1 cnc lathe machine nurfaizey b. abdul hamid 26 february 2008

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CNC Lathe Machine

Nurfaizey b. Abdul Hamid

26 February 2008

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CONTENTS

1. Introduction to CNC

2. Operations and Capabilities

3. CNC Lathe Programmable Axes

4. CNC Lathe Programming

5. CNC Lathe Programming Example

FAKULTI KEJURUTERAAN MEKANIKALUNIVERSITI TEKNIKAL MALAYSIA MELAKA

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1. INTRODUCTIONFAKULTI KEJURUTERAAN MEKANIKAL

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

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 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

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 components with all the advantages associated with CNC.


CNC Lathe Machine(www.okuma.co.jp)

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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 manufacture the component.


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Typical steps that have to taken by the operator to produce a component:1. Choosing the right cutting tool for the operation2. Place the cutting tool in the machine’s turret3. Tighten the tools4. Place the workpiece onto the work holding device5. Tighten the workpiece6. Set the zero point (datum)7. Choosing the right speed8. Check the turning direction of the spindle9. Choosing the right feed rate10. Start the spindle11. Start the coolant motor12. Start programme13. Stop the coolant motor14. Stop the spindle motor15. Remove workpiece from the machine16. Dimensional inspection of the component

FAKULTI KEJURUTERAAN MEKANIKALUNIVERSITI TEKNIKAL MALAYSIA MELAKA2. OPERATION & CAPABILITIES

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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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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.


Programme stage in manufacturing process

4. CNC PROGRAMMING

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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

FAKULTI KEJURUTERAAN MEKANIKALUNIVERSITI TEKNIKAL MALAYSIA MELAKA4. CNC PROGRAMMING –(cont’d)

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Basic Programming - Program Configuration

Generally a program consists of:1. Program Name2. Sequence Name and Sequence label3. Coordinates and commands4. Remarks5. 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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Program Name (Program Number)

Program name designationO_ _ _ _

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 -OK2. OAB12 -OK3. 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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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 -OK2. NAT02 -OK3. N1AT2 -tak OK (alphabet and numeric-

berselang-seli) 4. N123 tak sama N0123


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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.


Circular cutting (counter c/wise)G03

Circular cutting (clockwise)G02

Straight line cuttingG01

PositioningG00

CONTENTSG-Code

Circular cutting (counter c/wise)G03

Circular cutting (clockwise)G02

Straight line cuttingG01

PositioningG00

CONTENTSG-Code

4. CNC PROGRAMMING –(cont’d)

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Absolute programmingG90

Call of finish turning cycle (LAP)G87

Call of rough bar turning cycle (LAP)G85

Start of transverse shape designation (LAP)G82

Start of longitudinal shape designation (LAP)G81

End of shape designation (LAP)G80

Tapping compound fixed cycleG77/G78

Transverse grooving/drilling compound fixed cycleG74

Longitudinal grooving compound fixed cycleG73

Longitudinal compound fixed thread cutting cycleG71

Maximum Spindle speed designationG50

Tool nose radius composition: rightG42

Tool nose radius composition: leftG41

Tool nose radius composition: CancelG40

DwellG04

CONTENTSG-Code

Absolute programmingG90

Call of finish turning cycle (LAP)G87

Call of rough bar turning cycle (LAP)G85

Start of transverse shape designation (LAP)G82

Start of longitudinal shape designation (LAP)G81

End of shape designation (LAP)G80

Tapping compound fixed cycleG77/G78

Transverse grooving/drilling compound fixed cycleG74

Longitudinal grooving compound fixed cycleG73

Longitudinal compound fixed thread cutting cycleG71

Maximum Spindle speed designationG50

Tool nose radius composition: rightG42

Tool nose radius composition: leftG41

Tool nose radius composition: CancelG40

DwellG04

CONTENTSG-Code


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Low gearM41

High speed gearM42

Coolant offM09

Coolant onM08

Spindle stopM05

Spindle counterclockwise rotationM04

Spindle clockwise rotationM03

End of programM02

Optional stopM01

Program stopM00

CONTENTSM-code

Cancel of G96 (direct spindle speed)G97

Constant speed cutting ONG96

Feed per revolution mode (mm/min)G95

Feed per minute mode (mm/min)G94

Incremental programmingG91

CONTENTSG-Code

Low gearM41

High speed gearM42

Coolant offM09

Coolant onM08

Spindle stopM05

Spindle counterclockwise rotationM04

Spindle clockwise rotationM03

End of programM02

Optional stopM01

Program stopM00

CONTENTSM-code

Cancel of G96 (direct spindle speed)G97

Constant speed cutting ONG96

Feed per revolution mode (mm/min)G95

Feed per minute mode (mm/min)G94

Incremental programmingG91

CONTENTSG-Code


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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 millimetersX90.1 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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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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Tool Selection

Selection of a cutting tool is made by 4 digit figures following a

character TT_ _ _ _Example: T 02 02

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 NumberTool Number

Tool Offset NumberTool Number

Tool nose radius compensation


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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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Example:T0101S2000 M03G00 X188 Z204 X188G01 X185 Z120 F0.5 X190

Z100 X200G00 X300 Z300M5 (Spindle stop)M2 (End of program)

In the above example:1. T0101 commands the machine to select tool number 12. S2000 Sets the spindle speed to 2000 rpm3. M03 Commands the spindle to rotate in clockwise

direction speed determined by previous S code. In this case, 2000 rpm.

4. M05 Stops the spindle


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Coolant on/off (M08, M09)

Example:T0101S2000 M03G00 X188 Z204

X185M08G01 X185 Z120 F0.5

X190 Z100

X200G00 X300 Z300M5M09M2


Coolant OffM09

Coolant OnM08

Coolant OffM09

Coolant OnM08


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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 01S2000 M03G00 X188 Z204X185M00 (Operation cycle stop here)M08 (Operation cycle continues here when CYCLE START

button is pressed)


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G01 X185 Z120 F0.5 X190

Z100 X200M01 (Operation cycle Stop if OPTIONAL STOP button is

switched on)G00 X300 Z300M5 (Spindle stop)M09 (Coolant off) M2 (End of program)


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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 01S2000 M03G00 X188 Z204

X185M5M2


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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 cuttingT0101S2000 M03G00 X188 Z204 X185M08G01 X185 Z120 F0.5 X190 Z100 X200G00 X300 Z300M5M09M2


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Dwell (G04) & maximum spindle speed (G50)

Program will pause for F_secondG04 F_

Specify the max spindle speed (S_ _ _ _) allowed in the program

G50 S_


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* Refer to handout

FAKULTI KEJURUTERAAN MEKANIKALUNIVERSITI TEKNIKAL MALAYSIA MELAKA5. PROGRAMMING EXAMPLE

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THE END


THANK YOU

1 cnc lathe machine nurfaizey b. abdul hamid 26 february 2008

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