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Modern University For Technology and Information

Mechanical Engineering Department

Lectures Notes of

Computer Aided

Manufacturing

MENG 304

Prepared By Asoc.Prof. Omar Koura

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Vision

The vision of the Faculty of Engineering at MTI university is to be a

center of excellence in engineering education and scientific research in

national and global regions. The Faculty of Engineering aims to prepare

graduates meet the needs of society and contribute to sustainable

development.

Mission

The Faculty of Engineering MTI university aims to develop

distinguished graduates that can enhance in the scientific and

professional status, through the various programs which fulfill the needs

of local and regional markets. The Faculty of Engineering hopes to

provide the graduates a highly academic level to keep up the global

developments.

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Lecture Note 1 : Computer Numerical Control (CNC)

➢ Introduction

• CNC stands for computer numerical control.

• CNC uses numerical data to control various types of machines:

- Machine tools:

o Turning centers

o Machining centers o Drilling o Grinding machines

- Forming machines:

o Punching machines o Blanking machines o Sheet metal works

- Laser cutting machines

- Robots

- Electronic assembly systems

➢ Difference between Manual and Automated machine tools

Machine tools are machines that can remove material in the form of chip from a raw

material using a cutting tool with certain form and specification.

The cutting is produced as the machine is generating relative motions between the raw

material and the cutting tool. Hence, to manufacture any part on manually operated

machine tool, the components shown in figure 1.1 must be available.

Fig 1.1: Production components on Manual machine

5-Operator

1-Raw material

2-Cutting tools

7-Measuring equipment 6-Handling equipment

3-Operation sheet

4-Machine tool

Product

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➢ Production components on Manual machine

1. Raw material

2. Appropriate cutting tools

3. An operation sheet that contains the sequence of operations, the required tool type

and the cutting conditions that will be followed to produce the product. Some users

do not consider this item to be necessary as they rely upon the experiences and skill

of the operator, but, even if the same operator is used and if he is highly skilled, no

guarantee that when producing several parts.

4. A machine that holds the raw material, holds the tools, and can produce the relative

motions between both the raw material and the tools (rotational motion, translation

motions) to provide the feed, cutting speed & depth of cut.

5. Operator that carries out the following main functions: -

• Read the operation sheet line by line,

• Analyze and process mentally the contents of each line.

6. Handling equipment if the raw material is quite heavy to handle it manually

7. Measuring instruments to check the resulted dimension

However, if the operator’s functions are carried out by some controlling mechanical,

hydraulic and/or electrical elements, then the machine is an automated machine tool. It,

also follows that the form and format of the process sheet that holds the sequence of

operation and cutting conditions should be changed to suit the unit that will read the

instruction given in the newly formatted program carrier, figure 1.2. If the FORMAT

of the data fed to the machine through reading the program carrier is written in an Alfa

– Numerical instruction and the machine utilizes a computer to process the instructions,

then it is a Computerized Numerical Control Machine Tool. (CNC).

Fig 1.2: Production components on Automated machine

5-Control system

1-Raw material

2-Cutting tools

Measuring equipment Handling equipment

3-Part Program

4-Machine tool

Product

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➢ Advantages of CNC

The main advantages are: -

• Efficiency.

• Accuracy where CNC machines provide an extraordinarily high level of

accuracy.

• Productivity as wasted motion is cut out of the CNC operations program.

• CNC machines provide consistent, dependable, and repeatable performance.

• Less downtime and reduced part-handling time.

• No need to route parts to other machines, since one CNC machine can conduct

multiple operations

• CNCs provide great manufacturing flexibility, speedy changeovers, and

improved efficiency.

• Less rejected parts and this is an important issue, since rejection of partly/fully

manufactured parts does not mean material losses, but also labor cost,

depreciation of machine cost.

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Lecture Note 2: Component of CNC Machine Tool

CNC machine is an integration of so many engineering systems. Figure 2.1 shows the

main components of CNC Machine Tool. It mainly consists of:-

Fig 2.1 : Main components of CNC machines

1. Mechanical components

This covers all mechanical components (bed, columns, slides, ball screws,

turrets, table, carriages, saddles, spindle and bearing, linear and torque

transmission elements, tool changer mechanisms, chip removal mechanisms and

guards) in the CVC machines.

2. Lubricating System

It covers all the lubricating systems for the slides of the machine, ball screws

supporting bearings, spindle bearings, table components, indexing turret

components and tool Changer components.

3. Hydraulic System

It covers the hydraulic systems needed for the counterbalance systems,

automatic tool changer and hydraulic actuators.

CNC

System

Mechanical

Systems

Lubricating

System

Hydraulic

System

Coolant

System

Electrical

Panel

1. CPU

2. SCU

3. OCP

4. MCP

5. PLC

6. OPD

CPU Central Processing Unit

SCU Servo Control Unit

OCP Operating Control Panel

MCP Machine Control Panel

PLC Programmable Logic Controller

OPD Other Peripheral Devices

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4. Coolant System

Some CNC machines are equipped with two types of coolant systems; one is

continuous flooding of coolant and the other is a spraying system.

5. Electrical Systems

The main function of the electrical panel is to provide the different systems by

regulated stepped down voltages. It houses the relays, circuit breakers, push

buttons, switches, contactors, overload protectors, ……. etc

6. CNC Systems

As illustrated in CNC System mainly consists of:-

• Central Processing Unit (CPU)

It is the brain of the system. Its main function is to retrieve the

stored input data from the Memory in the form of the part program,

works with the Speed Control Unit to decode the data, transform

the decoded data into position and velocity signal. It receives, also,

the actual position and produces a corrective action.

Again, it calculates errors in the system such as lead screw pitch

error, tool wear, backlash, …. etc and develop a compensating

signal to correct the situation. It carries out several safety checks

and energies the shutting down of the system when necessary.

• Servo Control Unit (SCU)

The Servo control unit receives the decoded position and velocity

signals from the CPU and generates command values which are fed

to the Servo Drive Units. The later are coupled with the axes and

spindle motors.

• Programmable logic controller (PLC)

It is the controller which replaced the old, wired relays in the early NC

machines. It is responsible for the implementation of all the logics to the

system.

• Operator control panel (OCP)

It is the user interface with the different systems.

Figure 2.2 shows an operator control panel. The operator control panel provides the

user interface to facilitate a two-way communication between the user, CNC system

and the machine tool. OCP mainly consists of:-

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Fig 2.2: Operator control panel

• The display unit displays all related information of the CNC system, such as:-

• Information on the block being executed and its sequence number, the

actual position, feed rate, rotational speed, active G and M

• Actual position value, set or actual difference, current feed rate,

spindle speed

• Alarm messages

If something is not in the correct order alarm must be communicated to

the operator. This is in the form of alarm messages.

• Soft key designations

• All types of entered data, machine data …… etc

• Indicators to indicates:-

• Feed hold status which means that the motion of slides are inhibited

• Program in action which means that the program is being executed and in

progress

• Zero set which means that the reference zero is set and the slide is at this

zero

• Tool compensation which means that the CPU is considering the

compensation

• The slides are in motion

• Alphabetic – Numeric keyboard

This is very similar to a computer keyboard. It is used for editing the part

program, tool data, machine parameters …. It has:-

• Alphabetic characters (A, B, C, ……., Z)

• Numeric (0, 1, 2, 3, ……9)

• Other characters (+, -, *, /, $, £, ……)

Display Unit Alphabetic –

Numeric

Keyboard

Indicators

Cursor Movement

pages

Editing keys

F

I

L

E

S

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• Cursor Movements Buttons

Those Buttons are used to move the cursor one character right or left or line up

or line down.

