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Chapter 40
NC/CNC Processes and Adaptive Control: A(4) and A(5) Levels of
Automation
MET 33800 Manufacturing Processes
Before you begin: Turn on the sound on your computer. There is audio to accompany this presentation.
Yardstick of Automation
Chapter 40 - 2
A(4) Judgment
Chapter 40 - 3
A(3) Diligence
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Terminology - ReviewNUMERICAL CONTROL (NC)
The term Numerical Control applies to all numerically programmable machine tools including Computer Numerically Controlled machines.
COMPUTER NUMERICAL CONTROL (CNC)
Microprocessor based machine control units with memory and program editing capability.
Allows direct interface with communication network.
Incorporates subroutine (canned cycle) capability.
Chapter 40 - 4
Terminology - ReviewDISTRIBUTIVE NUMERICAL CONTROL (DNC)
Central computer used as a centralized program storage and communication device linked to a series of CNC machines.
FLEXIBLE MANUFACTURING SYSTEM (FMS)
Central computer controlling a group of CNC machines linked with a programmable, automated material handling device.
Chapter 40 - 5
Basic Principles of NCAdvantages:
1. Multiple operations on same machine.
2. Flexibility, easy to incorporate changes.
3. Complex surface capability.
4. Improved quality repeatability and accuracy.
5. Reduced setup time reduced cost.
6. Retention of manufacturing skill in program.
7. Reduced lead-time improved production planning and control.
Chapter 40 - 6
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Basic Principles of NCDisadvantages:
1. Higher initial investment machine and support services.
2. Increased engineering support required (Note that this is a good thing if you don’t own the firm).
3. Increased maintenance cost and support.
4. Specialized operator skills required.
5. May not be cost effective for low production runs.
Chapter 40 - 7
NC System Elements:
1. Part program.
2. Program input method.
3. Machine control unit.
4. Drive system.
5. Machine tool.
6. Feedback system.
Basic Principles of NC
Chapter 40 - 8
Part Programming Formats1. Word Address: data entered with single letter address. Standard:
ANSI/EIA RS-274-D. (N, G, and M are addresses) Example:
N010 G01 X0100 Y0100 Z0100 F50 T0101 S1500 M03 <EOB>
2. Fixed Sequential: data must be entered in a specific order without address (obsolete). All blocks must me same length, decimal points are assumed. Example:
010 01 000100 000100 000100 00050 0101 1500 03 <CR>
3. Tab Sequential: similar to fixed sequential, <TAB> character required between words. Example:
010<TAB>01<TAB>000100<TAB><TAB>00025<TAB><TAB><CR>
Chapter 40 - 9
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Part Programming
Chapter 40 - 10
Part ProgrammingG code - Preparatory Functions:
Changes control mode of machine.
Motion commands.
Fixed cycle commands.
Dimension unit selection commands.
Positioning system commands.
Coordinate system setting commands.
N010 G01 X0100 Y0100 Z0100 F50 T0101 S1500 M03 <EOB>
Chapter 40 - 11
M code - Miscellaneous Functions:
Controls auxiliary functions (on/off).
Program stop.
End of program.
Spindle rotation.
Tool change.
Coolant control.
N010 G01 X0100 Y0100 Z0100 F50 T0101 S1500 M03 <EOB>
Part Programming
Chapter 40 - 12
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X,Y,Z code: Primary Axis Designation
A,B,C code: Rotary Axis Designation
N010 G01 X0100 Y0100 Z0100 F50 T0101 S1500 M03 <EOB>
Part Programming
Chapter 40 - 13
N code: Block (Statement) Number
S code: Spindle Speed - Direct rpm, sfm, or coded value
T code: Tool Number/Location
F code: Feedrate Command - ipm, ipr, mm/min or mm/rev depending on mode.
N010 G01 X0100 Y0100 Z0100 F50 T0101 S1500 M03 <EOB>
Part Programming
Chapter 40 - 14
Part Programming
Chapter 40 - 15
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Part Programming - CAM
Chapter 40 - 16
Part Programming - CAM
Chapter 40 - 17
NC System Elements:
1. Part program.
2. Program input method.
3. Machine control unit.
4. Drive system.
5. Machine tool.
6. Feedback system.
Basic Principles of NC
Chapter 40 - 18
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Program Input Method1. Punched Tape 1" wide with 8 tracks. Material
paper or Mylar.
