What are Grippers? Here's everything you need to know

What types of Gripper are available? How do they work?

With this sheer breadth of use cases, Grippers form a core part of any robotics solution and you’re going to find endless choice as a result. Let’s cover everything you need to know to select the right Gripper for your task.

First, the basics: the parts of the Gripper that actually grip an object are called the Jaws (or “fingers”). You’ll see these jaws in either an angular layout (think of a pair of pliers or alligator clips), concentric layout (where the jaws are arranged in an arc with a central space between them, like your hand) or most traditionally, a parallel layout (where the jaws are in line with each other and can move closer together or close apart, like a wrench).

These types of Grippers - called “Impactive” Grippers - are by far and away the most common type, but you may also require “Ingressive” (where the gripper enters the object, like a needle entering a piece of fabric), “Astrictive” Grippers (where magnetic or suction force is used to handle an object) or the even more academically-named “Contigutive” Grippers (where you might use e.g. glue or the force of freezing to create an adhesive effect on the object, rather than actually picking up and moving it).

For an Impactive Gripper, you’ll want to make sure that the jaws are tipped with an appropriate material. It might be fine to have a rugged material when your robot is handling wood or metal but if you’ve had the good fortune to be chosen as Apple’s latest iPhone packaging company, you had better make sure you have soft rubber tips to handle those scratch-prone electronics or you’ll have an angry CEO on the phone in no time.

With a basic Gripper type selected, you now need to consider the method of actuation - in simpler terms, how the Gripper is powered. There are three primary types of actuation you might want to use for your Gripper: electric, pneumatic and hydraulic. 

Electric actuation is the most common and uses a combination of motors, servos and occasionally even a gearbox in order to precisely control your Gripper. Electric actuation can generate large grip force on an object but excels best in situations that require soft gripping force or accurate motions. 

Be warned though, all those servos and motors make for a larger Gripper which can take up a lot of space on a crowded shop floor.

Next up is pneumatic power. Pneumatically-actuated Grippers can move extremely fast, often able to apply heavy grip force in a fraction of a second (keep your eye out for any mention of a Gripper’s “closing time” if this is an important factor for you). The drawbacks are that they need a supply of air to compress and they struggle with being gentle.

Lastly, when you just need sheer grip force, hydraulic Grippers are a wise choice. These grippers use compressed hydraulic fluid to shift immense weights (just like how a car jack works) and are most often found in heavy manufacturing situations, like mineral processing or car manufacturing. 

As liquid moves slower than air, you’ll find a hydraulic Gripper cannot match the closing times of a pneumatic Gripper nor with all that power can they provide the same soft touch as a servo-driven, electrically-actuated gripper.

When evaluating these options, give thought to whether the actuation power is needed in the robotic arm or the Gripper - For example, it takes a lot of grip force to hold a paintbrush in place, but not much arm strength to run it up and down a wall. Conversely, if you’re lifting a heavy object across a room, you’ll need to ensure that the robot arm’s payload - that’s how much weight it can handle - is up to the task.

And don’t forget - the payload for your robotic arm must include the weight of the Gripper you’ve just attached to it.

One more thing on force - maximum grip force is often the first factor we consider, but minimum grip force is important too: the Gripper you use to pick up a solid aluminum block is unlikely to be the one you want for picking tomatoes off a vine. 

For situations where soft force is important, consider a “compliant Gripper” - this means an end-effector specifically designed for a certain object, weight or force ratio and generally designed for objects on the smaller side, like this DIY hobby gripper for a piece of fruit. These are harder to come by off-the-shelf, but for delicate or niche applications in crowded environments where an expensive, active force feedback system is less appropriate, they tick all the boxes.

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With the basics of Grippers covered, it’s worth covering some of the advanced options you’ll see on some Gripper suppliers’ websites:

• Some Grippers come with automatic depth compensation, lost grip detection or even automatic payload calculation. These add-on features can help reduce programming time, help handle more complex operating environments and reduce cycle times.

• Many Grippers come with a secondary function, such as a hose built into the center of the gripper platform. Imagine our paint brush example from earlier - a Gripper with a hose could spray paint onto a canvas or water onto the brush it’s grasping. Being strategic with gripper selection here can cut down the number of robots you need for your operation and further reduce cycle times.

Finally and perhaps most importantly, don’t forget about safety. Ordinarily, your robots will operate only in a walled-off area. However, when your business demands collaborative working (Co-botting), safety features become paramount. The best Grippers on the market today will come packed with sensors to ensure your robots don’t violate Asimov’s Laws. 

‍Simple sensors can detect a collision and stop moving (for example, to prevent pinning a human being after an accidental strike), whereas more advanced applications can use computer vision to “see” potential threats and react appropriately, such as proactively stopping if an unexpected object crosses their path. For added peace of mind, look out for TÜV and ISO 10218 safety certifications on your chosen gripper.

Next steps

Regardless of your application, there’s likely to be an appropriate Gripper for it. You’ll want to ensure the Gripper you select has an M8 4 or 8-pin connector with maximum compatibility with the widest variety of robot arms, but some manufacturers have specific, plug-and-play connections with end-effector suppliers like OnRobot or Robotiq.

If you’re looking to find the perfect pairing of robot arm and end-effector for your application, RO1 by Standard Bots comes with a variety of grippers out of the box, universal M8 connectors, integration with OnRobot end-effectors and is the best choice for machine shops large and small:

1. Affordable: RO1 is the most affordable robotic arm in its class, starting at almost half the price of incumbent competitors. 
2. All-Seeing: RO1 is equipped with best-in-class vision systems. Easy no-code programming makes it easy to detect the smallest of defects and imperfections.
3. Collaborative: RO1 comes equipped with safety sensors and built-in collision detection, for safe operation anywhere on your shop floor.

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Speak to our solutions team today to organize a free, 30-day onsite trial and get expert advice on everything you need to deploy your first robot.