• Pages Buttons

Those move the cursor to the start of the part program, or to the end of the part

program, or one page up , or one page down.

• Editing Keys

Editing keys which shifts the cursor one word, delete a word, delete a

block…… etc

• File Keys

Those keys are used to store a part program , survey the different part programs

stored in the memory, delete a file………etc

Machine Control Panel This panel, fig 2.3, is the interface between the operator and the hardware of the

machine.

It is used to set the machine in the proper status before running any part program. Its

main function is to:-

• Establish the zero position of each slide

• Setting the workpieces

• Setting the tools and cutters

• Loading and checking the tool offsets

• Testing the part program through executing it block by block

• Running the program

• Selecting the Mode of operation :-

o Manual Mode

o Manual Data Input (MDI) Mode

o Automatic Mode

o Block by Block Mode

o Zero (Reference) Mode

o Drafting Mode

o Parameters Mode

The Panel contains :-

o Emergency Button (EM). It shuts down all Power, Inhibit all

movements ……

o ON/OFF switch of the Machine Control Panel (switch no. 1).

o Cycle Start “S” is used when starting the execution of the part program

o Feed Hold/start “H” which inhibit the feed motion of the slides

o Set of Indicators for :-

▪ Emergency Button is ON

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▪ Feed Hold is ON

▪ Lubrication is ON

▪ Machine is at Zero Position

▪ Cycle is running

o Buttons for the different Modes of Operation which are:-

Fig 2.3 : Machine Operating Panel

• Manual Mode (MM) in which all manual operation can be carried out when

pressing Push Button “MM”; such as:-

• running and stopping of spindle speed motor (Push Buttons No. 2),

• running of coolant pump (Push Buttons No. 3).

• indexing of turret (Push Buttons No. 4).

• moving any slide (Push Buttons No. 5). The movement of any slide is

carried out by pressing the corresponding push Button (e.g. +X or –X or

+Z ……). The feed rate or the rotational speed can be pre-entered through

the push Button No. 6. The movement of the slide at the maximum

traverse rate is obtained when pressing the Push Button “R” together with

the any of the axis Push Button. Jogging the axis is resulted by setting the

selector No. 7 to the Jogged value (10, 1, 0.1, 0.01, 0.001 mm) and then

pressing any of the axis Push Button.

• Speed Override selector No. 8 is used to change the programmed speed

by ± 100% of its value. This provides the possibility to increase or

decrease the cutting speed value online while cutting without actually

changing the programmed value.

ON/OFF

OFF OFF

ON ON CW

CCW

+Y

-Y

+X -X

+Z

-Z

EM

6 7 8 9

5

2 3 4

R

1

MM AM BM MDI ZM DM PM

S

H

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• Feed Override selector No. 9 is used to change the programmed feed by

± 100% of its value. This provides the possibility to increase or decrease

the feed rate value online while cutting without changing the

programmed value.

• Automatic Mode (AM)

In this mode the machine is ready to execute the part program continuously. As soon as

the Cycle Start Button “S” is pressed, the machine works on the first block. While

cutting in one block, the following block in the part program is transferred from the

buffer memory to the CPU for processing ready to be executed as soon as the current

block is finished. The execution stops if the Hold/Start Button “H” . This causes the

freezing of the slide movements . On re-pressing “H” the execution commences

working again .

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• Block Mode (BM)

In this mode the machine executes the part program block by block. It stops between

the two blocks until the cycle start Button is pressed. This allows the operator to test

the part program.

• Manual Data Input Mode (MDI)

In this mode editing of part program and working with the file directories are possible.

• Zero Mode (ZM)

Sometimes this is known as Reference Module. It is used to set the Zero Datum of the

coordinates (X, Y, Z) of the part program.

• Drafting Mode (DM)

In this module the part program may be checked by tracing the tool path on the screen.

This can be done offline or online.

• Parameter Mode (PM)

Some CNC Machines require certain values to be introduced to the controllers, such

as:-

• Soft travelling Limits for the axes which terminate the movement of the slide

if it reached certain value. This is used as an extra safety if the hardware

limits failed to function.

• Configuration values between the machine and its peripherals

• Tool tables

Figure 2.4 shows an integrated panel for both the operator and the machine.

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Fig 2.4 : Operator and machine panel

• Other peripheral devices (OPD)

Those are the external devices that are linked with the CNC machines such as

communicating equipment, external computer unit, tape reader, …. etc

Difference between Open and Closed loop control systems

Automatic control is being used on a wide scale in the engineering circles . To

have a control system certain component must exist:-

- An input target value such as request to move the table to the position at 50

mm or to run the main motor at a speed of 200rpm or This is converted as an

input desired signal that corresponds exactly to the input target value.

- A controlling system-controlled element which is the part that we need to

control such as the sliding table of a machine

- The controlling elements that issue the desired command signal

- The controlled element moves to almost the required value, since the received

signal is distorted by the disturbance signal initiated from the environmental

noise, vibration, friction, inertia of moving parts.

This system is known as Open loop control system, figure 2.5.

Fig 2.5: Block diagram for open loop control system

Operator control

panel

Machine Control

Panel

Required input Target

Controlling system

Desired input signal

Correct Controlled signal

Controlled element

Disturbance signal

Distorted Controlled signal

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To avoid this lack of accuracy two other elements are introduced:-

- A measuring device to measure the achieved position and feedback the signal of

the achieved position to an error detector.

- An error detector that compares the input desired signal with the received signal

from the measuring device and issues an error signal (the resultant of both) to the

servo running the controlled element.

This system is known as Close loop control system, figure 2.6.

Fig 2.6: Block diagram for closed loop control system

Disturbance signal

Required input Target

Controlling system

Desired input signal

Error signal

Controlled

element

Measured signal

Error detector

Measuring system

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Lecture Note 3: Axes and Format

Axes nomenclature and designation

International ISO standards defined the terminology used with the CNC axes. It

consists of the definition of Linear (main , secondary, and auxiliary) axes and

rotational (main and auxiliary) axes.

Linear axes

In CNC machines more than one element is allowed to move along a linear

axis. In the gantry machine with two milling heads,

figure 3.1, the following linear motions exit:-

• Each head slides along the gross rail

• The spindle of each head moves up and down in a normal direction to the

table

• The gantry moves in the direction indicated along the table

• The cross rail moves up and down in the same direction as the direction of the

spindles

To order a particular drive to operate, it is necessary to define the motion of

that drive. For this reason a standard has been issued to define the axes.

Fig 3.1: Gantry machine with two milling heads

The standard has defined that CNC machines can have up to 3 sets of

linear motions.

The first set is given the name of “the main axes” as its origin in the

nearest to the main spindle of the machine. Those are given the notation X,

Y and Z.

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The next to it is the set of the secondary axes. Those are given the

notation U, V and W.

The far set of axes from the main spindle is the auxiliary set. Those are

given the notation P, Q and R.

The axes in each set are parallel which mean that U and P are parallel to X ,

V and Q are parallel to Y and W, R are parallel to Z. But the standard has

indicated that no junior axis will be named in a machine except if its senior

is present. Applying this to the gantry machine, if head 2 is the main unit,

then head 1 is the nearest to it (secondary unit) and the cross rail with the

gantry is the auxiliary unit. It follows that head 2 will move in a lateral

and vertical directions, head 1 will move in a lateral and vertical directions,

the cross rail will move in lateral direction and the gantry will move along

the table.

Each of those direction must be defined as a name and sense of direction.

The standard defined the axis in the following sequence:-

• Axis Z must be defined first, and it is the axis of the main spindle

irrespective of being vertical or horizontal. If a machine has no

spindle (as in shaper), the Z axis is defined as the normal to the

machined surface when the machine is set at zero tilt.

