SlideShare ist ein Scribd-Unternehmen logo
1 von 32
Downloaden Sie, um offline zu lesen
NC and CNC machines and Control Programming
Introduction to NC and CNC machines
CNC controls and RS274 programming
History of CNC
1949
US Air Force asks MIT to develop a "numerically controlled"
machine.
1952
Prototype NC machine demonstrated (punched tape input)
1980-
CNC machines (computer used to link directly to controller)
1990-
DNC: external computer “drip feeds” control programmer
to machine tool controller
Motivation and uses
To manufacture complex curved geometries in 2D or 3D
was extremely expensive by mechanical means (which
usually would require complex jigs to control the cutter
motions)
Machining components with repeatable accuracy
Unmanned machining operations
Advantages of CNC
- Easier to program;
- Easy storage of existing programs;
- Easy to change a program
- Avoids human errors
- NC machines are safer to operate
- Complex geometry is produced as cheaply as simple ones
- Usually generates closer tolerances than manual machines
Conventional milling machines
Vertical milling machine
Vertical Milling machine architecture
Conventional milling machines
Horizontal Milling machine architecture
Conventional milling machines
How does the table move along X- Y- and Z- axes ?
NC machines
Motion control is done by: servo-controlled motors
~
S e r v o C o n tr o lle r
C o u n te r C o m p a r a to r
E n c o d e r A /C M o to r
In p u t ( c o n v e r te d fr o m a n a lo g to d ig ita l v a lu e )
T a b le
L e a d s c r e w
CNC terminology
BLU: basic length unit 
smallest programmable move of each axis.
Controller: (Machine Control Unit, MCU) 
Electronic and computerized interface between operator and m/c
Controller components:
1. Data Processing Unit (DPU)
2. Control-Loops Unit (CLU)
Controller components
Data Processing Unit:
Input device [RS-232 port/ Tape Reader/ Punched Tape Reader]
Data Reading Circuits and Parity Checking Circuits
Decoders to distribute data to the axes controllers.
Control Loops Unit:
Interpolator to supply machine-motion commands between data points
Position control loop hardware for each axis of motion
Types of CNC machines
Based on Motion Type:
Point-to-Point or Continuous path
Based on Control Loops:
Open loop or Closed loop
Based on Power Supply:
Electric or Hydraulic or Pneumatic
Based on Positioning System
Incremental or Absolute
Open Loop vs. Closed Loop controls
Open loop control of a Point-to-Point NC drilling machine
NOTE: this machine uses stepper motor control
Components of Servo-motor controlled CNC
Motor speed control
Two types of encoder configurations
Motor lead screw rotation table moves
position sensed by encoder
feedback
Motion Control and feedback
Encoder outputs: electrical pulses (e.g. 500 pulses per revolution)
Rotation of the motor  linear motion of the table: by the leadscrew
The pitch of the leadscrew: horizontal distance between successive threads
One thread in a screw  single start screw: Dist moved in 1 rev = pitch
Two threads in screw  double start screw: Dist moved in 1 rev = 2* pitch
Example 1
A Stepping motor of 20 steps per revolution moves a machine table
through a leadscrew of 0.2 mm pitch.
(a) What is the BLU of the system ?
(b) If the motor receives 2000 pulses per minute, what is the linear
velocity in inch/min ?
Example 2
A DC servo-motor is coupled to a leadscrew (pitch 5mm) of a machine table.
A digital encoder, which emits 500 pulses per revolution, is mounted on the
leadscrew. If the motor rotates at 600 rpm, find
