3. CNC (Computer Numeric Control)
Computer Numeric Control (CNC) is the automation of machine
tools that are operated by precisely programmed commands encoded
on a storage medium (computer command module, usually located
on the device) as opposed to controlled manually by hand wheels or
levers, or mechanically automated by cams alone.
In modern CNC systems, end-to-end component design is highly
automated using computer-aided design (CAD) and computer-aided
manufacturing (CAM) programs.
1955 - US Air Force define a need to develop a machine tool
capable of machining complex and close tolerance aircraft parts.
1959 - MIT is the contractor and builds the machine for the project.
MIT announces Automatic Programmed Tools (APT) programming
1960 - Direct Numerical Control (DNC). This eliminates paper
tape and allows programmers to send files directly to machine tools
1980’s - CNC machine is introduced. Unix and PC based systems
1997 - PC- Windows operating system is attached to CNC.
11. HMC MACHINE
Spindle in a horizontal
encourages chips to fall away.
HMCs are high-precision.
Used for tight-tolerance.
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
14. Programming Key Letters
O - Program number
N - Sequence number
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. Table of Important G codes
G00 - Rapid Transverse
G01 - Linear Interpolation
G02 - Circular Interpolation (CW)
G03 - Circular Interpolation (CCW)
G20/G70 - Inch units
G8 - Cancel canned cycles
G81 - Drilling cycle
G82 - Counter boring cycle
G83 - Deep hole drilling cycle
G90 - Abosolute positioning
G91 - Incremental positioning
16. Table of Important M codes
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
19. Tools of Machine
Posses hardness and strength at
Able to withstand when heat is
Angle of the cutting face
Flute width, number of flutes,
teeth, and margin size
20. CUTTING FLUIDS / COOLANT
Lubricating during cutting process.
Cooling the work piece at high cutting
Improving tool life.
Improving surface finish.
Flushing away chips from the cutting
Corrosion protection of the machined
Production rate is very high.
Complex surfaces need to be machined.
Flexibility in job change , automatic tool settings.
More safe , higher productivity , better quality.
Less paper work , faster prototype production.