• X axis is defined second and it must be horizontal. If the Z axis

happens to be horizontal, The second horizontal axis is the X axis. If

the Z axis happens to be vertical, the X axis is the horizontal with the

longer traverse.

• The Y axis is determined automatically after defining Z and X axes.

• The sense of the motion along the Z axis follows the safety rule

which states that if the tool is running away from the work holding

place the sense is positive and vice versa.

• The senses of the other two axes are defined using the thumb rule,

figure 3.2. Pointing at positive direction of Z axis results in positive

X and positive Y.

Linear motion Rotation

Fig 3.2: sense of motions

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As an application to the gantry machine, head 2 will has X, Y and Z as its

motion axes. But head 2 is allowed to move only in two di rections (Y and

Z). Thus axis X is not used with the main unit. Same directions are given to

head 1. Thus they will be given V and W, leaving U unused. The cross rail

is designed to move laterally, so it will be given R. The gantry is designed

to move in a direction along the table, so it should have been given P, but

as the notation of the senior axis is not used, so it will be given X. Thus if

an order is given Y3 Z-5 R9 then head 2 will move in the positive

direction 3 mm and down towards the workpiece 5 mm, while the cross rail

will move away from the workpiece surface 9 mm.

Rotational axes

The standard defined 5 rotations about five axes. A, B and C are rotations

about X, Y and Z axes respectively. The other two (E and F) are arbitrary.

They can be rotated about any other axis. The sense is as given in figure

3.2, when looking to the positive direction of the X axis and using the

right-hand rule, the rotation of “A” will be positive. The same is for

rotations B and C.

1. CNC Programming

The objective of this part is to understand how to program CNC machines. This

includes the following items.

a. What is the part program?

b. The format of CNC part program and its structure.

• Define the function of N codes.

• Define the function of G codes.

• Define the function of coordinate codes.

• Define the function of F and S codes.

• Define the function of T codes. data.

• Define the function of M codes.

c. Describe a toolpath.

What Is the Part Program?

A part program is an ordered sequence of commands that describes all the operations

performed by the machine. These commands use codes that combine numbers and

letters.

A part program is like computer software, with a very specific purpose.

Manufacturing of each workpiece requires its own part program. These programs are

then stored in the CNC machine or on computer disks.

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Steps followed to create a part program

1. The first step is to select the correct work holder.

2. The part programs

➢ Table of Contents

3. determine the location of the program zero, which acts as the starting point for the

program. Figure 3.3 compares the location of program zero on the mill and the

lathe.

4. From this starting point, the part programmer records the sequence of cutting

operations.

Fig 3.3 Common location for program zero on the lathe.

5. Finally, the programmer adds instructions for the machine

a. Common location for program zero on the mill.

b. Cutting speeds, tool changes, etc.

6. Checking the correctness of the part program through:

a. Dry run the program.

b. Preview the toolpath on the machine screen

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Program structure

Main program Subroutines

➢ Program Blocks and Addresses

A part program is nothing more than a long column of lines containing numbers and

letters. Each letter and number pairing acts as an instruction for the CNC.

A part program is made up of blocks. Figure 3.4 shows two blocks of a sample part

program. One block is equivalent to one line of the program. An actual part program

might contain hundreds of blocks. Within each block, there is a series of words. Each

word is the pairing of an address letter and a number.

The order of the words is very important. One after another, the words of a block tell

the machine what operation to perform, where to perform it, and how fast (or slow)

to perform it.

Fig 3.4: Part programs consist of blocks, words, address

/ P1200

O10…… *

….

…

…

O120 …..M99*.

/ P1210

O10…… *

….

…

…

O120 …..M99*.

N001 G02 … *

N005 X……… *

.

N90 P1200 M98 *

N95 G….

N150 Y….. *

N200 P1200 M98*

N205 G.. Z.. *

.

N300 P1210 M98*

N305 …. *

.

N500 … M30 *

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➢ Block Numbering

Every program block starts with an N code. The N code acts as the name or title of a

block, figure 3.5.

Fig 3.5: Block number

The purpose of these codes is to help the part programmer organize the program

blocks. A programmer can also find a block by searching for its N code number.

G Codes

In many program blocks, G codes follow the N codes. These

codes tell the computer what operation should be performed. Each

G code contains up to two numbers, and each number matches a

operation or command.

In Figure 1, the first G code, G00, tells the machine that it should rapidly position the

tool at a certain location. The second G code, G01, tells it to move the tool along a

linear path at a certain feed rate. In every shop, G00, G01, and other codes have the

same.

The following table summarizes the most general ones. function Meaning Format

G0 Rapid motion N... G00 X... S...

G1 Linear motion N... G01 X... Z... F... S... M...

G2 Clockwise arc N... G02 X... Z... R... F... S... M...

G3 Counterclockwise arc N... G03 X... Z... R... F... S... M...

G17 X-Y plane

G18 X-Z plane

G19 Y – Z plane

G40 Cancel compensation

G41 Inward compensation

G42 Outward compensation

G45 Length compensation

G53 Suppress Zero shift

G54 Zero offset N... G50 X... Y...

G70 Inch system Differs from M/C to another

G71 Metric system Differs from M/C to another

G80 Cancel fixed cycle

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G75 -

G79 and

G81 –

G89

Fixed cycles

G90 Absolute coordinate

G91 Relative coordinate

G93 Unit of feed is mm/rev Differs from M/C to another

G94 Feed is mm/min Differs from M/C to another

G95 Unit of speed is rpm Differs from M/C to another

G96 Speed in m/min Differs from M/C to another

Fanuc G-Code List (Lathe)

G code Description

G00 Rapid traverse

G01 Linear interpolation

G02 Circular interpolation CW

G03 Circular interpolation CCW

G04 Dwell

G09 Exact stop

G10 Programmable data input

G20 Input in inch

G21 Input in mm

G22 Stored stroke check function on

G23 Stored stroke check function off

G27 Reference position return check

G28 Return to reference position

G32 Thread cutting

G40 Tool nose radius compensation cancel

G41 Tool nose radius compensation left

G42 Tool nose radius compensation right

G70 Finish machining cycle

G71 Turning cycle

G72 Facing cycle

G73 Pattern repeating cycle

G74 Peck drilling cycle

G75 Grooving cycle

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G76 Threading cycle

G92 Coordinate system setting or max. spindle speed setting

G94 Feed Per Minute

G95 Feed Per Revolution

G96 Constant surface speed control

G97 Constant surface speed control cancels

Fanuc G-Code List (Mill)