(a) The linear velocity of the table
(b) The BLU of the machine
(c) The frequency of pulses emitted by the encoder.
Manual NC programming
Part program: A computer program to specify
- Which tool should be loaded on the machine spindle;
- What are the cutting conditions (speed, feed, coolant ON/OFF etc)
- The start point and end point of a motion segment
- how to move the tool with respect to the machine.
Standard Part programming language: RS 274-D (Gerber, GN-code)
History of CNC
The RS274-D is a word address format
Each line of program == 1 block
Each block is composed of several instructions, or (words)
Sequence and format of words:
N3 G2 X+1.4 Y+1.4 Z+1.4 I1.4 J1.4 K1.4 F3.2 S4 T4 M2
sequence no
preparatory function
destination coordinates dist to center of circle
feed rate spindle speed
tool
miscellaneous function
Manual Part Programming Example
Tool size = 0.25 inch,
Feed rate = 6 inch per minute,
Cutting speed = 300 rpm,
Tool start position: 2.0, 2.0
Programming in inches
(4, 4)
(2, 2)
5”
p0
p1
p2
5”
2.5”
1”
45°
p3
p4
p5
Motion of tool:
p0  p1  p2  p3  p4  p5  p1  p0
Spindle CCW
(4, 4)
(2, 2)
5”
p0
p1
p2
5”
2.5”
1”
45°
p3
p4
p5
1. Set up the programming parameters
N010 G70 G90 G94 G97 M04
Programming in inches
Use absolute coordinates
Spindle speed in rpm
Feed in ipm
Flood coolant ON
(4, 4)
(2, 2)
5”
p0
p1
p2
5”
2.5”
1”
45°
p3
p4
p5
2. Set up the machining conditions
N020 G17 G75 F6.0 S300 T1001 M08
Machine moves in XY-plane
Feed rate
Tool no.
Spindle speed
Use full-circle interpolation
(4, 4)
(2, 2)
5”
p0
p1
p2
5”
2.5”
1”
45°
p3
p4
p5
3. Move tool from p0 to p1 in straight line
N030 G01 X3.875 Y3.698
Linear interpolation
target coordinates
(4, 4)
(2, 2)
5”
p0
p1
p2
5”
2.5”
1”
45°
p3
p4
p5
4. Cut profile from p1 to p2
N040 G01 X3.875 Y9.125
Linear interpolation
target coordinates
N040 G01 Y9.125
X-coordinate does not change  no need to program it
or
(4, 4)
(2, 2)
5”
p0
p1
p2
5”
2.5”
1”
45°
p3
p4
p5
5. Cut profile from p2 to p3
N050 G01 X5.634 Y9.125
Linear interpolation
target coordinates
1
”
p
3
.
1
2
5
(
x
,y
)
(
6
.
5
,9
)
y
=
9
+
0
.
1
2
5
=
9
.
1
2
5
(
6
.
5
-
x
)
2
+
0
.
1
2
5
2
=
(
1
-
0
.
1
2
5
)
2
x
=
5
.
6
3
4
coordinates of center of circle
(4, 4)
(2, 2)
5”
p0
p1
p2
5”
2.5”
1”
45°
p3
p4
p5
6. Cut along circle from p3 to p4
N060 G03 X7.366 Y9.125 I6.5 J9.0
circular interpolation, CCW motion
target coordinates
(4, 4)
(2, 2)
5”
p0
p1
p2
5”
2.5”
1”
45°
p3
p4
p5
7. Cut from p4 to p5
N070 G01 X9.302
target coordinates (Y is unchanged)
Linear interpolation
(4, 4)
(2, 2)
5”
p0
p1
p2
5”
2.5”
1”
45°
p3
p4
p5
8. Cut from p5 to p1
N080 G01 X3.875 Y3.698
target coordinates (see step 3)
Linear interpolation
(4, 4)
(2, 2)
5”
p0
p1
p2
5”
2.5”
1”
45°
p3
p4
p5
9. Return to home position, stop program
N090 G01 X2.0 Y2.0 M30
end of data
target coordinates (see step 3)
Linear interpolation
N100 M00
program stop
Automatic Part Programming
Software programs can automatic generation of CNC data
Make 3D model
Define Tool
CNC data
Simulate
cutting
Automatic part programming and DNC
Very complex part shapes  very large NC program
NC controller memory may not handle HUGE part program
computer feeds few blocks of
NC program to controller
When almost all blocks executed,
controller requests more blocks
Summary
CNC machines allow precise and repeatable control in machining
CNC lathes, Milling machines, etc. are all controlled by NC programs
NC programs can be generated manually, automatically
Additional references: RS274D code descriptions

