If Operation Is Stopped At A Wrong Position - Mitsubishi Electric Melsec-F FX3GC Series User Manual

FX /FX /FX /FX /FX
3S 3G 3GC 3U 3UC
Built-in Positioning Functions
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 ON until the speed is reduced to the
creep speed. The zero return 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 sufficiently slow. The zero return instruction will not reduce the speed before
stopping. For this reason, if the creep speed is not slow enough, the operation may not be stopped at the
specified position due to inertia.
• Devices for the near-point signal (DOG)
- DSZR instruction
Detection of (the rear end and the front end of) the near-point signal (DOG) will be affected by the input
filter and the scan time of the sequence program.
Secure 1 scan time or more from the rear end of the DOG to turning ON of the zero-point signal.
- ZRN instruction
If an input X000 to X007 (X000 to X005 for FX
signal (DOG), the PLC interruption function will be used to stop the operation. Under the following
condition, however, operation may be affected by the input filter or 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 higher (X006 or higher for FX
etc.)) is specified. If an input relay X010 or higher (X006 or higher for FX
near-point signal (DOG), the effects of the input filter will apply.
• If the 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 - 186
PLC User's Manual - Positioning Control Edition
Longer than
1 scan time.
Feed screw
Backlash
(clearance/play)
PLC) of the main unit is specified for the near-point
3S
Operation direction
Rear end Front end
DOG
Table
13 Troubleshooting
13.4 If Operation Is Stopped at a Wrong Position
PLC) (or other device (auxiliary relay,
3S
PLC) is specified for the
3S