2. Magnetic Disk or Tape Also can be used as output media.
3. Manual Data Input (MDI) Input via MCU mounted keyboard.
4. RS-232 Interface Serial connector allowing DNC or interface with microprocessor based technology.
Chapter 40 - 19
Chapter 40 - 20
NC System Elements:
1. Part program.
2. Program input method.
3. Machine control unit.
4. Drive system.
5. Machine tool.
6. Feedback system.
Basic Principles of NC
Chapter 40 - 21
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Machine Control Unit The Machine Control Unit (MCU) is the device that
translates input information into electrical pulses, voltages, and/or frequencies.
MCU also compares the input information with the feedback.
Chapter 40 - 22
Control and Feedback Systems
Chapter 40 - 23
NC Control Systems
Chapter 40 - 24
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NC Control Systems
Chapter 40 - 25
NC Control Systems1. Positioning (Point-to-Point): Machining occurs at the end
point of the motion only. Path from beginning to end point of motion and speed of motion irrelevant. Typically used on drilling machine tables.
2. Straight-cut Control: Machining can occur along any path parallel to the machines axes. Typically used on simple turning machines.
Chapter 40 - 26
3. Contouring (Continuous Path): Multi-axis motions possible. Requires interpolation for each axis feedrate.
Linear Interpolation Straight line movement.
Circular Interpolation Arcs and circles in one plane.
Helical Interpolation Two axes circular and one axis linear interpolation or three axes circular interpolation.
Parabolic and Cubic Interpolation Allows complex shapes.
NC Control Systems
Chapter 40 - 27
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NC Control Systems
Chapter 40 - 28
NC Control Systems
Chapter 40 - 29
NC Control Systems
Five-Axis Machine X, Y and Z linear plus B and C rotary.Chapter 40 - 30
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NC Control Systems
Axis system for turning center with primary spindle, sub-spindle and three tool turrets. Additionally, both spindles have C-axis ability.
Chapter 40 - 31
NC ControlSystems
Chapter 40 - 32
NC Control Systems
Helical Interpolation
Parabolic and Cubic Interpolation
Chapter 40 - 33
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NC System Elements:
1. Part program.
2. Program input method.
3. Machine control unit.
4. Drive system.
5. Machine tool.
6. Feedback system.
Basic Principles of NC
Chapter 40 - 34
Drive SystemsSpindle Drives
DC Motors ( voltage rpm): high torque, simple control circuitry, low cost.
AC Motors ( frequency rpm): lower energy usage, no AC/DC conversion.
Axis Drives
Stepper motors digital device that works by electrical pulse.
AC and DC Servo Motors analog devices.
Chapter 40 - 35
NC System Elements:
1. Part program.
2. Program input method.
3. Machine control unit.
4. Drive system.
5. Machine tool.
6. Feedback system.
Basic Principles of NC
Chapter 40 - 36
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Machine ToolsTypes:
Metal Removal – all types of traditional chip removal machine tools.
Unconventional machining – includes non-traditional machining such as EDM and laser.
Fabrication – welding, cutting, forming, etc.
Special-purpose applications – assembly machines tool grinding.
Machining Centers – incorporate tool changers.
Chapter 40 - 37
Machine Tools
Chapter 40 - 38
MachineTools
Chapter 40 - 39
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MachineTools
Chapter 40 - 40
Machine Tools – Tool Grinder
Chapter 40 - 41
Machining Centers
Chapter 40 - 42
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MachiningCenters
Chapter 40 - 43
Machining Centers
Chapter 40 - 44
Machining Centers
Chapter 40 - 45
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Machining Centers
Chapter 40 - 46
Machining Centers
Chapter 40 - 47
Machine Tools
Chapter 40 - 48
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Machine Tools
Chapter 40 - 49
Machine Tools
Chapter 40 - 50
NC System Elements:
1. Part program.
2. Program input method.
3. Machine control unit.
4. Drive system.
5. Machine tool.
6. Feedback system.
Basic Principles of NC
Chapter 40 - 51
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Feedback Systems1. Open Loop No feedback signal to axis drive motors.
Utilizes stepper motors. A(3) Automation - Diligence
Chapter 40 - 52
Feedback Systems2. Closed Loop Indirect closed loop has the transducer,
resolver, and/or tachometer located on the axis drive motor or ballscrew. A(4) Automation: Judgment
Chapter 40 - 53
Feedback Systems3. Closed Loop Direct closed loop incorporates a
position and velocity feedback link to machine control unit. Transducer, resolver, and/or tachometer attached to machine tool slide. A(4) Automation: Judgment
Chapter 40 - 54
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The End – See Oncourse for Videos
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