G code Description

G00 Rapid traverse

G01 Linear interpolation

G02 Circular interpolation CW

G03 Circular interpolation CCW

G04 Dwell

G17 X Y plane selection

G18 Z X plane selection

G19 Y Z plane selection

G28 Return to reference position

G30 2nd, 3rd, and 4th reference position return

G40 Cutter compensations cancel

G41 Cutter compensation left

G42 Cutter compensation right

G43 Tool length compensation + direction

G44 Tool length compensation – direction

G49 Tool length compensation cancel

G53 Machine coordinate system selection

G54 Workpiece coordinate system 1 selection

G55 Workpiece coordinate system 2 selection

G56 Workpiece coordinate system 3 selection

G57 Workpiece coordinate system 4 selection

G58 Workpiece coordinate system 5 selection

G59 Workpiece coordinate system 6 selection

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G68 Coordinate rotation

G69 Coordinate rotations cancel

G73 Peck drilling cycle

G74 Left-spiral cutting circle

G76 Fine boring cycle

G80 Canned cycle cancels

G81 Drilling cycle, spot boring cycle

G82 Drilling cycle or counter boring cycle

G83 Peck drilling cycle

G84 Tapping cycle

G85 Boring cycle

G86 Boring cycle

G87 Back boring cycle

G88 Boring cycle

G89 Boring cycle

G90 Absolute command

G91 Increment command

G92 Setting for work coordinate system or clamp at maximum spindle speed

G98 Return to initial point in canned cycle

G99 Return to R point in canned cycle

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CNC G codes

G00 - Positioning at rapid speed; Mill and Lathe G01 - Linear interpolation (machining a straight line); Mill and Lathe G02 - Circular interpolation clockwise (machining arcs); Mill and Lathe G03 - Circular interpolation, counter clockwise; Mill and Lathe G04 - Mill and Lathe, Dwell G09 - Mill and Lathe, Exact stop G10 - Setting offsets in the program; Mill and Lathe G12 - Circular pocket milling, clockwise; Mill G13 - Circular pocket milling, counter clockwise; Mill G17 - X-Y plane for arc machining; Mill and Lathe with live tooling G18 - Z-X plane for arc machining; Mill and Lathe with live tooling G19 - Z-Y plane for arc machining; Mill and Lathe with live tooling G20 - Inch units; Mill and Lathe G21 - Metric units; Mill and Lathe G27 - Reference return check; Mill and Lathe G28 - Automatic return through reference point; Mill and Lathe G29 - Move to location through reference point; Mill and Lathe (slightly different for each machine) G31 - Skip function; Mill and Lathe G32 - Thread cutting; Lathe G33 - Thread cutting; Mill G40 - Cancel diameter offset; Mill. Cancel tool nose offset; Lathe G41 - Cutter compensation left; Mill. Tool nose radius compensation left; Lathe G42 - Cutter compensation right; Mill. Tool nose radius compensation right; Lathe G43 - Tool length compensation; Mill G44 - Tool length compensation cancel; Mill (sometimes G49) G50 - Set coordinate system and maximum RPM; Lathe G52 - Local coordinate system setting; Mill and Lathe G53 - Machine coordinate system setting; Mill and Lathe G54~G59 - Workpiece coordinate system settings #1 t0 #6; Mill and Lathe G61 - Exact stop check; Mill and Lathe G65 - Custom macro call; Mill and Lathe G70 - Finish cycle; Lathe G71 - Rough turning cycle; Lathe G72 - Rough facing cycle; Lathe G73 - Irregular rough turning cycle; Lathe G73 - Chip break drilling cycle; Mill G74 - Left hand tapping; Mill G74 - Face grooving or chip break drilling; Lathe G75 - OD groove pecking; Lathe G76 - Fine boring cycle; Mill G76 - Threading cycle; Lathe G80 - Cancel cycles; Mill and Lathe G81 - Drill cycle; Mill and Lathe G82 - Drill cycle with dwell; Mill G83 - Peck drilling cycle; Mill G84 - Tapping cycle; Mill and Lathe G85 - Bore in, bore out; Mill and Lathe G86 - Bore in, rapid out; Mill and Lathe G87 - Back boring cycle; Mill G90 - Absolute programming G91 - Incremental programming G92 - Reposition origin point; Mill G92 - Thread cutting cycle; Lathe G94 - Per minute feed; Mill G95 - Per revolution feed; Mill

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G96 - Constant surface speed control; Lathe G97 - Constant surface speed cancel G98 - Per minute feed; Lathe G99 - Per revolution feed; Lathe

CNC M Codes

M00 - Program stop; Mill and Lathe M01 - Optional program stop; Lathe and Mill M02 - Program end; Lathe and Mill M03 - Spindle on clockwise; Lathe and Mill M04 - Spindle on counter clockwise; Lathe and Mill M05 - Spindle off; Lathe and Mill M06 - Tool change; Mill M08 - Coolant on; Lathe and Mill M09 - Coolant off; Lathe and Mill M10 - Chuck or rotary table clamp; Lathe and Mill M11 - Chuck or rotary table clamp off; Lathe and Mill M19 - Orient spindle; Lathe and Mill M30 - Program end, return to start; Lathe and Mill M97 - Local sub-routine call; Lathe and Mill M98 - Sub-program call; Lathe and Mill M99 - End of sub program; Lathe and Mill

List of G-codes commonly found on FANUC and similarly designed controls for milling and turning[edit]

Code Description Milling

( M ) Turning

( T ) Corollary info

G00 Rapid positioning M T

On 2- or 3-axis moves, G00 (unlike G01) traditionally does not necessarily move in a single straight line between start point and end point. It moves each axis at its max speed until its vector quantity is achieved. Shorter vector usually finishes first (given similar axis speeds). This matters because it may yield a dogleg or hockey-stick motion, which the programmer needs to consider, depending on what obstacles are nearby, to avoid a crash. Some machines offer interpolated rapids as a feature for ease of programming (safe to assume a straight line).

G01 Linear interpolation M T

The most common workhorse code for feeding during a cut. The program specs the start and end points, and the control automatically calculates (interpolates) the intermediate points to pass through that yield a straight line (hence "linear"). The control then calculates the angular velocities at which to turn the axis leadscrews via their servomotors or stepper motors. The computer performs thousands of

25

calculations per second, and the motors react quickly to each input. Thus the actual toolpath of the machining takes place with the given feed rate on a path that is accurately linear to within very small limits.

G02 Circular interpolation,

clockwise M T

Very similar in concept to G01. Again, the control interpolates intermediate points and commands the servo- or stepper motors to rotate the amount needed for the leadscrew to translate the motion to the correct tool tip positioning. This process repeated thousands of times per minute generates the desired toolpath. In the case of G02, the interpolation generates a circle rather than a line. As with G01, the actual toolpath of the machining takes place with the given feed rate on a path that accurately matches the ideal (in G02's case, a circle) to within very small limits. In fact, the interpolation is so precise (when all conditions are correct) that milling an interpolated circle can obviate operations such as drilling, and often even fine boring. Addresses for radius or arc center: G02 and G03 take either an R address (for the radius desired on the part) or IJK addresses (for the component vectors that define the vector from the arc start point to the arc center point). Cutter comp: On most controls you cannot start G41 or G42 in G02 or G03 modes. You must already have compensated in an earlier G01 block. Often, a short linear lead-in movement is programmed, merely to allow cutter compensation before the main action, the circle-cutting, begins. Full circles: When the arc start point and the arc end point are identical, the tool cuts a 360° arc (a full circle). (Some older controls do not support this because arcs cannot cross between quadrants of the cartesian system. Instead, they require four quarter-circle arcs programmed back-to-back.)

G03 Circular interpolation,

counterclockwise M T Same corollary info as for G02.

G04 Dwell M T

Takes an address for dwell period (may be X, U, or P). The dwell period is specified by a control parameter, typically set to milliseconds. Some machines can accept either X1.0 (s) or P1000 (ms), which are

26

equivalent. Choosing dwell duration: Often the dwell needs only to last one or two full spindle rotations. This is typically much less than one second. Be aware when choosing a duration value that a long dwell is a waste of cycle time. In some situations it won't matter, but for high-volume repetitive production (over thousands of cycles), it is worth calculating that perhaps you only need 100 ms, and you can call it 200 to be safe, but 1000 is just a waste (too long).

G05 P10000 High-precision contour

control (HPCC) M

Uses a deep look-ahead buffer and simulation processing to provide better axis movement acceleration and deceleration during contour milling

G05.1 Q1. AI Advanced Preview

Control M

Uses a deep look-ahead buffer and simulation processing to provide better axis movement acceleration and deceleration during contour milling

G06.1 Non-uniform rational B-spline (NURBS)

Machining M

Activates Non-Uniform Rational B Spline for complex curve and waveform machining (this code is confirmed in Mazatrol 640M ISO Programming)

G07 Imaginary axis

designation M

G09 Exact stops check,

non-modal M T The modal version is G61.

