Summary Automatically Programmed Tool (APT) Full Notes
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Gate
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Gate
Automatically Program Tool (APT) is a high-level computer programming language used to generate instructions for controlling machine tools and manufacturing processes. Developed in the 1950s, APT revolutionized the field of Computer Numerical Control (CNC) by allowing engineers and machinists to de...
IENG 475 COMPUTER-CONTROLLED MANUFACTURING SYSTEMS 2/2/2015
HAND OUT 02: APT PROGRAMMING NOTES
APT stands for Automatically Programmed Tool. It is a language that defines the tool path with respect to the part
geometry, and often forms the basis for post-processor generated NC files.
The APT language consists of four types of statements. Geometry statements will be used to specify the elemental
features defining the part shape. Motion statements are used to specify the path taken by the tool. Post-processor
statements control the machinery, controlling coolants as well as the feeds and speeds. Auxiliary statements
complete the picture, specifying the part, required tools, etc. The following sections describe each of the APT
statements.
Geometry Statements
All geometric elements must be defined before tool motion may be programmed. Geometry statements associate a
symbol with a description of the geometric element and its parameters. The general form for a geometry statement
is:
symbol = geometric type/parametric description
The symbol consists of up to six alpha-numeric characters, containing at least one alpha character, and avoiding
APT reserved words. The symbols provide a means to name the geometric features. The equals sign separates the
symbol from the geometric type.
The geometric type describes these features. POINT, LINE, PLANE, and CIRCLE are valid APT geometric
types. The forward slash character separates the geometric type from the parametric description of the feature.
The parametric description specifies the location and size of the feature. It may include dimensional data, positional
data, and other APT words relating the feature to previously defined APT symbols. The APT language provides a
rich means to specify the geometry, as is evidenced by the following examples.
To specify a point:
P0 = POINT/1.0, 1.2, 1.3 specifies a point at XYZ coordinates 1.0, 1.2, and 1.3,
respectively.
P1 = POINT/INTOF L1, L2 specifies a point at the intersection of lines L1 and L2, which
must have been defined prior to the statement.
P2 = POINT/YLARGE, INTOF, L3, C1 specifies a point at the intersection of line L3 and circle C1 at
a Y position above the center point of the circle.
To specify a line:
L1 = LINE/P0, P1 specifies a line by two points, previously defined.
L1 = LINE/1.0, 1.2, 1.3, 2.0, 2.1, 2.3 specifies a line by two points, given as explicit coordinates.
L2 = LINE/P2, PARLEL, L1 specifies a line through point P2 and parallel to line L1.
L3 = LINE/P1, RIGHT, TANTO, C1 specifies a line through point P1 and tangent to circle C1 on
the right side of the center point.
L4 = LINE/P1, ATANGL, 45, L1 specifies a line through point P1 at an angle of 45 o to line L1.
IENG 475 HO 02 APT Programming Notes Page 1 of 5 Printed: 11:30 AM
, IENG 475 COMPUTER-CONTROLLED MANUFACTURING SYSTEMS 2/2/2015
To specify a plane:
PL0 = PLANE/P0, P1, P2 specifies a plane through three, non-colinear, previously
defined points.
PL1 = PLANE/P3, PARLEL, PL0 specifies a plane through a point P3 parallel to a plane PL0.
To specify a circle:
C0 = CIRCLE/CENTER, P0, RADIUS, 1.0 specifies a circle of radius 1 from a center point of P0.
Lines and planes extend infinitely. Circles are always complete. The same geometry may be defined only once, and
may not have more than one symbol.
Motion Statements
The format for motion commands follows the pattern:
motion/description
The initial motion starts from a home position, and takes the form:
FROM/P0 or FROM/ 0.0, 1.0, 2.0
The FROM motion statement occurs only once for each set of a motion type, at the start of the set of motions.
Contouring motion – is the most common motion used in APT programming, and these statements specify the tool
path continuously throughout the motion. They make use of three surfaces: (a) drive; (b) check; and (c) part
surfaces.
Drive surfaces represent the surface along which the vertical edges of the tool will follow. Part surfaces specify the
surfaces the tip of the tool will follow. And check surfaces describe where the tool will come to rest after it has
completed the motion of the current step. There are four locations for the tool to stop with respect to a check
surface. These four possibilities each have their own modifier words.
The TO modifier stops the tool when the first surface of the tool would come into contact with the check surface.
The ON modifier stops the tool where the center point of the tool would come into contact with the check surface.
The PAST modifier stops the tool where the last surface of the tool would contact the check surface. And the
TANTO modifier stops the tool at the point of circular tangency with the edge of the tool.
The initial contouring motion statement is the GO/TO, which defines the initial drive, part and check surfaces. It
takes the form:
GO/TO, drive surface, TO, part surface, TO, check surface
An example would be:
GO/TO, L1, TO, PL1, TO, L2 specifying that the tool should use line L1 as the drive surface, plane P1
as the part surface, and line L2 as the check surface.
Note: the GOTO and the GO/TO statements are not the same. The former specifies point to point motion (see
below), and the latter initiates contouring motion.
Continuing contouring motion statements are given from the vantage point of a person sitting on the top of the tool.
The motion words are: (a) GOLFT; (b) GORGT; (c) GOFWD; (d) GOBACK; (e) GOUP; and (f) GODOWN.
The sense of these words depends on the direction the tool has been coming from, and is depicted in Figure 2:
IENG 475 HO 02 APT Programming Notes Page 2 of 5 Printed: 11:30 AM
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