SCARA Robot

SCARA stands for Selective Compliance Assembly Robot Arm, which, in terms of describing a robot arm is very accurate. "Selective compliance" means the arm is stiff along the vertical axis but has controlled flexibility in the horizontal plane. In assembly work that's a useful property. You can push a component downward with controlled force without the arm buckling, while the horizontal flexibility absorbs small misalignments during insertion without jamming.

In speed terms, a SCARA is generally faster than a 6-axis articulated arm for flat-plane pick and place. It has fewer axes to coordinate, less moving mass, and a structure that keeps inertia low. For a high-volume assembly or packaging operation where the movement is essentially two-dimensional, that translates to more parts per hour for less money.

It won't substitute for a 6-axis arm where you need 3D reach or complex approach angles. There's no wrist articulation to tilt or rotate a tool in all directions. But if the task fits within what a SCARA can do, it'll do it faster and cost less to buy and run.

The arm on a SCARA robot has 4 axes in total, a shoulder rotation, an elbow rotation, a vertical Z slide, and a wrist rotation around the vertical axis. The shoulder and elbow joints both rotate around vertical axes, sweeping the arm across a roughly circular horizontal workspace. The Z slide raises and lowers the end-of-arm-tooling, and the wrist rotates the tool for orientation.

Most of the arm's mass sits close to the base. That's a significant part of why SCARAs are fast. There's no heavy forearm hanging at full extension the way a 6-axis arm has when it reaches out, so acceleration and deceleration are quicker and the robot can sustain tight cycle times over a full shift without mechanical stress accumulating.

The working envelope is relatively flat. SCARAs aren't suited to reaching around obstacles or approaching a part from multiple angles. Within their disc-shaped workspace, though, positional accuracy is high and consistent.