Numerical control machine-tools
учебно-методический материал по английскому языку (11 класс)

Numerical control machine tools

What machine tools do you know? What is numerical?

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When machining a workpiece on a metalworking machine, the tool performs relative movements (strokes). The combination of movements repeated in the manufacture of every part is called a machining cycle. Each cycle is characterized by the magnitude of the moves and their sequence. In the general case, the machine control program is a sequence of commands that ensure the proper work of machine tool elements.

When manually controlling the machine tool, the worker sets the required sequence of commands. He studies the drawing and technical documentation and draws up a work program, processes the workpiece, controls the part, compares it with the drawing and, if there is a mismatch, eliminates inaccuracies.

With automatic machine control, the required sequence of commands is set by the program. The most flexible and fast readjustments are possessed by machine tools with programmed control, which set the program of work in alphanumeric code.

According to the type of control, program-controlled machines are divided into machines with cyclic program control systems (CPU) and machines with numerical control systems (CNC).

The CPU allows programming the machine cycle (partially or fully), the processing mode and tool change and set the amount of movement of the machine actuators. It is a closed-type analog control system and has a sufficiently high flexibility. This means that it provides an easy change in the sequence of switching on the equipment (electrical, hydraulic, pneumatic, etc.) that controls the elements of the cycle.  

The advantages of CPU are simplicity of design and maintenance, as well as low cost; the disadvantage is the labor intensity of size adjustment of the stops and cams.

Machine tools with CPUs are used in medium, high volume and mass production of parts of simple geometric shapes. The systems of the CPU are equipped with turning-turret, turning-copying, vertical milling, copy-milling, vertical drilling machines, aggregate machines, industrial robots, etc.

Numerical control of machine tools (CNC) means control (by a program specified in the alphabetical code) by the movement of the machine parts, their speed of movement, the sequence of the processing cycle, the cutting mode, and various auxiliary functions.

The numerical program control of metal-cutting machines is the management of the machine’s working elements when processing a workpiece according to the control program, which is a sequence of commands in alphanumeric code.

The CNC Unit is placed near the machine (in one or two cabinets) or directly on the machine. All data required for processing the workpiece on the CNC machine tool is received from the control program, which contains two types of information — geometric and technological. Geometric information — the coordinates of the reference points of the toolpath, and technological information — data on speed, feed, number of the tool, etc.

The advantages of CNC are:

1. High performance.
2. The combination of accuracy, productivity, and the flexibility of the equipment     enables the integrated automation of single and mass production.
3. Parts are interchangeable, which reduces the time required for fitting work during assembly.
4. The terms of transition to the manufacture of new parts are significantly reduced.
5. The cycle time for manufacturing parts is shortened, and work in progress is reduced.
6. Mechanical engineering is reequipped with new equipment based on modern electronics and computer technology.

Questions:

1. What is a machining cycle?
2. What is a machine control program?
3. What types of program-controlled machines are divided into according to the type of control?
4. What is numerical control of machine tools?
5. Where is the CNC Unit placed?
6. How is all data required for processing the workpiece on the CNC machine tool received?
7. What are the advantages of CNC?

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