CNC Lathe Machine
Nurfaizey b. Abdul Hamid
1 26 February 2008
FAKULTI KEJURUTERAAN MEKANIKAL
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
CONTENTS
1. Introduction to CNC
2. Operations and Capabilities
3. CNC Lathe Programmable Axes
4. CNC Lathe Programming
5. CNC Lathe Programming Example
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1. INTRODUCTION
Introduction to Computer Numerical Control (CNC)
CNC is defined as ‘Control of machine tools and other manufacturing
equipment using computer programs’ (R.R.Kibbe, 2006).
Since the earliest days of production manufacturing involving the precision
of duplication of parts, manufacturing engineers and industrial technologists
have sought ways to increase dimensional accuracy and to increase the
speed of production.
After the development of computers, CNC had been used to control
machines in order to get high degree of repeatable precision.
The precision dimensional requirements that are the mainstay of the
machining processes, such as drilling, turning and milling, have made CNC
ideal to control the machines.
Today, CNC is not only limited to machining processes. It also appears in
many other types of manufacturing processes.
CNC is also used for robotic spot welding, wire welding, robotic assembly,
pipe and tube bending, laser and plasma arc cutting, wood routers, flame
and abrasive water jet cutting, electro-discharge machining (EDM), spray
3 painting and etc.
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1. INTRODUCTION – (cont’d)
The Advantages of Computer Numerical Control (CNC)
Higher production rate
High degree of repeatable precision
Lower reject rate
Reduce tooling cost
Less handling by operators
Able to produce complex shapes
CNC Lathe Machines CNC Lathe Machine
(www.okuma.co.jp)
A CNC lathe machine does the same operations as the conventional lathe
machine. It is used to produce component with circular cross section using
turning operations and related tasks such as drilling, boring, tapping and
reaming.
The main difference is the use of CNC to control the operation of the
machine.
Using computer programs, CNC lathe machines are able to produce
4 components with all the advantages associated with CNC.
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2. OPERATION & CAPABILITIES
The Operations of CNC Lathe Machine
Plane turning (Melarik lurus)
Taper turning (Melarik tirus)
Facing (Merata permukaan)
Parting off (Memotong)
Threading (Membenang)
Knurling (Membunga)
Drilling/reaming (Membuat lubang)
Boring (Membesarkan lubang)
Polishing (Menggilap)
CNC Lathe Machine Capabilities
Can operate in long period without operator’s supervision.
Can operate using numerical control program to produce various
components.
Programs can be created, stored, and can be used whenever needed to
5 manufacture the component.
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2. OPERATION & CAPABILITIES
Typical steps that have to taken by the operator to produce a component:
1. Choosing the right cutting tool for the operation
2. Place the cutting tool in the machine’s turret
3. Tighten the tools
4. Place the workpiece onto the work holding device
5. Tighten the workpiece
6. Set the zero point (datum)
7. Choosing the right speed
8. Check the turning direction of the spindle
9. Choosing the right feed rate
10. Start the spindle
11. Start the coolant motor
12. Start programme
13. Stop the coolant motor
14. Stop the spindle motor
15. Remove workpiece from the machine
16. Dimensional inspection of the component
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3. CNC PROGRAMMABLE AXES
The Programmable Axes on CNC Lathe Machine
Every CNC machine tool is designed to position the workpiece and cutting
tools to perform cutting operations.
Each machine has a definite three dimensional volume of space in which
tools and workpieces may be moved about and positioned.
On CNC lathe machines, the spindle axis is Z and the cross slide is X (figure
below).
The fundamental programmable axes of CNC lathe machine
(R.R.Kibbe, 2006)
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4. CNC PROGRAMMING
CNC Lathe - Basic Programming Concept
The purpose of NC programming is to write a sequence of events to be
done, a set of cutting tool to be used and a set of machine control functions
to be used to apply the tools and position the workpiece properly.
The program stage in manufacturing process is as shown below.
