Why read this: Understanding the basics of industrial robots can put manufacturers on stronger ground when dealing with suppliers. It will also help prepare them for a future with more industrial robots and automation in the factory floors. This article will cover 7 types of industrial robots and the tasks they are made to perform.
What is an industrial robot?
An industrial robot is a reprogrammable, automated mechanical device with the ability of assisting or replacing a human employee in a variety of tasks in manufacturing.
Different categories of industrial robots
There are seven main categories of industrial robots available on the market: Articulated, Cartesian, SCARA, polar, delta, cylindrical and collaborative.
Articulated robots' movement and design resemble a human arm. A typical articulated arm has six axes (ranging from two to 10 axes/joints). Each joint is considered an axis. The more joints a robot has, the bigger its range of motion gets (also called degree of freedom).
Articulated robots are highly flexible as all their joints are revolute, meaning they can rotate, as opposed to prismatic joints, which move linearly. They have a limited ability in avoiding obstacles though.
- Use: Articulated robots are used in applications such as pick and place, arc welding, spot welding, packaging, machine tending, material handling. The ability to produce arcs (or similar patterns) in hard to reach places makes articulated robots a good candidate for the automotive industry, but for safety reasons, they often require dedicated work cells that take up additional space on the factory floor.
These robots (also called gantry robots) use the Cartesian Coordinate system (X, Y and Z) for linear movements across the three axes (forwards and backwards, up and down and side to side). All three joints are prismatic so the movement is restricted to being linear.
- Use: Cartesian robots are mainly used for CNC machining and 3D printing, but they can also be used in assembly or pick and place applications, not without a limitation on the size of the parts though.
SCARA robots (Selective Compliance Assembly Robot Arm) are similar to Cartesian robots as they move in 3 axes, but they are also able to rotate. They are generally faster and more flexible but less precise than Cartesian robots.
- Use: Applications include assembly, palletizing and pick and place of small parts such as screws.
Polar robots (also called spherical robots) are a combination of two rotational joints (revolute) and one linear joint (prismatic). Their design creates a spherical-shaped working space. Polar robots’ main disadvantages are their incompatibility with other robots and their accuracy (e.g compared to a Cartesian robot).
- Use: Polar robots can be used for injection moulding, painting, arc welding, spot welding, assembly applications, as those tasks require the ability of rotation
Delta robots (also called parallel robots) have a smart design due to the strategic placement of all motors on the base, making the moving parts (joints) of the robot very light, compared to other robots. Comprised of three arms, the joint of each arm is controlled in parallel, creating a dome-shaped robot.
- Use: This design results in high-speed and precise operation and that is why Delta robots are primarily used in pick and place applications. Additional operations include adhesive dispensing, soldering, assembly etc. Delta robots cannot carry payloads that exceed 3 kgs and that limits the tool designs and the tasks it can handle.
Cylindrical robots have at least one revolute joint at the base and at least one prismatic joint to connect the links (movable parts of the robot between joints). This design leads to a cylindrical-shaped workspace and therefore limits them to just two degrees of freedom. Thus, the space in which they can operate is confined
- Use: Cylindrical robots are typically used in tight workspaces and they are a perfect fit for objects that need to have a round symmetry (e.g wires, pipes). Grinding, assembly, spot welding applications make use of cylindrical robots.
Collaborative robots (cobots) enable human-robot interaction in a safe work environment, without the need for fences or other safety measures taken in traditional industrial robot applications. However, safety measures lead to a decrease in operation speed. Instead of replacing employees, cobots are programmed by the employees’ hands (hand guiding) and then replicate the demonstrated movement. A standard cobot is able to carry up to 15 kgs and this creates a limitation on the range of products it can manage.
- Use: Collaborative robots have a wide range of applications like machine tending, pick and place, assembly, arc welding, but are generally not suited for heavy duty applications or very high speed tasks.
Basic knowledge of industrial robots and terminology (e.g. number of axes, degrees of freedom, types of joints etc.) will help manufacturers when looking for robot solutions. Being able to make better sense of your options will help when dealing with suppliers.
Understanding the basics of industrial robots might also prove an important skill in the future. As the International Federation of Robotics have forecasted there will be a 12% increase in industrial robots sales per year in the period from 2020-2022.
Knowledge of the different solution types can also put you in a better negotiating position when buying a robot. For example, a pick and place application of a small electronic part does not necessarily need a six-axis articulated robot. The same procedure can be performed by a Cartesian robot which is usually a lot cheaper. Knowing things like these could save you money in the longer run.