Which robot type typically has a single vertical axis and two parallel planar joints, providing fast, clean movements suitable for assembly?

• A. SCARA
• B. polar
• C. cartesian
• D. articulated

Answer: (A)

For fast, clean assembly movements you want motion confined to a plane with a simple, stiff mechanism, plus a way to reach up or down. This robot type achieves that with two rotary joints operating in a common plane (the parallel planar joints) to position the end effector quickly and precisely, while a vertical axis handles lifting or lowering. The planar, two-joint arrangement acts like a compact 2R arm in the horizontal plane, giving high speed and good repeatability, which are ideal for pick-and-place and assembly tasks. The vertical axis adds the necessary Z movement without complicating the planar motion, keeping movements clean and predictable.

Other options don’t match this setup: polar robots rely on a rotating base and a moving arm rather than two parallel planar joints; cartesian robots use three orthogonal linear axes rather than planar rotary joints in a single plane; articulated robots have multiple rotary joints that create more flexible, multi-plane motion, which isn’t as optimized for fast, straight-line assembly movements.