8 Programme stage in manufacturing process
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4. CNC PROGRAMMING –(cont’d)
CNC Program Standard Code
Most modern CNC programming is done in the word address format
Preparatory function codes or G codes. Usually noted in uppercase (G)
Programmable axes dimensional information for positioning tools and
workpieces (X, Y, Z, a, b, c)
Miscellaneous function codes or M codes. Usually noted in uppercase (M)
Various other letter codes such as I, J, K, F, S and R
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4. CNC PROGRAMMING –(cont’d)
Basic Programming - Program Configuration
Generally a program consists of:
1. Program Name
2. Sequence Name and Sequence label
3. Coordinates and commands
4. Remarks
5. End of program block
This information is presented using ALPHABATIC CHARACTERS and
NUMERIC CHARACTERS. Each line of characters is called a BLOCK.
O________ (Can be omitted if only one program in the file)
N________ G_X_Z_S_T_M_
:
:
M2
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4. CNC PROGRAMMING –(cont’d)
Program Name (Program Number)
Program name designation
O_ _ _ _
Up to 4 characters can be used
The characters can be numeric
Alphabetic character must be a head of numeric character.
Example: Program name
1. O1234 -OK
2. OAB12 -OK
3. O1AA2 - Tak OK- after AA (sama)
4. O123 = O0123
Program name can be omitted if there is only one main program in the file.
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4. CNC PROGRAMMING –(cont’d)
Sequence Name and Label
A sequence name is defined as a name assigned to a block. Numeric or
alphabetic characters following after “N” are designated for a sequence
name.
N_____
Sequence name must be placed at the beginning of a block. However it is
not essential to include sequence name in program
Sequence name may be specified in any order.
Example: Program name
1. N1234 -OK
2. NAT02 -OK
3. N1AT2 -tak OK (alphabet and numeric-berselang-seli)
4. N123 tak sama N0123
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4. CNC PROGRAMMING –(cont’d)
Commands
Machine carries out its tasks by following the commands written in a
program. These commands are presented by groups of codes, so called G
code and M code. Each code commands the machine to do specific action.
For example:
1. G00 commands the machine to move the cutter at a rapid speed to a
specific point in the work.
2. M08 commands the machine to start spraying coolant through the
nozzles.
G-Code CONTENTS
G00 Positioning
G01 Straight line cutting
G02 Circular cutting (clockwise)
13 G03 Circular cutting (counter c/wise)
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4. CNC PROGRAMMING –(cont’d)
G-Code CONTENTS
G04 Dwell
G40 Tool nose radius composition: Cancel
G41 Tool nose radius composition: left
G42 Tool nose radius composition: right
G50 Maximum Spindle speed designation
G71 Longitudinal compound fixed thread cutting cycle
G73 Longitudinal grooving compound fixed cycle
G74 Transverse grooving/drilling compound fixed cycle
G77/G78 Tapping compound fixed cycle
G80 End of shape designation (LAP)
G81 Start of longitudinal shape designation (LAP)
G82 Start of transverse shape designation (LAP)
G85 Call of rough bar turning cycle (LAP)
G87 Call of finish turning cycle (LAP)
G90 Absolute programming
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4. CNC PROGRAMMING –(cont’d)
G-Code CONTENTS
G91 Incremental programming
G94 Feed per minute mode (mm/min)
G95 Feed per revolution mode (mm/min)
G96 Constant speed cutting ON
G97 Cancel of G96 (direct spindle speed)
M-code CONTENTS
M00 Program stop
M01 Optional stop
M02 End of program
M03 Spindle clockwise rotation
M04 Spindle counterclockwise rotation
M05 Spindle stop
M08 Coolant on
M09 Coolant off
M41 Low gear
15 M42 High speed gear
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4. CNC PROGRAMMING –(cont’d)
Coordinates
In order to let the machine know where it should move the tool, the
coordinate point have to be specified. The coordinate value is represented
by X, Z, A, C, I and K-axis. However, only X and Z-axis is being concerned
in this class.
X±_____.___ Z ±_____.___
In default parameter setting, the unit system is in millimeters
X90.1 is effectively 90.1 mm or 90100μm
Also by default, the unit system allow 3 significant digits after the decimal
point. X0.001
Decimal point is not essential if integer value is assigned.