Weitere ähnliche Inhalte

Ähnlich wie 9_CNC (1).ppt

nc and cnc dp
nc and cnc dpnc and cnc dp
nc and cnc dpDpulast
 
Numerical control and CNC
Numerical control and CNCNumerical control and CNC
Numerical control and CNCnmahi96
 
IRJET- Automatic Mini CNC Machine for PCB Drawing using Arduino
IRJET- Automatic Mini CNC Machine for PCB Drawing using ArduinoIRJET- Automatic Mini CNC Machine for PCB Drawing using Arduino
IRJET- Automatic Mini CNC Machine for PCB Drawing using ArduinoIRJET Journal
 
Me761 a lecture-4 cnc
Me761 a lecture-4 cncMe761 a lecture-4 cnc
Me761 a lecture-4 cncAshok Mannava
 
introduction to cnc machines
 introduction to cnc machines introduction to cnc machines
introduction to cnc machinesSTAY CURIOUS
 
Recent Advancement of CNC Technology
Recent Advancement of CNC TechnologyRecent Advancement of CNC Technology
Recent Advancement of CNC TechnologyDebiprasad Sena
 
IV REPORT.doc
IV REPORT.docIV REPORT.doc
IV REPORT.docNinNoon
 
Product manufacturing cnc edm
Product manufacturing  cnc edmProduct manufacturing  cnc edm
Product manufacturing cnc edmGaurav Gunjan
 
CNC -Intro to mfg.pptx
CNC -Intro to mfg.pptxCNC -Intro to mfg.pptx
CNC -Intro to mfg.pptxPECUG1
 
Introduction to CNC machines.pptx
Introduction to CNC machines.pptxIntroduction to CNC machines.pptx
Introduction to CNC machines.pptxDr.M BALA THEJA
 
Cnc pgrming seminar-
Cnc pgrming   seminar-Cnc pgrming   seminar-
Cnc pgrming seminar-abhipawar123
 

Ähnlich wie 9_CNC (1).ppt (20)

PPT ON BHEL HARIDWAR
PPT ON BHEL HARIDWARPPT ON BHEL HARIDWAR
PPT ON BHEL HARIDWAR
 
nc and cnc dp
nc and cnc dpnc and cnc dp
nc and cnc dp
 
CNC1.ppt
CNC1.pptCNC1.ppt
CNC1.ppt
 
Numerical control and CNC
Numerical control and CNCNumerical control and CNC
Numerical control and CNC
 
IRJET- Automatic Mini CNC Machine for PCB Drawing using Arduino
IRJET- Automatic Mini CNC Machine for PCB Drawing using ArduinoIRJET- Automatic Mini CNC Machine for PCB Drawing using Arduino
IRJET- Automatic Mini CNC Machine for PCB Drawing using Arduino
 
CNC1.ppt
CNC1.pptCNC1.ppt
CNC1.ppt
 
CNC1.ppt
CNC1.pptCNC1.ppt
CNC1.ppt
 
CNC1 (1).ppt
CNC1 (1).pptCNC1 (1).ppt
CNC1 (1).ppt
 
Cnc1
Cnc1Cnc1
Cnc1
 
CNC Training.ppt
CNC Training.pptCNC Training.ppt
CNC Training.ppt
 
Me761 a lecture-4 cnc
Me761 a lecture-4 cncMe761 a lecture-4 cnc
Me761 a lecture-4 cnc
 
introduction to cnc machines
 introduction to cnc machines introduction to cnc machines
introduction to cnc machines
 
Recent Advancement of CNC Technology
Recent Advancement of CNC TechnologyRecent Advancement of CNC Technology
Recent Advancement of CNC Technology
 
Ncmachine (1)
Ncmachine (1)Ncmachine (1)
Ncmachine (1)
 
IV REPORT.doc
IV REPORT.docIV REPORT.doc
IV REPORT.doc
 
Cnc
CncCnc
Cnc
 
Product manufacturing cnc edm
Product manufacturing  cnc edmProduct manufacturing  cnc edm
Product manufacturing cnc edm
 
CNC -Intro to mfg.pptx
CNC -Intro to mfg.pptxCNC -Intro to mfg.pptx
CNC -Intro to mfg.pptx
 
Introduction to CNC machines.pptx
Introduction to CNC machines.pptxIntroduction to CNC machines.pptx
Introduction to CNC machines.pptx
 
Cnc pgrming seminar-
Cnc pgrming   seminar-Cnc pgrming   seminar-
Cnc pgrming seminar-
 

Kürzlich hochgeladen

Gender Bias in Engineer, Honors 203 Project
Gender Bias in Engineer, Honors 203 ProjectGender Bias in Engineer, Honors 203 Project
Gender Bias in Engineer, Honors 203 Projectreemakb03
 
nvidia AI-gtc 2024 partial slide deck.pptx
nvidia AI-gtc 2024 partial slide deck.pptxnvidia AI-gtc 2024 partial slide deck.pptx
nvidia AI-gtc 2024 partial slide deck.pptxjasonsedano2
 
