The SCARA, or Selectively Compliant Assembly Robot Arm, was invented by Professor Hiroshi Makino of Yamanashi University (Japan) in the early 1980s. SCARA robots typically employ a single revolute wrist with the axis of rotation parallel to the other two revolute joints. Since the base link typically houses the actuators for the first two joints, the actuators can be very large and the moving links relatively light. Thus, very high angular speeds are obtainable with this design. The arm is very stiff in the vertical (z-axis), but relatively compliant in the x-y plane, which makes it ideal for tasks such as inserting pegs or other fasteners into holes.
