FUNDAMENTALS OF CNC & PART PROGRAMMING - UNIT - 4 CAD&M

ME8691
COMPUTER AIDED DESIGN & MANUFACTURING
UNIT 4 – FUNDAMENTALS OF CNC
AND PART PROGRAMING
S.BALAMURUGAN
ASSISTANT PROFESSOR
MECHANICAL ENGINEERING
AAA COLLEGE OF ENGINEEERING & TECHNOLOGY

HISTORY & DEVELOPMENT OF TECHNOLOGY
CONVENTIONAL MACHINE
NC MACHINE
(1948 US Air force, MIT 21
Months)
(http://museum.mit.edu/150/86)
1952 - Cincinnati Milacron
Hydrotel Machine
1959: The MIT team showcase
the CNC-milled aluminum
ashtray is handed out as part
of the press kit.
CNC MACHINE
• During the Cold War time, the
development of automation was
addressed.
• At that time, the company Parsons Works
was commissioned by the U.S. Navy to
increase the productivity of its production
line for helicopter blades.
• John T. Parsons then motorized the axes
of the machines for making these blades.
• Working with IBM, he studied the
possibilities of controlling these machines
by computer. This was the starting point
of the CNC machining method.
• In 1952, Richard Kegg, in collaboration
with MIT, developed the first CNC milling
machine: the Cincinnati Milacron
Hydrotel.
• Five years later, in 1958, he filed a patent
for a “Motor Controlled Apparatus for
Positioning Machine Tool”. This was the
commercial birth of this technology.
ME 8691 COMPUTER AIDED DESIGN & MANUFACTURING S.BALAMURUGAN, AP/MECHANICAL, AAACET

NC – NUMERICAL CONTROL MACHINE
• Numerical control is a programmable
automation in which actions are
controlled by means of coded
numbers, letters & other symbols.
• The numerical data is required for
producing a part is maintained on
Punched Tape.
• The data is arranged in the form of
blocks of information.
• The block contains Cutting speed,
Feed, Dimensional information &
Contour form
ELEMENTS OF NC SYSTEM
1. Machine Control Unit
2. Machine Tool
3. Part Program & Drawings

ELEMENTS OF NC SYSTEM
MACHINE CONTROL UNIT(MCU) - Data Processing Unit (DPU)
• It consists of Tape Reader, Decoding Circuits, Feed Control Units.
• Tape reader receives the coded data from punched tape.
• The tape reader reads the data & passes data to the Buffer storage through
decoding circuits.
• The buffer storage stores the received information, till it is required & transfers it to
the required area.
• All the operations like Tool movement, Tool change, Speed & Feed Change
can be controlled by MCU.
MACHINE TOOL & NC TOOLING
• It is the manufacturing arm of NC machine
tool system.
• It receives the raw material & perform
different operations like Turning, Milling,
Drilling, Grinding etc.
• Receive the information from MCU. Based
on the information, the desired shape & size
is modified.

PUNCH CARDS - HOLLERITH CARDS OR IBM CARDS
• Punched Tape – Data is fed by automatic means. – Eliminate the operator errors.
• Punched tape uses a binary coded decimal system for containing operating
information of NC tool.
• Instructions Holes in Binary format Decoded in MCU Electric Pulse
• Electric pulses fed to the servo systems & mechanisms.
• These are paper cards in which holes may be punched by hand or machine to
represent computer data and instructions.
• The cards were fed into a card reader connected to a computer, which converted
the sequence of holes to digital information.

CNC - COMPUTER NUMERICAL CONTROL
• CNC is the numerical control system in which a
dedicated computer is built into the control to
perform basic and advanced NC functions.
• CNC controls are implemented by software
programs.
• CNC is a computer assisted process to control
general purpose machines from instructions
generated by a processor and stored in a
memory system.

NC MACHINE – DIRECT NUMERICAL CONTROL (DNC)
• In this type, a mainframe computer is used to coordinate the simultaneous
operations of a number NC machines.
• The tasks performed by the computer are to program and edit part
programs as well as download part programs to NC machines.
• Machine tool controllers have limited memory and a part program may
contain few thousands of blocks. So the program is stored in a separate
computer and sent directly to the machine, one block at a time.
• 1960s technology
• Two way communication.

