Robot Grippers & End Effectors
The success of just about any robot application relies heavily on the design and performance of the robot gripper or end effector. As the interface between the automation and the part, it is essential that the gripper is able to perform the task required reliably and without damaging the part being handled or any other part of the process where the gripper or part may interact. The main considerations for any application are the type of gripper, the method of power, plus the size and weight of the gripper in relation to the robot model being used for the application.
As the number of robot applications have expanded, so too have the different types of gripper which have been developed to suit the ever-growing range of tasks. The simplest gripper concept is the vacuum cup. These are used either singly, or in multiples, to collect items and pass them to another part of the process. This type of gripper is widely used when picking items from above, but they do have limitations including low levels of accuracy, so although great for simple tasks, they are not generally suited to precision applications. Another gripper that can be used to pick metal items from above, is the electro-magnetic gripper. This can be positioned on the part and then, once energised, uses the magnetic field to retain the part whilst being moved. Turning off the magnetic field releases the part at the end of the task.
Finger grippers, often configured as two-finger parallel or angular action types or three-finger chuck jaw types, which can be either pneumatically or electrically powered, are useful for a wide range of tasks. For example, these are often found in applications where cylindrical products, such as shafts are being handled. The three-finger type has the added benefit of being able to “centre” a part when picked from a slightly imprecise position, and the two-finger type can be used to handle many different product types.
For palletising applications, there are a wide range of gripper designs available including: vacuum types, parallel action clamp grippers – used to handle boxes and bag style grippers – used to handle sacks of produce such as chemicals, grain or dog food, etc.
There are now also a wide range of highly sophisticated gripper systems available, including servo operated types, which can be programmed to handle or manipulate a range of different product types and “soft” grippers which are able to mimic the operation of human fingers to pick and manipulate delicate products of differing shapes and sizes, such as fresh fruit.
So far, we have talked mainly about the gripping systems themselves – the actual interface between the robot and the part; however, there are a multitude of other robot end-effectors and accessories available today, such as those which sit between the gripper and the robot. These include compliant force feedback systems, collision detection systems and automatic tool changers, which make it possible for robots to perform the multitude of tasks required of them in today’s modern manufacturing environment.