What are the key factors used to classify industrial robots?
Cylindrical robots are relatively simple and compact, and their limited range of motion makes them easy to program. They are less common than their more complex cousins. Still, they are especially suited for applications like grinding processes, palletizing, welding (especially spot welding), and material handling, for example, loading and unloading semiconductor wafers into cassettes in an integrated circuit fabrication operation (Figure 3). Cylindrical robots typically move at speeds of 1 to 10 m/s, and they can be designed to carry heavy loads. Applications for
cylindrical robots can be found in automotive, pharmaceutical, food and beverage, aerospace, electronics, and other industries. Parallel/Delta robot i s a manipulator whose arms have links that form a closed loop structure. While other robots, like cylindrical or Cartesian topologies, are named after their motion, the delta robot is named for its upside-down triangular shape. Delta robots have 2 to 6 axes, with 2- and 3-axis designs being the most common. Like 2-axis Cartesian robots, 2-axis delta robots don't technically meet the requirements of ISO 8373 to be called robots. Delta robots are designed for speed rather than strength. They are mounted above the work area and perform functions like pick- and-place, sorting, disassembly, and packaging. They are often found above a conveyor, moving parts down a production line. The gripper is connected to long, slender mechanical linkages. These linkages lead to three or four large motors at the robot's base. The other end of the linkages is attached to a tooling plate where the EOAT attaches. The RBTX-IGUS-0047 from Igus is an example of a 3-axis delta robot. It has a working space diameter of 660 mm and can handle a maximum load of 5 kg. When handling a load of 0.5 kg, it
can perform 30 picks per minute move with a maximum speed of 0.7 m/s and an acceleration of 2 m/s2. It has a repeatability of ±0.5 mm (Figure 4).
Figure 4: Three-axis delta robot and controller (left). (Image source: DigiKey)
Polar robot (spherical robot) is a manipulator with two rotary joints and one prismatic joint, whose axes form a polar coordinate system. One of the rotary joints enables a polar robot to rotate around the vertical axis that extends up from the base. The second rotary joint is at right angles to the first rotary joint and enables the robot arm to swing up and down. Finally, the prismatic joint enables the robot arm to extend or retract from the vertical axis.
Figure 3: This cylindrical robot has one rotary and prismatic joint. (Image source: Association for Advancing Automation)
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