DISTRIBUTED NUMERICAL CONTROL
• Network consisting of central
computer connected to machine
tool MCUs, which are CNC.
• Present technology
• Two way communication
NC MACHINE – DISTRIBUTED NUMERICAL CONTROL (DNC)

CLASSIFICATION OF CNC – MOTION TYPE
POINT – POINT SYSTEM
• It is used in some CNC machines such as
drilling, boring and tapping machines…etc.
• The control equipment for use with them are
known as point-to-point control equipment.
• Feed rates need not to be programmed.
• In theses machine tools, each axis is driven
separately
CONTINUOUS PATH SYSTEMS
• It is used in CNC machine tools such as milling
machines.
• These machines require simultaneous control
of axes.
• Feed rates need to be programmed.
• Contouring machines can also be used as point
to-point machines, but it will be uneconomical
to use them unless the work piece also requires
having a contouring operation to be performed
on it.

CNC MACHINE AXIS & DIRECTION
MILLING MACHINE TURNING MACHINE

FIXED ZERO v/s FLOATING ZERO
FIXED ZERO
• Origin is always located at some position on
M/C table (usually at south west corner/Lower
left-hand) of the tables & all tool location are
defined with respect to this zero.
FLOATING ZERO
• Very common with CNC M/C used now a days.
• Operator sets zero point at any convenient
position on M/C table.
• The Coordinate system is knows as work
coordinate system (WCS)

CNC – COMPUTERISED NUMERICAL CONTROL
• CNC – Computer + Numerical Control
• Numerical control is a programmable automation in which process is
controlled by Numbers, Letters & Symbols.
• CNC machining is a process used in the manufacturing sector that
involves the use of computers to control machine tools like lathes, Mills &
Grinders.
NEED OF CNC MACHINING
• To manufacture complex curved
geometries in 2D or 3D was extremely
expensive by mechanical means (which
usually would require complex jigs to
control the cutter motions)
• Machining components with high
Repeatability and Precision
• Unmanned machining operations
• To improve production planning and to
increase productivity
• To survive in global market CNC machines
are must to achieve close tolerances.

CNC – COMPUTERISED NUMERICAL CONTROL
INPUT DEVICES
• These are the devices which are used to input the part program in the CNC
machine.
• Commonly used input devices - Punch Tape Reader, Magnetic Tape Reader &
Computer via RS-232-C communication.

CNC MACHINE COMPONENTS
MACHINE CONTROL UNIT (MCU)
It is the heart of the CNC machine. It performs all
the controlling action of the CNC machine, the
various functions performed by the MCU are
• It reads the coded instructions fed into it.
• It decodes the coded instruction.
• It implements interpolation ( linear, circular and
helical ) to generate axis motion commands.
• It feeds the axis motion commands to the
amplifier circuits for driving the axis mechanisms.
• It receives the feedback signals of position and
speed for each drive axis.
• It implements the auxiliary control functions such
as coolant or spindle on/off and tool change.
MACHINE TOOL
• A CNC machine tool always has a slide table and
a spindle to control of the position and speed.
• The machine table is controlled in X and Y axis
direction and the spindle is controlled in the Z
axis direction.

DRIVING SYSTEM
• The driving system of a CNC machine
consists of amplifier circuits, drive motors
and ball lead screw.
• The MCU feeds the signals (i.e. of
position and speed) of each axis to the
amplifier circuits.
• The control signals are augmented
(increased) to actuate the drive motors &
the actuated drive motors rotate the ball
lead screw to position the machine table.
STEPPER MOTOR SERVO MOTOR
• It is a pulse-driven motor that changes
the angular position of the rotor in
steps.
• Open loop position control systems.
• When switching on an inkjet printer;
the controller will move the ink jet
carrier to the extreme left and right to
establish the end positions. It activates
an end limit switch.
• A servomotor is a rotary actuator or
linear actuator that allows for precise
control of angular or linear position,
velocity and acceleration
• Closed-loop control system.
• A servomotor will immediately turn to
whatever angle the controller instructs it
to, regardless of the initial position at
power up.

TYPES OF STEPPER MOTOR
PERMANENT MAGNET VARIABLE RELUCTANCE
• Rotor is a permanent magnet.
• PM motor rotor has no teeth and is designed
to be magnetized at a right angle to its axis.
• Figure shows a simple, 90⁰ PM motor with four
phases (A-D).
• Applying current to each phase in sequence
will cause the rotor to rotate by adjusting to the
changing magnetic fields.
• Low speed, relatively high torque
• Low cost motors with typical step angle
ranging between 7.5⁰ to 15⁰
• The cylindrical rotor is made of soft steel and has
four poles
• If 4 rotor teeth, 90⁰ apart and 6 stator poles, 60⁰
apart.
• Electromagnetic field is produced by activating
the stator coils in sequence.
• It attracts the metal rotor. When the windings are
energized in a re occurring sequence of 2, 3, 1,
and so on, the motor will rotate in a 30⁰ step
angle.
• In the non-energized condition, there is no
magnetic flux in the air gap, as the stator is an
electromagnet and the rotor is a piece of soft
iron.

