Anatomy of a Cartesian gantry (3D)

← Robot list · Cartesian gantry page

Turn the robot with the mouse or your finger. Click an axis (a coloured circle or a card) to light up its ring and its axis and to read its description, press X-ray to look inside at the motors, gearboxes, controller and cables, and move each joint with its slider.

The whole bridge slides along two parallel rails, driven by a motor and a belt (or a rack and pinion). A prismatic joint (P).

The carriage slides along the beam of the bridge, across the rails.

A vertical rod, driven by a ball screw, goes down to the part. The tool is at its end.

The posts and the rails carry everything. Their stiffness decides the precision. The frame is fixed to the floor.

The tool at the end of the Z axis. A Cartesian robot cannot orient it, unless a fourth rotary axis is added.

What is inside each joint?

Three motors (servo or stepper), one per axis, with belts, rack and pinion or ball screws that turn the rotation into a straight motion (seen in X-ray).
Linear guides: rails with recirculating-ball carriages that carry the load and give a straight, rigid motion.
Limit switches and homing: incremental encoders do not know the position at power-on, so each axis first goes to a switch.
Cable chains carry the cables of the moving axes without breaking them.
Controller: often a PLC or a CNC controller in a cabinet next to the frame; the same machine is a 3D printer or a milling machine when the tool changes.

The three travels are in cm as on the gantry page: the tool position is simply (q1, q2, height). The three joints are prismatic (P): there is no angle. The model is simplified: the real inside depends on the make.