15 Robot End Effector Types and Selection Criteria

December 2, 2022

A right end effector can make or break the functioning of a robotic arm. Though other components (drives, motors, belts, reduction gear, links, etc.) equally play their role in carrying out a job, the end effector interacts with the surroundings and helps make improved decisions.

The robot end effector is also responsible for the safety of workers and products around them, so advanced sensors are combined with grippers for robotic process tools to make the job safe and efficient.

Let's dive into the following guide to cover every aspect of an end effector, including its types and subtypes and their differences. Not every option is suitable for a particular job and worth the investment, so we also cover various points at the end as selection criteria to choose the right robotic end effector for your business.

Robot End Effector Types

What is an End Effector in a Robot?

The end effector is an important part of a robotic arm, as it allows the cobot to carry out various jobs. It is attached to the robotic arm's end and serves like a human hand.

Often, the robotic arm has fingers attached to it, though the number of fingers can differ depending on the task required. At the minimum level, a robotic arm comprises two fingers to "interact" with the environment in which it is installed and operated.

Robots have a broad range of applications, from picking and placing to grinding, spot welding, and painting. The accuracy of a robot's work depends on various factors, including the right end effector for the particular job.

However, note that an end effector can be used for various tasks, given a robotic arm doesn't need a spacious room to function and can be easily moved to another place to carry out jobs.

Different Types of End Effectors

Generally, the world of robot end effectors witnesses new inventions every day. Yet, all the types and subtypes of these tools can be classified into the following categories:

  • Robotic Grippers
  • Robotic Process Tools
  • Robotic Sensors

An end effector doesn't need to have only one type mentioned above. Depending on the type of job required, a robot's end effector can be a combination of its various types or sub-types.

For instance, modern-day robotic arms consist of end effectors that combine a gripper's and sensor's functionality for precise and safe functioning in the hybrid workspace.

Now, let's dive deep into the different types of end effectors and explore their various sub-types, including the suitable task for each type.

Robotic Grippers — Their Types, Sub-Types, and Differences

Robotic grippers are the most common and widely used end effector type since it enables the robot to "grip" things.

With the help of a gripper attached at the end, a robotic arm can act like a human hand. It can grab things; thus, tasks like picking, sorting, placing, and assembling become easier.

Robotic grippers are further classified into the following:

  • Electric Grippers
  • Pneumatic Grippers
  • Suction Cups
  • Magnetic Grippers
  • Mechanical Grippers
  • Impactive Grippers
  • Ingressive Grippers
  • Astrictive Grippers
  • Contigutive Grippers
  • Bernoulli Grippers
  • Electrostatic Grippers
  • Capillary Grippers
  • Cryogenic Grippers
  • Ultrasonic Grippers
  • Intrusive Grippers

The following is a quick overview of all the gripper types, including the right application for each.

Electric Grippers

These grippers are best-known for their accuracy and speed, making them ideal for tasks including precision and efficiency. As the name suggests, these grippers have fingers powered by electric motors.

Advanced electric grippers with fast electric motors are widely used for machine handling, tending, bin picking, picking, placing, etc.

Pneumatic Grippers

Pneumatic grippers are employed in pneumatic systems. Their "gripper jaws" (fingers) are more often used for grabbing or holding different parts, products, or materials.

Also, pneumatic grippers have a simple working mechanism where compressed air is forced through a piston, allowing the gripper to achieve the required movement by moving, stacking, inserting, or orienting the material.

Pneumatic grippers are further divided into two types according to their movement:

  • Angular pneumatic grippers : Angular grippers or angular jaws allow for precise object handling and radial movement. However, they also need more space than parallel pneumatic grippers because they move away from the object when open.
  • Parallel pneumatic grippers : Parallel grippers are more used than angular grippers precisely due to their simple design and compensation for some dimensional variation. They also require less space than angular grippers since they open and close parallel to the object they are grabbing/holding.

Suction Cups

Also known as vacuum grippers, suction cups are used for many applications while offering the right integration, improved safety, and stronger grips. They are also inexpensive and easily replaceable than other gripper types.

Moreover, suction cups are typically used for lifting and gripping jobs. Though suction cups might not be the best solution for perforated materials, they are great for manual or automated handling applications.

Magnetic Grippers

While suction cups are unsuitable for perforated materials, magnetic grippers provide a feasible solution for ferrous materials. They have a similar design to suction cups and use a magnetic surface to "pull" and grab the object.

Magnetic grippers have various benefits over suction cups, though their functionality is limited to handling ferrous material. Since they use magnetic power to pick objects, they provide higher accuracy and safety (the magnetic power doesn't drop objects, unlike compressed air).

