11 - Manufacturing engineering in thermal spraying by advanced robot systems and process kinematics

Abstract

Plasma physics and material science have dominated academic research in thermal spray technologies in recent decades. Value adding by creation and manufacturing of competitive products with advanced coating technologies needs a state-of-the-art approach in manufacturing engineering. Thinking in process chains and managing all steps of them with a focus on product performance, reliability and customer satisfaction are an indispensable methodology for modern manufacturing engineering with complex technologies. Materials mechanics and the understanding of process-induced residual stresses and their interaction with operational load stresses are further issues in product development of coatings and layer composite structures. Intensive heat and mass transfer have a distinct influence on coating properties. The same is true for the torch trajectories and robot kinematics programming with their influence on local resolution of these parameters and subsequently on the achievable dimensional tolerances and reproducibility in industrial processes. For high process reproducibility and optimized coating quality in thermal spray applications on complex-shaped geometries and system components, APS (atmospheric plasma spraying), HVOF (high-velocity oxygen fuel) and other torches are guided by advanced robot systems. The trajectory of the torch, the spray angle and the relative speed between torch and component are crucial factors that affect the coating microstructure and phase composition and the mechanical, thermophysical and electrophysical properties and especially the residual stress distribution. Thus, the requirement of high-performance thermally sprayed coatings with narrow dimensional and functional tolerances leads to challenges in the field of robot-assisted handling, and software tools for efficient and precise trajectory generation and robot programming are demanded. By appropriate data exchange, the automatically generated torch trajectory and speed profile can be integrated in FE (finite element) models in order to analyse their influence on the heat and mass transfer during deposition. Last, but not the least, the process variants have to be matched to meet the best fit of functional requirements of the coating product in its specific application field. Modelling and simulation concepts are shown to demonstrate their potential and benefit for industrial product development.