Vacuum Robot Manual
4000-0315 Rev 1
27
Setting the Z-Axis Brake
The Z-axis brake prevents the Z column from backdriving with the force
of gravity. Line 20 of the Robot Parameter File lists the Z-axis
parameters:
• First parameter is the numerical port ID used for turning the brake on
or off. If there is a brake, the number is normally 4, and if there is no
brake, the number is 0.
• Second parameter is the Z-axis Gain offset. If there is a brake, the
offset is 0. If there is no brake, the offset is 1000. This value sets the
bias voltage in the motor output to counter gravity.
• Third parameter is always 0.
If there is a brake and the first parameter is set correctly, the controller
engages the brake port automatically when the SVOF (servo off) or ABM
(abort motion) command is executed or disengages the brake when the
SVON command is executed. The brake is activated when the Z-axis
servo motor is turned off or a motor position error occurs.
To manually engage or disengage the brake, send the OUTP command
from the Teach Pendant or EQT command line, as in the following steps.
CAUTION: Make sure the end effector is clear of obstacles before
turning off the brake and Z-axis servo motor. The Z axis can drop
under the force of gravity if the brake and the servo are off. Wafer and
robot damage can result.
1. To turn off the servo motor, enter the command:
SVOF Z
This causes the Z-axis brake to turn on.
2. To turn off the brake, enter:
OUTP 4,1
3. Manually move the Z column a short distance. The brake re-engages
because a position error is registered.
4. Re-send the command
OUTP 4,1
The brake should remain off. You can now move the Z column manually.
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