Robot joints: The 6 different types explained

What is a robot joint exactly?

Robot joints enable movement in robots by connecting two rigid links. The type of joint determines the range and nature of movement possible. 

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These joints allow robots to complete tasks with various levels of flexibility and dexterity. The most advanced versions can even allow bots to operate at superhuman levels. 

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Rotary joints: Movement around an axis

Rotary joints, as the name suggests, enable rotational movement around an axis. These joints allow robots to twist and turn, which is essential for mobility and manipulation.

There are several types of rotary joints out there: 

• Single-axis rotation (revolute joints). The most common type is the revolute joint, which provides rotation around a single axis. Robotic arms typically have more than one revolute joint, allowing them to bend at the elbow and move from side to side. 
• Multi-directional mobility (spherical joints). For more complex movement, spherical joints provide rotation in multiple directions. These joints have three perpendicular axes of rotation, similar to a ball and socket in your shoulder. Spherical joints are useful for robotic hands, which allows them to maneuver objects with skill. 
• Combined rotation and sliding (cylindrical joints). Cylindrical joints enable both rotation around an axis and sliding along that axis. They&#;re useful when rotation alone is not enough, such as in robotic fingers or legs. The combination of revolute and prismatic joints in cylinders allows for grasping, walking, and other coordinated movements that require controlled sliding and rotation.

We&#;ll get into each of these types of robotic joints in more detail below. 

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Linear joints: Straight-line motions

Linear joints enable robots to move in a straight line. These joints typically consist of a movable element that slides or glides along a set of rails or guides. 

The most common types are prismatic and slider joints:

• Prismatic joints allow for sliding motion in one direction. An example is a drawer &#; it can only move in and out along one axis. Industrial robots often use prismatic joints to extend and retract robotic arms. This allows the arm to reach farther without needing a larger base.
• Slider joints enable two plates to slide over each other in a plane. They&#;re commonly found in X-Y tables that move in two dimensions. These joints give robots a wide range of motion within a flat surface. 3D printers frequently use slider joints to control the print head. By moving it in the X and Y axes, the print head can access the entire print bed.

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Twisting joints: Enabling rotation

Twisting joints, known as revolute joints, allow for rotation around a single axis. They&#;re one of the simplest yet most useful types of robot joints. 

How twisting joints work 

A twisting joint has two links connected by a pin, serving as the rotation axis. One link stays fixed, while the other rotates around the pin. Many twisting joints can rotate a full 360 degrees, but often have limits built in for specific uses. 

The joint is powered by an actuator, like an electric motor, which provides the force needed for rotation.

Applications of twisting joints 

Twisting joints are all around us in robotics and automation. 

They&#;re often found in robotic arms and hands, and are a perfect fit for tasks that involve:

• Assembly: Screwing components together, precisely placing parts, or any task that needs a rotating motion.
• Packaging: Opening jars, twisting caps, or rotating items for optimal placement in boxes.
• Machining: Rotating workpieces for cutting/milling, operating grinding tools, or polishing surfaces.

Examples of twisting joints

Here are some specific examples of real-world robots and their use cases:

• RO1 by Standard Bots (machine tending): This collaborative robot is known for its flexibility. Its twisting joints allow it to carefully and precisely position both small and large components during machine tending operations. 
• ABB IRB (auto assembly): This industrial robot utilizes multiple twisting joints to precisely tighten bolts on car chassis, ensuring consistent quality throughout the assembly line.
  
• Yaskawa Motoman GP8 (food processing): Equipped with a specialized gripper, this robot uses twisting joints to swiftly remove lids from jars prior to filling on a high-speed production line.

The world of industrial robots is big and keeps changing with every evolving technology. There are many different robots in the market, and deciding which one to use is crucial. The types of industrial robots vary depending on the intended function. 

Research estimates that there will be over 375 million jobs lost by , with artificial intelligence displacing over 40% of the jobs worldwide over the next 15 years. Additionally, forecasts suggest significant growth in the robotics industry, with sales projected to reach $43.32 billion by . In this article, we will delve into eight types of industrial robots, examining their key features, and discussing the advantages and disadvantages of integrating them into your industry.