G10 Programmable data

input M T

Modifies the value of work coordinate and tool offsets

G11 Data write cancel M T

G17 XY plane selection M

G18 ZX plane selection M T

G19 YZ plane selection M

G20 Programming in inches M T Somewhat uncommon except in USA and (to lesser extent) Canada and UK. However, in the global marketplace,

27

competence with both G20 and G21 always stands some chance of being necessary at any time. The usual minimum increment in G20 is one ten-thousandth of an inch (0.0001"), which is a larger distance than the usual minimum increment in G21 (one thousandth of a millimeter, .001 mm, that is, one micrometer). This physical difference sometimes favors G21 programming.

G21 Programming

in millimeters (mm) M T

Prevalent worldwide. However, in the global marketplace, competence with both G20 and G21 always stands some chance of being necessary at any time.

G28

Return to home position (machine zero, aka machine reference

point)

M T

Takes X Y Z addresses which define the intermediate point that the tool tip will pass through on its way home to machine zero. They are in terms of part zero (aka program zero), NOT machine zero.

G30

Return to secondary home position (machine

zero, aka machine reference point)

M T

Takes a P address specifying which machine zero point to use if the machine has several secondary points (P1 to P4). Takes X Y Z addresses that define the intermediate point that the tool tip passes through on its way home to machine zero. These are expressed in terms of part zero (aka program zero), NOT machine zero.

G31 Feed until skip function M Used for probes and tool length measurement systems.

G32 Single-point threading, longhand style (if not

using a cycle, e.g., G76)

T

Similar to G01 linear interpolation, except with automatic spindle synchronization for single-point threading.

G33 Constant-pitch threading M

G33 Single-point threading, longhand style (if not

using a cycle, e.g., G76)

T Some lathe controls assign this mode to G33 rather than G32.

G34 Variable-pitch threading M

28

G40 Tool radius

compensation off M T

Turn off cutter radius compensation (CRC). Cancels G41 or G42.

G41 Tool radius

compensation left M T

Turn on cutter radius compensation (CRC), left, for climb milling. Milling: Given righthand-helix cutter and M03 spindle direction, G41 corresponds to climb milling (down milling). Takes an address (D or H) that calls an offset register value for radius. Turning: Often needs no D or H address on lathes, because whatever tool is active automatically calls its geometry offsets with it. (Each turret station is bound to its geometry offset register.)

G41 and G42 for milling has been partially automated and obviated (although not completely) since CAM programming has become more common. CAM systems let the user program as if using a zero-diameter cutter. The fundamental concept of cutter radius compensation is still in play (i.e., that the surface produced will be distance R away from the cutter centre), but the programming mindset is different. The human does not choreograph the toolpath with conscious, painstaking attention to G41, G42, and G40, because the CAM software takes care of that. The software has various CRC mode selections, such as computer, control, wear, reverse wear, off, some of which do not use G41/G42 at all (good for roughing, or wide finish tolerances), and others that use it so that the wear offset can still be tweaked at the machine (better for tight finish tolerances).

G42 Tool radius

compensation right M T

Turn on cutter radius compensation (CRC), right, for conventional milling. Similar corollary info as for G41. Given righthand-helix cutter and M03 spindle direction, G42 corresponds to conventional milling (up milling).

G43 Tool height offset

compensation negative M

Takes an address, usually H, to call the tool length offset register value. The value is negative because it will be added to the gauge line position. G43 is the commonly used version (vs G44).

G44 Tool height offset

compensation positive M

Takes an address, usually H, to call the tool length offset register value. The value is positive because it will be subtracted from the gauge line position. G44 is the seldom-used version (vs G43).

29

G45 Axis offset single

increase M

G46 Axis offset single

decrease M

G47 Axis offset double

increase M

G48 Axis offset double

decrease M

G49 Tool length offset

compensation cancel M Cancels G43 or G44.

G50 Define the maximum

spindle speed T

Takes an S address integer, which is interpreted as rpm. Without this feature, G96 mode (CSS) would rev the spindle to "wide open throttle" when closely approaching the axis of rotation.

G50 Scaling function cancel M

G50 Position register

(programming of vector from part zero to tool tip)

T

Position register is one of the original methods to relate the part (program) coordinate system to the tool position, which indirectly relates it to the machine coordinate system, the only position the control really "knows". Not commonly programmed anymore because G54 to G59 (WCSs) are a better, newer method. Called via G50 for turning, G92 for milling. Those G addresses also have alternate meanings (which see). Position register can still be useful for datum shift programming. The "manual absolute" switch, which has very few useful applications in WCS contexts, was more useful in position register contexts, because it allowed the operator to move the tool to a certain distance from the part (for example, by touching off a 2.0000" gage) and then declare to the control what the distance-to-go shall be (2.0000).

G52 Local coordinate system

(LCS) M

Temporarily shifts program zero to a new location. It is simply "an offset from an offset", that is, an additional offset added onto the WCS offset. This simplifies programming in some cases. The typical example is moving from part to part in a multipart setup. With G54 active, G52 X140.0 Y170.0 shifts program zero 140 mm over in X and 170 mm over in Y. When the part "over there" is done, G52 X0 Y0 returns program zero to normal G54 (by reducing G52 offset to nothing). The same result can also be achieved (1) using multiple WCS origins, G54/G55/G56/G57/G58/G59; (2) on newer controls, G54.1 P1/P2/P3/etc. (all the way up to P48); or (3) using G10 for programmable data input, in which the program can write new offset values to the offset registers.[8] The method to use

30

depends on shop-specific application.

G53 Machine coordinate

system

M T

Takes absolute coordinates (X,Y,Z,A,B,C) with reference to machine zero rather than program zero. Can be helpful for tool changes. Nonmodal and absolute only. Subsequent blocks are interpreted as "back to G54" even if it is not explicitly programmed.

G54 to G59 Work coordinate systems (WCSs)

M T

Have largely replaced position register (G50 and G92). Each tuple of axis offsets relates program zero directly to machine zero. Standard is 6 tuples (G54 to G59), with optional extensibility to 48 more via G54.1 P1 to P48.

G54.1 P1 to P48

Extended work coordinate systems

M T

Up to 48 more WCSs besides the 6 provided as standard by G54 to G59. Note floating-point extension of G-code data type (formerly all integers). Other examples have also evolved (e.g., G84.2). Modern controls have the hardware to handle it.

G61 Exact stop check, modal M T Can be canceled with G64. The non-modal version is G09.

G62 Automatic corner

override M T

G64 Default cutting mode

(cancel exact stop check mode)

M T Cancels G61.

G68 Rotate coordinate

system M

Rotates coordinate system in the current plane given with G17, G18, or G19. Center of rotation is given with two parameters, which vary with each vendor's implementation. Rotate with angle given with argument R. This can be used, for instance, to align the coordinate system with a misaligned part. It can also be used to repeat movement sequences around a center. Not all vendors support coordinate system rotation.

G69 Turn off coordinate

system rotation M Cancels G68.

G70

Fixed cycle, multiple repetitive cycle, for finishing (including

contours)

T

G71

Fixed cycle, multiple repetitive cycle, for

roughing (Z-axis emphasis)

T

G72

Fixed cycle, multiple repetitive cycle, for roughing (X-axis

emphasis)

T

G73

Fixed cycle, multiple repetitive cycle, for

roughing, with pattern repetition

T

31

G73

Peck drilling cycle for milling – high-speed (NO

full retraction from pecks)

M

Retracts only as far as a clearance increment (system parameter). For when chip breaking is the main concern, but chip clogging of flutes is not. Compare G83.

