The components of an NC machine are Program of instructions, machine control unit(MCU) and the machine tool.
As the name says program of instructions, the programmer plans the sequence of operations to be taken place and writes it using numerical codes. These codes are punched in the punch cards also called tape readers. These codes are sent to the machine control unit that continuously converts the codes into machine tool movement. The machine tool is the main component of the NC machine as it executes the program written. The block diagram for NC machine is shown below.
Just like the NC machine, CNC machine is used for the various manufacturing process, mostly metal cutting processes. The machine tool in CNC is controlled by the programs written just like the NC machine.
Now, the difference is that in NC machine the programs are fed into the punch cards and in CNC machine the programs are written with the help of keyboard that is directly fed to the computers.
These programs are stored in the computer memory which can be used for different parts and these are not needed to be repeated many times. The programs can be easily edited according to the requirement. The block diagram for CNC machine is as shown.
Working Of CNC Machine-
The CNC machine works with the execution of the programs at the machine tool. The program is customized with CNC machining language called G-codes or M codes. Using these codes the description of the operation that is to be perform is written. The description of coordinates, the location of the machine tool, speed and feed rates.
At first from the 2D drawing the program is written and loaded in the computer for a trial run which is called cutting air. In this trial run program, the mistakes of a programmer can be rectified thereby saving the time and machine work, wastage of metal. If the trial run runs successfully, the program is run for the final machining operation.
You can refer to this paper for more concept about NC and CNC machine:- Paper
|DESCRIPTION||NC MACHINE||CNC MACHINE|
|FULL FORM||Numeric Control Machine||Computer Numeical Control Machine|
|CONCEPT||Programs are stored in punch card and the MCU processes it for the movement of machine tool||Programs are written through the computer and stored in the memory for machine tool operation|
|STORAGE||Punch cards are used||Directly stored in computer memory|
|CODES||Numeric, symbols, letters||G-codes and M-codes|
|MAINTENANCE AND COST||Less maintenance so the the maintenance cost is less||High maintenance so the the maintenance cost is high|
|PROGRAM EXECUTION||Requires more time for executing the program||Requires less time for the program execution|
|ACCURACY||Less compared to CNC||High|
|OPERATOR SKILL||Highly skilled operator is required||Semi-skilled operators|
|RUNNING TIME||Cannot run continously||Can run for 24 hours|