An Automatic Spray Printing Method for Curved Patterns Using Industrial Robots

Abstract

This paper proposes an automatic trajectory planning method for high-precision pattern printing on complex curved surfaces using industrial robots. A seed-face neighborhood growth algorithm with dual-angle constraints is developed to perform adaptive curvature-based surface segmentation. Combined with a concave polygon decomposition strategy, this method addresses the problem of trajectory fractures in regions with abrupt curvature and complex boundaries, which is a common limitation of traditional slicing methods. Continuous smooth trajectories are generated by intersecting parallel slicing planes with the segmented regions, followed by Lagrange interpolation and raster-style path planning. Coordinated control of the spray head is realized via robot inverse kinematics. An experimental platform consisting of a six-degree-of-freedom industrial robot and a rotating multi-head spraying tool is built to validate the method. Simulations and experiments confirm that continuous trajectories can be generated for patterns with complex concave polygonal boundaries, and all paths are collision-free and reachable. Quantitative evaluation on cylindrical and spherical substrates using a coordinate measuring machine shows that the trajectory accuracy error is $\le 0.12$ mm, which verifies the geometric accuracy and robustness of the proposed method. The geometric approach demonstrates strong applicability for precision printing on typical curved surfaces, and provides a reliable foundation for industrial curved electronics manufacturing. Further validation on highly complex free-form surfaces will be pursued in future work.