The NC (Numeric Control) and CNC (Computer Numeric Control) are the systems implemented with the various machining tools in the various industries and factories. These Controls mainly differentiated by the fact that NC is the traditional control which allows the use of prerecorded information in the machining process. In contrast, CNC goes one step further by providing more flexibility and capability. CNC’s are capable of handling the logical functions.
The advancement in technology provided ways to produce an entity in bulk in an automated manner, and this was useful for the large scale industries. The mass production units in these industries use automatic machines or transfer lines and special purpose machines as the amount of the item needed is huge without any variation.
However, in the case where the different variety of components are needed to be produced along with the discontinuous requirement of the products (i.e., for job or batch production), the general-purpose machines are used. These traditional general-purpose machines require a skilled operator for giving the inputs to the machines. The work of an operator is not only handling the machine but also processing the information like reading drawing and checking dimensions.
While the disadvantage of these general-purpose machines is that their working entirely depends upon the operator. If the operator commits some mistake because of tiredness or inattention, it will result in the production of defective components. This is the reason the NC and CNC’s were developed to reduce the manual control elements.
Content: NC Vs CNC
|Basis for comparison||NC||CNC|
|Stands for||Numerical Control||Computer Numerical Control|
|Input mechanism||Punched tapes and punched cards||Program is fed with the help of the keyboard|
|Modification in the machine programs||Done by changing the information in the punched cards.||Can be accomplished by using a computer|
|Alteration in operation parameters||Not possible||Can be possibly changed|
|Memory to store instructions||Not available||Memory storage is present in the computer|
|Cost||Less expensive||Highly expensive|
|Accuracy||NC is moderately accurate||Extensively accurate|
|Operators||Must be highly skilled||Not much skills are required|
|Time consumption||Requires more time||Needs less time|
Definition of NC
NC (Numeric Control) systems use fixed logical functions to handle a machine tool or the machining process. NC specifies the control of the machine movements and various different functions with the help of instructions represented as a sequence of numbers. The electronic control systems drive these NC’s. Although, we cannot change the functions in the NC, meaning it is not programmable, due to the rigid wiring of the control logic and it is considered as hardwired.
In order to feed the instructions into the NC machines, the external medium is used, such as paper tape or magnetic tape. It reads the information from this tape processing it steps by step, which is stored in the memory of the control system known as ‘buffer storage’. Therefore, when the machine is operating on a single instruction block, it reads the next block from the tape and saves it in the memory of the machine control system.
Definition of CNC
The CNC stands for Computer Numerical Control, it is generated by merging the computer with the Numerical control. So, how is it different from the NC systems? It uses internal microprocessors (computers) which are comprised of memory registers. The memory registers stores various routines that can successfully manipulate logical functions. As a result, a machine operator is capable of altering the program on the control itself. This is very advantageous for the CNC machines.
Unlike NC machines, CNC machines stores the programs and logical functions in the special computer chips this is why it is called as softwired.
Features of CNC
The supplementary features of the CNC that were not available with the NC machines are:
- The part program can act as the input to the controller unit with the help of a keyboard or a paper tape so that it can be read by the tape reader within a control unit.
- The inserted part program can be repeatedly used.
- We can also revise and optimize part program at the machine tool itself.
- It uses special sub-programs made for repetitive machining sequences in order to reduce the input information.
- CNC machines can also show the results in a different form without actually executing the part program over the machine tool.
- CNC machines also permit the coverage for any changes in the modifications in the dimensions of the cutting tool.
- It also provides information on machine utilization that is useful to the management.
Key Differences Between NC and CNC
- In NC machines, the instruction are given to the machine through punched cards. As against, CNC uses the computer for giving the input to the machine.
- The NC programs can only be modified by changing the information in the punched cards. On the contrary, CNC programs can be changed directly from the computer.
- In NC machines, the operational parameters can not be altered. Conversely, in CNC machines, we can alter the operational parameters.
- Except for punched cards, there is no other mechanism is available in the NC for the storage of the information. In contrast, CNC uses computers chips for memory storage.
- CNC machines are costly and require more maintenance as compared to the NC machines.
- The accuracy and flexibility of the CNC controls is higher than the NC controls.
- NC machines require more time and expert operators for developing the products. On the other hand, CNC’s are fast and more automated and does not require much manual work.
The main distinguishing factor between NC and CNC machines is that the NC uses the punched cards directly for controlling the machine tools. On the other hand, CNC employs computers that interfaces with different MCU’s (Machine Control Units) from which the information flows.