VI. Make a short report on numerical control and the role it plays in automation.

Date: 2015-10-07; view: 424.

V. Find in the text the names of 5 machines. Mention the function of every machine.

Text 9b

Translate the text in written form using a dictionary:

from nc to cnc

Numerically controlled (NC) machine tools are machines that are automatically operated by commands that are received by their processing units. NC machines were first developed soon after World War II and made it possible for large quantities of the desired components to be very precisely and efficiently produced (machined) in a reliable repetitive manner. These early machines were often fed instructions which were punched onto paper tapes or punch cards. In the 1960s NC machines largely gave way to CNC, or computer numerical control, machines. (GE had its NC 550 workhorse for many years until they came out with their first CNC (model 1050) in August 1974.).

Numerical Control (NC) was the precursor of today's Computer Numerical Control (CNC), which controls the automation of machine tools and the inherent tool processes for which they are designed. The CNC machine tool is the servo actuator of the CAD/CAM (Computer Assisted Design/Computer Assisted Manufacturing) technology both literally and figuratively. CNC inherits from NC the essential character of by-the-numbers interpolation of transition points in the work envelope of a multi-axis motion platform, based on the separation of programming from operations. The set of instructions, or "program" (usually an ASCII text file in which, in its simplest form, a line of text specifies the axial coordinates of a point in the work envelope) is prepared from a blueprint or CAD file and transferred to the memory of the CNC via floppy drive, serial data interface or a network connection. Once stored in the CNC memory and selected, the program is executed by pressing the appropriate key on the machine operator panel.

Text 9c

Look through the text and do the tasks below:

Microcomputers and numerical control

Traditional numerical control (NC) is based upon the movement being controlled via a pre-prepared punched paper tape. The development of microprocessors and compact computers has extended the sophistication of the control available, so that the term "computer numerical control”(CNC) is used.

Numerical control machine tools have been used for many years prior to the development of the microelectronics. The application of microcomputers allows for more sophisticated control. When metal is machined, its cutting properties can vary throughout the workpiece¹, particularly if it is a forging² or casting³. Microcomputers can add a further aspect of adaptive control by reacting to the current power consumption⁴, torque, etc. of the driving motors.

Due to the nature of microcomputer systems a distributed processing approach⁵ can be adopted for the control of the various functions of a machine tool. This also allows a modular approach to the development of the hardware and software. In addition, greater operator interaction for unexpected situations is possible due to the work cycle not being restricted to preprogrammed punched paper tape.

Instead of being a substantial part of the cost of a machine tool, the use of microcomputers makes the numerical control cost less and adds relatively little to the cost of the machine tool.

The calculation of optimum tool life⁶ from theoretical laws, for example, is not practical because of the variations in the properties of the actual workpiece. Optimum tool life more realistically should be based upon actual experience. It is feasible⁷ nowadays to monitor and analyse data to recalculate continuously optimum tool life.

Notes:

¹workpiece – заготовка

²forging – поковка

³casting – отливка

⁴consumption – потребление, расход

⁵ approach – концепция; метод; подход

⁶ tool life – стойкость инструмента

⁷ feasible – осуществимый; возможный