NURBS function closed-loop mapping trajectory planning of serial robotic plasma cladding for complex surface coatings

In order to solve the problem of the trajectory planning of robotic plasma cladding for complex surface coating, the concept of non-uniform rational B-spline (NURBS) function open-/closed-loop mapping is proposed firstly in this work to explore the new approach of the trajectory planning for complex NURBS surfaces. The trajectory planning is carried out by a 2D-NURBS curve C(u) on a 2D plane, which is mapped on a predefined 3D-NURBS surface S(u,v) using the NURBS surface function to form a 3D mapping curve named NURBS function mapping (NURBS-FM) curve. Using the fixed step (FS) interpolation, the equal chord length (ECL) interpolation, the equal arc length (EAL) interpolation, and the equal bow height (EBH) interpolation, etc., a complex curve can be interpolated. The FS/ECL/EAL/EBH can be defined as constraint. Depending on where the constraint is applied, the NURBS-FM can be divided into open-loop mapping and closed-loop mapping. The NURBS function open-loop mapping (NURBS-FOLM) is carried out along the route of u -> C(u) -> S(u,v), while the NURBS function closed-loop mapping (NURBS-FCLM) along the route of u -> C(u) -> S(u,v) -> u -> .... The constraint is applied to the 2D-NURBS curve in NURBS-FOLM, while to the 3D NURBS-FM curve in NURBS-FCLM. The NURBS-FOLM and NURBS-FCLM can ensure that the interpolation points on the 2D-NURBS curve and 3D NURBS-FM curve have the ECL/EAL/EBH characteristics, respectively. When the 3D NURBS-FM curve is regarded as plasma cladding trajectory, the NURBS-FCLM can provide engineers with a new ECL/EAL/EBH interpolation method for cladding trajectory. Using the NURBS-FCLM approach based on the serial robotic plasma cladding, a high entropy alloy coating is prepared on Q235 substrate which employed the AlCoCrCuNiNb high entropy alloy powder with optimized parameters (Ar flow, ion gas flow, current, powder feeding speed, cladding feedrate) = (6L/min, 1.7L/min, 115A, 15 mm/s, 1.4 mm/s). The formation of the complex spacial curve coating on the complex surface is well without obvious defects. The simulation and experiment verify that the NURBS-FCLM is feasible and effective. It provides the technical and theoretical basis for the serial robotic plasma cladding trajectory planning of complex surface coating. With the increasing application of complex parts in various industries, the NURBS-FOLM and NURBS-FCLM technologies have more and more broad application prospects in the manufacturing of new complex product coatings and remanufacturing of old ones based on serial robotic laser/arc cladding platform.

Automated summary

This study proposes the concept of non-uniform rational B-spline (NURBS) function open-/closed-loop mapping and applies it to the trajectory planning of robotic plasma cladding. The interpolation of complex surfaces is achieved using different interpolation methods. The results show that this method is feasible and effective for the planning of complex surface coatings.