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Loading...Computer Numerical Control of Machine Tools
G.E. Thyer
Second edition
Second-generation numerical
control: NC machine tools
Third-generation numerical
control: CNC and DNC
machine tools
2.8 Computer numerical control
2.9 Direct numerical control (DNC)
Flexible manufacturing cells
Tool facilities
Work mounting
2.10 Adaptive control
2.11 Applications of numerically
controlled machines
2.12 Cost of manufacture
Variable costs
Fixed costs
2.13 Break-even charts
Example of the use of break-even
charts
Questions
Preface
Preface to the firstedition
Acknowledgements
1 Principles ofmachinetools
1.1 Materialcutting techniques
1.2 Material removal techniques on
machine tools
1.3 Function of machine tools
1.4 Size and form
1.5 Kinematic principles of operationof
machine tools
Generation
Copying
Forming
1.6 Surface texture
Questions
2 Control of machine tools 7
2.1 Levels of control
2.2 Zero level of control
2.3 First level of control
2.4 Second level of control
2.5 Third level of control
2.6 Fourth level of control
2.7 Fifth level of control: numerical
control
First-generation numerical
control
3 Construction of machine tools
3.1 Constructional features
3.2 Power units
3.3 Providing the cutting speed
AC motors
DC motors
Fluid motors
3.4 Power units for moving the carriages
holding tool or work
DC Motors
Milling and drilling work
Vices
Grid plates
Fixtures
Pallets
Subtables
Work handling
3.14 Linkingstructure
Milling and drilling machines
Turning centres
Cast iron structures
Concrete structures
Welded frameworks
3.15 Overall considerations
Swarf removal
Positioning of transducers
Machining accuracy
Machine accuracy
Safety of machines
Ergonomic design
Questions
7 Informationstorage
7.1 Input signals
ISO codes
Binary coded decimal (BCD)
Parity
7.2 Indirect methods of input
7.3 Punched cards
7.4 Magnetic tape
7.5 Magnetic discs
7.6 Punched tape
Punched tape materials
Dimensions of punched tape
Punchedtape codes
Production of punched tape
Punched tape readers
Pneumatic tape readers
Electromechanical tape readers
Photo-electric tape readers
Behind the tape reader (BTR)
7.7 Blockformats
Fixed sequentialsystem
Tab sequential system
Word addressed system
Questions
Cubic interpolation
4.7 Selection of control mode
4.8 Adaptive control
Questions
Stepper motors 67 104 131
3.5 Power units for ancillary services
3.6 Speed control units
Control of cutting speed
Stepped drives
Steplessly variable drives
3.7 Control of feed rates
Fluid motors
3.8 Control of translational (linear)
movements
Slideways
Slideway forms
Cylindrical guideways
Veeguideways
Flat and dovetail guideways
Hydrostatic slideways
Linear bearings with balls, rollers
or needles
Surface coatings
3.9 Control of rotational movements
Rotatingspindles
Plain bearings
Ball or roller bearings
Fluid bearings
3.10 Actuatingmechanisms
Screw and nut
Rack and pinion
Ram and piston
3.11 Toolholders
Grinding wheels
Spark erosion
Machining centres
3.12 Tool changing arrangements
Manual tool changing
Tool identification
Tool holding on machining
centres
Tool turret
Tool magazines
Automatic tool changers
Tool holding on turning centres
Tool identification
Manual tool changing
Tool turrets
Tool magazines
Tool holding on sheet metal
working CNC machines
3.13 Workholders
Output transducers
5.1 Transducers
5.2 Positional transducers
Accuracy and resolution
Positioning of transducers
In-process measurement
Probes
Linear transducers
Rotary transducers
Analogue and digital output
Absolute, semi-absolute and
incremental
Principles of operation of output
transducers
5.3 Optical gratings
Crossed optical gratings
Parallel opticalgratings
4 Modesof operation
4.1 Designation of axes on NCmachine
tools
Zaxis
Xaxis
Taxis
Examples of nomenclature of axes 93
Angular positioning ofheadstock 97
4.2 Linear and rotary motions
Movement on Zaxis
Movement on Xaxis
Movement on Taxis
Reversed movement of work
Rotary movement
4.3 Machineoperatingsystems
4.4 Positioning control (symbol P)
Response time, damping and
hunting
Unidirectional movement
4.5 Line motion control (symbol L)
4.6 Contouring control (symbol C)
Linear interpolation
Circular interpolation
Parabolic interpolation
47 91 5.4 Encoders 118
i Absolute encoders
Pulsegenerating encoders
5.5 Inductosyns
Linear inductive Inductosyns
Rotary inductive Inductosyns
Capacitive Inductosyns
5.6 Magnescales
Questions
8 Structure of partprograms
8.1 Part programs
8.2 Types of control information
8.3 Word addressed format
8.4 Optional block skip character (/)
8.5 Sequence or block number (N)
8.6 Preparatory function (G)
8.7 Dimensional information words (X
Y, Zetc.)
