Pneumatic grippers are devices designed to hold an object using pneumatic, electric or hydraulic operated jaws or fingers. Grippers can be used as single devices or as a part of pick and place, manufacturing systems. Grippers can be used to pick up/hold various size objects from very small items such as semiconductors to very large items like car chassis or engines. Grippers are frequently added to industrial robots in order to allow robots interactions with objects.
Grippers can be divided into 2 main categories by type of holding objects:
External – the simplest and most popular method of holding objects. When the gripper jaws close, the closing force of the gripper holds that object.
Internal – When the access to objects exterior is required then an internal grip is necessary. Jaws or finger hold the object from the centre. In this case, the opening force of the gripper is used to hold the object.
What to consider when choosing the gripper:
Shape , orientation and dimensional variation - If the object has two opposing flat surfaces, then 2 jaw parallel gripper is desired since it can handle some dimensional variation. Jaws can also be designed to handle cylindrical objects with the 2 jaw concept. Keep in mind that a retention or encompassing grip requires much less force.
Weight - Grip force must be adequate to secure the object while the desired operation is performed on the object. The type of jaw design must be part of the force requirement. Keep in mind that you should add a safety factor to the amount of force that you select and air pressure is a factor to keep in mind.
Accessibility- This applies both to the work being performed on the object and the amount of room for the gripper jaws. If the work is to the exterior of the object then it may require an internal grip. Angular grippers are usually less expensive but require additional space for jaw movement.
Environmental - Harsh environment or clean room applications require grippers designed for those purposes.
Retention of the Object - When air pressure is lost, the gripper will relax its grip on the object and the object may be dropped. There are spring assist grippers designed for this type application.