February 2012 19 – 311
19.2.9 Readjusting the trip dog for reference end position
For position capture using a conventional motor encoder (not an EnDat encoder), one reference
pulse is produced at each revolution of the encoder. To ensure that always the same reference pulse
is evaluated when the machine is switched on, a trigger signal is used (PLC input).
The trigger signal should be at the correct axis position, in the center between two reference pulses;
see figure.
8 Set the display to REF. --> You can now see the current axis position referenced to the machine
datum.
8 Reference the axis concerned at a low speed of the newly mounted motor.
8 Read the display and compare the value for this axis to that in MP960.x.
8 Position the axis with M91 to the value of MP960.x (e.g. 321.456 mm) and check, whether
the axis is approximately at the correct position. (The exact position will be determined later.
--> See ”Resetting the machine datum” on page 19 – 312.)
Ask the machine operator.
8 Starting from this point, position the axis with M91 by half the value in MP1054.x (distance
covered in one motor revolution) in the traverse direction specified in MP1320.x.
If, for example, the motor is directly coupled, the spindle pitch 10 mm and the traverse direction
positive, the position would be 321.456 mm + 5 mm = 326.456 mm.
8 Adjust the trip dog at this position. Ask the OEM for the related PLC input and observe this input,
e.g., with the integrated oscilloscope or in the PLC logic diagram.
8 Restart the machine several times and test referencing. --> The reference mark must always be
evaluated at the same position.
Further information --> See ”Reference run” on page 20 – 323.
Reference pulse
Closed
Open
Trip dog
"Reference end position"
Traverse direction MP1320
Measuring length
Desired reference pulse
The OEMs frequently provide instructions for adjusting the trip dog. Use these instructions!
The following brief description is only one possibility.
You may have to expand the traverse range (software limit switches).
(The software limit switches are defined as of MP910.x. The operator may have limited the
traverse range even further.)
If available, you can also use a PWM 9 to observe the reference mark.
--> See ”PWM 9 encoder diagnostic kit” on page 30 – 564.
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