The cost of compressed air used in suction cups is also eliminated in magnetic grippers. Eventually, the operators don't have to worry about air running out, air loss, or refilling air for the magnetic gripper to work.

Mechanical Grippers

A mechanical gripper has a simple design manufactured with various mechanically operated fingers. Generally, at least two fingers serve the purpose, though this type of gripper can be upgraded to many fingers depending on the job required.

Also, the fingers attached to the gripper can have various shapes, such as hooks, forks, clamps, or other complex designs to carry a job. These fingers help the gripper move and rotate, though they have limited force and position control functionality.

Impactive Gripper

An impactive gripper is a popular end effector in robotics and "impacts" force against the object's surface to grab it. Its design can be simple or complex depending on the task, though it typically comprises jaws or claw-like parts in general manufacturing applications.

Also, these jaws or claw-like components allow the impactive gripper to pick, place, relocate, or reorient the material. This way, they interact with the environment and help complete a task faster than other robotic end effectors.

Ingressive Gripper

Ingressive grippers are another type of end effector with sharp-point surfaces to grab the objects. These grippers cannot be used in places where a fixed object's shape is a priority since they "physically penetrate" inside the object's surface to pick it.

Also, their sharp-point surfaces, such as pins, hackles, or needles, are better options where fingers fail to grab the object. Their general application spans over industries dealing with textile, glass fiber, and carbon handling.

Astrictive Gripper

The functionality of an astrictive gripper depends heavily on the type of vacuum used since they have Magento or electroadhesion properties to grab objects.

The "astrictive" in the end effector refers to the binding force that the field produces to form an air movement (also known as vacuum suction). The phenomena used in astrictive grippers are magnetism or electrostatic charge displacement, allowing them to move freely and pick objects.

Contigutive Gripper

Contigutive grippers are popular in places where direct contact with the object is mandatory to carry a job. They also exhibit adhesion like the gripper types mentioned above, though their functionality requires straightaway contacting the products in use.

Thus, contigutive grippers are used in applications where glue, freezing, surface tension, or similar procedures are carried out. Also, maintenance is an important factor in the long-term functionality of contigutive grippers since direct contact with things like glue can also make them messy.

Bernoulli Grippers

While contigutive grippers require direct contact with the object, Bernoulli robotic end effectors maintain a non-contact gripping. They are pneumatic manipulators which work on Bernoulli's principle.

According to Bernoulli's principle, the airflow between the end effector and the object should be exploited to create a lifting force. Such an approach works like a suction cup, bringing the object closer to the gripper without actually touching it.

Textile industry, photovoltaic cell handling, and semiconductor manufacturing industries are beaming with the invention of Bernoulli grippers. However, the mechanism of a Bernoulli end effector is complex and requires a careful operation.

Electrostatic Grippers

When the product is fragile and needs careful handling, electrostatic grippers come into play. They work on the electrostatic charge principle and bring a charge difference between the object to be grasped and the end effector.

The result is an exploited electrostatic charge which can grab and handle delicate products without scratching/damaging them. In modern-day electrostatic grippers, the end effector is capable of activating the charge difference itself.

Capillary Gripper

Capillary grippers have a complex mechanism, yet they are becoming a popular option in robotics, thanks to their fast droplet formation with just an ON/OFF piston sider control.

Simply put, a capillary gripper grasps the object by utilizing a liquid meniscus's surface tension (capillary action) between two solid surfaces. However, note that the capillary gripper has expertise in complex-shaped micro-objects (capturing and releasing) with its applications in micro and nanoscale industries.

Cryogenic Gripper

Where electrostatic grippers polarize the object by utilizing a gripping force, cryogenic end effectors freeze a small amount of liquid to generate ice. This ice is then utilized to create a lifting force to grasp the object.

Furthermore, cryogenic grippers have vast applications in the food and textile industries, where the objects need to be handled carefully and without any damage. They also help keep the required shape and texture of the food without ruining its formula.

Ultrasonic Gripper

Ultrasonic grippers have slightly more complex manufacturing and operation processes than other end effectors. However, they offer a greater advantage over other options by offering micro-level and macro-level lifting applications.

Such functionality makes ultrasonic grippers suitable for many tasks, including screw-handling, photovoltaic cell, laser, gasket-handling, and Si substrate handling.

Intrusive Gripper

Intrusive grippers contain various fingers (two, three, even five) to carry out a job uniformly. The work on the principle of force friction by resisting the motion when the object to be grabbed comes in contact with the end effector.