8.8 Decimal point
8.9 Feed rate (F)
8.10 Spindlespeed (S)
8.11 Tool number (T)
Tool offset values
8.12 Miscellaneous function (M)
8.13 End of block (EOB)
8.14 Heidenhain plain-language
programming
8.15 Word addressed programmingof
plotters
Questions
6 Principlesof operationof NCmachine
tools
6.1 Basicprinciples
Positional (static) error
Reference (kinematic) error
Tool wear error
6.2 Closed loopsystems
6.3 Openloopsystems
6.4 Input signals
Methods of input
Questions
Rotation 190
Preset absolute registers
9.17 Writing the part program
9.18 Checking (proving) the program
Graphics
Dryrun
Stepping
Questions
10.8 Setting turning centres or CNC
lathes
Setting the work
Work datums onturning centres 211
10.9 Setting of lathetools
Settingon themachine
10.10 Tool offsets
Presetting of tools
Qualified tooling
Use of sensor probes
10.11 Tool nose radius compensation
Questions
12 Part programming forlathe work
12.1 Example program 3
12.2 Position of the zero datums
12.3 Size of work blanks
12.4 Sequenceof operations
12.5 Construction of part program 3
12.6 Tool tip radius compensation
Assignments
9 Writing part programs 24
9.1 Creating part programs
9.2 What the programmer has to know
9.3 Drawings for numerically
controlled machines
Absolute and incremental
dimensions
Position of datum
9.4 The component
Size of blank
Material of the workpiece
Amount of material to be removed 160
Surface texture
Dimensional tolerance
Rigidity of the component
9.5 Work holding positions
9.6 The machine tool
Selection of cutting tools
Shapes of cutting tools
Spindle speeds
Spindle speed using magic three
method
Capacity of machine tools
(amount of movement)
9.7 The control system
Positioning (point-to-point)
Linear interpolation
9.8 Circular interpolation
Single-quadrant circular
interpolation
Multiquadrant circular
interpolation
9.9 Parabolic interpolation
9.10 Polar coordinates
9.11 Cutter diameter compensation
Tool nose radius compensation
9.12 Screw thread cutting
9.13 Dwell
9.14 Programming aids
Manufacturers 5 canned cycles
Standardized canned cycles
9.15 Subroutines
Looping
Macros
9.16 Other programming aids
Mirror imaging
Scaling
159 10 Settingup NCmachinetools 215
10.1 Setting-up procedure
Floating zero
Machine reference datum
10.2 Setting millingand drilling
machines
Setting Xand Tdatums on milling
and drilling machines
Aligning the datum edges
Setting the datum point (machine
setting point)
Using a setting mandrel
Using a wiggler
Using an optical centre finder
10.3 Use of sensor probes on milling and
drilling machines
Spindle mounted probes
Aligning and establishing work
datum
Checking work datums
Checking work blanksize
Checking presence and depth of
hole
Checking size of work
Checking size of hole
10.4 Setting milling and drillingtools
Setting the tools to the Zdatum
Moving thespindle
Determination of Zoffset values
Preset tools tospecified lengths
Tool presetting fixtures
Use of spindle mounted sensor
probes-Zaxis datum
10.5 Use oftablemounted sensorprobes
for tool setting on machining centres 209
10.6 Tool length compensation
10.7 Cutter diameter compensation
13 Computer-aided part programming
13.1 Computer-aided programming
13.2 Using the computer as a text editor
13.3 Using the computer as a graphical
simulator
13.4 Part programming languages
APT (Automatically Programmed
Tools)
Postprocessor
13.5 Conversational programming
Conversational programming of
grinding machines
Conversational control systems
Heidenhain dialogue
programming
13.6 Computer-aided machining (CAM)
Stage1Geometric definition of
the shape of the component
Stage 2 Machining instructions
Stage 3 Postprocessing
Editing of part programs
Advantages of CAM
CAM Example1
CAM Example 2
Questions
Appendix A Preparatory functions:
G codes
Appendix B Miscellaneous functions:
Mcodes
AppendixCComputer fundamentals
Index
11 Part programmingformilling and
drilling work
11.1 Example program1
11.2 Position of thezero datums
11.3 Work holding method and machine
setting point
Coordinates for work changing 218
11.4 Sequence of operations
Spot drilling
Drilling operation
Milling thesteps
11.5 Speeds and feeds for the tools to be
used
Coordinates for tool changing
11.6 Construction of part program1
11.7 Example program 2
Calculation of position of corner
clearing holes
Calculation of position of centre
of end mill
Calculation of points oftangency 230
Calculation of arc centre offsets 231
11.8 Construction of part program 2
Assignments
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