Presentation OfIndustrial Training
on“INTRODUCTION TO CNC
MACHINES”
BHARAT HEAVY ELECTRICALS LIMITED,
HARIDWARBY:
DIKSHA GANGWARB. Tech. (EC) Final YearSRMSCET1101431026
CONTENTS •About BHEL
•CNC Introduction•History of CNC Machines•CNC Machines-How do they look like?•Elements of CNC Machines•Block Diagram of CNC Machines•How CNC works•Control: Open loop and Closed loop•Modes of Operation•Features of CNC machinery•CNC Programming Basics•Advantages of CNC•Challenges•Conclusion
About BHEL•Bharat Heavy Electrical Limited is power plant equipment manufacturer based in New Delhi, India
•It was established in 1964
•It has 17 manufacturing units
•It manufactures gas turbines, steam turbines, generators and boilers
•It is 7th largest power plant equipment manufacturer in the world
A computer numerical control system is a system in which actions are controlled by direct insertion of numerical data at some point
CNC Introduction
Definition:
History of CNC Machines
●The CNC machines were first introduced in the 1950s by Prof. John T Parson●First CNC machine was built at Massachusetts Institute of Technology in 1953●Modern CNC Machine are improving further as the technology is changing with a variety of functions according to applications.
CNC Machines- How do they look like?
Slides
Controller
Display
AutomatedTool changer
Chip collection and removal
Elements of CNC Machine
A CNC machine consist of following 6 major elements:
i. Input Device
ii. Machine Control Unit
iii.Machine Tool
iv.Driving System
v. Feedback Devices
vi.Display Unit
Input Device
•Floppy Disk•USB Flash Drive•Serial Communication etc.
Machine Control Unit
i. Data Processing Unit (DPU)
ii. Control Loop Unit
Driving system
•DC Motor•Stepper Motor
Feedback Devices
i. Positional Feedback Devices• Linear Transducer• Rotary Encoder
ii. Velocity Feedback Device
Display Unit
• Shows position of machine slide, part programmes etc.• Can also show graphics simulation of tool path so that part programmes may be verified
Block diagram of CNC Machine
How CNC Works
*Controlled by G and M codes.
*These are number values and co-ordinates.
*Each number or code is assigned to a particular operation.
*Typed in manually to CAD by machine operators.
*G & M codes are automatically generated by the computer software.
Controls: Open loop and Closed loop
In open loop systems the slide may overshoot or may not reach desired position because of inertia, wear and tear and friction, hence inaccurate machining.
In closed loop systems the position sensors are used to correct slide movements and achieve higher accuracy and repeatability
Modes of Operation
●Manual mode
●Manual Data Input (MDI) Mode
●Automatic Mode
●Input and output Mode
Manual Mode
Movement of machine slide carried out manually by pressing particular jog button(+ or -)Axis is selected through axis selector switchMachine slide movement may also be achieved by using a hand wheel
Manual Data Input (MDI) Mode
part programs are fed manually for each movement of machine tool by the operator
Automatic Mode
The part program is executed continuouslyWhile one block is being executed, next block is read by the system and kept ready for execution
Input and Output Mode
The part programs and machine information like machine setup data can be loaded into and unloaded from memory of the system or floppy disks, USB flash derives etc.
Features of CNC Machinery
•The tool or material moves automatically.
•Tools can operate in 1-5 axes.
•Larger machines have a machine control unit (MCU) which manages operations.
•Movement is controlled by motors (actuators).
•Feedback is provided by sensors (transducers)
•Tools can be changed automatically.
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.
Examples of G codes
G81 Drilling cycle
G82 Counter boring cycle
G83 Deep hole drilling cycle
G90 Absolute positioning
G91 Incremental positioning
Examples of M codes
M02 : Program end
M06 : Tool change
M08 : Coolant on
M09 : Coolant off
M30 : Program stop, reset to start
Advantages of CNC
Increased productivity
Consistent quality
Automatic material handling
High accuracy
Reliable operation
Reduced manpower
Increased operation safety
Challenges
i. Costly setup, skilled operators required
ii. Programming knowledge required
iii. Maintenance is difficult
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.
Thank You
Top Related