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M800VW/M80VW Series Connection and Setup Manual
26 Setting the Position Detection System
26.2 Adjustment of Reference Position Return in Relative Position Detection System
[Grid point]
The position encoder has a Z-phase that generates one pulse per rotation. The 0-point position of this Z-phase is the grid
point.
Thus, there is a grid point per rotation of the position encoder, and the machine has many grid points at a regular pitch.
The grid point can be set at intervals of grid space by setting the grid space (#2029 grspc). Thus, multiple grid points can be
set per encoder rotation.
[Grid amount]
The grid amount is the distance from where the near-point detection limit switch leaves the near-point dog to the grid point
(electrical zero point) as the dog-type reference position return is executed.
The grid amount can be confirmed on the DRIVE MONITOR screen.
After setting the grid mask, the grid amount shows the distance from the grid mask OFF to the grid point.
[G28 rapid traverse rate (#2025 G28rap)]
Set the feedrate for dog-type reference position return in manual operation and the automatic operation.
The rapid traverse rate (#2001 rapid) is applied for the feedrate during the high-speed reference position return.
[G28 approach speed (#2026 G28crp)]
Set the approach speed to the reference position after decelerating to a stop by the near-dog detection. Since the G28
approach speed is accelerated and decelerated in steps (no-acceleration/deceleration), the mechanical shock, etc. could
occur if the speed is too large. The G28 approach speed should be set between 100 and 300 mm/min., or within 500 mm/min.
at the fastest.
[Reference position shift amount (#2027 G28sft)]
When shifting the reference position from the electrical zero point, set the shift amount.
The shifting direction can be set only in the reference position return direction.
If the reference position shift amount is "0", the grid point (electrical zero point) will be the reference position.
[Grid mask amount (#2028 grmask)]
The first grid point after the dog OFF is regarded as the electrical zero point.
If the grid point is at the position where the near-point dog is kicked OFF, the position of electrical zero point may be at the grid
point where the dog is kicked OFF or at the next grid point because of the delay of the limit switch operation. This causes a
deviation of reference position by the amount of the grid space. Thus, the position that the dog is kicked OFF needs to be at
the approximate center of the grid space.
Adjustments are made by setting the grid mask amount or changing the near-point dog.
Setting the grid mask has the same effect as lengthening the near-point dog. Refer to the previous procedures for detailed
setting.
[Grid space (#2029 grspc)]
Set the distance between grids.
Set either the ball screw pitch value (#2218 PIT) or the movement amount per motor rotation as the normal grid space. To
make the grid space smaller, set a divisor of the grid space.
[Calculation method for movement amount per motor rotation]
When linear feed mechanism is a ball screw:
The movement amount per motor rotation = the motor side gear ration / the machine side gear ratio x the ball screw pitch
When linear feed mechanism is a rack and pinion:
The movement amount per motor rotation = the motor side gear ration / the machine side gear ratio x number of pinion
gear teeth x the rack pitch
For the rotary axis:
The movement angle per motor rotation = the motor side gear ration / the machine side gear ratio x 360
IB-1501612-C
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