Gripper Classification and Offset
Gripper Classification
Two-Finger Gripper
When the target object is not suitable for vacuum picking and cannot be magnetized, it is recommended to use a two-finger gripper. The two-finger gripper can stably pick objects with complex shapes. The figure below shows the picking of small rings with a two-finger gripper.
Magnetic Gripper
When picking metal objects embedded in a metal sheet, it is difficult to insert the gripper to grip the sides, and only the upper surfaces are available for picking. In such cases, a magnetic gripper can be used. The magnetic gripper tightly attaches to the upper surface of the object, ensuring stable pickup.
Gripper Offset
Concept of Offset
Gripper offset refers to a type of gripper structure. The following section will introduce two types of gripper offset.
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Horizontal offset of gripper
This involves adjusting the gripper’s position when picking the target object so that the gripper has a fixed horizontal distance (i.e. offset radius) from the robot flange pose. The figure below illustrates the offset radius “r” in the horizontal plane between point 1 (robot flange pose) and point 2 (the gripper’s pick point).
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Angle offset of gripper
This involves adjusting the orientation or angle of the TCP when picking the target object. By rotating the TCP at a specific angle, the robot can reach objects that require a non-standard approach angle. The figure below illustrates the angle offset between point 1 (the robot) and point 2 (the gripper).
Advantages of Offset
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Avoid wrist singularity
In actual projects, target objects often come in various forms and poses. The gripper offset helps avoid singularities in picking.
In the figures above, the pick point has a horizontal distance from the robot flange pose.
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Increase bin clearance rate in limited space
The limited bin space, size or shape of the gripper, and position of the target object can pose challenges to picking, impacting the bin clearance rate. When a gripper without offset is used, it is prone to collide with surrounding scenes. The figures below show such a case.
In this case, you should apply an offset to the gripper, corresponding to the green part in the figure below, to pick the objects in the corners. Parts in the figure: 1. Extension arm, 2. Buffering device, 3. Sensor mounting frame, 4. Pneumatic cylinder of gripper, 5. Finger gripper, 6. Gripper finger sleeve, 7. sensor.
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Increase picking radius
If the robot model, the workstation and the requirements of the picking radius do not match, you can extend the picking radius with the tool offset.