SERVO MOTOR
• Servomotors are special electromechanical devices that produce precise
degrees of rotation.
• The servomotors are used in a closed-loop servo system as shown in Figure
A reference input is sent to the servo amplifier, which controls the speed of
the servomotor.
• A feedback device is mounted on the machine, which is an encoder.
• This device changes mechanical motion into electrical signals and is used as
a feedback.
• This feedback is sent to the error detector , which compares the actual
operation with that of the reference input.
• If there is an error, that error is fed directly to the amplifier, which will be used
to make necessary corrections in control action.
• DC servo motor
• AC servo motor
• Brushless DC motor.

OPEN LOOP SYSTEM CLOSED LOOP SYSTEM
• It is a system that involves feeding of
tape, interpretation of information by
Tape reader, Storing the data in buffer
storage, converting it into electrical
signal and sending this signal to the
control unit.
• It is a system that carries an additional
feedback device along with a
transducer, accompanied by a
comparator.
• It is a simpler & Cheaper system • It is more complicated & costly than the
open loop system
• Feedback device is absent • Feedback device is present
• With no feedback device, chance of
error is always present
• As the comparator compares the
obtained slide motion, chance of error
greatly reduced.

OPEN LOOP VS CLOSED LOOP SYSTEM

FEEDBACK SYSTEM
• This system consists of transducers that act as sensors.
• It contains position and speed transducers that continuously monitor the
position and speed of the cutting tool located at any instant.
• The MCU receives the signals from these transducers.
• MCU uses the difference between the reference signals and feedback
signals to generate the control signals for correcting the position and speed
errors.
ROTARY ENCODER LINEAR ENCODER

ENCODERS
• Linear Encoder uses a transducer to
measure the distance between two points.
• It consists of a glass disc with accurately
etched lines at regular intervals.
• This line make & break this photoelectric
beam which generates a pulse signal.
• This signal is amplified to give a square
wave output.
• Number of signals generated per revolution
depends on the number of lines on the disc.
• A Rotary Encoder collects data and
provides feedback based on the rotation of
an object.
• Absolute Rotary Encoders - Angular positions
• Incremental Rotary Encoders - Distance, speed,
and position.

SLIDEWAYS
HYDROSTATIC SLIDEWAY
• Air or oil is pumped into the small pockets or cavities machined into the
carriage or slides which are in contact with the guide way.
• The pressure of fluid gradually reduces to atmospheric pressure as it
sweeps out from the pockets, through the gap between slide and guide
ways.
• The hydro-static guide way provides almost a friction-less condition for the
movement of the slide.
• For the efficient operation it is very important that the fluids and guide ways
are kept clean.
• Hydro-static guide ways need a very large surface area to provide adequate
support.

RECIRCULATING BALL SCREW
• A recirculating ball screw consists a
screw, a nut and a series of balls.
• In recirculating ball screw, the sliding
friction gets replaced by rolling friction.
• Rolling friction is very less in recirculating
ball screw,
• The threads of screw and nut in
recirculating ball screw are semicircular,
so that they can accommodate rolling
balls.
• Almost no heat generation in recirculating
ball screw due to negligible friction, it can
be used at very high speeds up to 10
m/min.
DISADVANTAGES
• Buckling of screw is serious problem at
critical speed
• It require high degree of cleanliness
Also Known as
• BALL BEARING SCREW
• BALL SCREW.
APPLICATIONS
• Machine tools controls
• Hospital beds adjusters
• Aircraft landing gear retractors
• Automobile steering gears

AUTOMATIC TOOL CHANGER (ATC)
• It is a device which can automatically change the
tool from the tool magazine to the machine spindle
as per the CNC program.
• ATC is used in CNC machine tools to improve
• Tool carrying capacity of the machine.
• Reducing the non-productive time.
• 16 – 24 Tools used, Nowadays 160 – 350 Tools.
• MCU receives the tool change command signal.
• Move the spindle to its fixed tool change
position.(Home Position –Tool post Top Position)
• Same time, Tool magazine indexed to proper
position.
• The tool changer (Gripper Plate) engages the tool
in the spindle & tool in the magazine at that time.
• Both tools are removed from their position by tool
changer, & turns by 180° to swap both tools.
• Old tool sent to Tool magazine
• New tool engaged to Spindle.