G74 Peck drilling cycle for

turning T

G74

Tapping cycle for milling, lefthand

thread, M04 spindle direction

M See notes at G84.

G75 Peck grooving cycle for

turning T

G76 Fine boring cycle for

milling M

Includes OSS and shift (oriented spindle stop and shift tool off centerline for retraction)

G76 Threading cycle for

turning, multiple repetitive cycle

T

G80 Cancel canned cycle M T

Milling: Cancels all cycles such as G73, G81, G83, etc. Z-axis returns either to Z-initial level or R level, as programmed (G98 or G99, respectively). Turning: Usually not needed on lathes, because a new group-1 G address (G00 to G03) cancels whatever cycle was active.

G81 Simple drilling cycle M No dwell built in

G82 Drilling cycle with dwell M

Dwells at hole bottom (Z-depth) for the number of milliseconds specified by the P address. Good for when hole bottom finish matters. Good for spot drilling because the divot is certain to clean up evenly. Consider the "choosing dwell duration" note at G04.

G83 Peck drilling cycle (full retraction from pecks)

M Returns to R-level after each peck. Good for clearing flutes of chips. Compare G73.

G84 Tapping cycle, righthand

thread, M03 spindle direction

M

G74 and G84 are the righthand and left hand "pair" for old-school tapping with a non-rigid toolholder ("tapping head" style). Compare the rigid tapping "pair", G84.2 and G84.3.

G84.2 Tapping cycle, righthand

thread, M03 spindle direction, rigid toolholder

M

See notes at G84. Rigid tapping synchronizes speed and feed according to the desired thread helix. That is, it synchronizes degrees of spindle rotation with microns of axial travel. Therefore, it can use a rigid toolholder to hold the tap. This feature is not available on old machines or newer low-end machines, which must use "tapping head" motion (G74/G84).

G84.3

Tapping cycle, lefthand

thread, M04 spindle direction, rigid toolholder

M

See notes at G84 and G84.2.

32

G85 boring cycle, feed

in/feed out M

• Good cycle for a reamer.

• In some cases good for single-point boring tool, although in other cases the lack of depth of cut on the way back out is bad for surface finish, in which case, G76 (OSS/shift) can be used instead.

• If need dwell at hole bottom, see G89.

G86 boring cycle, feed

in/spindle stop/rapid out M

Boring tool leaves a slight score mark on the way back out. Appropriate cycle for some applications; for others, G76 (OSS/shift) can be used instead.

G87 boring cycle, backboring M

For backboring. Returns to initial level only (G98); this cycle cannot use G99 because its R level is on the far side of the part, away from the spindle headstock.

G88 boring cycle, feed

in/spindle stop/manual operation

M

G89 boring cycle, feed in/dwell/feed out

M G89 is like G85 but with dwell added at bottom of hole.

G90 Absolute programming M T (B)

Positioning defined with reference to part zero. Milling: Always as above. Turning: Sometimes as above (Fanuc group type B and similarly designed), but on most lathes (Fanuc group type A and similarly designed), G90/G91 are not used for absolute/incremental modes. Instead, U and W are the incremental addresses and X and Z are the absolute addresses. On these lathes, G90 is instead a fixed cycle address for roughing.

G90 Fixed cycle, simple cycle, for roughing (Z-axis emphasis)

T (A) When not serving for absolute programming (above)

G91 Incremental

programming M T (B)

Positioning defined with reference to previous position. Milling: Always as above. Turning: Sometimes as above (Fanuc group type B and similarly designed), but on most lathes (Fanuc group type A and similarly designed), G90/G91 are not used for absolute/incremental modes. Instead, U and W are the incremental addresses and X and Z are the absolute addresses. On these lathes, G90 is a fixed cycle address for roughing.

G92 Position register

(programming of vector from part zero to tool tip)

M T (B)

Same corollary info as at G50 position register. Milling: Always as above. Turning: Sometimes as above (Fanuc

33

group type B and similarly designed), but on most lathes (Fanuc group type A and similarly designed), position register is G50.

G92 Threading cycle, simple

cycle T (A)

G94 Feedrate per minute M T (B) On group type A lathes, feedrate per minute is G98.

G94 Fixed cycle, simple cycle, for roughing (X-axis emphasis)

T (A) When not serving for feedrate per minute (above)

G95 Feedrate per revolution M T (B) On group type A lathes, feedrate per revolution is G99.

G96 Constant surface speed

(CSS) T

Varies spindle speed automatically to achieve a constant surface speed. See speeds and feeds. Takes an S address integer, which is interpreted as sfm in G20 mode or as m/min in G21 mode.

G97 Constant spindle speed M T

Takes an S address integer, which is interpreted as rev/min (rpm). The default speed mode per system parameter if no mode is programmed.

G98 Return to initial Z level in

canned cycle M

G98 Feedrate per minute

(group type A) T (A)

Feedrate per minute is G94 on group type B.

G99 Return to R level in

canned cycle M

G99 Feedrate per revolution

(group type A) T (A)

Feedrate per revolution is G95 on group type B.

G100 Tool length

measurement M

List of M-codes commonly found on FANUC and similarly designed controls for

milling and turning[edit]

Some older controls require M codes to be in separate blocks (that is, not on the

same line).

Code Description Milling

( M )

Turning

( T ) Corollary info

M00 Compulsory stop M T

Non-optional machine always

stops on reaching M00 in the

program execution.

M01 Optional stop M T Machine only stops at M01 if

operator pushes the optional

34

stop button.

M02 End of program M T

Program ends; execution may

or may not return to program

top (depending on the

control); may or may not reset

register values. M02 was the

original program-end code,

now considered obsolete, but

still supported for backward

compatibility. Many modern

controls treat M02 as

equivalent

to M30. See M30 for

additional discussion of

control status upon executing

M02 or M30.

M03

Spindle on

(clockwise

rotation)

M T

The speed of the spindle is

determined by the address S,

in either revolutions per

minute (G97 mode; default)

or surface feet per minute or

[surface] meters per minute

(G96 mode [CSS] under

either G20 or G21).

The right-hand rule can be

used to determine which

direction is clockwise and

which direction is

counterclockwise.

Right-hand-helix screws

moving in the tightening

direction (and

right-hand-helix flutes

spinning in the cutting

direction) are defined as

moving in the M03 direction

and are labelled "clockwise"

by convention. The M03

direction is always M03

regardless of local vantage

point and local CW/CCW

distinction.

35

M04

Spindle on

(counterclockwise

rotation)

M T See comment above at M03.

M05 Spindle stop M T

M06 Automatic tool

change (ATC) M

T

(some-times)

Many lathes do not use M06

because the T address itself

indexes the turret.

Programming on any machine

tool requires knowing which

method that machine uses. To

understand how the T address

works and how it interacts (or

not) with M06, one must study

the various methods, such as

lathe turret programming,

ATC fixed tool selection,

ATC random memory tool

selection.

M07 Coolant on (mist) M T

M08 Coolant on (flood) M T

M09 Coolant off M T

M10 Pallet clamp on M For machining centers with

pallet changers

M11 Pallet clamp off M For machining centers with

pallet changers

M13

Spindle on

(clockwise

rotation) and

coolant on (flood)

M

This one M-code does the

work of both M03 and M08. It

is not unusual for specific

machine models to have such

combined commands, which

make for shorter, more

quickly written programs.

M19 Spindle

orientation M T

Spindle orientation is more

often called within cycles

(automatically) or during

setup (manually), but it is also

available under program

control via M19. The

abbreviation OSS (oriented

spindle stop) may be seen in

reference to an oriented stop

within cycles.

The relevance of spindle

orientation has increased as

36

technology has advanced.

