ppt on cnc
- 1. CNC MACHINE By – Pankaj Dhut
- 2. CONTENTS 1. HISTORY 2. CNC INTRODUCTION 3. ELEMENTS OF CNC 4. BLOCK DIAGRAM OF CNC . TYPES OF CNC MACHINE 6. HOW CNC WORKS? 7. FEATURES OF CNC MACHINES 8. CNC PROGRAMMING BASICS 9. COMMON FORMAT OF A BLOCK 10. PROGRAMMING KEY LETTERS 11. ADVANTAGES 12. CHALLENGES 13. CONCLUSION 14. REFERENCES
- 3. HISTORY • The first NC machines were built in the 1940s and 1950s by Prof. John T Parson. • 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.
- 4. CNC INTRODUCTION A numerical control system in which the data handling, control sequences, and response to input is determined by an on-board computer system at the machine tool.
- 5. TYPES OF CNC MACHINE. • Plasma. • Spring forming. • Laser Cutting machine. • Flame cutting machine. • Electric Discharge Machine. • Water Jet. • Welding. • CNC Punch Press.
- 6. 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
- 7. Block diagram of CNC Machine
- 8. OPEN LOOP AND CLOSED LOOP CONTROLS 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
- 9. 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.
- 10. 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) • Tool magazines are used to change tools automatically.
- 11. 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.
- 12. CNC PROGRAMMING Important things to know: • Coordinate System • Units, incremental or absolute positioning • Coordinates: X,Y,Z, RX,RY,RZ • Feed rate and spindle speed • Coolant Control: On/Off, Flood, Mist • Tool Control: Tool and tool parameters Programming consists of a series of instructions in form of letter codes •Preparatory Codes: G codes- Initial machining setup and establishing operating conditions N codes- specify program line number to executed by the MCU •Axis Codes: X,Y,Z Used to specify motion of the slide along X, Y, Z direction •Feed and Speed Codes: F and S Specify feed and spindle speed •Tool codes: T – specify tool number •Miscellaneous codes – M codes For coolant control and other activities
- 13. COMMON FORMAT OF A BLOCK Sequence # Preparatory Function Dimension Words Feed Rate Spindle Function Tool Function Misc. Function N50 G90 G01 X1.40Y2.25 F10 S1500 T01 M03 Individual Words
- 14. PROGRAMMING KEY LETTERS • O - Program number (Used for program identification) • N - Sequence number (Used for line identification) • G - Preparatory function • X - X axis designation • Y - Y axis designation • Z - Z axis designation • R - Radius designation • F – Feed rate designation • S - Spindle speed designation • H - Tool length offset designation • D - Tool radius offset designation • T - Tool Designation • M - Miscellaneous function
- 15. Advantages of CNC i. - Easier to program; ii. - Easy storage of existing programs; iii. - Easy to change a program iv. - Avoids human errors v. - CNC machines are safe to operate vi. - Complex geometry is produced as cheaply as simple ones vii. - Usually generates closer tolerances than manual machines
- 16. CHALLENGES i. COSTLY SETUP, SKILLED OPERATORS. ii. COMPUTERS, PROGRAMMING KNOWLEDGE REQUIRED. iii. MAINTENANCE IS DIFFICULT.
- 17. 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.
- 18. REFERENCES Manual of CNC from BHEL Jhansi http://en.wikipedia.org/wiki/computer_numerical_control http://www.motioncontrol.com/articles/gearheads-modular- spindle-drives http://www.seminarprojects.com/cnc
- 19. THANK YOU