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8 ZERO POINT RETURN CONTROL
8.2.7 Zero point return method (5): Count method 1)
The machine starts a machine zero point return.
1)
(The machine starts acceleration specified in " Pr.53 Zero point return acceleration time selection" in the
direction set in " Pr.46 Zero point return direction", and moves at " Pr.48 Zero point return speed".)
2)
The machine detects near-point dog ON and starts deceleration.
3)
The machine decelerates to " Pr.49 Creep speed" and then moves at the creep speed.
At the first zero point signal issued after the machine has moved the movement amount set in
" Pr.52 Setting for the movement amount after near-point dog ON" after near-point dog ON, pulse output
4)
from the D75P2 stops and "deviation counter clear output" is output to the drive unit.
After the completion of "deviation counter clear output", the zero point return complete flag (RX(n+2)0,
5)
RX(n+5)0) turns from OFF to ON and the zero point return request flag (RX(n+1)F, RX(n+4)F) turns from
ON to OFF.
Adjust the movement amount after
activation at the near-point dog to
the center of the high zero point
signal interval as far as possible.
If the movement amount setting
after activation at the near-point dog
interferes with the zero point signal,
the machine zero point return stopping
position may deviate by a revolution of
the servomotor.
Machine zero point return start
(Positioning start signal)
Zero point return request flag
[RX(n+1)F, RX(n+4)F]
Zero point return complete flag
[RX(n+2)0, RX(n+5)0]
Deviation counter clear output
Axis operation status
[RWrn+7, RWrn+15]
Md.44 Movement amount
after near-point dog ON
Current feed value
[RWrn+0 to 1, RWrn+8 to 9]
Md.30 Machine feed value
The following shows an operation outline of the "count method 1)" zero point return
method.
Operation chart
Pr. 48 Zero point return speed
V
1)
Near-point dog OFF
First zero point after travel by " Pr. 52
Setting for the movement amount
after near-point dog ON"
Zero point signal
ON
OFF
ON
OFF
OFF
Standing by In zero point return
0
Inconsistent
Inconsistent
Value the machine moved is stored
Fig. 8.11 Count method1) machine zero point return
Pr.52 Setting for the movement amount
after near-point dog ON
Pr. 49 Creep speed
t
2) 3) 4) 5)
Md.44 Movement amount after near-point dog ON
There is no problem even if deactivation at
the near-point dog occurs during machine zero
ON
point return.
However, deactivation at the near-point dog
should be as far from the zero position as
possible, due to the following reason.
If deactivation at the near-point dog occurs at
the end of machine zero point return, the motor
is not stopped in the second action until the
Equivalent
to 1 servo
upper or lower limit is reached when repetitive
motor
machine zero point return cycles occur.
rotation
If the zero point return retry function has been
invalidated, an error is caused upon detection
of the limit.
ON
Standing by
Value of *1.
Zero point address
8 - 16
MELSEC-A
*
1
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