Choosing an end-effector for your robot can sometimes be confusing. In fact, a lot of different options are available which might suit your application. When looking for a robot gripper you want it to be reliable, repeatable, precise and safe. Some robot grippers out there are touted as super accurate with good repeatability, but what happens if the air or electricity runs out… The object that is in the gripper can fall and break and/or injure the human workers that are near the robot. This is why all of our Robot Grippers are self-locking. With the growing presence of the collaborative robot in the manufacturing world, we wanted to make a safe robotic Gripper that will keep its grasp on the object if the energy source runs out or if there is a fail in the programming method.
Self-Locking
All Robotiq Grippers incorporate the same self-locking method. The fingers are activated by an electric source to grasp a certain object, when the power is released, the Gripper stays in the same position and locks itself on the object. This means that there is no need to apply a constant force on an object during the grasping motion. If a 2-Finger Adaptive Gripper is grasping a flat object, the programmer will have to set a position and a force to achieve the grasping. Then the Robot Gripper will close its fingers until it reaches that certain position. Once this position is reached, even if the object is applying pressure against the fingers, the self-locking principle will allow the fingers to have a solid grip on the object and remain in the exact given position.
In the following video (at approx. 25 seconds) you can see the self-locking concept at work on a 3-Finger Adaptive Gripper. As the fingers are powered up, they grasp the object and close around it. As the position or force is reached, the power is removed from the fingers. As the worker takes the part, the self-locking concept keeps the fingers tight around the object. The power is then brought back on line to open the fingers. Another example can be observed at 1:53 in the video.
Safety
This concept brings a new level of safety to the robotic cell. The self-locking ability allows the cell to power down without any risk. When using a robot in collaborative mode, you want to make sure the cell is 100% safe for the user. If a collision occurs and power is shut down for any reason, a regular robot gripper can unlock, release its position and drop the object it is grasping. This situation can cause a lot of problems and place the operator at undue risk in an unsafe environment. By using a self-locking gripper, regardless of whatever happens to the power source, the object stays in position and the risks are reduced to 0 (reducing your risk assessment reflexion).
In another situation, where this becomes imperative, think about a fast moving robot that is carrying objects. If the robot gripper cannot reach the required force, say... because of a leak in the air system, this means that the gripper that grasps the object is not applying enough force on the object. This might result in slippage or a possible flying object. A Robotiq Gripper is able to reach a requested force and hold it steady, for as long as necessary, so long as the programming is not asking it to open its fingers again.
Programming
For end-users of the Robotiq Gripper, you should consider this principle in your programming. In fact, by self-locking, the Gripper doesn’t need to be fed by power throughout the grasping operation. Once the position or force is reached, the current can be removed from the Robot Gripper and the object will still stay in place. This concept is quite counter-intuitive because a lot of grippers out there need to be fed constantly. This means less programming and less energy used by the robotic cell. You should note this in your programming, that the Robotiq Gripper has been designed to receive a certain amount of current to achieve a grasping motion and not to be constantly fed, since using the Gripper with constant current to force against objects can cause major problems for the Gripper.
Hopefully this blog has helped you to understand how Robotiq Grippers work. If you still have problems with the self-locking concept or how to program the Gripper to make the best use of this concept or just need further information, please contact our support team (support@robotiq.com).
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