Machine home position return
The FX-1GM PGU has a built-in current value register (storing the absolute address) which is
incremented/decremented by the forward pulse or backward pulse it generates.
This allows the machine position to be calculated at all times.
When the operation is started for the first time,
it
is necessary
to
teach the current machine position
to the register.
A
machine home position return DRV
ZRN
(DRIVE ZERO
RETURN)
instruction is prepared to execute
this operation automatically.
DRV
ZRN
is an independent instruction which is not accompanied by address instructions, unlike
DRV
ABS
or DRV instructions. It is operated in the following sequence:
Switch
to
turn the motor
OFF
at
Backward limit
switch
LSR
DOG
fl
L
Home return sequence switch
the forward limit
Motor
Creep speed
J~@
Initial position
t
'
Home position return speed
Details
of
machine home
position return are
described
on
page 25.
Pulses of the zero-point signal (PGO) sent from the drive unit
to
the
PGU
are counted, and operations are stopped when the count reaches the
This point is considered designated value. These pulses are normally
1
pulse per each motor
the home position. rotation.
-
r
DOG
Switch Configurations
Generally, DOG switches are configured as either a single point or a regional signal.
In
single
point operations, the DOG switch is only switched
ON
when the DOG table is at the start of
home return deceleration. Thereafter,
it
is switched OFF.
DOGSwtchONthmughwtrqon
DOG Switch
ON
for a
single position
\;J
Automatic forward
'
.
. .
. .> . .
.
. . . . . . . .
'
Manual forward
if the initial position is situated within the
ON
region
of
In the above case, if the DOG table is initially situated
the dog switch, the machine home return operation can
within the home deceleration area, it will not be detected
be executed after advancing to out of range automat-
by the DOG switch. Hence manual forward must be
ically.
driven before the automatic mode can be switched
ON.
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11
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