ME 440 – C/NC Machine Tools
Solution of Assignment 4
Student Name*
ID#*
Fall 2014
Introduction
In this assignment, an APT program to machine a Wankel (rotary) engine rotor is considered.
First part of the assignment defines various geometric entities while the second part
concentrates on the development of the APT program that specifically employs these entities
to describe the motion of the cutting tools.
Part A:
The geometric entities are illustrated in Figure 1.
Y
L2
C2
C5
C4
L1
P1
C1
C3
P0
X
Z
P0
P1
X
PL2
PL1
Fig. 1 Geometric entities to be used in the APT program.
Part B:
The listing of the APT program using the geometric entities introduced in Part A is given in
the Appendix. Notice that no attempt is made to improve the efficiency of the program (i.e.
the machining operations) for the sake of not obscuring its clarity. As can be seen from Table
1, there are five sections to the program that defines the cutter’s motion.
–1–
Student Name*
ID#*
ME 440 – C/NC Machine Tools
Solution of Assignment 4
Fall 2014
Table 1. Machining operations
Section
Machining Operation
1
Rough machining of the outer profile
2
Surface finishing of the outer profile
3
Surface finishing of the top surface
4
Rough finishing of the hole at the center
5
Surface finishing of the hole at the center
Once the drive-, part-, and check surfaces are determined correctly, defining contouring
motion is quite straightforward. Similarly, the time required to complete the machining
operation could be expressed as
c1c2 k 
T
2
(1)
In Eqn. (1), c1, c2, k, ,  are the experimental parameters. It is critical to note that climbmilling is to employed in all finishing operations for the given problem as it leads to a much
better surface-finish than its counterpart,. Unfortunately, a serious mistake about how the
contouring motion is defined for up- and climb-milling has been detected in some of your
solutions. As mentioned in one of the lectures; a milling tool, by design, can cut material
when it is rotated in only one particular direction (that direction is usually clockwise). Hence,
if it spins in the opposite direction (i.e. counter-clockwise); the tool will not be able to remove
any material as the cutting edges do not directly face the workpiece. Consequently,
programmers do have a control over the milling operation by simply changing the direction of
the feed/cutter motion (not the direction of the spindle rotation!). As a rule of thumb, one
must examine the cross-section of the cutting tool: when the cutting edges are opposing the
feed, the resulting operation becomes up-milling. So beware!
As a final note, a new statement called INDIRV (which stands for “IN DIRection of a
Vector) is utilized in the APT program to resolve the ambiguity that might occur at the startup of a contouring motion. In this statement, the direction of the contouring motion is
specified by a vector which has projections i, j, k along the X-, Y-, and Z axes respectively.
For instance,

INDIRV/1,0,0 means the direction is along +X axis;

INDIRV/-1,0,0 means the direction is along –Xaxis;

INDIRV/0,1,0 means the direction is along +Yaxis;

INDIRV/1,1,0 means the direction is along the line which makes 45o with the X
axis.
–2–
Student Name*
ID#*
ME 440 – C/NC Machine Tools
Solution of Assignment 4
Fall 2014
Part C:
Some advantages of the APT programming are as follows:

It is a programming environment enabling the use of many advanced features of highlevel languages (e.g. arithmetic operations, arrays, conditionals, branching, etc.)

The APT vocabulary is in English and most commands are easy to remember.

With APT, one can handle very sophisticated machining jobs.

All APT programs are portable.
As you have already discovered, there are some major disadvantages associated with the APT
programming:

