February 2012 19 – 297
Gantry axes
with two linear
encoders
Figure: Example of a combination of gantry and master-slave torque drive
8 Always try to mount the position encoder as exactly as possible to its original position!
8 Ask the machine manufacturer which MP list is active.
8 In MP860.x (datum for synchronous control), set the bit 0 for the slave axis to 0.
--> After the reference marks have been traversed, no compensating motion is made.
8 The slave axis must be displayed. --> Enter the slave axis in MP7291.x.
8 Set the display to REF. --> Now you can see the current positions of the axes referenced to the
machine datum.
8 Set the position display step in MP7290.x to the highest resolution.
8 Reference the gantry axes (master and slave).
If a position encoder fails in a gantry combination, the machine datum stays as it is because of the
second position encoder.
As the mechanical structure is rigid (portal, etc.), the unchanged axis can be used to find the value
for MP960.x for the axis to be reset.
Machine manufacturers may use special MP lists or MP subfiles for gantry operation.
See ”Changes by the PLC” on page 31 – 572.
Sometimes the axis compensations and kinematics settings need to be deactivated before you
can reset the machine datum. --> Ask the machine manufacturer.
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