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12 CONTROL AUXILIARY FUNCTIONS
12.2 Auxiliary functions specifically for machine zero point returns
12.2.1 Zero point return retry function
1) The movement starts in the " Pr.46 Zero point return direction" by a machine zero point return start.
2) The operation decelerates when the limit
3) After stopping due to the limit signal OFF detection, the operation moves at the " Pr.48 Zero point return
speed" in the opposite direction of the " Pr.46 Zero point return direction".
4) The operation decelerates when the near-point dog turns OFF.
5) After stopping due to the near-point dog OFF, a machine zero point return is carried out in the " Pr.46
Zero point return direction".
The auxiliary functions specifically for machine zero point returns include the "zero
point retry function" and "zero point shift function". Each function is executed by
parameter setting.
When the workpiece goes past the zero point without stopping during positioning
control, it may not move back in the direction of the zero point although a machine zero
point return is commanded, depending on the workpiece position. This normally means
the workpiece has to be moved to a position before the near-point dog by a JOG
operation, etc., to start the machine zero point return again. However, by using the
zero point return retry function, a machine zero point return can be carried out
regardless of the workpiece position.
The details shown below explain about the "zero point return retry function".
(1) Control details
(2) Precautions during control
(3) Setting the zero point return retry function
(1) Control details
The following drawing shows the operation of the zero point return retry function.
(a) Zero point return retry operation when the workpiece is within the range
between the upper and lower limits.
5)
4)
ON
Near-point dog
Zero point signal
Fig. 12.1 Zero point return retry operation by limit signal detection
signal
OFF is detected.
1)
6)
12 - 4
MELSEC-A
2)
3)
Limit signal OFF
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