Assembly Robot Definition

Assembly robots are automated machines that independently perform repeated tasks in a company. They are programmed to precisely manipulate, grasp and move different components when assembling parts. Assembly robots are made of these parts:

• Robotic arm: It substitutes a human arm to lift and place parts assembled in the industry.

• End-effector: It enables the robots to pick up the parts once assembled.

• Sensors: Guide the robots on how much pressure and where to position it.

• Vision systems: Installed near the assembly robot arm to make it more precise while performing tasks.

8 Different Types Of Industrial Robots

1. Cartesian Robots

Cartesian robot systems resemble gantry or small cranes and use X, Y, and Z coordinates to move different axes. These robots look similar to and operate in the same manner as gantry cranes. 

The axes work in a coordinated motion through a motion controller. Every axis is driven by a linear actuator, such as a linear motor or a ball screw which allows for accurate and independent movement.

Cartesian robots have a structure that controls the motion in the horizontal plane and a robotic arm that moves vertically. Therefore, it could be designed to move in the x-y axes or through the x, y and z axes. 

The robotic arm can also move in a horizontal plane. Depending on the gantry robot's use, the robotic arm has a mechanical tool attached.

Key Features of Cartesian Robots

• Cartesian robots have X, Y, and Z linear axes with a rectangular coordinate system.

• Has a CNC control system.

• These robots have two actuators; a linear motor and a ball screw.

• The load capacity is dependent on the application.

• Cartesian robots have the proper precision, allowing accurate and repetitive tasks.

Pros

• They are easy to build, program, and configure.

Cons

• They need a big space for operation.

2. Articulated Robots

Do you know which of the most common types of industrial robot is made to function like an arm? The only correct answer is articulated robots. Global articulated robots will reach $17 billion by . These are the most versatile and widely used types of industrial robots. 

They have a series of interconnected segments, referred to as links, attached to moveable joints. The design offers dexterity and flexibility, making these specific robots perfect for industrial tasks requiring precision.

Key Features of Articulated Robots

• Articulated robots have an offline programming software option.

• They use three different programming languages: KAREL, KRL and RAPID.

• They offer precision for all industrial applications.

• Some articulated robots are so good that their speed exceeds 10 meters per second.

Pros

• It allows flexibility during movement.

• Performs lots of different tasks as articulated robots can work at high speeds.

• Easy to align to multiple planes, thus improving versatility.

Cons

• Articulated robots are complex in nature and, thus, expensive to manufacture and operate.

• Since these types of industrial robots have multiple joints, the programming aspect is complicated.

3. SCARA Robots

Selective Compliance Articulated Robot Arms (SCARA) are known for their speed and accuracy. The precision is on the next level and is ideal for tasks within a single plane. The layout consists of two rotary joints, sophisticated control software and a linear joint. 

SCARA achieves the right results through joint configuration that allows for high rigidity and flexibility on the horizontal plane.

Key Features of SCARA Robots

• Lightning-fast speed.

• It has a joint configuration with one linear joint and two rotary joints.

• These robots have advanced servo motors and path planning.

Pros

• They offer superior high-speed performance.

• These robots offer high rigidity and accuracy for all tasks.

• There are many options, as these models are made for different applications.

Cons

• Even though they offer high speeds, SCARA robots limit their payload.

• These robots have restricted workspace. Therefore, you are limited to the size of operations that these gadgets can handle.

4. Polar Robots

These are also called spherical robots. They have a combination of linear joints and rotational joints. With these robots, you are in a position to create spherical working space for any industrial operations. It is essential to know that the first-ever industrial robots were polar robots.

Key Features of Polar Robots

• They are spherical.

• The robots have an exciting structure with two rotational joints for horizontal and vertical rotation and one robotic arm extension.

Pro

• These robots have good lifting abilities thanks to their sturdy joints.

Cons

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• Since polar robots have a complicated design, the initial investment and operations are quite expensive.

• These robots take up considerable space due to their bulky design.

• Polar robots also have a complicated design, which makes it hard to understand their operation at first.

5. Collaborative Robots

These are also called cobots due to their ability to work collaboratively with humans. Such types of industrial robots can simultaneously collaborate with people and also handle automated tasks. Cobots have built-in sensors to detect humans and obstacles, making them safe for any working environment.

Key Features of Collaborative Robots

• They have linear and rotational joints.

• The robots use Ruby, GUIs and touch interfaces.

