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4. OPERATION
4.4.8 Count type front end reference home position return
POINT
This home position return method depends on the timin
g
of readin
g
Proximit
y
do
g
(
DOG
)
that has detected the front end of a proximit
y
do
g
.
Hence, if a home position return is made at the creep speed of 100r/min, an
error of
200 pulses will occur in the home position. The error of the home
position is larger as the creep speed is higher.
The position where the axis, which had started decelerating at the front end of a proximity dog, has
moved the after-proximity dog moving distance and home position shift distance is defined as a home
position. A home position return that does not depend on the Z-phase signal can be made. The home
position may change if the creep speed varies.
(1) Signals, parameters
Set the input signals and parameters as indicated below.
Item Device/Parameter used Description
Manual home position return mode
selection
Automatic/manual selection (MD0) MD0 is switched on.
Count type dog front end reference
home position return
Parameter No.8
6: Select the count type dog front end reference.
Home position return direction Parameter No.8
Refer to Section 4.4.1 (2) in this section and select the home
position return direction.
Dog input polarity Parameter No.8
Refer to Section 4.4.1 (2) in this section and select the dog input
polarity.
Home position return speed Parameter No.9 Set the speed till the dog is detected.
Creep speed Parameter No.10 Set the speed after the dog is detected.
Home position shift distance Parameter No.11
Set when the home position is moved from where the axis has
passed the proximity dog rear end.
Moving distance after proximity dog Parameter No.43
Set the moving distance after the axis has passed the proximity dog
rear end.
Home position return acceleration/
deceleration time constants
Parameter No.41
Use the acceleration/deceleration time constants set in parameter
No. 41.
Home position return position data Parameter No.42
Used to set the current position on completion of home position
return.
Program
Select the program including the
"ZRT" command that executes a
home position return.
(2) Timing chart
The following shows the timing chart that starts after selection of the program including the "ZRT"
command.
ON
OFF
ON
OFF
ON
OFF
Home position return
completion (ZP)
Proximity dog (DOG)
Forward rotation
start (ST1)
5ms or more
3ms or less
Proximity dog (DOG)
Creep speed
Moving distance after proximity dog
Home position shift distance
Home position return speed
ON
OFF
ON
OFF
Movement complete (PED)
Automatic/manual
selection (MD0)
Home position address
Parameter No. 42
Servo motor speed
Forward
rotation
0 r/min
The address on completion of home position return is the value automatically set in parameter No.42
(home position return position data).