Industrial robots are automated machines built to perform repetitive, hazardous, and tough tasks more quickly, efficiently, and precisely than humans. They reduce human dependency and boost the productivity and capacity of the process they are a part of. Choosing the right robot from the right manufacturer is the key to building a successful industrial business.

In this article, we provide a complete overview of the different types of robots used in industries. We list down their advantages, disadvantages, and some applications to understand how their design affects their industrial applications.

Introduction

The concept of robots is not new to humans. Mentions of devices built to help humans with their day-to-day activities can be found in various ancient mythological books and artifacts. However, it was only in the 19th century that significant developments in robotics enabled by new mechanical, electrical, and electronic technologies were brought in. 

As the capabilities of electromechanical systems seemed to peak out, advancements in information and communication technology made it possible for robots to evolve further and offer better features than ever before. Robots have become an essential part of our lives and are used in almost all industries today. 

A typical industrial robot is made of the following functional elements:

• Controller: It is the component that provides the robot with the memory and processing power necessary for operation. The robot’s controller acts as the brain of the whole control system.

• Sensors: Robots use sensors to gather data from their surrounding environments. Sensors are the eyes and ears of the robot.

• Drive and Power Source: A robot can use electrical, pneumatic, hydraulic, or any other drive to draw and convert the power required for its operation.

• Robotic arm: Designed to mimic a human arm, robotic arms are structures made of several segments connected by joints/linkages. The joints can be programmed to move in the desired direction.

• End of the arm tooling (EOAT)/end effectors: EOATs are customized equipment/actuators connected at the end of a robotic arm used to perform specific operations such as welding, material handling, painting, assembly, etc. Some industrial robots support the swapping of EOATs to let them perform different operations.

What are the different types of industrial robots, and what are their applications?

Different types of industrial robots exist in the market, all of which have their own set of strengths and weaknesses. This section explains the working of the most common types of industrial robots and lists out some of their advantages, disadvantages, and applications.

Cartesian Robots

Cartesian robots, also known as gantry robots, are the type of industrial robots that perform linear movements in space. They move along the x, y, and z axes, which are all orthogonal/perpendicular to each other. Cartesian robots form a cuboidal working area/envelope.

These robots get their name from the cartesian coordinate system, which represents points in space as a function of their shortest distances from the predefined axes. The cartesian coordinate system was developed by René Descartes, a notable french mathematician known for connecting geometry with algebra (previously considered separate) through his works.

Key advantages of cartesian robots:

1. Simple design and operation: Cartesian robots are preferred for their simplicity. Since they only move along the x, y, and z axes in a straight line, they are easy to build, program, and operate.

2. High accuracy: Owing to the ease of design and operation, cartesian robots can be precisely controlled. Their movements are extremely accurate, making them perfect for high-precision applications.

3. Affordable: The simple structure of cartesian robots and their ability to be reconfigured for various processes makes them cost-effective.

Key disadvantages of cartesian robots:

1. Take up more space: Of all the industrial robots, cartesian robots require the most space to operate.

2. Limited speed and acceleration: Cartesian robot movements are slow, making them unsuitable for certain applications requiring rapid operations.

3. Lack of flexibility: Cartesian robots are suitable only for the specific movements they are designed for. It’s tough to adapt them for anything else.

Cartesian robots are used for pick-and-place applications, which are common in packaging and inspection. They are also used for enabling automation in cutting, plotting, 3D printing, and CNC applications.

Articulated Robots

Articulated robots are industrial robots with rotary joints. The joints are typically powered by servo motors and are called the robot's axes. The movements of simple articulated robots resemble that of a human arm. In complex setups, the number of such joints can go up to and even exceed 10. Articulated robots are also called jointed arm robots.

Key advantages of articulated robots:

1. Greater flexibility: Articulated robots have multiple rotary joints that make them suitable for various kinds of motions.

2. High speed: Articulated robots can work at high speeds and are excellent tools for improving the productivity of the process they are a part of.

