Although, you cannot match the speed and repeatipility of pneumatic grippers, but if you have to go for the better control of the gripper than electric one is way on the top.
The pnuematic grippers have a very limited band of force control. Although, you can always change the air pressure for varying the force but it is not easily done and also due to stiction, the gripper jaws are hard to move at lower pressure, so the objects can not be handled delicately with these grippers.
And for electric grippers, it is usually easy to get feedback on the positioning of gripper, due to the encoders incorporated in electric motors. This is quite usefull in detecting errors online. where as, to provide this feature in pneumatic grippers we have to add extra sensors.
Over and all the electric grippers have much more to offer now. And given to their declining costs they seem a much better option than pneumatic grippers.
The speed and cost of pneumatic grippers are hard to beat. As long as you are automating low-mix, high-volume and looking for the best deal, pnewmatic grippers are the best deal. But if you are using high-mix applications and looking for flexible automation, using programmable electric grippers is a better option.
Now adays electric grippers are being used more than pnaumatic because they are less expensive, Cleaner and leaves a neat and clean look on the circuit , they are small , Using encoders one can make sure that whether the part has been picked up by the gripper or not .
Jon, I find it interesting that you point out that electrically operated grippers are coming on strong despite the decades of development of pneumatic grippers. Many decades ago, my father, who worked at an Army electronics lab, was convinced that hydralics and pneumatics would overtake electrical devices in control applications. He even brought home some prototyping parts from the lab. Well, with improvements in electrical motors and control circuitry, things didn't quite work out that way. Looks like something similar is going on in this application area.
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