Choosing a Robot Gripper is always a critical component in the design of a robotic cell. You may want to look at the following tips to learn the basics of gripper selection for your specific parts.
The choice of your gripper will be significant for the success or the failure of the integration of your robotic cell. You want to have an end-effector that is precise, simple and that can handle as many of your different parts as possible. Even though, you have to figure out exactly what kind of parts will be handled by this gripper. Here is a list of points that we systematically look at when helping a customer to choose a robotic gripper. The most important thing is to start the process with an open mind towards which type of gripper you will need. A gripper can work well and have good features, but if it dosen't suit your application in the end it wont really be that much of an advantage.
DimensionThe minimum and maximum size are really important data. Although, you may want to measure other geometric positions on your part(s) to see where the gripper can produce the best grasp. Internal and external geometry should be measured in order to have a maximum of possibilities when selecting a gripper.
WeightThe maximum weight of the parts has to be known for 2 different reasons. First, to know if you are respecting the gripper and robot payload. Second, to make sure your gripper has the required gripping force to handle your parts. To have further information on these aspects, take a look at a past blog post on Payload vs Grip-Force.
MaterialThe material composition of your parts can be a very limiting aspect of the gripping solution. In fact, even if the the dimension and weight can be handle by the gripper, the material needs to be compatible with the gripper to insure a good grasp on the part(s). For example, some grippers cannot be use in the handling of fragile items (think food, ceramic, wax, thin metal or plastic, etc.) because they will damage the item you want to grasp. But with our Adaptive Grippers, the gripping surface can be adapted to reduce the impact on fragile part surfaces, thus force-controlled grippers can also be part of the solution.
Non-symmetrical, tubular, spherical, and tapered parts are a real headache for robot cell designers. It is really important to consider the shape of the parts when looking at a gripper. Some gripper manufacturers have options, like different fingertips, that can be added to the gripper to suit specific applications. Ask if the gripper can be adapted to your specific application.
Number of PartsThe more different parts you have in your process the more adaptive your cell should be. Either you use a tool changer or an Adaptive Gripper, either way you will have to make sure all your parts can be grasp correctly by the robot tool. Tool changers are big and expensive, but can work on a virtual infinity of parts with the right custom tools. While an Adaptive Gripper such as the 2-Finger Adaptive Gripper-200 can grasp very different kinds of parts using one single end-effector.
Also, you should think about your production, will it change or evolve over time? If the assembly line has been creating the same parts for the past 10 years, it might not change very often. On the other hand, if the assembly line is incorporating new parts every year, you should consider that the gripper should be able to adjust to these additions. Interestingly, you might even consider using your gripper for other applications. Consider this factor in the choice of a gripper. Make sure the gripper can be adapted to future potential operations of the robotic cell.
By determining your part specifications, you can now compare this data with the available gripper specifications. With the shapes and dimension of the parts that have to be handle, you can determine the stroke of the gripper you will need. Considering the material and the weight of the parts, the necessary gripping force can be calculated. And by asking yourself what are the different parts that will be handle by the gripper you can see if your robotic cell needs a tool changer or if a single gripper will work well.
Hopefully these tips will help you with your design. Before you start to look at a gripper solution, we recommend putting together a spreadsheet with all your part information so that the robot integrator or gripper manufacturer can quickly determine your needs and make accurate recommendations.