• NC program preparation may be tedious and difficult if the part to be machined has a complex geometry. The main difficulty is to find out the Computer Aided Part Programming: geometry. The main difficulty is to find out the cutter locations during the machining. Computers may be used to assist the programmers in preparing the NC codes. 2004 1
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• NC program preparation may be tedious and difficult if the part to be machined has a complex geometry. The main difficulty is to find out the
Computer Aided Part Programming:
geometry. The main difficulty is to find out the cutter locations during the machining. Computers may be used to assist the programmers in preparing the NC codes.
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Advantages of applying computer-aided part programming include the following:
• It reduces the manual calculations involves indetermining the geometric characteristics of thedetermining the geometric characteristics of thepart.
• It provides the cutter path simulation.
• It provides tool collision checking.
• It shortens the program preparation time.
• It makes the program preparation easier.
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• The Aerospace Industries Association sponsored the work that led to the first part programming language, developed in MIT in 1955.
• This was called: Automatically Programmed Tools (APT).
APT
• This was called: Automatically Programmed Tools (APT).• APT is an English like simple programming language which
basically produce the Cutter Location (CL) data. • Using the cutter location data, the program can generate
the actual NC codes by using a postprocessor .
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APT Characteristics
•Three-dimensional unbounded surfaces and points are
defined to represent the part to be made
•Surfaces are defined in a X-Y-Z coordinate system
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•In Programming, the tool does all the moving; the part is
stationary.
•Linear interpolation is used for curved tool paths
APT Statement Types (5)
•Identification
•Geometry
•Motion
•Postprocessor (feed, speed, coolant, 0
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•Postprocessor (feed, speed, coolant, 0
etc.)
•Auxiliary (tool, tolerance, part, 0 etc.)
The general format for geometric statements is:
<Symbol> = Geometric Type/ Definitional
ModifiersModifiers
PointsPoints
Point (POINT)
PTA = POINT/ 3,4,5
y
(3, 4, 5)
PTA
x
z
Point (POINT)
PTB = POINT/ INTOF, LIN1, LIN2
LIN2
LIN1PTB
Point (POINT)
PTD = POINT/ YSMALL, INTOF, LIN3, C1
PTD = POINT/ XSMALL, INTOF, LIN3, C1
PTC = POINT/ YLARGE, INTOF, LIN3, C1
PTC = POINT/ XLARGE, INTOF, LIN3, C1 PTC
y
PTD
LIN3
C1
x
Point (POINT)
PTE = POINT/ YLARGE, INTOF, C1, C2
PTE = POINT/ XLARGE, INTOF, C1, C2
PTF = POINT/ YSMALL, INTOF, C1, C2
PTF = POINT/ XSMALL, INTOF, C1, C2
y
C1
PTE
x
C2
PTE
PTF
Point (POINT)
PT7 = POINT/ CENTER, C6
C6
y
PT7
x
Point (POINT)
PT11 = POINT/ P63, RADIUS, 7.3, ATANGLE, 27
y
27°
P63 = 3.1, 6.7
PT11
x
7.3
Pattern (PATERN)
<Symbol> = PATERN/ LINEAR, <start>, <end>, <n>
PATG = PATERN/ LINEAR, P16, PT3, 6
PTZ = POINT/ PATG, 5
PT3
PTZ = POINT/ PATG, 5
P16
PTZ
PATG
Pattern (PATERN)
<Symbol> = PATERN/ COPY, PAT1, ON, PAT2
PAT7 = PATERN/ COPY, PAT1, ON, PAT2
PAT2
PAT1
3
2
1
1
2
3
4
5
6
7
8
9
10
11
12
Grid = PAT7
Pattern (PATERN)
SAME: after the pattern designator will force that pattern
sequence no.s to follow their original sequence.
PAT8 = PATERN/ COPY, PAT1, ON, PAT2, SAME
1 2 3 4
5 6 7 8
9 10 11 12
PAT8
Pattern (PATERN)
UNLIKE: the sequence of points will be reversed on the 2nd
cycle from that of the 1st & the 3rd will be reversed from the
second & so on.
PAT11 = PATERN/ COPY, PAT1, ON, PAT2, UNLIKEPAT11 = PATERN/ COPY, PAT1, ON, PAT2, UNLIKE
1 2 3 4
57 68
9 10 11 12
PAT11
Pattern (PATERN)
PAT12 = PATERN/ COPY, PAT1, UNLIKE, ON, PAT2
1 6 7 121
2
3 4
5
6 7
8
9 10
11
12
PAT12
LinesLines
Line (LINE)
LIN1 = LINE/ P1, P2
y
LIN1
P1
P2
x
Line (LINE)
LIN4 = LINE/ PT6, 15, -30, 3
PT6
y
L4 (15, -30, 3)
x
Line (LINE)
LIN10 = LINE/ 20, 3.5, 0.2, 31, 6.2, 1.3
(31, 6.2, 1.3)
y
(20, 3.5, 0.2)
L10
x
Line (LINE)
L12 = LINE/ PT4, ATANGLE, 20
L14 = LINE/ PT1, ATANGLE, 40
L15 = LINE/ 32, -3, 2, ATANGLE, -15
L16 = LINE/ PT3, ATANGLE, 40, YAXIS
yPT3 L14
x
L16
PT3
PT1
L14
L12
PT4
(32, -3, 2)L15
40°
40° 20°
15°
Line (LINE)
LIN = LINE/ POINT, SLOPE, NUMERICAL VALUE, LINE
LINE2
y
P1
LINE1
x
LINE2 = LINE/ P1, SLOPE, 0.6, LINE1
Line (LINE)
LIN = LINE/ POINT, ATANGL, ANGLE (in degrees), LINE
LINE2
y
P1
LINE1
x
LINE2 = LINE/ P1, ATANGL, 30, LINE1
30°
Line (LINE)
LIN = LINE/ SLOPE, SLOPE VALUE, INTERC, MODIFIER, d
where the slope value is y/x. The modifier options are [XAXIS,
YAXIS], and d is the corresponding intercept value on the selected
axis (i.e., modifier).
y
x
y
(6,0) Point of X-Intercept
LINE1
LINE1 = LINE/ SLOPE, 1, INTERC, x-axis, 6
Line (LINE)
LIN = LINE/ ATANGL, DEGREES, INTERC, MODIFIER, d
The modifier options are [XAXIS, YAXIS], and d is the
corresponding intercept value on the selected axis (i.e.,
modifier).
y
x
y
d
LINE1
θ = 30°
LINE1 = LINE/ ATANGL, 30, INTERC, d
Line (LINE)
The LEFT & RIGHT modifier indicates whether the line
is at the left or right tangent point, depending on how
• 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 APTis 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