Why Choosing the Correct End of Arm Tooling is Important?
If you don’t have the right end of arm tooling for your application, it might not matter how good of a robot you pick. Robots and the end of arm tooling go hand in hand together.
(Please read my other blog “5 Major Factors to Consider When Choosing a Robot” to get a better idea on how to choose a robot)
Case 1: Let’s pick an application for a vacuum gripper, a bottle pack out machine. The bottles have flat caps and are fairly easy to get a seal with almost any vacuum cups that are the right size.
Everything should go smoothly, right? That’s where it gets dangerous. Since the bottles are heavy, and the boxes that they go in are tight, the same vacuum cup with bellows will not work as good as the vacuum cups without any bellows. You have the risk of bottles peeling off from the cups easier with no bellows however, you lose a lot of the positional accuracy of the robot since bellows will introduce flexibility with the weight of the bottles. If the pack out boxes are too tight, the robot selection might not really matter if your bottles are drooping because of the wrong vacuum cup selection.
Case 2: Let me give you a different application. A flexible feeding solution, Flexibowl with a Scara robot, Intelligent Actuator’s really fast IXA. My goto candy at the quarantine, Starbursts as the parts (I like the pink ones the best..). Let’s go with a parallel gripper to pick up these parts and place them in a stationary nest.
The parallel gripper was picked for this application because it was the cost-effective solution.
Now, let’s think about the application. A camera looks at the bowl, and finds a Starburst that is available to pick. Camera locates the candy, gives the coordinates to the robot. Sounds simple, works for about a couple of minutes and then the customer starts seeing crushed Starbursts. It turns out, the available Starburst pattern doesn’t actually look if there are any candies around it. So when the candies end up next to each other, the fingers of the parallel gripper crushes the candy that’s next to the one the robot is going to pick.
Parallel gripper was picked because of cost savings. However, with the time that got spent on vision programming made this solution way more expensive than a vacuum pick solution.
Case 3: This time I am going to give an example from the quotation stage of an application. A simple deburring application. Robot will pick up a part from a nest, debur it, and bring it back to its place.
A vacuum gripper might be able to get this application done, however, it is going to make the robot programming a little bit harder compared to using a 2 finger gripper. In a deburring application, depending on the amount of material that needs to be taken off, a vacuum grip might see a lot of lateral forces acting on the cup which might result in the part falling off the gripper. Going at a slower pace might help but now the programmer needs to take this into consideration. On the other hand, using a 2 finger gripper, having the clamping force high, the probability of the part falling out of the finger is lower.
Case 4: This time, we chose the right gripper and selected the OnRobot RG2 for the application. The goal was to save some cost so the very versatile default fingers were used in a very critical precise application. Robot’s repeatability specs are well under the specifications that the part needs to be at.
Customer realizes that the Cognex vision system picks up some variability in the finished part, at the inspection process. The vision system gets checked, the robot positions get checked but nothing could be found. It takes 2 days of engineering time to troubleshoot the system that the part was slipping slightly from the fingers of the gripper. The need for this application was to get a custom set of machined fingers that fits the parts exactly right so we could use the full power of the awesome RG2 gripper.
To sum up, choosing the right end of arm tooling will make a project go smoother and might actually be more important than which robot to use in some cases. When a challenging application gets presented to me, I think about how to handle the part because if I succeed at that portion of the project, the rest will be easier.
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