Brooks Automation
P/N: PFD0-DI-00010, Rev 5.0.0, April 9, 2022
Gripper Support
Copyright © 2022, Brooks Automation, Inc.
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The motor has a 12-tooth pinion gear cut directly on the motor shaft. This pinion drives a pair of opposing
racks to open and close a set of finger mounts which are attached to linear ball slides. Various fingers
can be attached to the finger mounts.
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. So 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 1000ms delay after an EStop 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 5.0 or later and PAC files
PreciseFlex™ DD6 Proto_A10A May 2021 or later.
Controlling the 23N spring Gripper
Precise 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. Precise
makes this routine available to customers upon request. This routine is also available in the Precise
Command Server Software.
Gripper Squeeze (Simple Method)
The 23N gripper spring applies a closing force of approximately 7 Newtons at a finger opening of 103mm,
which is halfway between a portrait titer plate grip at 83mm and a landscape titer plate grip at
123mm. The force is closer to 6N in portrait mode and 8N in landscape mode and 9-10N at the full open
homing position. These closing forces are adequate to prevent dropping light payloads 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 23N gripper can apply about 18N of force at its rated current of 1.26A. When closing
the fingers the motor adds its force to the spring force, so a maximum closing force of about 24-26N 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.
For the 23N gripper the formula for determining the approximate gripper squeeze is 7N +( Rated
Current/1.26Amps)X18N for squeeze and ( Rated Current/1.26Amps)X18N –9N for gripper opening force.