Vertical- Machining - Center - VMC -LMW-Machine-Tool-Division.pptx
Vertical- Machining - Center - VMC -LMW-Machine-Tool-Division.pptxVertical- Machining - Center - VMC -LMW-Machine-Tool-Division.pptx
Vertical- Machining - Center - VMC -LMW-Machine-Tool-Division.pptxLMW Machine Tool Division
 
دليل تجارب الاسفلت المختبرية - Asphalt Experiments Guide Laboratory
دليل تجارب الاسفلت المختبرية - Asphalt Experiments Guide Laboratoryدليل تجارب الاسفلت المختبرية - Asphalt Experiments Guide Laboratory
دليل تجارب الاسفلت المختبرية - Asphalt Experiments Guide LaboratoryBahzad5
 
Guardians and Glitches: Navigating the Duality of Gen AI in AppSec
Guardians and Glitches: Navigating the Duality of Gen AI in AppSecGuardians and Glitches: Navigating the Duality of Gen AI in AppSec
Guardians and Glitches: Navigating the Duality of Gen AI in AppSecTrupti Shiralkar, CISSP
 
Multicomponent Spiral Wound Membrane Separation Model.pdf
Multicomponent Spiral Wound Membrane Separation Model.pdfMulticomponent Spiral Wound Membrane Separation Model.pdf
Multicomponent Spiral Wound Membrane Separation Model.pdfGiovanaGhasary1
 
The relationship between iot and communication technology
The relationship between iot and communication technologyThe relationship between iot and communication technology
The relationship between iot and communication technologyabdulkadirmukarram03
 
Basic Principle of Electrochemical Sensor
Basic Principle of  Electrochemical SensorBasic Principle of  Electrochemical Sensor
Basic Principle of Electrochemical SensorTanvir Moin
 
Quasi-Stochastic Approximation: Algorithm Design Principles with Applications...
Quasi-Stochastic Approximation: Algorithm Design Principles with Applications...Quasi-Stochastic Approximation: Algorithm Design Principles with Applications...
Quasi-Stochastic Approximation: Algorithm Design Principles with Applications...Sean Meyn
 
UNIT4_ESD_wfffffggggggggggggith_ARM.pptx
UNIT4_ESD_wfffffggggggggggggith_ARM.pptxUNIT4_ESD_wfffffggggggggggggith_ARM.pptx
UNIT4_ESD_wfffffggggggggggggith_ARM.pptxrealme6igamerr
 
Mohs Scale of Hardness, Hardness Scale.pptx
Mohs Scale of Hardness, Hardness Scale.pptxMohs Scale of Hardness, Hardness Scale.pptx
Mohs Scale of Hardness, Hardness Scale.pptxKISHAN KUMAR
 
EPE3163_Hydro power stations_Unit2_Lect2.pptx
EPE3163_Hydro power stations_Unit2_Lect2.pptxEPE3163_Hydro power stations_Unit2_Lect2.pptx
EPE3163_Hydro power stations_Unit2_Lect2.pptxJoseeMusabyimana
 
Clutches and brkesSelect any 3 position random motion out of real world and d...
Clutches and brkesSelect any 3 position random motion out of real world and d...Clutches and brkesSelect any 3 position random motion out of real world and d...
Clutches and brkesSelect any 3 position random motion out of real world and d...sahb78428
 
Summer training report on BUILDING CONSTRUCTION for DIPLOMA Students.pdf
Summer training report on BUILDING CONSTRUCTION for DIPLOMA Students.pdfSummer training report on BUILDING CONSTRUCTION for DIPLOMA Students.pdf
Summer training report on BUILDING CONSTRUCTION for DIPLOMA Students.pdfNaveenVerma126
 
Graphics Primitives and CG Display Devices
Graphics Primitives and CG Display DevicesGraphics Primitives and CG Display Devices
Graphics Primitives and CG Display DevicesDIPIKA83
 
solar wireless electric vechicle charging system
solar wireless electric vechicle charging systemsolar wireless electric vechicle charging system
solar wireless electric vechicle charging systemgokuldongala
 