A few of the long list of applications of intrusive grippers include spot-welding, surgical robotics, spray-painting, etc. They are widely employed in areas where human safety is at risk.

Also, needle grippers are a sub-type of intrusive grippers which, with their optimal holding force, are popular for picking objects which cannot be lifted using a vacuum.

What are Robot Process Tools?

Robot process tools are also grippers, yet with advanced functionality. Think of a gripper as a component to pick or grab an object. When combined with robot process tools, these general grippers can function as tools for robot welding, 3D printing, spot-welding, painting, machine handling, etc.

One common example of robot process tools is to think of anything you might want to do with them. If it is painting, the end effector can be manufactured with brushes; if it is welding, cutting components will be attached to the end effector.

Similarly, material removal tools, welding torches, and drills are other examples of robot process tools. Even more, these tools attached to the end effectors can also be used as "tool changers" (changing screws, etc.) --- to take the tool carrying capacity of a machine to another level.

In simple words, the following are some of the popular examples of robotic process tools in the market:

  • Robotic welding tools
  • Robotic painting brushes
  • Robotic cutting tools
  • Robotic drilling tools
  • Robotic material removal tools
  • Robotic welding torches
  • Robotic tool changers

Robot Sensors — Their Advancement, Functioning, and Properties

Sensors are game-changers in a robotic arm as they provide improved safety and enhanced efficiency and take the overall robot functionality to another level.

Sensors are attached to the end effectors (grippers or robot processing tools) as programmable sensor-orientation devices. These tiny gadgets can "sense" (observe) the surroundings and make the right type of movement according to that.

Whether you are employing industrial robots or robotic arms, sensors are a must to attach to the end effectors. Especially in a hybrid workspace where workers operate and work along with the robotic arms, sensors allow for higher accuracy and safety.

However, sensors are not only used for safety; they can also comprise the entire end effector. For instance, sensors can be used as end effectors to read the barcode of various products during the picking and placing process. They can also assemble or sort products based on various criteria (color, shape, etc.).

Like other components, sensors also have levels of technology; there are ultrasonic sensors, infrared sensors, laser scanners, and 2D and 3D cameras. Though all serve the same purpose (to scan and observe), they differ in their inspection levels as advanced sensors are more accurate and safe than old-generation sensors.

Lastly, sensors can observe various factors to determine their path movement. This includes force, light, sound, chemical, temperature, and distance.

Multi-functional sensors can detect many factors at once to provide even better accuracy. For instance, they can detect light and inspect sound to determine where a particular machine/object is located. They can also detect the temperature and chemicals in the air to determine their next step without causing an explosion.

How to Pick the Right End Effector for Your Business? The Selection Criteria

An end effector is a crucial part of a robotic arm, yet the long list of its types and sub-types is enough to confuse business and warehouse owners.

When selecting the right end effector for your business, note that there are no fixed selection criteria. It's because to consider which end effector would be the best investment is to understand what you are trying to achieve and your priorities.

To simplify:

  1. You can start by selecting whether the task you need an end effector for requires a single gripper or a combination of grippers for robotic process tools.
  2. Sensors are mandatory to add to your end effector, so consider which generation or level of precision is needed in your sensory part.
  3. Next, make a list of various types of end effectors that can deliver the right action for the required job.
  4. Make a list of factors that will be impacting the end effector and its functionality in the future. For instance, consider its mechanism (simple or complex), installation, coding, operation, etc.
  5. Also, consider the factors that the business revenue would fulfill: initial end effector cost, staff training, maintenance costs, availability of replaceable parts, upgradation, daily inspection costs, etc.
  6. Lastly, choose an end effector that meets your selection criteria to do the job.

Note that you need not always select an end effector for one job only. Robotic arms can tend to various tasks without causing many hurdles.

Thus, you can select an end effector which offers multi-functionality (like selecting a gripper with a robotic process tool to do both spot-welding and cutting in the welding industry).

Bottom Line

Selecting the right robotic end effector boosts the workspace's efficiency, productivity, and safety. It also increases the workflow and reduces the risks of errors. Though the world of robotics is full of different types of end effectors, they can be typically classified into grippers, robotic process tools, and sensors.

Gripper "grips" an object. There are various sub-types of grippers, each suitable for handling different materials and jobs.

Robotic process tools take the functionality of grippers to the next level by offering advanced tools such as for cutting, drilling, painting, etc.

Sensors improve accuracy, safety, and speed by observing the environment and help the robotic arm make better decisions for the suitable path movement.

Follow us on social media:

Reach out to learn more about how B2E Automation's solutions can help transform your business.