SCARA stands for Selective Compliance Assembly Robot Arm. Two horizontal links swing like a human arm on a table, a third axis moves straight up and down, and a fourth rotates the tool. The design is deliberately rigid in the vertical direction and slightly compliant horizontally, which helps when pressing a pin into a hole that is not perfectly aligned.
Because the heavy motors stay near the base and the arm only fights gravity on one axis, SCARAs are very fast for short pick-and-place moves and repeatable to hundredths of a millimetre.
They are everywhere in electronics: placing connectors on circuit boards, screwing down covers, loading small parts into test fixtures. What they cannot do is approach a part from the side or tilt a tool.
