Expt-9 CNC Trainer.pptx

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Hyderabad Campus
Exp.9:CNCtrainer

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Aim of the experiment
 Aim: To study the features of the CNC Lathe and Milling
OBJECTIVE:
 To write a CNC part program for a given drawing and prepare the component on CNC
lathe and milling

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Introduction CNC
 Form of programmable automation.
 Mechanical actions of machine tool are controlled by
program.
 The program is in form of alphanumeric data.
 After a job is finished the program of instructions can
be changed to process a new job.

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*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.
History of CNC

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*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
Elements of CNC machine

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*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.
Features of CNC machine

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Servo
motors
Display
unit
Slides
Controller
Automatic tool
exchanger
Spindle
CNC machine

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Block Diagram CNC machine

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The part program is a sequence of instructions, which describe the work, which has to be done
on a part, in the form required by a computer under the control of a numerical control computer
program. It is the task of preparing a program sheet from a drawing sheet. All data is fed into the
numerical control system using a standardized format.
Programming is where all the machining data are compiled and where the data are translated
into a language which can be understood by the control system of the machine tool. The
machining data is as follows:
Machining sequence classification of process, tool start up point, cutting depth, tool path, etc.
Cutting conditions, spindle speed, feed rate, coolant, etc.
Selection of cutting tools.
Part programming of CNC machine

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While preparing a part program, need to perform the following steps:
Determine the startup procedure, which includes the extraction of dimensional data from
part drawings and data regarding surface quality requirements on the machined
component.
Select the tool and determine the tool offset.
Set up the zero position for the workpiece.
Select the speed and rotation of the spindle.
Set up the tool motions according to the profile required.
Return the cutting tool to the reference point after completion of work.
End the program by stopping the spindle and coolant.
Part programming of CNC machine

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 The part programming contains the list of coordinate values along the X, Y and Z directions of
the entire tool path to finish the component.
 The program should also contain information, such as feed and speed. Each of the necessary
instructions for a particular operation given in the part program is known as an NC word.
 A group of such NC words constitutes a complete NC instruction, known as block.
 The most common codes used when programming NC machines tools are G-codes (preparatory
functions), and M codes (miscellaneous functions). Other codes such as F, S, D, and T are used
for machine functions such as feed, speed, cutter diameter offset, tool number, etc.
Part programming of CNC machine

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Part programming of CNC machine

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*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
Part programming Key latters

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*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.
How CNCworks

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1. Prepare the drawing of the job required as per the dimensions.
2. Write a part program for the job to be machined on the CNC turning machine.
3. Place the job in the chuck and set the tool according to the operation to be
performed on the machine.
4. Close the door of the CNC machine after the placement of the workpiece.
5. Start the machine and run the program.
6. Remove the job after completion of the work.
Procedure

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G00 Rapid Transverse
G01 Linear Interpolation
G02 Circular Interpolation, CW
G03 Circular Interpolation, CCW
G17 XY Plane,G18 XZ Plane,G19 YZ
Plane
G20/G70 Inch units
G21/G71 Metric Units
G40 Cutter compensation cancel
G41 Cutter compensation left
G42 Cutter compensation right
G43 Tool length compensation (plus)
G43 Tool length compensation (plus)
G44 Tool length compensation (minus)
G49 Tool length compensation cancel
G80 Cancel canned cycles
G81 Drilling cycle
G82 Counter boring cycle
G83 Deep hole drilling cycle
G90 Absolute positioning
G91 Incremental positioning
Important G codes

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*M00 Program stop
*M01 Optional program stop
*M02 Program end
*M03 Spindle on clockwise
*M04 Spindle on counterclockwise
*M05 Spindle stop
*M06 Tool change
*M08 Coolant on
*M09 Coolant off
*M10 Clamps on
*M11 Clamps off
*M30 Program stop, reset to start
Important M codes

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Hyderabad Campus
THANKYOU

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Lab report
 What is a CNC part programming?
What are G-codes and M-codes? Why they are used?
What is a NC word and NC block?
What is the difference between NC and CNC machine?