Although 4- and 5-axis

contour milling and

CNC single-pointing have

depended on spindle position

encoders for decades, before

the advent of widespread live

tooling and mill-turn/turn-mill

systems, it was not as often

relevant in "regular"

(non-"special") machining for

the operator (as opposed to the

machine) to know the angular

orientation of a spindle as it is

today, except in certain

contexts (such as tool change,

or G76 fine boring cycles with

choreographed tool

retraction). Most milling of

features indexed around a

turned workpiece was

accomplished with separate

operations on indexing

head setups; in a sense,

indexing heads were

originally invented as separate

pieces of equipment, to be

used in separate operations,

which could provide precise

spindle orientation in a world

where it otherwise mostly

didn't exist (and didn't need

to). But as CAD/CAM and

multiaccess CNC machining

with multiple rotary-cutter

axes becomes the norm, even

for "regular" (non-"special")

applications, machinists now

frequently care about stepping

just about any spindle through

its 360° with precision.

M21 Mirror, X-axis M

M21 Tailstock forward T

M22 Mirror, Y-axis M

M22 Tailstock

backward T

37

M23 Mirror OFF M

M23 Thread gradual

pullout ON T

M24 Thread gradual

pullout OFF T

M30

End of program,

with return to

program top

M T

Today, M30 is considered the

standard program-end code,

and returns execution to the

top of the program. Most

controls also still support the

original program-end

code, M02, usually by treating

it as equivalent to

M30. Additional

info: Compare M02 with

M30. First, M02 was created,

in the days when the punched

tape was expected to be short

enough to splice into a

continuous loop (which is why

on old controls, M02 triggered

no tape rewinding).[10] The

other program-end code, M30,

was added later to

accommodate longer punched

tapes, which were wound on

a reel and thus needed

rewinding before another

cycle could start.[10] On many

newer controls, there is no

longer a difference in how the

codes are executed—both act

like M30.

M41 Gear selects –

gear 1 T

M42 Gear selects –

gear 2 T

M43 Gear selects –

gear 3 T

M44 Gear selects –

gear 4 T

M48 Feedrate override

allowed M T

MFO (manual feedrate

override)

M49 Feedrate override

NOT allowed M T

Prevent MFO (manual

feedrate override). This rule is

38

also usually called

(automatically) within tapping

cycles or single-point

threading cycles, where feed

is precisely correlated to

speed. Same

with SSO (spindle speed

override) and feed hold

button. Some controls can

provide SSO and MFO during

threading.

M52 Unload Last tool

from spindle M T Also empty spindle.

M60 Automatic pallet

change (APC) M For machining centers with

pallet changers

M98 Subprogram call M T

Takes an address P to specify

which subprogram to call, for

example, "M98 P8979" calls

subprogram O8979.

M99 Subprogram end M T

Usually placed at end of

subprogram, where it returns

execution control to the main

program. The default is that

control returns to the block

following the M98 call in the

main program. Return to a

different block number can be

specified by a P address. M99

can also be used in main

program with block skip for

endless loop of main program

on bar work on lathes (until

operator toggles block skip).

39

➢ X, Y, and Z Codes - U, V and W codes - P, Q and R codes

After the G code, the X code, Y code, and Z code tell the machine

where to go. Referring to Figure 3.6, the cutting tool would rapidly position itself at

the location marked X3.0, Y-2.5, Z-1.0 first. Then, move along a straight line until it

reached the X12.0, Y2.0 location. The Z-axis location remains the same.

Fig 3.6: X, Y & Z

➢ F and S Codes

F code and S code tell the machine "how fast to do it." These codes are

used to set the feed and speed for the machine as it

performs a cutting operation that in figure 3.7 and figure 3.8.

Fig 3.7. Feed and speed on the mill. Fig 3.8. Feed and speed on the lathe.

In the program blocks shown in Figure 3.9, the first block does not contain F or S

codes. The rapid positioning of the tool does not require a specific speed or feed.

However, once the cutting tool begins to contact the workpiece in the second block,

F and S codes are needed to set the feed and speed rates.

40

Fig 3.9: F and S codes

➢ T and M Codes

The last spaces in a program block are reserved for T codes and M codes. T codes tell

the computer to choose a specific tool, and M codes might tell the computer a

miscellaneous command in figure 3.10.

Fig 10: T and M

The following table summarizes the most general ones.

Function Meaning Remarks

M0 Compulsory stop Program stops

M1 Optional stop M2 End of program

M3 Clockwise rotation CW rotation of the spindle

M4 Counter clock. Rotation CCW rotation of the spindle M5 Stop spindle

M6 Change tool M7 Run coolant

M9 Stop coolant

M20 cancel mirror image Differs from M/C to another M21 mirror image around X-axis Differs from M/C to another

M22 mirror image around Y-axis Differs from M/C to another

M24 mirror image around X and Y – axes Differs from M/C to another M30 End of program-rewind Differs from M/C to another

M98 Call subroutine Differs from M/C to another M99 End subroutine Differs from M/C to another

41

Exercise 1: write the part program for manufacturing the part in fig 1. The material is a

block 87 x 68 x 10 mm made of St 50. The feed used is 50 mm / min, the rotational

speed is 300 rpm, the depth of cut not to exceed 5 mm and the tool is 12 mm end mill

fitted in turret face no 2, with its tip adjusted at z = 0

Steps:

1. Fix the zero datum of the part. Assume

2. Determine the direction of motion. Assume anti-clock wise

3. Determine the corresponding points at which the equation of the curve changes

4. Decide upon the type of motion between each two corresponding points

5. Write the part program. It consists of 4 sections:

a. Identifying blocks b. Preparatory blocks

c. Main motion blocks d. End block

/ Part no 1 – Base plate Part Program name

N005F50 S300 M3 runs the spindle 300 rpm clockwise & be

ready

to move with feed rate 50 mm/min

30.25

15.13

20.11 60.00

15R

25R

23.01 42.1

20.38

X axis

X axis

Y axis

Z axis 40

10 60

Machine surface

42

N010 G0 Z0 Go with fast traverse to level Z = 0

N015 X0 Y0 T2 M6 Go with fast traverse to the location X = 0 &

Y = 0, then change to tool no. 2

N020 Z-39 move the head fast towards the table to level

Z = -39 mm

N025 G1 Z-53 M7 Runs the coolant, then move the head with

feed

50 mm/min towards the table to level Z

= -53 mm

N030 X38.01 Move on a straight line with the same feed to

location X = 38.01 mm

N035 X80.11 Y20.38 Move on a straight line with the same feed to

location X = 38.01 & Y = 20.38 mm

N040 Y35.38 Move on a straight line with the same feed to

location Y = 35.38 mm

N045 G3 X55.11 Y60.38 R25 F20 Move on a counter-clock arc with

feed

20 mm/min to location X = 55.11 & Y

= 60.38

With a radius R = 25

N050 G1 X20.11 F50 Move on a straight line with feed

= 50 mm/min

To location X = 20.11 mm

N055 X0 Y30.13 Move on a straight line with the same feed to

location X = 0 & Y = 30.13 mm

N060 Y15 Move on a straight line to location

Y = 15 mm

N065 G2 X15 Y0 R15 F20 Move on a clockwise arc with feed

20 mm/min to location X = 15 & Y = 0 with

a radius R = 15

N070 G1 Z-39 F50 M9 Move the head up to level Z = -39 mm with a

Feed rate F = 50 mm/min, then stop the

coolant

N075 G0 Z0 Go with fast traverse to level Z = 0

N080 X0 Y0 M5 Go with fast traverse to the location X = 0 &

Y = 0, then stop spindle

N085 M30 End of program

43

Lecture Note 4: Offsetting the cutter left or right

➢ Introduction

• Two different G-Codes to apply cutter compensation depending on the direction

of the cut.

