bhel jhansi

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BUNDELKHAND INSTITUTE OF ENGINEERING AND TECHNOLOGY JHANSI

BY :NAME

INDUSTRIAL TRAINING SEMINAR

INTRODUCTION TO CNC MACHINEFrom

BHEL JHANSI

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INDEXIntroduction of BHEL

Products

History

Introduction to CNC

Need of CNC

Types of CNC Machine

Block Diagram of CNC Machines

Working of CNC Machine

Elements of CNC

Input devices

Machine control unit

Driving System

Feedback System

Display Unit

CNC Programming Basics

Advantages

Challenges

Conclusions

BHEL

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BHEL is India's largest engineering and manufacturing Enterprise.

Established in 1956. Got 'Maharatna' status by the Government of India on 1

February 2013. More than 150 project sites across India and abroad. The company has added more than 1,24,000 MW to the

country's installed power generating capacity so far.

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PRODUCTS

Locomotive Plant Boilers Auxiliaries Plant. Transformer. Power electronics. Electrical machines. Insulator Plant Oil field equipment.

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HISTORY

The first NC machines were built in the 1940s and 1950s by Prof. John T Parson.

US Air Force teamed up with MIT to develop a programmable milling machine (1949).

CNC machine came into existence after evolution of computer around 1980.

Modern CNC Machine are improving further as the technology is changing with a variety of functions according to applications.

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INTRODUCTION

Numerical control is a method of automatically operating a manufacturing machine based on a code of letters, numbers, and special characters.

The numerical data required to produce a part is provided to a machine in the form of a program, called part program or CNC program.

The program is translated into the appropriate electrical signals for input to motors that run the machine.

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NEED OF CNC

Increase production rate. Stabilize manufacturing costs. Highly accurate over traditional machines. More operations can be performed with each

setup Repeatability, reduced scrap loss, and high production rates.

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TYPES OF CNC MACHINES

There are many different types of CNC Machines used in industry, Such as:

Mills and Machining Centers Lathes and Turning Centers. Drilling Machines Wire cut Machines. Flame and Laser-Cutting Machines

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BLOCK DIAGRAM

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WORKING OF CNC

All computer controlled machines are able to accurately and repeatedly control motion in various directions. Each of these directions of motion is called an axis. Depending on the machine type there are commonly two to five axes.

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Open loop and Closed loop controls

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Elements of CNC Machine

Input Device Machine Control Unit Machine Tool Driving System Feedback Devices Display Unit

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Input Devices

Floppy Disk Drive. USB Flash Drive. Serial communication.

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Machine Control Unit Data Processing Unit On receiving a part programme, the DPU firstly interprets and encodes the

part programme into internal machine codes.

Control Loop Unit Data from the DPU are converted into electrical signals in the CLU to control

the driving system to perform the required motions.

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Driving System This system usually uses electric motors although hydraulic motors are

sometimes used for large machine tools. DC servo motor The principle of operation is based on the rotation of an armature winding

in a permanently energized magnetic field. Stepper Motor A stepper motor is a device that converts the electrical pulses into discrete

mechanical rotational motions of the motor shaft

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FEEDBACK DEVICES

Positional Feed Back Devices

A linear transducer is a device mounted on the machine table to

measure the actual displacement of the slide.

Velocity Feedback Device

The actual speed of the motor can be measured in terms of voltage

generated from a tachometer mounted at the end of the motor shaft.

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Display UnitThe Display Unit serves as an interactive device between the machine and the operator. Operator Control PanelTo facilitate two-way communication between the user, CNC system and the machine tool. Video Display Unit (VDU). Keyboard. Machine Control Panel (MCP)It is the direct interface between operator and the NC system, enabling the operation of the machine through the CNC system.

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CNC Programming Basics

CNC instructions are called part program commands.

When running, a part program is interpreted one command line at a time until all

lines are completed.

Commands, which are also referred to as blocks, are made up of words which

each begin with a letter address and end with a numerical value.

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Advantages Easier to program; Easy storage of existing programs; Easy to change a program Avoids human errors CNC machines are safe to operate Complex geometry is produced as cheaply as simple ones Usually generates closer tolerances than manual machines

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Challenges

Costly setup, skilled operators Computers, programming knowledge required Maintenance is difficult

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Conclusion The advantage of a CNC system are that the operation of a conventional

machine is removed and the part production is made automatic. It reduces the labor work and hence highly efficient in the manufacturing

process. BHEL generally uses CNC machines to achieve its manufacturing targets. For

manufacturing works of large scale it is very difficult to work with manual machines as they are time consuming. CNC machines have their wide scope because they are easy to handle, the work becomes easier and jobs are done with perfection.

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THANK YOU