Question

Which of the following is NOT correct about Direct numerical control (DNC) machines?
1. the part program is transmitted to the machine tool directly from the computer memory.
2. The tape reader is omitted in DNC machines.
3. A number of machines are controlled by a computer through direct connection and in real time.
4. In a DNC, data can’t be collected and transferred from the machine tools back to the computer.

Answer 1

Correct Answer - Option 4 : In a DNC, data can’t be collected and transferred from the machine tools back to the computer.

Explanation:

Direct Numerical Control (DMC):

• Direct numerical control (DNC) can be described as various types of manufacturing systems in which that multiple NC machines or CNC machines are remotely controlled from a host computer or DNC control of multiple machines tools by a single computer through a direct connection. 
• Direct numerical control (DNC) is defined “as a system that integrates multiple machines by direct connection through a central computer”.
• The central computer is designed to provide instructions on demand to each machine's tools. The central computer also retrieves data from machines. Therefore, there is two-way information is exchanged between the central computer and each of the machine tools.

Following are the functions of the DNC machine:​​

• For using the collecting the data storage and editing programs for all machine tools connected to it and transfer it to the computer.
• The tape reader is omitted in DNC machines.
• To give the stored programs to the connected machines on demand.
• For to post-process part programs written in higher-level languages like APT.
• To combine CAD with CAM by having a common database.
• The part program is transmitted to the machine tool directly from the computer memory.
• To provide a link between a central computer and various plant computers connected through modems and networks even though the plants may be placed several kilometers away from each other in real-time.​