If Operation Is Stopped At A Wrong Position - Mitsubishi MELSEC-F FX3U Series User Manual

FX /FX Series PLC User's Manual - Positioning Control Edition
3U 3UC
Built-in Positioning Function
13.4

If Operation Is Stopped at a Wrong Position

If operation is stopped at a wrong position, check the following items.
1) Check whether the electronic gear of the servo amplifier (drive unit) is set properly.
→ For the electronic gear setting method of the MELSERVO Series, refer to Subsection 4.6.2.
2) Check whether the origin is set properly.
• Properly set the DOG so that the near-point signal (DOG) can be kept at the ON status until the speed
is reduced to the creep speed. This instruction will start speed reduction at the front end of the DOG,
and will stop the operation at the rear end of the DOG or at detection of the first zero-phase signal after
passing the rear end of the DOG. After that, the current value register will be cleared (reset to "0"). If
the speed is not reduced to the creep speed before detecting the rear end of the DOG, the operation
may not be stopped at the specified position.
• The creep speed should be low enough. The zero return instruction will not reduce the speed before
stop. For this reason, if the creep speed is not low enough, the operation may not be stopped at the
specified position due to inertia.
• Devices for near-point signal (DOG)
- DSZR instruction
If an input (X000 to X017)
the near-point signal (DOG) will be monitored (detected) at 1-ms intervals (interruption). Under the
following condition, however, monitoring (detection) of the near-point signal (DOG) rear end may be
affected by the time constant at input or the scan time of the sequence program, and the operation
may not be stopped at the specified position.
a) An input number of X020 or below or the other device (auxiliary relay, etc.) is specified.
*1.To use FX
- ZRN instruction
If an input (X000 to X007) of the main unit is specified for the near-point input signal, the interruption
function will be adopted to stop the operation. Under the following condition, however, operation may
be affected by the scan time of the sequence program, and the operation may not be stopped at the
specified position.
a) An input number of X010 or below or the other device (auxiliary relay, etc.) is specified. If input
relay X010 or below is specified for the near-point signal, the input filter (10 ms) will be adopted.
• If DSZR instruction is used:
Since the zero-phase signal of the servo motor is used, adjust the relation between the rear end of the
DOG and the zero-phase signal as shown in the following figure. If fine adjustment of the origin
position is needed, adjust the position of the near-point signal (DOG).
Zero-phase signal
3) If reciprocating operation (operation in the forward rotation direction and then reverse rotation direction) is
not stopped at the specified position: The built-in positioning function cannot correct the mechanical
backlash (clearance, play) during positioning operation. If it is necessary to correct the backlash,
preliminarily set the number of output pulses considering the backlash that may be caused when
changing the transfer direction.
B - 160
*1
of main unit is specified for the near-point signal (DOG), the rear end of
-16M , specify an input in the range of X000 to X007.
3U
Rear end
Feed screw
Backlash
(clearance, play)
DOG
Table
13 Troubleshooting
13.4 If Operation Is Stopped at a Wrong Position