For simple machining tasks (just like the one we have here), the APT programming

seems to be relatively more complicated than its counterpart.
Due to the success of advanced CAD/CAM packages which can generate NC
programs directly, the APT programming is becoming obsolete. Hence, the
commercial APT development tools are quite scarce in metal cutting industry.
[*] REMARK: If this is a group project, ONLY the name of the group (which you’ve
selected) is written. Names of the contributing group members, their student ID numbers
along with their signatures must be included to the last page of the report:
The group members who contributed to the preparation of this report are as follows:
Name
Student ID #
Signature
–3–
Student Name*
ID#*
ME 440 – C/NC Machine Tools
Solution of Assignment 4
Fall 2014
APPENDIX: APT Program Listing
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$$ ME 440: C/NC MACHINE TOOLS (FALL 2005/2006) $$
$$
*** SOLUTION OF HW#4 ***
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$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
PARTNO WANKEL ROTOR
MACHIN/MAZAK,9,OPTION,2,0
$$ POSTPROCESSOR NAME & OPTIONS
UNITS/MM
$$
$$ DEFINITION OF GEOMETRIC ENTITIES (SEE TEXT)
$$
P0 = POINT/0,0,50.0
P1 = POINT/49.0,58.0,50.0
C1 = CIRCLE/CENTER,165.03,58.0,RADIUS,155.0
C2 = CIRCLE/CENTER,-9.015,-42.485,RADIUS,155.0
C3 = CIRCLE/CENTER,-9.015,158.485,RADIUS,155.0
C4 = CIRCLE/CENTER,49.0,58.0,RADIUS,50.0
C5 = CIRCLE/CENTER,49.0,58.0,RADIUS,60.0
L1 = LINE/XAXIS,58.0
L2 = LINE/YAXIS,49.0
PL1 = PLANE/XYPLAN,-20.0
PL2 = PLANE/XYPLAN,-2.0
$$
$$ MACRO FOR ROUGHING OUTER PROFILE (UP-MILLING)
$$ A – AXIAL DEPTH; R – RADIAL DEPTH
$$
ROSFC = MACRO/A,R
THICK/A,R,R
GO/C3,PL1,C1
TLRGT,TLOFPS,GOFWD/C3,PAST,C2
GOLFT/C2,PAST,C1
GOLFT/C1,PAST,C3
RAPID;GOTO/P0
TERMAC
$$
$$ MACRO FOR FINISHING OUTER PROFILE (CLIMB-MILLING)
$$ A – AXIAL DEPTH
$$
FOSFC = MACRO/A
THICK/A,0,0
GO/C1,PL1,C3
TLLFT,TLOFPS,GOFWD/C1,PAST,C2
GORGT/C2,PAST,C3
GORGT/C3,PAST,C1
RAPID;GOTO/P0
TERMAC
–4–
Student Name*
ID#*
ME 440 – C/NC Machine Tools
Solution of Assignment 4
Fall 2014
$$
$$ MACRO FOR FINISHING TOP SURFACE (CLIMB-MILLING)
$$ R – RADIAL DEPTH
$$
TOPSFC = MACRO/R
THICK/0,R,R
GO/ON,L1,PL2,C5
TLLFT,TLONPS,GOLFT/C5,PAST,L1
GOFWD/C5,PAST,L1
GOFWD/C5,ON,L1
RAPID;GOTO/P0
TERMAC
$$
$$ MACRO FOR ROUGH-CUTTING OF THE CENTER HOLE (UP-MILLING)
$$ A – AXIAL DEPTH; R – RADIAL DEPTH; F – FEEDRATE
$$
RCUTCH = MACRO/A,R,F
THICK/A,R,R
GO/ON,L1,PL1,ON,L2,40
$$ PLUNGING
INDIRV/-1,0,0
$$ RESOLVES AMBIGUITY IN DIR.
TLRGT,TLOFPS,GOFWD/ON,L1,C4,F
GORGT/C4,PAST,L1
GOFWD/C4,PAST,L1
GOFWD/C4,ON,L1
RAPID;GOTO/P1
TERMAC
$$
$$ MACRO FOR SURF. FINISHING OF THE CENTER HOLE(CLIMB-MILLING)
$$ A – AXIAL DEPTH; F – FEEDRATE
$$
FCUTCH = MACRO/A,F
THICK/A,0,0
GO/ON,L1,PL1,ON,L2,40
$$ PLUNGING
INDIRV/1,0,0
$$ RESOLVES AMBIGUITY IN DIR.
TLLFT,TLOFPS,GOFWD/ON,L1,C4,F
GOLFT/C4,PAST,L1
GOFWD/C4,PAST,L1
GOFWD/C4,ON,L1
RAPID;GOTO/P1
TERMAC
$$
$$ DEFINITION OF MACHINING CONDITIONS
$$
CUTTER/19.05
TOLER/0.01
SPINDL/600,CLW
COOLNT/ON
–5–
Student Name*
ID#*
ME 440 – C/NC Machine Tools
Solution of Assignment 4
$$
$$ DEFINITION OF CUTTER MOTION
$$
FROM/P0
$$
$$ ROUGH-CUTTING OF OUTER PROFILE
$$
FEDRAT/100
CALL/ROSFC,A=10.0,R=32.0 $$ REMOVE CORNERS (A = 10 MM)
CALL/ROSFC,A=10.0,R=14.0 $$ DITTO
CALL/ROSFC,A=10.0,R=0.5
$$ ROUGH CUTTING PERIMETER
CALL/ROSFC,A=0,R=32.0
$$ REMOVE CORNERS (A = 20 MM)
CALL/ROSFC,A=0,R=14.0
$$ DITTO
CALL/ROSFC,A=0,R=0.5
$$ ROUGH CUTTING PERIMETER
$$
$$ SURFACE FINISHING OF OUTER PROFILE
$$
FEDRAT/70
CALL/FOSFC,A=10.0
CALL/FOSFC,A=0
$$
$$ SURFACE FINISHING OF TOP SURFACE
$$
CALL/TOPSFC,R=12.0
CALL/TOPSFC,R=0.5
CALL/TOPSFC,R=0
$$
$$ ROUGH-CUTTING OF THE CIRCLE AT CENTER
$$
RAPID;GOTO/P1
CALL/RCUTCH,A=10.0,R=0.5,F=100
CALL/RCUTCH,A=0,R=0.5,F=100
$$
$$ SURFACE FINISHING OF THE CIRCLE AT CENTER
$$
CALL/FCUTCH,A=10.0,F=70
CALL/FCUTCH,A=0,F=70
RAPID;GOTO/P0
SPINDL/OFF
COOLNT/OFF
END
FINI
–6–
Fall 2014