Transcript Applications of CAD Systems

Applications of CAD Systems
Chapter 11: Numerical Control
Ζήσης Κ. Πλίτσης
Computerized process planning without human
intervention realized by adding Numerical Control
(NC) capabilities to machine tools.
Numerical Control refers to the use of coded
numerical information in the automatic control of
equipment positioning and have to do with motion
(of cutting tools or the part against a rotating tool),
positioning, inserting etc.
The production steps stored in a Part Program.
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Περιεχόμενα
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Introduction
Hardware Configuration of an NC Machine
Tool
Types of NC System
NC/CNC/DNC
Basic Concepts for Part Programming
Manual Part Programming
Computer Assisted Part Programming
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Περιεχόμενα
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Introduction
Hardware Configuration of an NC Machine
Tool
Types of NC System
NC/CNC/DNC
Basic Concepts for Part Programming
Manual Part Programming
Computer Assisted Part Programming
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Introduction / History
In 1940s John Parsons devised a method for manufacture of
smooth shapes, relied on recording the location of the center
of large number of holes and feeding this information to a
machine tool to drive the cutter. The Air Corps was impressed
by the idea and the task was subcontracted to the
Servomechanisms Laboratory of MIT
In 1952 a modified 3-axis Cincinnati Hydrotel milling machine was
demonstrated by MIT, the term numerical control was coined
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Introduction
According to Electronic Industries Association (EIA):
“Numerical Control is a system in which actions are controlled by
direct insertion of numerical data at some point. The system
must automatically interpret at least some portion of this data.”
The part program is a set of statements that a machine control
system can interpret and converted them into signals that
move the spindles and drive the machine tool
Today the part program can be generated directly from the CAD
database by NC software and then can be the input for a NC
machine tool
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Περιεχόμενα
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Introduction
Hardware Configuration of an NC Machine
Tool
Types of NC System
NC/CNC/DNC
Basic Concepts for Part Programming
Manual Part Programming
Computer Assisted Part Programming
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Hardware Configuration of an
NC Machine Tool
A typical NC machine tool contains the Machine
Control Unit (MCU) and the machine tool itself.
The MCU includes
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the Data Processing Unit (DPU)
and
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the Control Loop Unit (CLU)
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Hardware Configuration of an
NC Machine Tool
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DPU reads the part program, decodes it, processes the
information and passes it to the CLU
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CLU convert the information to control signals and drives the
mechanism, receives feedback (about position and velocity)
and instructs DPU to read new instructions
Axis of a machine tool is defined as a path along which relative
motion between the cutting tool and the workpiece occurs and
a machine can have more than one axis.
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Περιεχόμενα
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Introduction
Hardware Configuration of an NC Machine
Tool
Types of NC System
NC/CNC/DNC
Basic Concepts for Part Programming
Manual Part Programming
Computer Assisted Part Programming
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Types of NC System Used
Point-to-Point NC controllers – PTP
When the path of the tool relative to the work
piece is not important, maybe when the tool
is not in contact with the workpiece
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Contouring (continuous) NC systems
When the motion of the tool relative to the part
being machined is important
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Περιεχόμενα
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Introduction
Hardware Configuration of an NC Machine
Tool
Types of NC System
NC/CNC/DNC
Basic Concepts for Part Programming
