5
Programming Tool Movements
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5.5 Path Contours - Polar Coordinates
Helical interpolation
A helix is the combination of a circular movement in
a main plane and a linear movement perpendicular
to the plane.
A helix is programmed only in polar coordinates.
Applications:
You can use helical interpolation with form cutters
to machine:
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Large-diameter internal and external threads
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Lubrication grooves
input
Fig. 5.40: Helix: a combination of circular and linear paths
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Total incremental angle of tool traverse on the helix
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Total height of the helix
Input angle
Always witer the sanw sign for din&ion of rotation and incremental input angle The TNC may otherwise move
the tool on an incorrect path.
Calculate the incremental polar coordinate angle IPA as follows:
IPA = n 360”; where
n = number of revolutions of the helical path.
For IPA you can enter any value from -5400” to +5400” (n = 15).
-_
Input height
Enter the helix height H in the tool axis, The height is calculated as:
H=nxP,
n = number of thread revolutions
P = thread pitch
Radius compensation
Enter the radius compensation for the helix accord-
ing to the table at right.
Internal thread Work direction
Rotation Radius camp.
Right-hand z+
DR+ RL
Left-hand Z+
DR- RR
Right-hand z-
DR- RR
Left-hand
z- DR+ RL
External thread Work direction Rotation Radius camp.
Right-hand z+
DR+ RR
Left-hand z+
DR- RL
Right-hand
z- DR- RL
Left-hand z- DR+ RR
Fig. 5.41: The shape of the helix determines the direction of rotatron
and the radius comcensation
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TNC 370
5-33
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