How to Choose the Correct Gripper For Your Robot Application

August 2020

Choosing the Correct Gripper for Your Robot Application

Looking at an automation application, it can sometimes be obvious in which way the overall concept will come out. Either a linear or rotary system, a pick and place system, or it might end up as a robotic application. Like any design process, the devil is always in the detail, and it is when we start looking at the end of arm tooling (EOAT), such as a gripper and other machine-specific details, where careful design decisions have to be made.

Regarding both industrial and collaborative robot applications, the size of the robot is usually dictated by reach. However, some large robotic applications require a heavy payload. Regardless of the weight of the product, a precise design analysis has to be carried out to ensure whatever is selected will securely grip the product.

End of Arm Tooling Design Considerations

There are other factors other than the product itself that will influence your selection. In addition to the product, the speed of the process, the level of precision required, and even the environment it is to be used in will need consideration. If it is a collaborative robot application as opposed to an industrial robot application, then the selection process can go down a completely different route.

Speed

When it comes to speed, we have to consider the speed of the robot as well as how fast the EOAT will be able to pick up your product. As a rule of thumb, vacuum grippers or cups are usually the best for speed. The vacuum supply can be switched even before the EOAT tooling has reached the product, minimising response times. This is suited to applications where you have large, flat surfaces. However, if your product is not suited to vacuum, then robotic fingers may be a better option.

For collaborative robot applications, you also need to risk assess and determine whether or not your EOAT will add additional risks. To ensure you are complying ISO/TS 15066 should be referenced. This provides guidelines for the design and implementation of a collaborative workspace that controls risk. There are many collaborative grippers and EOAT tooling available from companies such as On Robot and Schunk.

To help overcome speed issues in industrial and collaborative robot applications, the EOAT could be fitted with dual or multiple heads. By doing this, you will effectively be saving on a robot move. When one gripper is picking up or unloading, the second gripper can then have a component ready for loading. All the robot has to do is rotate its end axis rather than going back to pick and place another component.

 Environment

The environment may dictate your gripper selection. If it is going to be a harsh, dusty, or even wet environment, then careful product selection is essential. This is where the grippers ingress protection or IP comes into play. This specifies how well the gripper is sealed and, therefore, what environment it can be used in. As an example, a device with an IP number of IP1X (X would be replaced with a number) would have a rating to protect against solid objects greater than 50mm in diameter. IPX9K would be protected against high temperature and high-pressure water jets. As you can see, the IP rating is a crucial factor.

Even if your gripper meets the required IP rating, certain grippers can’t be used. In ATEX rated (possibility of explosions as a result of sparks or arcing), this may have to be hydraulic or pneumatic grippers only. In the food industry, however, hydraulic grippers would not be allowed in case there was a leak resulting in contamination.

Precision

Where precision is required, electric grippers could be a sensible consideration. Electric grippers such as the OnRobot RG-2 FT gripper have inbuilt gripper finger force monitoring cells. Insertion processes can be achieved faster and more precise. This gripper can easily insert pins, for instance, where humans would struggle. Due to the advanced sensor technology, during assembly, the gripper gives the robot the ability to feel when the part has been mounted correctly. In addition to the two-finger grippers, there are also three-finger options.

Require More Advice?

It may be that the EOAT tooling that you require doesn’t exist. SP Automation and Robotics and SP Elements (Cobots) have been supplying fully automated solutions to industries since 1984. As we already design EOAT into our systems, we are here to help and advise you on your applications. There are many risks associated with the selection of EOAT, get it wrong, and it could cost you £1000’s and even a life.

Contact Us