Manual Part Programming
Computer Assisted Part Programming
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NC/CNC/DNC
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Third generation of machine tools uses integrated circuits and
memory technology wildly used in computer hardware
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Computer Numerical Control (CNC, about 1970) program
needs loading into the MCU once, the controller resembles a
personal computer, it is a special-purpose computer for control
of machine tools with CPU, ROM, RAM, hard disk
communication ports, key pad, display monitor etc.
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Today PC-based NC are available which use general-purpose
PC with servo-control board.
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NC/CNC/DNC
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Direct Numerical Control is a system that uses a central
computer to control several machines at the same time
Distributed Numerical Control (DNC): the central computer
downloads complete programs to the CNC machines, which
can be workstations or PCs, and can get the information for
the machine operations.
The speed of the system is increased, large files can be handled
and the number of machine tools used is expanded.
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Direct numerical control
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DNC
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Περιεχόμενα
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Introduction
Hardware Configuration of an NC Machine
Tool
Types of NC System
NC/CNC/DNC
Basic Concepts for Part Programming
Manual Part Programming
Computer Assisted Part Programming
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Basic Concepts for Part
Programming
Part programming contains geometric information
about the part and motion information to move the
cutting tool with respect to the workpiece
The first thing to be defined is the
Coordinate System and then some-one can
continue with the Syntax of Part Programming
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Coordinate System
Main 3 Axes forming a right-hand coordinate system,
by convention z axis moves the cutting tool away
from the workpiece, in details:
The z axis, parallel to the spindle for rotating
workpiece, and parallel to the machine tool axis for
rotating tool, as a milling, drilling, or boring machine
The x axis, in the direction of the tool movement for
the first case, and points to the right when someone is facing the machine.
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Coordinate System
There can be more axes because of secondary slide motions in
addition to the primary x, y and z directions, and the rotary
motions around axes parallel to x, y and z axes.
These axes can be labeled u, v and w (for the first case) and a, b
and c (for the second).
The machine tools can be classified according to the number of
axes they provide to control position and orientation. For
example, there are 2-axis, 3-axis and 5-axis milling machines.
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Syntax of Part Programming
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Various formats and well defined syntax with
variations due to differences between machines
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Use of a sequence of blocks containing commands
to set machine parameters as speed etc
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Each command has an identifying letter followed by
an associated number
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Syntax of Part Programming
Some identifying letters for the commands:
 Sequence number (N code)
 Preparatory command (G code)
 Dimension words (X, Y, Z, A and B words)
 Feed commands (F code)
 Speed commands (S code)
 Tool selection (T code)
 Miscellaneous (M code)
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Syntax of Part Programming
Formats for the commands arranged to form a block:
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Fixed sequential format
Block address format
Tab sequential format
Word address format
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For example: N040 G00 X0 Y0 Z300 T01 M06
N: identifier number, G: preparatory commands,
X,Y and Z: coordinates along the x, y and z axis
T: the tool number and M: miscellaneous commands
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Περιεχόμενα
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