AUTOMATIC TOOL CHANGER (ATC)

AUTOMATIC PALLET CHANGER
• Automatic Pallet Changer (APC) is a device which can automatically change the
pallet to/from machine to pallet stand.
• By this Mechanism, the pallet with the finished component and the pallet with a raw
component could be exchanged automatically.
• Pallet is a transferable work table having `T’ slots or tapped holes for
component/fixture clamping.
• Used to avoid the machine waiting time during loading & unloading of component.
• Pallet is held on the machine table by locating pins and clamping mechanism to
ensure repeatability and accuracy
ROTARY PALLET CHANGER SYSTEM INVERTED U-PATH, LINEAR PALLET CHANGER SYSTEM

TOOL MAGAZINE
• Tool Magazine is a device which holds number
of tools.
• This magazine can automatically index to
enable ATC to pick the right tool and to replace
the used tool.
• Duplication of tools is possible & a new tool of
same type can be selected when a particular
tool is worn off.
DISC or DRUM TYPE TOOL MAGAZINE
• The disc type tool magazine rotates to get the
desired tool in position with the tool change arm.
• The tools are stored on the periphery of the
drum.
• Capacity – 12 – 30 Tools
CHAIN TYPE TOOL MAGAZINE
• When the number of tools is more than 50,
chain type tool magazine are used.
• The magazine is mounted overhead or as a
separate column.

MACHINING CENTRE• A machining center can be defined as a sophisticated CNC machine tool
controlled by a computer running programs driven by numerical data, which can
perform multiple machining operations like milling, drilling, tapping and boring
operations at the same location control by making use of several area and a
variety of tools with Automatic Tool Changer (ATC) unit
• ARBOR - A rotating shaft in a machine or power tool on which a milling cutter or
grinding wheel is fitted

• The total production time is increased due to the Non–Productive time.
• Total Production time = Non-Production Time + Machining Time
• Non–Productive time – Workpiece handling, Setup time, Tool change time,
Operator Delay
To overcome this, NC, CNC machine developed. It will reduce the Non-
Productive time.
• A part programmer specifies cutting speed, Feed rate, Depth of cut etc., on
the basis of his knowledge & experience to achieve desired levels of
manufacturing objectives such as accuracy, surface finish & productivity.
• This programmed values are offline mode & do not always extract the optimal
from the machine.
ADAPTIVE CONTROL SYSTEM - ACS
• The main idea in adaptive control is the improvement in production rate & part
quality by calculation and setting of the optimal variables during the machining
itself
• The concept of adaptive control aims at reducing the in-process machining time
by a real time control in operating parameters such as cutting speed, Feed rate,
Depth of cut etc., which can be adjusted automatically
DRAWBACK IN CONVENTIONAL MACHINE

ADAPTIVE CONTROL OPTIMISATION (ACO)
• The overall performance of the process is indicated by performance index(PI).
PI =
𝑴𝒂𝒕𝒆𝒓𝒊𝒂𝒍 𝑹𝒆𝒎𝒐𝒗𝒂𝒍 𝑹𝒂𝒕𝒆(𝑴𝑹𝑹)
𝑻𝒐𝒐𝒍 𝑾𝒆𝒂𝒓 𝑹𝒂𝒕𝒆 (𝑻𝑾𝑹)
• The system measures the
process parameters such as
Cutting torque, Tool temperature,
Tool Wear & Vibration by sensors.
• This information's are fed to the
ACO software along with
programmed feed rate, Spindle
speed & other constraints.
• The software computes the real
time performance index(PI) on the
basis of the MRR & TWR.
• This index is compared with the
set value & the software then
recomputes the feed rate &
spindle speed.
• This system used to maximize the
PI without violating the
constraints.
ADVANTAGES OF ADAPTIVE CONTROL
• Increased production rate
• Increased Tool life
• Increased accuracy by making
tolerances as a constraint
• Less Human Interaction

ADAPTIVE CONTROL CONSTRAINT (ACC)
• In this control, constraints are
placed on the measured process
variables.
• The system measures the process
parameters such as Cutting torque,
Tool temperature, Tool Wear, Tool
deflection & Vibration by sensors.
• The measured values of these
parameters are compared with the
set values with ACC software.
• It is ensured that at no time the
measured parameters exceed the
set value.
• ACC system is to manipulate the
spindle speed & feed rate to
maintain this into the set values.