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...Amil baba
 
Phase noise transfer functions.pptx
Phase noise transfer      functions.pptxPhase noise transfer      functions.pptx
Phase noise transfer functions.pptxSaiGouthamSunkara
 

Kürzlich hochgeladen (20)

Gender Bias in Engineer, Honors 203 Project
Gender Bias in Engineer, Honors 203 ProjectGender Bias in Engineer, Honors 203 Project
Gender Bias in Engineer, Honors 203 Project
 
nvidia AI-gtc 2024 partial slide deck.pptx
nvidia AI-gtc 2024 partial slide deck.pptxnvidia AI-gtc 2024 partial slide deck.pptx
nvidia AI-gtc 2024 partial slide deck.pptx
 
Vertical- Machining - Center - VMC -LMW-Machine-Tool-Division.pptx
Vertical- Machining - Center - VMC -LMW-Machine-Tool-Division.pptxVertical- Machining - Center - VMC -LMW-Machine-Tool-Division.pptx
Vertical- Machining - Center - VMC -LMW-Machine-Tool-Division.pptx
 
دليل تجارب الاسفلت المختبرية - Asphalt Experiments Guide Laboratory
دليل تجارب الاسفلت المختبرية - Asphalt Experiments Guide Laboratoryدليل تجارب الاسفلت المختبرية - Asphalt Experiments Guide Laboratory
دليل تجارب الاسفلت المختبرية - Asphalt Experiments Guide Laboratory
 
Guardians and Glitches: Navigating the Duality of Gen AI in AppSec
Guardians and Glitches: Navigating the Duality of Gen AI in AppSecGuardians and Glitches: Navigating the Duality of Gen AI in AppSec
Guardians and Glitches: Navigating the Duality of Gen AI in AppSec
 
Multicomponent Spiral Wound Membrane Separation Model.pdf
Multicomponent Spiral Wound Membrane Separation Model.pdfMulticomponent Spiral Wound Membrane Separation Model.pdf
Multicomponent Spiral Wound Membrane Separation Model.pdf
 
The relationship between iot and communication technology
The relationship between iot and communication technologyThe relationship between iot and communication technology
The relationship between iot and communication technology
 
Basic Principle of Electrochemical Sensor
Basic Principle of  Electrochemical SensorBasic Principle of  Electrochemical Sensor
Basic Principle of Electrochemical Sensor
 
Quasi-Stochastic Approximation: Algorithm Design Principles with Applications...
Quasi-Stochastic Approximation: Algorithm Design Principles with Applications...Quasi-Stochastic Approximation: Algorithm Design Principles with Applications...
Quasi-Stochastic Approximation: Algorithm Design Principles with Applications...
 
Litature Review: Research Paper work for Engineering
Litature Review: Research Paper work for EngineeringLitature Review: Research Paper work for Engineering
Litature Review: Research Paper work for Engineering
 
UNIT4_ESD_wfffffggggggggggggith_ARM.pptx
UNIT4_ESD_wfffffggggggggggggith_ARM.pptxUNIT4_ESD_wfffffggggggggggggith_ARM.pptx
UNIT4_ESD_wfffffggggggggggggith_ARM.pptx
 
Mohs Scale of Hardness, Hardness Scale.pptx
Mohs Scale of Hardness, Hardness Scale.pptxMohs Scale of Hardness, Hardness Scale.pptx
Mohs Scale of Hardness, Hardness Scale.pptx
 
EPE3163_Hydro power stations_Unit2_Lect2.pptx
EPE3163_Hydro power stations_Unit2_Lect2.pptxEPE3163_Hydro power stations_Unit2_Lect2.pptx
EPE3163_Hydro power stations_Unit2_Lect2.pptx
 
Clutches and brkesSelect any 3 position random motion out of real world and d...
Clutches and brkesSelect any 3 position random motion out of real world and d...Clutches and brkesSelect any 3 position random motion out of real world and d...
Clutches and brkesSelect any 3 position random motion out of real world and d...
 
