Robotics – Robots
A robot is a multi-axis machine designed to perform a complex series of mechanical actions automatically. Robots are typically controlled by a computer-based controller that runs kinematic algorithms that drives multiple motor in a coordinated motion to move from point A to B.
Industrial Robots are robotic system that are typically used for manufacturing. But with the advancement of today’s technology, we are finding industrial robots in several other business sectors. Medical care and amusement parks rides are just a couple of examples where industrial type robots are being used. But those are not the only type robots out there. Within the scope of this article, we are only focused on industrial robots used in manufacturing.
Typical applications of an industrial robot include welding, painting, assembly, disassembly, pick and place for printed circuit boards, packaging and labeling, palletizing, product inspection, and testing, grinding, finishing, dispensing and machine tending etc.. All are accomplished with high precision, speed, and endurance. Robots can assist in heavy payloads and repetitive actions without fatigue and errors. But that is not to say that a robot can work alone. An industrial robot must work in a safe environment. There is a lot of peripheral equipment around the robot to assist it in its task.
Below is a brief review of the various industrial robotics types that can be found in manufacturing.
SCARA Robots (Selective Compliance 3 Axis Robot Assembly)
The SCARA robot has a donut-shaped work envelope and consists of two parallel joints that provide compliance in one selected plane. The rotary shafts are positioned vertically, and the end effector attached to the arm moves horizontally. SCARA robots specialize in lateral movements and are mostly used for assembly applications. The advantages of the SCARA robot is its high speed and repeatability. The disadvantages are its limited payload and horizontal planar 360-degree motion and vertical travel.
Articulated Robot/Selective Compliance Arm
The Articulated robot is a multi-axis robot with rotary joints and are commonly called industrial robots. Articulated robots can range from simple two-jointed structures to systems with 10 or more interacting joints and materials. The more common industrial robots have a range of 4 to 6 axis and in certain cases 7th joint axis of motion. The articulated robot typically resembles a human arm in its mechanical configuration and motion. Because of its flexibility, reach and payload capability it is the most widely used robot in manufacturing. The articulated robot covers a wide range of applications that include but are not limited to arc welding, metal removal, material handling, machine tending, packaging, palletizing, dispensing. Its advantages are its product range for payload and reach. Its only disadvantages to other robot configurations would be its speed.
There are a couple of other robot styles that are like the articulated robot or industrial robot but are limited in their capabilities, such as the Polar Robot and the Cylindrical Robot. These robots are rarely found in manufacturing today but there are a few out there. Currently none of the leading robot manufacturers offer these style robots. When used, they are typically custom design and build.
The cartesian robot (also called linear robot) is a robot whose three principal axes are linear moving in straight lines). Cartesian robots are also called “gantry robots” have a rectangular configuration. These types of robots have three prismatic joints to deliver linear motion by sliding on its three perpendicular axes (X, Y and Z). They might also have an attached wrist to allow rotational movement. The typical applications of a cartesian robot are found in areas where there tight spaces like machine tending of an injection or blow mold operation or in a material handling operation where product has to be transported overhead over relatively long distances.
A Delta robot is a type of parallel robot that consists of three arms connected to universal joints at the base. The key design feature is the use of parallelograms in the arms, which maintains horizontal orientation of the end effector. Direct control of each joint to the end effector, the positioning of the end effector can be controlled easily with its arms resulting in very high-speed operation. Delta robots have popular usage in picking and packaging in factories because they can be quite fast, some executing up to 300 picks per minute. The disadvantage of the delta style robot is its payload. The Delta robot is typically used in the food industry, pharmaceuticals, electronics, flight simulators, automobile simulators and optical fiber alignment to name a few.
In recent years the robotics industry has introduced two robot software / firmware technologies (collaborative and cooperative robotics) that allow safe interaction between the robot and the operator.
Collaborative robots are a form of robotic automation design to work safely alongside human workers in a shared, collaborative workspace. In most applications, a collaborative robot is responsible for repetitive, menial tasks while a human worker completes more complex and thought-intensive tasks. Though the technology has come a long way from its conception it still has some significant drawbacks relative to payload and speed due to human safety. Thus, applying a collaborative robot to an application can be somewhat subjective in its RIO. Not all collaborative robots are the same. Just about every robot manufacturer offers their version of collaborative robots they all have their own definition of collaborative robots. So, when evaluating the use of collaborative robotics, one must weigh the cost to the benefit.
A cooperative robotic system incorporates the safety sensors with an industrial robot to safeguard the robotic work cell so that a robot and an operator can perform tasks within the work cell simultaneously while the robot is running in the automatic mode. The safety sensor establishes safety zones around the robot’s work peripheral to allow for the operator to move in and out of the work cell freely and safely. If the operator is outside the safety sensing zone the robot continues its programmed task at its programmed rate of speed. If the operator steps into the work cell safety zone let us say, zone one the robot will slow down to a safe operating speed and continue to run its programmed task (typically 10% of its programmed rate of speed). If the operator steps into say, safety zone 2 then the robot will come to a complete stop until the operator moves back out of zone 2 into zone. Thus, the robot will start back up to its safe operating rate resuming its programmed task where it left off when stopped.
The true benefits of cooperative robotics are:
> Production time saved
> The ability to provide a method of stopping the robot when an operator enters the robots designated safety work cell without muting the work cell safety circuit.
> Potential Material waste saved. Before the introduction of cooperative robotics an operator would have to perform several tasks to be able to enter the work cell which could be costly to productivity and potential product material waste.
>Cooperative robotics are more suited for assembly and machine tending type applications and are less suited for welding, sanding, grinding, milling, dispensing, polishing and buffing type applications.
Resources: Wikipedia, TechNavio Blog https://blog.technavio.com/blog/major-types-of-industrial-robots