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Product description
40
Festo – GDCP-CMMO-ST-EA-SY-EN – 2017-05c – English
Homing to reference switch (with index)
Requirement is for parameterisation of reference switch (NO, NC)
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FCT [...][Axis] Axis Options. Hom
ing with index evaluation is only possible in closed-loop operation.
Homing to reference switch
Controlled operation
1. Search for the reference switch with search speed in the parameterised direction.
–
Switch not found: position to stop, search in opposite direction
–
Switch not found in opposite direction: termination (error message 0x22)
2. Reference switch found:
–
position at crawling speed in opposite direction until the reference switch is disabled
3. Continue until first index impulse from sensor
–
Index impulse not found: termination after a motor revolution (fault message 0x23)
4. Index impulse found: position is accepted as the homing point.
Direction: positive
Direction: negative
Index pulse
Homing Switch
Index pulse
Homing Switch
1)
If the reference switch is enabled when a homing run starts, step 2 is executed immediately
2)
Homing option “Position to axis zero point”
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Tab. 2.34
Homing method – reference switch with index
The angle position of the encoder (index impulse) must be far enough from the reference switch. If the
distance between the switching flank on the reference switch and the index impulse is small, temper
ature factors or mechanical clearance can move the reference point when the homing run is repeated
by one index impulse, i.e. one motor revolution.
On positioning systems (OMS) with a reference switch, during assembly the angle posi
tion of the encoder is determined. Then the mechanism is installed at Festo in such a way
that the index impulse is far enough away from the reference switch.
Do
not
align factory-preinstalled reference switch mechanically.
Do not alter the attachment position of the motor.
