HEIDENHAIN TNC 122 Technical Manual - Manual (Page 20)

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TNC 122 9 Machine Integration 19
9.3.1 Traversing the Reference Marks
The reference marks of the axes should be traversed after the control is switched on. Machines
with the TNC 121 are usually equipped with scales that have a reference mark at each end. To
prevent the software limit switch ranges from being shifted, always traverse the reference mark
upon which the software limit switches are based.
If referencing is not desired, it can be deactivated with machine parameter MP1340.x or by pressing
the NO ENT key.
To traverse the reference marks, press the machine axis direction buttons. The sequence of axes is
determined by the user.
When the reference marks are crossed over,
•
the software limit switches are activated
•
the datum point last set is restored
If the position encoders have distance-coded reference marks, the machine datum is based on the
scale reference point (on linear encoders the scale reference point is the first reference mark after
the start of the measuring length; on angle encoders the scale reference point is marked).
Manual execution (standard process)
The reference mark is traversed with the axis-direction keys.
Automatic execution (not in TNC 122)
The direction of traverse and the speed when crossing over the reference marks is defined with
machine parameters (MP1320.x, MP1330.x). The sequence of functions when crossing over the
reference marks can be defined separately for each axis with MP1350.x.
A trip dog for the reference end position is necessary to prevent the traverse range from being
exceeded when the reference marks are crossed over. Install the trip dog at the end of the traverse
range. The trigger signal line from the trip dog is connected to a vacant PLC input. In the PLC
program, this PLC input is combined with the markers for “Reference end position” (M2556 to
M2558)
Encoders with distance-coded reference marks
Machine parameter MP1350.x=0
Reference marks
Closed
Open
Trip dog
"Reference end position"
Traverse direction MP1320.x