Wood Spray Painting CNC Machine Automation

On a typical machine the parts enter the spray booth on a conveyor or table. The gantry moves in X and Y and the gun carrier in Z; to paint edges and profiled surfaces the gun is angled with a rotation (C) and a tilt (A) axis. The part's shape and position are read by a scanner, light curtain or camera at the infeed, or taken from the part program (DXF).

The controller generates the painting path from the part contour itself. For the face, the gun travels back and forth over the part in parallel stripes; stripe spacing is chosen from the spray fan width with a given overlap. For the edges, the gun follows the contour at a set distance, angled towards the edge. If path speed drops at corners and short segments, paint builds up there; the path is therefore generated with look-ahead velocity planning and corner smoothing.

The gun opens and closes by position, not by time: it opens a set distance before the part edge and closes after passing it. The gun valve's opening and closing delay multiplied by path speed is used to move the trigger position ahead, so paint starts at the part edge even when speed changes. Film thickness is set by paint flow, path speed and stripe spacing and is stored as a recipe per paint and part type.

Depending on the paint and ventilation, an explosive atmosphere zone can form in the spray booth. Motors, sensors and electrical equipment in this zone are chosen for the zone (ATEX) or placed outside it; ventilation and booth doors are interlocked with machine motion.

In the ONX architecture part recognition, path generation and motion control are brought together in CODESYS running on an industrial PC. Path planning and interpolation are done by ONX's X CNC Library: it merges short segments within a contour tolerance, smooths corners and plans velocity against axis dynamics; the gun rotation and tilt axes are smoothed together with the path. Servo drives and remote I/O share one time base over EtherCAT.

Gun valves are triggered by fast outputs tied to axis position; trigger delay compensation and film thickness recipes live in the same controller. Conveyor, transfer to drying, cleaning cycle and booth interlocks are managed in the same CODESYS project.

Motion control of the painting machine is built on the same CODESYS and X CNC path planning platform ONX Control uses in its CNC router and 5-axis applications. We work out the axis layout and path strategy for your parts and paint together in a meeting.

A typical picture on older painting machines: a reciprocator moving back and forth with a fixed stroke, guns switching on and off regardless of part shape, and paint building up at corners. In a retrofit the booth, conveyor and guns are usually kept; motion moves to servo axes, a part scanner is added at the infeed, and path generation and gun triggering move into the controller.