Mitsubishi Electric MELSEC-L LD75P User Manual page 792

Trouble type
A setting of "1m = 1 pulse" is required in the
following system.
Electronic gear
• Ball screw pitch = 10mm
• Feedback pulses = 8192 pulse
The machine only moves to "10081230", although
positioning with a command value of "10081234"
carried out.
Error compensation How can the error be compensated?
The following values are currently set.
• [Pr.2] No. of pulses per rotation = 8192
• [Pr.3] Movement amount per rotation = 8000
When carrying out a count method machine OPR,
the message "Leave Sufficient Distance From The
OP Position To The Near-Point Dog OFF." appears.
Is there a problem if the distance is short?
In the near-point dog method machine OPR, the
stop positions are not uniform.
OPR
Can the machine OPR be carried out with the OPR
retry function when it is started with the near-point
dog ON and the upper/lower limit OFF?
Are ABS and INC positioning possible without
carrying out an OPR?
After an OPR, the OPR request flag sometimes
turns ON for no apparent reason.
The OPR complete flag ([Md.31] Status: b4)
sometimes turns ON when it shouldn't be ON.
The positioning start signal [Y10] is kept ON until
the BUSY signal is OFF, but is there any problem
with turning it OFF before the BUSY signal turns
Start
OFF?
The operation will not start even when the start
signal is turned ON.
790
Questions/Trouble Remedy
In this case, the following values will result.
• No. of pulses per rotation = 8192
• Movement amount per rotation = 10000
• Unit magnification = 10
Therefore, the "Movement amount per pulse" will become
"1.2207m".
This value is fixed by the machine system, so it cannot be
changed.
Thus, the setting "1m = 1pulse" cannot be achieved.
Reset [Pr.3] and [Pr.2] in the following order.
Calculate "8192/8000  10081230/10081234".
1)
2) Obtain the reduced value.
3) Set the numerator in "[Pr.3] Movement amount per rotation",
and the denominator in "[Pr.2] No. of pulses per rotation".
The near-point dog must be set to turn OFF at a position after the
OP is passed.
(When the machine OPR is started on the near-point dog on in a
count-method machine OPR, the machine enters a normal
machine OPR operation after returning to the near-point dog OFF
region.)
(If the near-point dog is turned OFF before the OP, and the
machine OPR is started between the near-point dog OFF position
and the OP, the machine will mistakenly interpret that its current
position is before the near-point dog ON position, and it will pass
over the OP and continue moving.)
Carry out the following measures.
1) Separate the near-point dog signal and zero signal detection
positions.
2) Lower the values in "[Pr.46] OPR speed" and "[Pr.47] Creep
speed".
3) Confirm whether the zero signal and near-point dog signal
turn ON normally.
4) Check that there is no play (backlash) in the machine
system.
A "Hardware stroke limit error" will occur and the operation will not
be carried out.
(The machine will interpret any position where the near-point dog
is ON as being within the working range, and that the upper/lower
limit is ON.)
They are possible.
In this case, the position where the power is turned ON is handled
as the current feed value "0".
The OPR request flag turns ON in the following cases.
1) When the power is turned ON.
2) When the PLC READY signal [YO] turns from OFF to ON.
3) When an OPR is carried out.
4) When the servo amplifier power is turned OFF.
If no problem is found when the above are checked, then it is
possible that the communication is being interrupted by "a fault in
the bus cable", "noise influence", etc.
Check whether the drive unit READY signal is weak or the power
supply is unstable.
After the BUSY signal turns ON, there is no problem with turning
[Y10] OFF before the BUSY signal turns OFF.
(The LD75 detects the rising edge (OFF  ON) of the positioning
start signal [Y10].)
Check the "[Md.26] Axis operation status" and "[Md.23] Axis error
No.".
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