July 2010 18 – 305
18.2.8 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 evaluted when the machine is switched on, a trigger signal is used (PLC
input).
The trigger signal should be at the corrcect axis position, as precisely as possible between two
reference pulses; see figure.
8 Set the display to REF. --> Now you can see the current actual position of the axis
referenced to the machine datum.
8 Reference the axis concerned at a low speed of the remounted motor.
8 Read the display and compare the value for this axis with the value in MP 960.x.
8 Position the axis with M91 to the value of MP 960.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 18 – 306.)
Ask the machine operator.
8 Starting from this point, position the axis with M91 by half the value in MP 1054.x (linear
distance of one motor revolution) in the traverse direction specified in MP 1320.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 oscillscope 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 19 – 317.
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 MP 910.x. It is also possible that the operator
has 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 Set” on page 29 – 566
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