SCARA Robot

Overview

The SCARA robot is a four-axis selective-compliance assembly arm built for fast, precise pick-and-place, screwdriving, and insertion. Its two rotary shoulder and elbow joints move in a horizontal plane, making the arm stiff vertically but compliant in the plane, which is exactly the behavior peg-in-hole assembly wants. A vertical quill at the tool end adds Z lift and tool rotation, giving four axes that cover the great majority of planar assembly tasks at short cycle times.

Construction

The arm anchors to the Base Assembly, a cast-iron pedestal bolted to the floor. The shoulder axis is the J1 Rotary Joint, an AC servo driving a Harmonic Reducer strain-wave gear with absolute feedback, which swings the Inner Arm Link. At its tip the J2 Rotary Joint drives the elbow through a timing-belt reduction and carries the Outer Arm Link.

The tool end is the Quill Assembly, built around a ball screw-spline shaft: a Z servo actuator turns the ball nut to lift the shaft while a theta servo turns the spline nut to rotate the tool, and a spring-applied brake holds the quill on power loss. End-effectors mount to the Tool Flange with air and signal pass-through. Motor and encoder runs route through the internal Internal Cabling.

All four axes are commanded by the Controller Cabinet cabinet, which houses the motion CPU, four servo drives, the power supply, a dual-channel safety I/O module, and a handheld teach pendant with an E-stop and a three-position enabling switch for safe jogging.