Mitsubishi Electric MELDAS 600M Series Instruction Manual page 390

(2) Reference point
The reference point is the point positioned to when the dog-type reference point return is executed.
Note that a separate setting method is used for the absolute position detection.
The reference point is the point positioned to with the manual reference point return and G28
command in the machining program.
Using parameters, the reference point can be shifted from the electrical zero point position.
(3) Grid point
The position detector 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 detector, and
the machine has many grid points at a set pitch.
The grid point can be set per grid space by setting the grid spacing (ZERO POINT RETURN
PARAM. 150004 Grspc). Thus, multiple grid points can be set per detector rotation.
(4) Grid space
The distance between the grid points is the grid space. The grid space can be set in mm
(millimeter) units in the ZERO POINT RETURN PARAM. 150004 Grspc.
(5) Grid amount
The grid amount expresses the distance from when the near-point detection limit switch leaves the
near-point dog and reaches the grid point (electrical zero point) when the dog-type reference point
return is executed.
The grid amount can be confirmed with "GRID AMOUNT" on the "ALM/DIAG" "SERVO
MONITOR" screen of the setting and display unit.
After setting the grid mask, the grid amount shows the distance from the grid mask OFF to the grid
point.
(6) Basic machine coordinate system zero point
The basic machine coordinate system is a coordinate system that expresses a position decided
characteristically for the machine.
The following positions are expressed with the machine coordinate system.
Usually, the machine coordinate zero point position is the same as the reference point position, but
it can be shifted with the parameters.
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3. Adjusting the Dog-Type Reference Point Return
• No. 1 to No. 4 reference point position
• Workpiece coordinate system zero point position
• Stored stroke limit position
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CHAPTER 3 MAINTENANCE
III – 4