a power point presentation on CNC machines

1. A Presentation Of
Industrial Training
on
“INTRODUCTION TO CNC MACHINES”
Submitted To: Submitted By:
Mrs.Kanika Jindal xxxxxx
Mr.Devendra Pratap Singh Roll No-xxxxxx
Ms.Gitanjali Anand Sec.-EC(VII-A)

2. 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

3. 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

4. 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:

5. 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.

6. CNC Machines- How do they look
like?
Slides
Controller
Display
Automated
Tool changer
Chip collection and removal

7. Elements of CNC Machine
A CNC machine consist of following 6 major
elements:
• Input Device
• Machine Control Unit
• Machine Tool
• Driving System
• Feedback Devices
• Display Unit

8. Input Device
• Floppy Disk
• USB Flash Drive
• Serial Communication etc.
Machine Control Unit
• Data Processing Unit (DPU)
• Control Loop Unit

9. Driving system
• DC Motor
• Stepper Motor
Feedback Devices
i. Positional Feedback Devices
• Linear Transducer
• Rotary Encoder
ii. Velocity Feedback Device

10. 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

11. Block diagram of CNC Machine

12. 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.

13. 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

14. Modes of Operation
• Manual mode
• Manual Data Input (MDI) Mode
• Automatic Mode
• Input and output Mode

15. Manual Mode
• Movement of machine slide carried out manually
by pressing particular jog button(+ or -)
• Axis is selected through axis selector switch
• Machine 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

16. Automatic Mode
• The part program is executed continuously
• While 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.

17. 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.

18. 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.

19. Examples of G codes
• G81 Drilling cycle
• G82 Counter boring cycle
• G83 Deep hole drilling cycle
• G90 Absolute positioning
• G91 Incremental positioning

20. Examples of M codes
• M02 : Program end
• M06 : Tool change
• M08 : Coolant on
• M09 : Coolant off
• M30 : Program stop, reset to start

21. Advantages of CNC
• Increased productivity
• Consistent quality
• Automatic material handling
• High accuracy
• Reliable operation
• Reduced manpower
• Increased operation safety

22. Challenges
• Costly setup, skilled operators required
• Programming knowledge required
• Maintenance is difficult

23. 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.

24. Thank You