06-03-2013, 03:57 PM
Study of CNC Machines And NC Machines.
CNC Machines.pptx (Size: 299.16 KB / Downloads: 72)
Numerical Control
Numerical Control is the operation of a machine using coded instructions which consists of letters, numbers, punctuation marks, and other symbols. This coded information is known as the Part Program
These types of systems are referred to as “hardwire controls” and were popular from the 1950’s to 1970’s.
Computer Numerical Control
CNC
NC machine with a microprocessor as an integral part of the MCU. Data handling, control sequences, and response to input is determined by the integrated microprocessor.
Started in the 1970s
Computer and Numerically Controlled Machines
Numerically Controlled (NC)
NC is the operation of M/c tool by a series of coded instructions consisting of numbers, letters of the alphabets and symbols, which the MCU (Machine Control Unit) can understand.
Computer numerically controlled (CNC)
When numerical control is performed under computer supervision, it is called computer numerical control (CNC). Computers are the control units of CNC machines. A programmer enters some information in the program, but the computer calculates all necessary data to get the job done.
For both NC and CNC systems, working principles are the same. Only the way in which the execution is controlled is different. Normally, new systems are faster, more powerful, and more versatile.
Important terms related to CNC machining
Machine Zero - Machine zero is a point at the origin of the machine’s coordinate measuring system. All the Axis movements and other dimensions are measured from this point. It is similar to the origin of coordinate measuring system.
Machine reference point - It refers to the initial point of return for the purpose of measuring/feedback systems. Whenever a CNC machine is switched on the feedback system has to be initialized by referring this point on every axis.
Work Zero - This is the origin for the measuring of dimensions of workpiece. The programmer is free to select it anywhere on the drawing.
Absolute measuring system - In this measuring system all the dimensions are made from the work zero, which defined. The machine control uses work zero as the reference point to position the tool during program execution. The main advantage of programming in absolute system is that any point can be readily changed without affecting subsequent dimensions.
CONCLUSION
The importance of lathes and milling machines even if they are conventional cannot be undermined. These machines have played a real important role in bringing about industrial revolution and have laid the foundations. But the bringing about of the new technology in the present era is very important. The conventional machines are required in small quantities whereas the CNC machines must be increased to improve the quantity and quality of production.