2.5 AXIS VS 3 AXIS MACHINE
• 2.5 axis machining requires that the machine have three axes, but only two
axes must be moving simultaneously at any one time.
• Operations, like drilling and most milling
• 3-axis machining requires that all three axes be moving at the same time.
• More complex operations, like the machining of sculptured surfaces required
in molds and airfoils.

G90 Absolute Positioning & G91 Incremental Positioning
Absolute Positioning Method (G90) Incremental Positioning Method (G91)

ABSOLUTE POSITIONING SYSTEM INCREMENTAL POSITIONING SYSTEM
• In this system, all the positions are
indicated from a reference point, which
is a fixed zero point or set point.
• In this method, the tool positions are
indicated with respect to previous
point.
• The coordinate of each point are
independent of each other.
• The coordinate if each point are
dependent on each other.
• If an error occurs into the dimensions
of any location, then the error will be
restricted to that location only.
• The main disadvantage of this system
is that if an error occurs into the
dimensions of any location, all the
locations marked after that will carry
the same error.
• Here, a reference point is must. • Reference point is not needed.

G90 Absolute Positioning & G91 Incremental Positioning

RAPID MOTION G00 & LINERA MOTION G01
• If there is no contact between tool & work piece, Use Rapid motion to save the time.
CIRCULAR INTERPOLATION MOTION G02 (CW) & G02 (CCW)

CUTTER COMPENSATION (G41, G42)
G40 – CUTTER COMPENSATION
CANCEL
• This code should be entered in
the separate line at the end of
the required operation.

CANNED CYCLE
G81 – SPOT DRILLING CANNED CYCLE
A canned cycle is used to simplify programming of a part. Canned cycles are defined for the most common Z-axis
repetitive operation.
• Drilling(G81 – SPOT DRILLING)
• G83 – PECK DRILL
• Tapping (G84) & Boring (G85).
The five operations in a canned cycle are:
1) Positioning of the X and Y axes.
2) Rapid traverse to the R plane.
3) The drilling, tapping, and boring for the canned cycle.
4) Operation at the bottom of hole.
5) Retraction to R plane (G99) or initial starting point (G98).

PART PROGRAM - MILLING
G21 G94
G91 G28 X0. Y0. Z0.
T01 M06
G43 H01 Z100.
G90 G54 G41 G00 X0.0 Y0.0 D01
M03 S1000 Z20.
G01 G41 G90 Z-5. F400.
G01 X0. Y125.
G03 X25. Y150. R25.
G01 X125. Y150.
G02 X150. Y125. R25.
G01 X150. Y25.
G03 X125. Y0. R25.
G01 X0. Y0.
G01 Z10.
G00 Z100.
G40
G91 G28 X0. Y0. Z0.
M30
• RADIUS – 25 mm
• Cutter Compensation
Program
• Tool – End Mill – 6 mm
• Diameter Offset – D01 – 3 mm

G21 G94
G91 G28 X0. Y0. Z0.
T01 M06
G90 G54 G42 G00 X25. Y25. D01
G43 H01 Z100.
M08
M03 S1000
G01 Z20.
G01 G90 Z-5. F400.
G01 X25. Y175.
G01 X175. Y175.
G01 X175. Y25.
G01 X25. Y25.
G01 Z10.
G40
G00 Z100.
M05
M09
G91 G28 X0. Y0. Z0.
M30

SUB PROGRAM – M98 & M99
G21 G94
T01 M06
G90 G54 G00 X-25. Y-25.
G43 H01 Z100.
M03 S1000
G01 Z0. F400.
M98 P1500 L10
G40
G00 Z100.
M05
G91 G28 X0. Y0.
M30
O1500
G91 Z-2. F400.
G90 G41 G01 X0. Y50. F400. D01
G01 X45. Y150.
G01 X105. Y150.
G01 X150. Y50.
G01 X150. Y25.
G01 X125. Y0.
G01 X25. Y0.
G01 X0. Y25.
M99