• When the material is to the left of the cutter, we use G41 and when it is to the

right, we use G42.

• G40 is used to turn it off.

• Ways to apply cutter compensation

➢ There are three different ways that cutter compensation.

• G42 P5.0; By using a 'P' value, the machine will offset the cutter by a defined

amount (5mm). This technique is usually used on small CNC machines without

a built-in tool table

• G42 X5.0; By using an 'X' value, it means the same thing.

• G42; On machines with a built-in tool table within their control system, cutter

compensation is just applied using a simple G42 (or G41) command

Larger industrial machinery normally uses this style of defining the radius of the tool

as the tooling information is entered into the tool table during the setup of the machine.

During the tool call line of our program, the machine pulls all the tooling information

into its memory and G42 is used to let the machine know that we wish to use cutter

compensation. No other information is needed.

Example 1

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G41 G40 Cutter Radius Compensation Example

N5 G00 G54 G64 G90 G17 X20 Y-20 Z50

N10 S450 M03 F250 D01 (12.5 MM DIA)

N20 Z5

N25 G01 Z0

N30 Z-5

N35 G41 X0 Y0

N40 X-48

N45 X-68 Y72

N50 X-28

N55 Y44

N60 X12 Y32

N65 X0 Y0

N70 G40 X20 Y-20

N75 G00 Z50

N80 Y100

N85 M30

Finished Part

After machining process completion, component will look like

Cutter Radius Compensation Example Finished Part

Explanation of CNC G-Code

G00 : Rapid traverse.

G54 : Zero Offset no. 1.

G90 : Absolute dimensioning system.

G17 : X-Y plan selection.

G41 : Cutter radius compensation activation (left hand side movement)

G40 : Cutter radius compensation de-active

S : Spindle speed

F : Axis motion feed

M : Cutter rotation (3=clockwise, 4=anti-clockwise)

D : Tool offset no

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Lecture Note 5: Cycles

➢ CNC Milling Cycles

CNC milling machine provided with machining software program in ready form by the

manufacturer. These are called machining cycles.

• Drilling Cycle. To drill the hole shown, the part program requires at least 5

blocks in figure 5.1:

Fig 5.1: Drilling Cycle

N10 G71 G94 G90 * Metric mode feed rate in mm/min and absolute

coordinate system

N20 G00 X10.00 Y 15.00 * Position the drilling tool at X = 10.00 and

Y= 15.00

N30 G00 Z-10.00 * Drill moves to approach (reference) plane in rapid

traverse.

N40 G01 Z-50.00 S800 F150 M03 * The spindle starts rotating at 800 rpm in

clockwise direction and the hole are

drilled at feed rate of 150 mm/minute.

N50 Z0 * Drill returns to reference plane

Fixed cycle for drilling a hole is applicable in figure 5.2 , where the complete drilling is

completed by giving information in a single block.

N10 G71 G94 G90 *

N20 G81 X10.00 Y15.00 Z-10 Z-50 S800 F150 M03 *

Hence the Format for drilling cycle is

N… G81 X… Y… Z… Z… S… F… M… *

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Fig 5.2: Fixed cycle for drilling

• Deep Hole Drilling Cycle (Peck Drilling Cycle). When the depth of hole is

more (l/d > 10) in figure 5.3, it is desirable to withdraw the drill from the hole at

regular intervals to avoid clogging due to chips in figure 5.4. Consider the work

piece shown in fig. The typical format for using deep hole drilling cycle is given

below:

Fig 5.3: Deep Hole Drilling Cycle

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Fig 5.4: Deep Hole Drilling Cycle chips

N10 G71 G94 G91 M03 S 1000 *

N20 G83 X 10.00 Y 10.00 R-10.00 Z-90.00 Q25.00 F100 *

• Threading cycle (tapping)

The tapping operation, involves positioning of tap at required X and Y position,

moving it rapidly to reference plane and feeding into the predrilled hole in the work

piece at given feed rate. In figure 5.5 The spindle rotation is then reversed, and the tap

is brought back to reference plane in figure 5.6 at the programmed feed rate. The

spindle rotation is again reversed to prepare for next tapping operation.

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Fig 5.5: Threading cycle (tapping)

Fig 5.6: reference plane

N001 G71 G91 M03 S 500 *

N004 G84 X10.00 Y10.00 R-10.00 Z-35.00 F60 *

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Boring Cycle. In the boring cycle the boring tool is fed to the required depth at the

given feed rate in figure 5.7. When the tool has reached the required depth, the

rotation of the tool is stopped, and the tool is withdrawn at a rapid feed rate up to the

reference plane.

Fig 5.7: Boring Cycle

• Face Milling canned cycle

In face milling cycle in figure 5.8:

• the cutter is moved in X and Y rapidly till located at the start point (Xs,Ys)

• The cutter is moved rapidly in Z till the approach plane

• The cutter is moved with the feed rate in Z till the required depth

• The cutter, then, moves with the feed rate in X and Y in a zigzag shape, fig till

it reaches the end point (Xe,Ye)

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• The cutter retracts rapidly the approach (initial) level or to the initial level

depending on the format of the cycle.

Fig 5.8 : Face milling

The Format is:

G77 Xs… X… Ys… Yi… Y… F…

Where:

• X and Y are the incremental distance to be milled along the X and Y axes

• Yi is the incremental step along Y axis

➢ Rectangular Pocket milling cycle

Figure 5.9. shows a rectangular pocket being milled.

Fig 5.9: rectangular pocket

Approach level

Initial

level

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The Format for roughing with a step in X is:

G78 X1… Y1… Z1… Z2… X2… X3… Y3… F…

The Format for roughing with a step in Y is:

G78 X1… Y1… Z1… Z2… Y2… X3… Y3… F…

The Format for finishing with a step in X is:

G79 X1… Y1… Z1… Z2… X2… X3… Y3… X4 F…

In this cycle the cutter after completing the roughing motion as in G78, it proceeds to

cut inside the peripheral the finishing depth (X4)

➢ Turning Cycles

• Straight Rough turning cycle

Fig 5.10: Straight rough turning cycle

The tool is positioned at the start point. It moves rapidly to the require diameter (X)

along the path “1”. In figure 5.10 It turns with the feed rate to the required length (Z)

along path “2”. It faces the shoulder to the initial diameter through path “3”. It retracts

rapidly to the initial position though path “4”. The Format is:

G77 X… Z… F…

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If it is a taper rough turning and the incremental movement of the tool along X is “I…”,

where I = , then the format is:

G77 X… Z… I… F…

• Facing Cycle

It is like straight rough turning with the movement illustrated in figure 5.11. Its format

is: G79 X… Z… F…

Fig 5.11: Facing cycle

• Threading cycle

Both straight and taper threads can be cut using the thread canned cycle, figure 5.12.

Fig 5.12: thread canned cycle

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The threading tool is positioned at the start point. The format is:

G78 X… Z… F…

Where F is the lead of the screw.

If it is a taper thread and the incremental movement of the tool along X is “I…”, then

the format is:

G78 X… Z… I… F…

• Rough and finish Profile turning cycles

Nowadays turning canned cycles are capable to perform multiple repetitive cycles,

which are more powerful canned cycles that automatically determine the number of

tools passes necessary to machine a part. Multiple repetitive cycles can machine most

combinations of tapers, chamfers, and contours. Examples of the profile turning are

shown in figure 5.13 and 5.14. The formats of those cycles will not be given, here, as

they differ completely from a control to another.

Fig 5.13: Rough profile turning cycle Fig 5.14: Profile facing cycle