HEIDENHAIN TNC 620 User Manual page 353

MOD functions | Changing the machine settings
Software limit switch with modulo axes
If you set software limit switches for modulo axes, make sure to
comply with the following basic conditions:
The lower limit is greater than -360° and less than +360°
The upper limit is not negative and less than +360°
The lower limit is not greater than the upper limit
The difference between the upper and the lower limit is less than
360°
If these conditions are not met, you will not be able to move the
modulo axis. The TNC 620 displays an error message.
If modulo limit switches are active, a movement is allowed if the
target position or an equivalent position is within the allowed
range. Equivalent positions are positions that differ from the target
positions by an offset of n  360° (where n is any integer). The
direction of motion is derived automatically because there is always
only one equivalent position that the axis can move to—with the
exception described below.
Example:
For the modulo axis C, the limit switches have been set to -80° and
+80°. The axis is at 0°. If you program L C+320 now, the C axis will
move to -40°.
If an axis is positioned outside the limit switch range, it can only be
moved towards the nearer limit switch.
Example:
The limit switches have been set to -90° and +90°. The C axis is at
-100°.
In this case, the C axis must move in the positive direction with its
next movement so that moving by L C+I5 works, while L C–I5 would
result in a limit switch violation.
Exception:
The axis is positioned exactly in the middle of the forbidden range.
Thus, the distance to both limit switches is the same. In this case,
the movement can go to either direction. This results in the special
situation that the axis can move to two equivalent positions if the
target position is within the allowed range. In this case, the axis
will be moved to the nearer equivalent position, i.e. the shorter
path is used. If both equivalent positions are equidistant (i.e., 180°
away), the control selects the direction of motion according to the
programmed value.
Example:
The limit switches have been set to C–90°, C+90° and the axis is at
180°.
If you program L C+0, the C axis will move to 0. The same is true
when programming L C-360, etc. However, if you program L C+360
(or L C+720, etc.), then the C axis will move to 360°.
HEIDENHAIN | TNC 620 | User's Manual for Setup, Testing and Running NC Programs | 01/2022
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