as possible in order to keep their costs down. Because of the ever-rising cost of labor, better machine tools, complete with electronic controls, were developed so that industry could produce more and better products at prices that were competitive with those offshore industries.

NC is being used on all types of machine tools from the simplest to the most complex. The most common machine tools are the single-spindle drilling machine, lathe, milling machine, turning center, and machining center.

1.1.Single-Spindle Drilling Machine

One of the simplest numerically controlled machine tools is the single-spindle drilling machine. Most drilling machines are programmed on three axes:

a. The X-axis controls the table movement to the right or left.

b. The Y-axis controls the table movement toward or away from the column. c. The Z-axis controls the up or down movement of the spindle to drill holes to depth.

1.2. Lathe

The engine lathe, one of the most productive machine tools, has been a very efficient means of producing round parts. Most lathes are programmed on two axes: a. The X-axis controls the cross motion (in or out) of the cutting tool.

b. The Z-axis controls the carriage travel toward or away from the headstock.

1.3.Milling Machine

The milling machine has always been one of the most versatile machine tools used in industry. Operations such as milling, contouring, gear cutting, drilling, boring and reaming are only a few of the many operations that can be performed on a milling machine.The milling machine can be programmed on three axes:

a. The X-axis controls the table movement to the right or left.

b. The Y-axis controls the table movement toward or away from the column. c. The Z-axis controls the vertical (up and down) movement of the knee or spindle.

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