Introduction
Hardware Configuration of an NC Machine
Tool
Types of NC System
NC/CNC/DNC
Basic Concepts for Part Programming
Manual Part Programming
Computer Assisted Part Programming
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Manual Part Programming
Part program manuscript
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Manual Part Programming
Example:
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Manual Part Programming
Answer:
N001
N002
N003
N004
N005
N006
N007
N008
N009
N010
N011
N012
G91
G71
G00
G01
G01
G01
G01
G01
G02
G01
G01
G01
EOB
EOB
X0.0 Y0.0 Z40.0 T0.1 M06 EOB
X65.0 Y0.0 Z-40.0 F950 S717 M03 EOB
X10.0 F350 M08 EOB
X110.0 EOB
Y70.0 EOB
X-40.86 EOB
X-28.28 Y0.0 I14.14 J5.0 EOB
X-40.86 EOB
Y-70.0 EOB
X-75.0 Y0.0 Z40.0 F950 M30
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Περιεχόμενα
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


Introduction
Hardware Configuration of an NC Machine
Tool
Types of NC System
NC/CNC/DNC
Basic Concepts for Part Programming
Manual Part Programming
Computer Assisted Part Programming
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Computer Assisted Part
Programming
The alternative to manual part programming is the use
of high-level programming language, which:
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Defines the geometry part in terms of basic
geometry elements (points, lines …)
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Instructs the machine about the cutting tool
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Computer Assisted Part
Programming
So the following procedures must be used to obtain the G-code:
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The programmer identifies the part geometry, cutter motions,
feeds, speeds and cutter parameters
The programmer codes the part geometry, cutter motion, feed
etc and this is the source using a programming language
The source is then compiled to produce the machine
independent list of cutter movements and other machine
control information (the cutter location control data file or CL
data file)
The CL data are processed by post-processor to generate
machine control data for the particular machine
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APT Language
The most comprehensive and widely used language is
Automatically Programmed Tool (APT) – the first prototype of
the APT system was developed at MIT in 1956.
The APT statements belong to one of the five types:
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Identification statements
Geometry statements
Motion statements
Post-processor statements
Auxiliary statements
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APT Language
Geometry statements, the general form of geometry
statement is:
Symbol = geometry_word/descriptive data
 In the case of points:
P1 = POINT/X, Y, Z
P2 = POINT/L1, L2
P3 = POINT/CENTER, C1
P4= POINT/YLARGE, INTOF,
P5= POINT/XLARGE, INTOF,
P6= POINT/XLARGE, INTOF,
P7= POINT/YLARGE, INTOF,
L1,
L1,
C1,
C1,
C1
C1
C1
C1
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APT Language
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In the case of lines:
L1 = LINE/X1, Y1, Z1, X2, Y2, Z2
L2 = LINE/P1, P2
L3 = LINE/P1, PARLEL, P2
L4 = LINE/P1, PERPTO, L0
L5 = LINE/P1, LEFT, TANTO, C1
L6 = LINE/P1, RIGHT, TANTO, C1
L7 = LINE/LEFT, TANTO, C1, LEFT, TANTO, C2
L8 = LINE/LEFT, TANTO, C1, RIGHT, TANTO, C2
L9 = LINE/RIGHT, TANTO, C1, LEFT, TANTO, C2
L10 = LINE/RIGHT, TANTO, C1, RIGHT, TANTO, C2
L11 = LINE/P1, ATANGL, L0
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APT Language
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In the case of circles:
C1 = CIRCLE/X, Y, Z, R
C2 = CIRCLE/CENTER, P1, RADIOUS, R
C3 = CIRCLE/CENTER, P1, TANTO, L0
C4 = CIRCLE/P1, P2, P3
C5 = CIRCLE/XSMALL, L1, XSMALL, L2, RADIOUS, R
…And the same with XLARGE, YLARGE or YSMALL
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In the case of planes:
PL1 = PLANE/P1, P2, P3
PL2 = PLANE/PARLEL, PL0, XLARGE, D
…And the same with XLARGE, YLARGE, YSMALL, ZLARGE or ZSMALL
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APT Language
Motion statements, with regard to point-to-point
operation there are three motion statements for
positioning the tool at a desired point:
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FROM/point_location
GOTO/point_location
GODLTA/Δx, Δy, Δz
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APT Language
Example 1:
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APT Language
Answer:
P0 = POINT/0.0, 3.0, 0.1
P1 = POINT/1.0, 1.0, 0.1
P2 = POINT/2.0, 1.0, 0.1
FROM/P0
GOTO/P1
GODLTA/0, 0, -0.7
GODLTA/0, 0, 0.7
GOTO/P2
GODLTA/0, 0, -0.7
GODLTA/0, 0, 0.7
GOTO/P0
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APT Language
Other Motion statements:
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GO/{TO}, Drive surface, {TO} Part surface, {TO},
Check surface
Or
GO/{TO}, Drive surface, {TO} Part surface, {TANTO},
Check surface
…And the same with PAST or ON instead of TO
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GOLFT/
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GORGT/
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GOUP/
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GODOWN/
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GOFWD/
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GOBACK/
For example:
GO/TO, L1, TO, PS, TANTO, C1
GO/PAST, L1, TO, PS, TANTO, C1

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APT Language
Example 2:
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APT Language
Answer:
FROM/SP
GO/TO, L1, TO, PS, ON, L4
GORGT/L1, PAST, L2
GOLFT/L2, PAST, L3
GOLFT/L3, PAST, C1
GOLFT/C1, PAST, L3
GOLFT/L3, PAST, L4
GOLFT/L4, PAST, L1
GOTO/SP
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APT Language
Example 3:
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APT Language
Answer:
FROM/SP
GO/TO, L1, TO, PS, ON, L6
GORGT/L1, PAST, L2
GORGT/L2, TANTO, C1
GOFWD/C1, TANTO, L3
GOFWD/L3, PAST, L4
GOLFT/L4, PAST, L5
GOLFT/L5, PAST, L6
GOLFT/L6, PAST, L1
GOTO/SP
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APT Language
Additional statements:
MACHIN/DRILL, 2