Summer training report on BUILDING CONSTRUCTION for DIPLOMA Students.pdf
Summer training report on BUILDING CONSTRUCTION for DIPLOMA Students.pdfSummer training report on BUILDING CONSTRUCTION for DIPLOMA Students.pdf
Summer training report on BUILDING CONSTRUCTION for DIPLOMA Students.pdf
 
Graphics Primitives and CG Display Devices
Graphics Primitives and CG Display DevicesGraphics Primitives and CG Display Devices
Graphics Primitives and CG Display Devices
 
solar wireless electric vechicle charging system
solar wireless electric vechicle charging systemsolar wireless electric vechicle charging system
solar wireless electric vechicle charging system
 
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...
 
Phase noise transfer functions.pptx
Phase noise transfer      functions.pptxPhase noise transfer      functions.pptx
Phase noise transfer functions.pptx
 
計劃趕得上變化
計劃趕得上變化計劃趕得上變化
計劃趕得上變化
 

9_CNC (1).ppt

  • 1. NC and CNC machines and Control Programming Introduction to NC and CNC machines CNC controls and RS274 programming
  • 2. History of CNC 1949 US Air Force asks MIT to develop a "numerically controlled" machine. 1952 Prototype NC machine demonstrated (punched tape input) 1980- CNC machines (computer used to link directly to controller) 1990- DNC: external computer “drip feeds” control programmer to machine tool controller
  • 3. Motivation and uses To manufacture complex curved geometries in 2D or 3D was extremely expensive by mechanical means (which usually would require complex jigs to control the cutter motions) Machining components with repeatable accuracy Unmanned machining operations
  • 4. Advantages of CNC - Easier to program; - Easy storage of existing programs; - Easy to change a program - Avoids human errors - NC machines are safer to operate - Complex geometry is produced as cheaply as simple ones - Usually generates closer tolerances than manual machines
  • 6. Vertical Milling machine architecture Conventional milling machines
  • 7. Horizontal Milling machine architecture Conventional milling machines How does the table move along X- Y- and Z- axes ?
  • 8. NC machines Motion control is done by: servo-controlled motors ~ S e r v o C o n tr o lle r C o u n te r C o m p a r a to r E n c o d e r A /C M o to r In p u t ( c o n v e r te d fr o m a n a lo g to d ig ita l v a lu e ) T a b le L e a d s c r e w
  • 9. CNC terminology BLU: basic length unit  smallest programmable move of each axis. Controller: (Machine Control Unit, MCU)  Electronic and computerized interface between operator and m/c Controller components: 1. Data Processing Unit (DPU) 2. Control-Loops Unit (CLU)
  • 10. Controller components Data Processing Unit: Input device [RS-232 port/ Tape Reader/ Punched Tape Reader] Data Reading Circuits and Parity Checking Circuits Decoders to distribute data to the axes controllers. Control Loops Unit: Interpolator to supply machine-motion commands between data points Position control loop hardware for each axis of motion
  • 11. Types of CNC machines Based on Motion Type: Point-to-Point or Continuous path Based on Control Loops: Open loop or Closed loop Based on Power Supply: Electric or Hydraulic or Pneumatic Based on Positioning System Incremental or Absolute
  • 12. Open Loop vs. Closed Loop controls
  • 13. Open loop control of a Point-to-Point NC drilling machine NOTE: this machine uses stepper motor control
  • 14. Components of Servo-motor controlled CNC Motor speed control Two types of encoder configurations Motor lead screw rotation table moves position sensed by encoder feedback
  • 15. Motion Control and feedback Encoder outputs: electrical pulses (e.g. 500 pulses per revolution) Rotation of the motor  linear motion of the table: by the leadscrew The pitch of the leadscrew: horizontal distance between successive threads One thread in a screw  single start screw: Dist moved in 1 rev = pitch Two threads in screw  double start screw: Dist moved in 1 rev = 2* pitch
