Brooks Automation 6. Software Reference
Part Number: PF40-DI-00010 Rev. A Controlling the PreciseFlex Servo Grippers
One finger mount is also attached to a spring return, which applies a continuous closing force to the
finger mounts as they are coupled together by the pinion. If power is lost, the gripper will close and
maintain a closing force so that it does not drop parts.
In order to avoid the gripper slamming closed from the spring force when motor power is disabled,
there is a 500ms delay after an E-Stop or power disable command is sent before the motor power is
cut off. During this period, the servo slowly closes the gripper.
In order to support “free” mode, in which the fingers can be moved back and forth freely by hand, in
free mode the servo counterbalances the spring by applying an opposing force based on finger
position.
Software Revision
The Spring Gripper functionality is fully supported by GPL version 3.1.P11 or later and PAC files
PFlex400S_Prod_B03 110913 or later. Some slightly earlier software versions were delivered to
beta customers.
Controlling the Gripper
Brooks has created a GPL software routine that controls the spring gripper. This routine includes
features for controlling the gripper squeeze force and detecting if a plate is present during a grip.
Brooks makes this routine available to customers upon request. This routine is also available in the
PreciseFlex Command Server Software for the PF400.
Gripper Squeeze (Simple Method)
The spring applies a closing force of approximately 7 Newtons at a finger opening of 103 mm, which
is halfway between a portrait titer plate grip at 83 mm and a landscape titer plate grip at 123 bmm.
The force is closer to 6 N in portrait mode and 8N in landscape mode and 9-10N at the full open
homing position. These closing forces appear adequate to prevent dropping titer plates weighing up
to 200 gms, and are selected to allow enough motor torque to overcome the spring and still provide
reasonable opening force for inside grips.
The motor for the 23 N gripper can apply about 18 N of force at its rated current of 1.26 A. When
closing the fingers the motor adds its force to the spring force, so a maximum closing force of about
24-26 N is possible, depending on portrait or landscape gripping. When opening, the motor must
oppose the spring force, so a maximum opening force of about 8- 12N is possible, depending on the
opening of the fingers.
The motor squeeze force can be limited by modifying the rated current of the motor. This can be
done by writing into the 5
th
field in Parameter Data Base # 10611. The motor current can be set
once and saved into flash or modified dynamically by a GPL program using the Controller.PDbNum
instruction.
Copyright © 2023, Brooks Automation
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