COOLNT/
For example: COOLNT/MIST COOLNT/FLOOD COOLNT/OF
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FEDRAT/
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SPINDL/
For example: SPINDL/ON SPINDL/1250, CCLW

TOOLNO/

TURRET/
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END

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APT Language
Other capabilities of APT, the macro facility, with use variable argument as in a
FORTRAN subroutine, for example:
P0 = POINT/0.0, 0.3, 0.1
FROM/P0
CALL/DRILL, X=1.0, Y=1.0, Z=0.1, DEPTH=0.7
CALL/DRILL, X=2.0, Y=1.0, Z=0.1, DEPTH=0.7
GOTO/P0
when the definition of the macro DRILL is:
DRILL = MACRO/X, Y, Z, DEPTH
GOTO/X,Y,Z
GODLTA/0,0, -DEPTH
GODLTA/0,0, DEPTH
TARMAC
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APT Language
Example 4 (1/2):
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APT Language
Example 4 (2/2):
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APT Language
Answer (1/4):
PARTNO PART11
MACHIN/MILL, 3
;machine selection
CLPRINT
;prints out CL data file
OUTTOL/0.002
SP =POINT/5,0,1
P1 =POINT/1,2,0.5
P2 =POINT/4,2,0.5
P3 =POINT/6,4,0.5
P4 =POINT/8,5,0.5
P5 =POINT/9,7,0.5
P6 =POINT/2,7,0.5
PL1 = PLANE/P1, P2, P3
PS = PLANE/PARALEL, PL1, ZSMALL, 0.5
;define part surface to be z = 0
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APT Language
Answer (2/4):
C1 = CIRCLE/CENTER, P4, RADIOUS, 1.0
L1 = LINE/P2, P3
L2 = LINE/P3, RIGHT, TANTO, C1
L3 = LINE/P5, LEFT, TANTO, C1
L4 = LINE/P5, P6
L5 = LINE/P6, P1
L4 = LINE/P1, P2
MILL = MACRO/CUT, SPIN, FEED, CLNT
CUTTER/CUT
FEDRAT/FEED
SPINDL/SPIN
COOLNT/CLNT
FROM/SP
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APT Language
Answer (3/4):
FROM/SP
GO/TO, L1, TO, PS, ON, L6
GORGT/L1, TO, L2
GORGT/L2, TANTO, C1
GOFWD/C1, TANTO, L3
GOFWD/L3, PAST, L4
GOLFT/L4, PAST, L5
GOLFT/L5, PAST, L6
GOLFT/L6, PAST, L1
GOTO/SP
TERMMAC
TURRET/4
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APT Language
Answer (4/4):
TURRET/4
CALL/MILL, CUT=0.52, SPIN=600, FEED=3.0, CLNT=ON
TURRET/6
CALL/MILL, CUT=0.5, SPIN=900, FEED=2.0, CLNT=ON
SPINDL/0
COOLNT/OFF
END
FINI
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Other Part Programming
Languages
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ADAPT (ADaptation APT) was the first attempt to adapt APT
programming system for smaller computers
AUTOSPOT (AUTOmatic Sytem for POsitioning Tools) was
developed by IBM and first introduced in 1962
EXAPT (EXtended subset of APT) was developed jointly in
German in about 1964 by several universities to adapt APT for
European use. It is compatible with APT and thus can use the
same processor as APT
COMPACT was developed by Manufacturing Data Systems,
Inc. (MDSI)
SPLIT (Sundstrand Processing Language Internally
Translated) was developed by Sundstrand Corporation,
intended for its own machine tools
MAPT (Micro-APT) is a subset of APT, to be run on the
microcomputers
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Τέλος