Numerical Control (NC), which will summarize the CNC machine tools before the CNC machine tools, and will pass to explain the CNC machines, is widely applied in all kinds of machine tools used in the processing of metal and other types of materials by removing chips. Some of these stalls are:
Lathe Machine
Milling Machine
Drilling Machine (Drilling Machine)
Boring Machine
Grinding Machine
All NC machine tools have their own unique capacity, operational capabilities and some characteristic features. For this reason, no processing feature that the machine does not have can be made to that machine.
Since there is no memory in NC machine tools, block data is read and processed sequentially in such machines. During the manufacture of a workpiece, the machine’s control unit (Machine Control Unit) reads all the data in a block and performs the required processing operations on the machine. After the operations are completed, they are passed to the next block. This process continues sequentially until the end of the program.
Part programs have different numerical (numeric) and alphanumeric (alpha-numeric) values and meanings according to their location and arrangement on the standard paper strip.
The physical design and construction of CNC machine tools are the same as NC machines. However, a number of functional features that are practically impossible and uneconomical to be made in NC machine tools have been added to such machines.
These features are;
The part programs loaded on the machine can be stored in the memory of the control unit, called from here and executed many times.
There is a special power supply that feeds the machine control unit. Even if the energy of the machine is cut off, the program etc. data is retained.
Changes that are planned to be made on the part program can be made easily and at any time. The modified program is both executed and stored in the memory in its final form.
Some routine operations are defined as cycles in the program and are used where necessary. (Hole drilling, hole enlargement, rectangular pocket milling, stepped and taper turning, radius turning etc.)
The programming of the operations that need to be repeated on a workpiece, except for the loops, are written once in the main program (Main Program) and they are named as Sub Program (Sub Program). During the implementation of the main program, these subprograms are called where necessary and the process is completed. As an example, we can give the program of the ADANA script. Here, a subprogram is written for the letter A. However, this program is applied only by making coordinate definitions at different X distances. Thus, the normal program is shortened by 40%.
When a part is programmed, it is normally machined on cutters of a certain type and diameter. During programming, certain dimensional shifts must be made, taking into account the cutter diameter. However, with the ease of Cutter Compensation, these shifts are made by the CNC Control Unit during the execution of the program. When the cutter used is broken and there is no other cutter of the same diameter, it provides the convenience of continuing the program from where it was left off with a cutter of different diameter. The control unit makes the necessary dimensional shifts according to the diameter of the new cutter.
Thanks to the computer, it reaches optimum values in position changes, number of revolutions and advances. As a result, ideal working conditions are provided in CNC machine tools. Since the diameter of the workpiece is constantly changing in the face turning process, the number of revolutions must also change accordingly (Constant Surface Speed). The resulting surface quality and precision are incomparably better than conventional machines (Conventional Machines).
As a result of the use of computers in the CNC control unit, it has the advantage of being able to communicate with many other computers and systems.
It is possible to simulate the part program graphically with the help of the Visual Display Unit before proceeding to the part production.
Changing the cutting tools is done without any manual intervention. For this, rotating turrets (Rotery Turrets) or crawler cutter magazines are used.