Key disadvantages of articulated robots:

1. Complex: Robots with rotary joints have to be made with a more complicated process than those that perform linear or lateral movements. The rotary joints require more parts and careful consideration to be built.

2. Expensive: As the structure of articulated robots is complex, they are challenging to manufacture and operate, which makes them costly to own and maintain.

Articulated robots are a class of robots that include several different types of machines. Hence, the list of applications is vast. To name a few, these robots are used in painting, coating,  welding, and packaging.

Cylindrical Robots

Cylindrical robots are industrial robots having a rotary joint at the base connected to a shaft with an arm having a prismatic joint. The robot has three axes of movement, two of which are linear and one being circular. The shaft connected to the base of the bot can rotate, and the arm can move up and down and even extend to form a cylindrical working envelope.

Here is a video showcasing the working of a cylindrical robot:

Though the history of cylindrical robots is not well documented, the American Machine and Foundry (AMZ) Versatran robot from the early 1960s can be considered the earliest cylindrical robot.

Key advantages of cylindrical robots:

1. High-load carrying capacity: Cylindrical robots can easily carry heavy objects with their powerful robotic arms.

Key disadvantages of cylindrical robots:

1. Take up more space: Cylindrical robots take up a lot of floor space and don’t offer many significant advantages, making them a less preferred option compared to other industrial robots.

Cylindrical robots can be used for welding automation, material handling, assembly operations, painting, and several other applications requiring working with a circular symmetry.

Delta Robots

Delta robots are industrial robots made on a rigid triangular frame. The frame is mounted right above the working area, with each arm hosting a high-torque servo motor. The shaft of the motor is connected to an arm called the “bicep, “ which extends in the perpendicular direction of the motor’s axis of rotation. The other end of the bicep is connected to rods arranged in a parallelogram shape. Depending on the application, the parallelogram-shaped rods can be connected to various EOAT manipulators.

Most of the robot's weight is from the motors connected at the base of the setup, which makes the moving parts light. The moving parts, therefore, possess low inertia and can accelerate quickly and work at high speeds.

Delta robots were developed by a team of researchers led by Dr. Reymond Clavel from the Swiss Federal Institute of Technology (EPFL) back in the 1980s. The inspiration for delta robots came from a visit to a chocolate factory where chocolate pralines were required to be placed in a box.^[1]

Key advantages of delta robots:

1. High-speed and acceleration: As the moving parts possess low inertia, delta robots can accelerate quickly and work at high speed.

Key disadvantages of delta robots:

1. Can’t carry heavy loads: The lightweight moving parts of the delta robot aren’t suitable for carrying heavy loads.

Delta robots are good at rapid pick and place applications required in the medical and food processing industry. They are also used in packing and soldering.

Polar Robots

Polar robots, or spherical robots, are industrial robots with two rotational and one linear joint. The rotary movement and the vertical lift of the robot are possible through the rotational joints. Linear joint facilitates the extension of the robotic arm that lets it extend its working space around it, resulting in a spherical working envelope. 

These robots get their name from the polar coordinate system, a coordinate system in which each point in space is characterized by its distance from the origin and the angle made by it with the axes about the origin.

The idea of polar robots was first conceived by Victor Scheinman in 1969 with his invention of the Stanford arm. It was one of the first electrically powered robot arms that could be moved in space under full computer control.

Key advantages of polar robots:

1. Good load-lifting capability: Polar robots can lift heavy objects easily owing to their powerful joints.

Key disadvantages of polar robots:

1. Large footprint: The design of polar robots doesn’t really make use of the available working space to its fullest which makes these robots bulky.

2. Complex design: Due to a large number of joints, polar robots are complex to design.

3. High costs: Because of a complex design, purchasing and maintaining delta robots is expensive.

Polar robots are mostly replaced by articulated robots these days due to the latter’s superior performance. They are still used for injection molding, material handling, welding, and some other generic applications.