Pros

• They are safe to operate since cobots have a safety feature to protect those around them.

• There is flexibility in reconfiguring these collaborative robots.

• Cobots have user-friendly software for individuals who do not have enough experience with robots.

Cons

• Since cobots have many safety features, these industrial robots have a high initial investment.

• The speed is limited since that&#;s the right way to keep humans safe.

• These types of industrial robots require approval since each country has its own rules on how robots should operate.

6. Delta Robots

These types of manufacturing robots are also called spider robots and are designed with a triangular frame. The rigid triangular frames are mounted above the working area, and each robotic arm hosts a high-torque servo motor. Most of these robots' weight is connected to the base, thus keeping the parts moving smoothly. The delta robots market analysis between and shows that it will increase by $1.41 billion depending on demand, safety, applications, and technological advancements in the delta robots world.

Key Features of Delta Robots

• Delta robots use TwinCAT, CodeSYS, and GUI programming systems.

• They have a triangular frame structure.

Pro

• Offer fast speed and acceleration since the parts are lightweight bars.

Con

• It is impossible for Delta robots to move around heavy items, therefore, do not purchase one if all your tasks are involving.

7. Cylindrical Robots

It is an industrial robot with a prismatic joint at the arm and a rotating joint at the base. Cylindrical robots have three axes of motion. The arm can move up and down and expand to form a cylindrical working space.

Key Features of Cylindrical Robots

• Cylindrical robots use different programming systems, including graphical user interfaces (GUIs).

• They use different types of controls, including servo controls, force control and encoders.

Pro

• Cylindrical robots have a huge load capacity and can easily carry heavy objects.

Cons

• Movement limitations exist with cylindrical robots since they can only move objects from one plane to the next.

• Cylindrical robots occupy lots of space, making them less popular in most industries.

8. Autonomous Mobile Robots (AMRs)

AMRs represent the true definition of how fast the industrial robotic industry is growing. The worldwide market for commercial service robots will grow to 33.8 billion in the next 10 years. The majority of them come in different sizes and shapes depending on their task. 

They include:

• Wheeled carts

• Autonomously guided vehicles (AGVs)

• Legged robots

• Spherical robots

• Flying robots, also called aerial drones

• Underwater robots

Key Features of Autonomous Mobile Robots

• AMRs utilize advanced sensors, cameras, and algorithms that provide the robot with information about its surroundings.

• AMRs are connected to the Internet of Things (IoT), allowing for real-time data exchange and integration with other systems.

Pros

• AMRs reduce human involvement in dangerous environments, enhancing workplace safety.

• Easily scalable to match increasing production demands without extensive infrastructure changes.

• AMRs can work continuously without breaks, increasing overall efficiency and productivity.

Cons

• The upfront investment for purchasing and implementing AMRs can be a substantial amount.

• Connected AMRs could be vulnerable to cyber-attacks if not properly secured.

Industrial Robotic Application

Different types of industrial robots are versatile and easy to program making them applicable in various industries. That includes:

• Picking and placing: The robotic arm is fitted with a vision device to identify different components from a conveyor belt, thus allowing it to select and sort different items.

• Welding: If you need precision welding services and are interested in industrial robots, these robots work perfectly. These linear robots with welding arms can achieve accurate welds in precise locations.

• Application of adhesive: Most companies use sealants and adhesives between parts. The robots are ideal for applying sealants or adhesives in precise quantities and in the correct location.

• Assembling different systems: Assembling means you might have to do one test repeatedly to put parts together for industrial application. Linear robots are perfect for repeated applications.

Add Industrial Robots To Your Company

Choosing the right industrial robots for your company depends on both the specific application and budget considerations.

Options range from collaborative robots (cobots) to articulated robots and delta robots, each offering distinct advantages and drawbacks. Understanding their key features and weighing these against your operational needs will help you make informed decisions for integrating automation into your processes.

In addition, incorporating force torque sensors into robotic systems enhances their functionality and safety. These sensors enable robots to perceive and respond to external forces, allowing for precise and adaptable interactions in tasks like assembly, material handling, and quality control. 

By providing real-time feedback on forces and torques, these sensors optimize performance, improve accuracy, and facilitate safer human-robot collaboration. Embracing this technology can significantly elevate your company's productivity and competitiveness in today's evolving industrial landscape.

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