Abstract: Multi-body blades have structural characteristics such as complex curved surfaces and small blade spacing. Plasma spraying is an important process of casting multi-body blades, which can strengthen and modify the surface of the blades, and the quality of the spraying directly determines the yield and performance of the blades. The path generation of the existing robot plasma spraying mainly relies on manual teaching, and the spraying distance and spraying angle during the spraying process cannot be quantified, resulting in uneven spraying quality, cumbersome teaching methods and low efficiency. Based on this, this paper proposes an interference-free path generation and smoothing method for plasma spraying of industrial robots for multi-body blades. Firstly, according to the CAD model, the multi-body blades surface is transformed into a non-uniform rational B-spline(NURBS) surface. Using the analytical characteristics of NURBS surface, the initial path points constrained the distance between spraying rows and spraying blade edges are generated. The spray flame flow is simplified as the Oriented bounding box(OBB) model, the interference surface is converted to a triangular surface, and the collision interference detection method based on separation axis detection is used to generate the spray attitude with the minimum spray inclination angle. The pose optimization method based on Spherical Spline Quaternion interpolation (Squad) interpolation is adopted for attitude smoothing to generate a non-interference and smooth spraying path. Through simulation and experimental verification, the proposed algorithm can effectively avoid the interference phenomenon in the process of spraying. Compared with the unsmoothed path, the proposed algorithm increases the operating efficiency of the robot by 52.6%, the vibration of the robot decreases, and the operation is more stable. The maximum joint acceleration decreases by 55.8%, the minimum decrease by 2.9%, the instantaneous acceleration of the end decreases by 39.6%, and the minimum decrease by 14.4%.

Key words: multi-body blade, robot spraying, interference detection, path smoothing