Mitsubishi A1SD75M3 User Manual page 715

APPENDICES
WORM GEAR
This is the basic screw in mechanisms that
position using screw rotation. Ball screws are
often used to reduce backlash and dimension
error.
1 rotation
by the motor
Lead (feedrate per screw rotation)
XY TABLE
This is a device that moves a table in the X
(latitudinal) and Y (longitudinal) directions so
that positioning can be carried out easily.
There are also commercially available
products.
X table
Base table
X axis
ZERO POINT
This is the reference position for positioning.
Positioning cannot start without a reference
point.
The zero point is normally set to the upper or
lower stroke limit.
This point is the reference.
Zero point
ZERO POINT RETURN METHOD
The zero point return methods are shown
below. The method used depends on the
machine structure, stopping accuracy, etc.
Machine zero point returns can be carried out
when the zero point return parameters are
written.
1) Near-point dog method.
2) Count method
3) Data setting method
Positioning
Worm gear
Y table Ball screw
X table
Y axis
ZERO POINT RETURN PARAMETER
This parameter is required when returning to
the zero point. It is determined by the machine
side design, so subsequent changes of this
parameter must be accompanied by changes
in the machine design.
The zero point is the reference for positioning
operations, so if the zero point is lost due to a
power failure during positioning, or because
the power is turned OFF and the machine is
moved manually, etc., it can be restored by
carrying out a machine zero point return.
When a machine zero point return command is
issued, the machine will move in search of the
near-point dog regardless of the current value,
and will stop at the zero point. At this time, the
current value will be rewritten to the zero point
address. Data cannot be written during
positioning. With the AD75, data is always
written for all axes (from 1 to 3 axes).
Refer to the term "NEAR-POINT DOG".
ZERO POINT RETURN REQUEST
This signal turns ON when there is an error
with the AD75. It will turn ON in the following
situations.
1) When the power is turned ON.
2) When the PLC READY signal turns from
OFF to ON.
3) When the machine zero point return starts.
4) When the servo amplifier power is turned
OFF.
The user judges whether to carry out a
machine zero point return in the above
situations.
ZERO POINT SHIFT FUNCTION
The zero point position can be shifted to the
plus or minus direction by executing a machine
zero point return and determining a shift
amount for the position at the completion of
the machine zero point return.
A zero point can be set at a position besides
the zero point position, or outside the dog
switch.
ZERO POINT SIGNAL
Indicates PG0 (detected once per revolution)
of the pulse encoder. Also called the Z phase.
(In the case of the SSCNET connection type,
data equivalent to the zero point signal is sent
from the servo amplifier.)
Appendix - 47
MELSEC-A