X90 is effective as X90. or X90.0
Example: X -70.711 Z100
X 90.001 Z90
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4. CNC PROGRAMMING –(cont’d)
Other code address include F, S, T, P, Q……
Where:
F = Feed rate (cutting)
S = Spindle speed (Rotation – clockwise @ counterclockwise)
T = Tool number and tool offset number
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4. CNC PROGRAMMING –(cont’d)
Tool Selection
Selection of a cutting tool is made by 4 digit figures following a
character T
T_ _ _ _ Example: T 02 02
Tool Offset Number
Tool Number
When Tool nose radius compensation function is used, selection of a
cutting tool is made by 6 digit figures.
T 02 02 02
Tool Offset Number
Tool Number
Tool nose radius compensation
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4. CNC PROGRAMMING –(cont’d)
Controlling The spindle (S, M03, M04, M05)
Logically the spindle must be rotating before the cutting process
commences. These codes are used to control the direction and its
speed.
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4. CNC PROGRAMMING –(cont’d)
Example:
T0101
S2000 M03
G00 X188 Z204
X188
G01 X185 Z120 F0.5
X190
Z100
X200
G00 X300 Z300
M5 (Spindle stop)
M2 (End of program)
In the above example:
1. T0101 commands the machine to select tool number 1
2. S2000 Sets the spindle speed to 2000 rpm
3. M03 Commands the spindle to rotate in clockwise direction speed
determined by previous S code. In this case, 2000 rpm.
20 4. M05 Stops the spindle
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4. CNC PROGRAMMING –(cont’d)
Coolant on/off (M08, M09)
M08 Coolant On
M09 Coolant Off
Example:
T0101
S2000 M03
G00 X188 Z204
X185
M08
G01 X185 Z120 F0.5
X190
Z100
X200
G00 X300 Z300
M5
M09
21 M2
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4. CNC PROGRAMMING –(cont’d)
Program Stop and Program End (M00, M01, M02)
M00 Program Stop. The machining cycle stops when this code is
encountered during program execution. Pressing CYCLE START at this
point will resume the operation.
M01 Optional Stop. M01 performs the same functions as M00, except,
it is only effective when the OPTIONAL STOP button on the control
panel is switched on. Pressing CYCLE START at this point will be resume
the operation.
M02 End of program. It must be included to indicate end of a
program. This code also resets the control.
Example:
T01 01 01
S2000 M03
G00 X188 Z204
X185
M00 (Operation cycle stop here)
M08 (Operation cycle continues here when CYCLE START button is
22 pressed)
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4. CNC PROGRAMMING –(cont’d)
G01 X185 Z120 F0.5
X190
Z100
X200
M01 (Operation cycle Stop if OPTIONAL STOP button is switched on)
G00 X300 Z300
M5 (Spindle stop)
M09 (Coolant off)
M2 (End of program)
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4. CNC PROGRAMMING –(cont’d)
Positioning (G00)
G00 commands the machine to position the cutter to a coordinate point
at rapid feed rate
G00 X_ _ _ _ . _ _ _ Z _ _ _ _ . _ _ _
X and Z designate the stopping point
Example
T01 01 01
S2000 M03
G00 X188 Z204
X185
M5
M2
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4. CNC PROGRAMMING –(cont’d)
Straight line cutting
This code commands the machine to move the cutter from current
position to the position specified by X and Z. Along a straight line a
feed rate specified by F.
G01 X_ _ _ _ . _ _ _ Z _ _ _ _ . _ _ _ F_ . _ _ _
Example straight line cutting
T0101
S2000 M03
G00 X188 Z204
X185
M08
G01 X185 Z120 F0.5
X190
Z100
X200
G00 X300 Z300
M5
M09
25 M2
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4. CNC PROGRAMMING –(cont’d)
Dwell (G04) & maximum spindle speed (G50)
Program will pause for F_second
G04 F_
Specify the max spindle speed (S_ _ _ _) allowed in the program
G50 S_
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5. PROGRAMMING EXAMPLE
* Refer to handout
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THE END
THANK YOU
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