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8 ZERO POINT RETURN CONTROL
8.2.8 Zero point return method (6): Count method 2)
The machine zero point return is started.
(The machine begins the acceleration designated in " Pr.53 Zero point return acceleration time
1)
selection", in the direction designated in " Pr.46 Zero point return direction". It then moves at the " Pr.48
Zero point return speed" when the acceleration is completed.)
2)
The machine begins decelerating when the near-point dog ON is detected.
The machine decelerates to the " Pr.49 Creep speed", and subsequently moves at that speed.
3)
The pulse output from the D75P2 will stop and the machine zero point return will be completed when the
4)
machine moves the movement amount set in " Pr.52 Setting for the movement amount after near-point
dog ON " from the near-point dog ON position.
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]
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 2)" zero point return
method.
The "count method 2)" method is effective when a "zero point signal" cannot be
received. (Note that compared to the "count method 1)" method, using this method will
result in more deviation in the stop position during machine zero point returns.)
Operation chart
Pr. 48 Zero point return speed
V
1)
ON
OFF
ON
OFF
OFF
In zero point return
Standing by
Inconsistent
0
Inconsistent
Value the machine moved is stored
Fig. 8.13 Count method 2) machine zero point return
Pr.52 Setting for the movement amount
after near-point dog ON
Pr. 49 Creep speed
t
2) 3)
4)
Md.44 Movement amount after near-point dog ON
There is no problem even if deactivation at the
ON
near-point dog occurs during machine zero point
return.
OFF
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 upper or
lower limit is reached when repetitive machine zero
point return cycles occur. 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 - 18
MELSEC-A
*
1
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