SCARA Robots

SCARA is an acronym for Selective Compliance Assembly Robot Arm/Selective Compliance Articulated Robot Arm. As the name suggests, SCARAs are specially articulated robots that come with rotational joins. They are mechanically compliant in the x-and-y-axis and rigid in the z-axis.

Prof. Hiroshi Makino developed the first prototype of a SCARA robot at Yamanashi University, Japan, back in 1978. The thing that differentiated it from other robots at that time was the way it carried out different tasks with limited motion.^[2] SCARA robots made their way to commercial manufacturing facilities in the year 1981 and offered great performance for the price.

Key advantages of SCARA robots:

1. Position repeatability: Of all the articulated robots, SCARAs are the ones having the best positioning repeatability.

2. Easy to mount and small footprint: SCARA robots are pivoted at the base, which can be easily mounted on a hard surface with a floor mount. The footprint of the mount is small, which prevents hindrance to nearby objects.

3. High speed for moderate loads: Instead of hanging over the working area (like delta robots), SCARAs can be firmly mounted on a surface which makes them more resilient to shocks. This allows them to work with heavier payloads at a faster pace compared to other types of robots like delta robots and cartesian robots.

Key disadvantages of SCARA robots:

1. Suitable for light/moderately heavy loads: SCARA robots are typically designed for handling loads weighing up to 10 Kg which makes them unsuitable for working with heavy objects. 

Key applications of SCARA robots include high-speed pick-and-place tasks that require high precision. They are highly versatile robots that can be used for applications such as engraving, material handling, and more.

Collaborative Robots

Collaborative robots or cobots are industrial robots that share their workspace with humans. These robots team up with humans and work on the tasks they are designed for. Since cobots are expected to be around humans, they are designed to be safe.

Cobots use different sensors to make sure they detect unexpected human behavior and operate safely. Sometimes cobots are made to work at a reduced pace and force when a human is nearby. However, even so, they have to maintain their productivity and efficiency to actually be worth using in the industrial space.

With so many constraints and components, cobots get very complex to design. They come at a high cost but ensure they boost the overall productivity of people working with them.

Key advantages of cobots:

1. Safe for humans: Cobots are completely safe for humans to work with. Unlike typical industrial robots, cobots come with soft exteriors and various sensors to let people work with them without the risk of getting injured.

2. User-friendly: Cobots come with a very user-friendly interface. They are built according to human behavior so that the interactions feel as natural as possible.

3. Adaptive and flexible: Cobots are easy to reconfigure for different applications.

Key disadvantages of cobots:

1. Limited speed: To ensure safety of people working around them, cobots have to work at a limited speed even when they are capable of ramping things up.

2. Expensive and large: Due to the addition of all the sensors required for safety features, cobots are expensive and typically bulkier than other robots that don’t work around humans.

3. Require various approvals: Countries across the world have different rules in place to ensure the robots collaborating with humans are absolutely safe to work with. Getting all permits necessary to build and commission cobots can be a lengthy process.

Cobots have a large number of applications, including screwing, polishing, sealing, bin pickup, and more.

Key Takeaways

From being simple mechanical tools for performing repetitive actions to being highly integrated and reliable entities that can be programmed to do just about anything, industrial robots have come a long way since they were first developed. Fast-paced innovations in artificial intelligence, combined with the latest developments in mechatronics, will continue to shape the next generation of industrial robots.

Suggested reading: Articles on Robotics - Wevolver

Check out the video and the table below for a quick recap of the entire discussion:

References

[1] Reymond Clavel, creator of the Delta Robot, reflects on his career, Swiss Federal Institute of Technology (EPFL) - School of Engineering, [Online], Available from:  https://sti.epfl.ch/reymond-clavel-creator-of-the-delta-robot-reflects-on-his-career/

[2] SCARA, Robot Hall of Fame powered by Carnegie Mellon, [Online], Available from: http://www.robothalloffame.org/inductees/06inductees/scara.html