CANNED CYCLE - DRILLING

G21 G94
G91 G28 X0. Y0. Z0.
TO1 M06
G17 G90 G54 G00 X20. Y20.
G43 H01 Z100.
M03 S1000 Z20.
G01 G90 Z-20. F300.
G90 Z5.
G01 G90 X80.
G01 G90 Z-20. F300.
G90 Z5.
G01 G90 Y80.
G01 G90 Z-20. F300.
G90 Z5.
G01 G90 X20.
G01 G90 Z-20. F300.
G90 Z5.
G01 G90 X50. Y50.
G01 G90 Z-20. F300.
G90 Z5.
G00 Z100.
G91 G28 X0. Y0. Z0.
M05
M30
G21 G94
G91 G28 X0. Y0. Z0.
TO1 M06
G17 G90 G54 G00 X20. Y20.
G43 H01 Z100.
M08
M03 S1000
G01 G90 Z20.
G90 G83 G99 Z – 20. Q2. R1. F10
G01 X80. Y20.
G01 X80. Y80.
G01 X20. Y80.
G01 X50. Y50.
G80
G00 Z100.
M09
G91 G28 X0. Y0. Z0.
M05
M30

PART PROGRAM - TURNING
G21 G95
M06 T01
G18 G54
G00 G90 X40. Z5.0
G73 U0.5 W0.5 R10.
G73 P10 Q70 U0.2 W0.2 F0.2
S1000
N10 G01 X14. Z1.0
N20 G01 Z-15.
N30 G03 X22. Z-19. R4.
N40 G01 X22. Z-34.
N50 G02 X34.0 Z-40. R6.
N60 G01 Z-50.
N70 X50. Z0.
G00 X60.0 Z50.
M05
M09
T02 (TOOL CHANGE)
(FINISH TURN CONTOUR)
G96 S200
M03 S2500
G01 G90 X49.0 Z5.0
M08
G70 P10 Q70 F0.15
G00 X60.0 Z50.0
M05
M09
M30
G73 – Pattern Repeating Cycle
G73 U… W… R…
G73 P… Q… U… W… F... S...
U: X-axis (radius value). This is the amount of material which will be cut in x-axis.
W: Z-axis. This is the amount of material which will be cut in z-axis.
R: Number of divisions. The number the contour will be repeated.
P - Contour Start block number, Q - Contour End block number
U - Finishing allowance in X-axis, W- Finishing allowance in Z-axis

PART PROGRAM - TURNINGG21 G95
M06 T01
G18 G54
G00 G90 X40. Z5.0
G73 U0.5 W0.5 R10.
G73 P10 Q70 U0.2 W0.2 F0.2
M03 S1000
N10 G01 X0. Z0.
N20 G03 X16. Z-8. R8.
N30 G01 X16. Z-15.
N40 G01 X26.0 Z-30.
N50 G03 X34.0 Z-35. R5.
N60 G01 X34. Z-50.
N70 X50. Z0.
G00 X60. Z50.
M05
M09
MO6 T02 (TOOL CHANGE)(FINISH TURN CONTOUR)
G96 S200
M03 S2500
G01 G90 X49. Z5.
M08
G70 P10 Q70 F0.15
G00 X60. Z50.
M05
M09
M30
G73 – Pattern Repeating Cycle
G73 U… W… R…
G73 P… Q… U… W… F... S...
U: X-axis (radius value). This is the amount of material which will be cut in x-axis.
W: Z-axis. This is the amount of material which will be cut in z-axis.
R: Number of divisions. The number the contour will be repeated.
P - Contour Start block number, Q - Contour End block number
U - Finishing allowance in X-axis, W- Finishing allowance in Z-axis

MACRO – CNC PROGRAMMING
• Macro programming is also known as Parametric
Programming.
• It means, we can control the program by external parameters.
• This program uses the #(variable) sign to represent values.
• Used for making Holes.
G21 G94
G91 G28 X0. Y0. Z0.
TO1 M06 (6 mm Drill)
G17 G90 G54 G00 X20. Y20.
G43 H01 Z100.
M08
M03 S1000
#1 = 10.
#2 = 100.
M98 P500 (Call Subprogram)
M05
M09
G91 G28 Z0.
TO2 M06 (12 mm Drill)
G17 G90 G54 G00 X20. Y20.
M03 S1000
G43 H02 Z100.
M08
#1 = 20.
#2 = 200.
M98 P500 (Call Subprogram)
M05
M09
G00 Z100.
G91 G28 Z0.
M30
#1 variable – Depth
#2 Variable – Feed Rate
O500 (Sub Program)
G90 G83 G99 Z-#1 Q2. R1. F#2
G01 X80. Y20.
G01 X80. Y80.
G01 X20. Y80.
G01 X50. Y50.
G80
M99

FUNDAMENTALS OF CNC & PART PROGRAMMING - UNIT - 4 CAD&M

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