  • 16. Example 1 A Stepping motor of 20 steps per revolution moves a machine table through a leadscrew of 0.2 mm pitch. (a) What is the BLU of the system ? (b) If the motor receives 2000 pulses per minute, what is the linear velocity in inch/min ?
  • 17. Example 2 A DC servo-motor is coupled to a leadscrew (pitch 5mm) of a machine table. A digital encoder, which emits 500 pulses per revolution, is mounted on the leadscrew. If the motor rotates at 600 rpm, find (a) The linear velocity of the table (b) The BLU of the machine (c) The frequency of pulses emitted by the encoder.
  • 18. Manual NC programming Part program: A computer program to specify - Which tool should be loaded on the machine spindle; - What are the cutting conditions (speed, feed, coolant ON/OFF etc) - The start point and end point of a motion segment - how to move the tool with respect to the machine. Standard Part programming language: RS 274-D (Gerber, GN-code)
  • 19. History of CNC The RS274-D is a word address format Each line of program == 1 block Each block is composed of several instructions, or (words) Sequence and format of words: N3 G2 X+1.4 Y+1.4 Z+1.4 I1.4 J1.4 K1.4 F3.2 S4 T4 M2 sequence no preparatory function destination coordinates dist to center of circle feed rate spindle speed tool miscellaneous function
  • 20. Manual Part Programming Example Tool size = 0.25 inch, Feed rate = 6 inch per minute, Cutting speed = 300 rpm, Tool start position: 2.0, 2.0 Programming in inches (4, 4) (2, 2) 5” p0 p1 p2 5” 2.5” 1” 45° p3 p4 p5 Motion of tool: p0  p1  p2  p3  p4  p5  p1  p0
  • 21. Spindle CCW (4, 4) (2, 2) 5” p0 p1 p2 5” 2.5” 1” 45° p3 p4 p5 1. Set up the programming parameters N010 G70 G90 G94 G97 M04 Programming in inches Use absolute coordinates Spindle speed in rpm Feed in ipm
  • 22. Flood coolant ON (4, 4) (2, 2) 5” p0 p1 p2 5” 2.5” 1” 45° p3 p4 p5 2. Set up the machining conditions N020 G17 G75 F6.0 S300 T1001 M08 Machine moves in XY-plane Feed rate Tool no. Spindle speed Use full-circle interpolation
  • 23. (4, 4) (2, 2) 5” p0 p1 p2 5” 2.5” 1” 45° p3 p4 p5 3. Move tool from p0 to p1 in straight line N030 G01 X3.875 Y3.698 Linear interpolation target coordinates
  • 24. (4, 4) (2, 2) 5” p0 p1 p2 5” 2.5” 1” 45° p3 p4 p5 4. Cut profile from p1 to p2 N040 G01 X3.875 Y9.125 Linear interpolation target coordinates N040 G01 Y9.125 X-coordinate does not change  no need to program it or
  • 25. (4, 4) (2, 2) 5” p0 p1 p2 5” 2.5” 1” 45° p3 p4 p5 5. Cut profile from p2 to p3 N050 G01 X5.634 Y9.125 Linear interpolation target coordinates 1 ” p 3 . 1 2 5 ( x ,y ) ( 6 . 5 ,9 ) y = 9 + 0 . 1 2 5 = 9 . 1 2 5 ( 6 . 5 - x ) 2 + 0 . 1 2 5 2 = ( 1 - 0 . 1 2 5 ) 2 x = 5 . 6 3 4
  • 26. coordinates of center of circle (4, 4) (2, 2) 5” p0 p1 p2 5” 2.5” 1” 45° p3 p4 p5 6. Cut along circle from p3 to p4 N060 G03 X7.366 Y9.125 I6.5 J9.0 circular interpolation, CCW motion target coordinates
  • 27. (4, 4) (2, 2) 5” p0 p1 p2 5” 2.5” 1” 45° p3 p4 p5 7. Cut from p4 to p5 N070 G01 X9.302 target coordinates (Y is unchanged) Linear interpolation
  • 28. (4, 4) (2, 2) 5” p0 p1 p2 5” 2.5” 1” 45° p3 p4 p5 8. Cut from p5 to p1 N080 G01 X3.875 Y3.698 target coordinates (see step 3) Linear interpolation
  • 29. (4, 4) (2, 2) 5” p0 p1 p2 5” 2.5” 1” 45° p3 p4 p5 9. Return to home position, stop program N090 G01 X2.0 Y2.0 M30 end of data target coordinates (see step 3) Linear interpolation N100 M00 program stop
  • 30. Automatic Part Programming Software programs can automatic generation of CNC data Make 3D model Define Tool CNC data Simulate cutting
  • 31. Automatic part programming and DNC Very complex part shapes  very large NC program NC controller memory may not handle HUGE part program computer feeds few blocks of NC program to controller When almost all blocks executed, controller requests more blocks
  • 32. Summary CNC machines allow precise and repeatable control in machining CNC lathes, Milling machines, etc. are all controlled by NC programs NC programs can be generated manually, automatically Additional references: RS274D code descriptions