Direct Numerical Control (DNC) is a process set in a manufacturing unit where a set of machines is controlled by a programmed computer with the help of a direct connection to the same.
Set of machines mentioned above use computer numerical control (CNC).
It is also called as distributed numerical control.
It is based on real-time data and involves data collection from the machines and passing the same to the mainframe, at regular intervals. The operator will be in control of the mainframe computer through remote accesses.
A DNC will not contain a tape reader. Instead, it has several part programs that are transferred to the machines from the computer memory.
In a few scenarios, the machine controllers will not be able to store the entire program because of the lack of memory space.
In such situations, the program is stored in a different computer and the directions are sent directly to the machines from that location.
The DNC is designed in such a way that it provides separate instructions to every machine on the system. In case, where the machine immediate control command, they are sent across immediately.
What does a DNC machine contain?
A DNC machine contains a mainframe computer, huge memory capacity, connectivity between the machines & computers, and machine tools.
Usually large organization uses DNC system because it is very costly.
Functions of Direct Numerical Control (DNC) system
- Central computer is used to store and edit the programs for all machine tools connected to it
- On requirement basis gives the stored program to the connected machines
- By having a common database it combines CAD with CAM
- Provides a link between central computer and plant computers connected through network even though plant computers are very far
- Direct numerical control avoids the usage of punched taps and the reader from the system.
- It helps the business to understand production performance by getting several reports and useful data from the machines.
- It helps in building a centralized control for the machines.
- Useful for time management and increased productivity.
- Convenient storage of part programs in several computer files.
- Helps the company to make higher-level decision
- It helps the business to increase computational ability
- It supports management information system effectively
- DNC is very expensive and it requires high automated areas
- Because of its central control system, if the computer fails then all the activities of machines would be stopped
Types of direct numerical control
RS232 – based DNC system: Operates with a switch box or multi-port cable connections to connect several machines.
Terminal-based DNC system: A CNC terminal is created to connect several programs.
Network-based system: Direct access to NC programs without installation of terminals and is thus highly efficient.
9 Major differences between Direct Numerical Control and Computer Numerical Control
- DNC means direct numerical control, CNC means computer numerical control.
- In CNC working operations can not be controlled remotely. But in DNC we can control working operations with remote.
- CNC transfers machine instructions. DNC controls the information and manages the information distribution to more verities of computers.
- CNC machine controls only one NC machine, whereas by using a DNC programmer you can control more than one NC machine as per the requirements.
- DNC systems can be placed at a distance from machines. Because it not an integral part of machines. But CNC is an integral part of machines.
- CNC system has low processing power, DNC system has high processing power.
- DNC did not remove the tape, while CNC is a feedback system.
- The maintenance cost of the DNC machine is low but the maintenance cost of the CNC system is high.
- CNC system amplifies the capacity of the particular computing machine tool. DNC system controls the equipment and also acts as a management information system.
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