In this article, you’ll learn what is a DNC machine with its Working principle, Types, Functions, Components, advantages, and more with PDF.
DNC Machine [Distributed Numerical Control System]
Direct numerical control (DNC) can be described as a various type of a manufacturing system in which that multiple NC machine 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. It is shown in the diagram below.
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 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 tool.
Overview of DNC Machine
A DNC is particularly described as “A system connecting a group of numerically controlled machines to memory for part program or machine program storage with provision for on-demand delivery of data to machines” by Electronic Industries Association (EIA).
In DNC, many NC machines are directly controlled by computers, removing enough hardware from a separate controller of each machine tools. The part-programs are downloaded to machines directly from a computer memory (thus bypassing tape readers).
The basic DNC system needs following the basic components are the mainframe computers, memory, communication networks, NC machine tools.
The communication network can be arranged either through connecting the remotely located computer, with long cables to the individual machine control directly or connecting the mainframe computer with a small computer at individual operator’s station called as satellite computer.
DNC systems are costly and preferably used in large organizations. The combination of DNC/CNC makes possible to eliminate the use of the programme as the input media for CNC machines.
DNC downloads computer programs directly into CNC computer memory. This decreases the amount of communication required between the central computer and each machine tool.
Functions of DNC System
Following are the functions of the DNC machine:
- For use the central computer for storage and editing programs for all machine tools connected to it.
- 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.
- 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 kilometres away from each other.
Components Used in DNC Machine
Following are the main components used in CNC machine:
- Central computer
- Bulk memory for storing programs
- Communication network
- NC machine
Types of DNC system
Following are the main two types of DNC system:
- Behind the Tape Reader (BTR) system
- Specialised MCU
1. Behind The Tape Reader (BTR) System
In this type of system, the computer is connected directly to the regular NC controller unit. The operation of the system is similar to conventional NC, except for the source of command instructions.
The controller unit employs two temporary storage buffers to get the blocks of instructions from the DNC computer and turn them into machine operations. The one buffer is getting a block of data, the other is providing control instructions to the specific machine tool. This system cost is very low.
2. Specialised MCU
In specialised MCU system, replace the normal controller unit with the special machine control unit. The special control unit is created to help communication between machine tools and computers. The specialised MCU configuration achieves a better balance between the accuracy of interpolation and the faster removal rate of the metal than is usually possible with the BTR system.
Advantages of DNC System
Following are the advantages of the DNC system:
- The DNC rejects the use of tape readers, which are absolutely the weakest component of the NC system.
- Time-sharing by central control makes it possible to keep close control over the entire machine shop.
- The huge memory of DNC allows it to store a large number of part programs for subsequent use. It also receives the memories of NC control unit.
- Presence of a central bulk memory allows the same program to be run on different machines at the same time without duplicating it at individual places.
Disadvantages of DNC System
Following are the disadvantages of the DNC system:
- DNC uses a central control and in an event of computer failure, the complete activities of the machine shop would come to a standstill.
- DNC is expensive and its use is practical in areas where high automation is required.
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