Thermal Scalar Field for Continuous three-dimensional Toolpath strategy using Wire Arc Additive Manufacturing for free-form thin parts

International audienceWire Arc Additive Manufacturing (WAAM) is revolutionizing the field of Additive Manufacturing (AM) by being the technological solution to manufacture thin-walled structures of large dimensions and medium geometric complexity at reduced cost with an excellent buy-to-fly ratio. Manufacturing parts with this technology is nowadays done through 2.5D strategies. This type of strategy consists in cutting a 3D model using planar layers parallel to each other. This 2.5D technique limits the complexity of the geometries that can be produced in WAAM without taking advantage of height deposit modulation. It also requires several start/stop phases of the arc during the transition from one layer to another, which leads to poor quality. This paper presents a new fast and efficient path planning strategy aiming at creating a continuous manufacturing path, thus increasing poor part quality. This strategy so called "Scalar Thermal Field for Continuous Toolpath" is generating a continuous spiral manufacturing toolpath for thin shaped parts. The modulation of deposition, by controlling the welding torch travel speed at constant wire feed rate, allows continuous deposition of material throughout the manufacturing process. The keypoint of the method is the use of a thermal scalar field associated with a 6-axis robotic arm kinematics which allows the manufacturing of closed parts after optimal closure point determination or direct manufacturing of opened parts with non-planar free edges. Validation of the presented method is performed by manufacturing three distinct parts : an opened, a closed part and a multi-branch part. The fabrication of these parts and their precise measurement have shown the reliability and the restitution capacity of our method which is clearly superior to 2.5D strategies nowadays commonly used in WAAM technology

Thermo mechanical simulation of overlaid layers made with wire arc additive manufacturing and GMAW cold metal transfer

A thermo mechanical simulation of the wire arc additive manufacturing WAAM process is presented in this work. The simulation consists in the deposition of 5 successive layers of 316 L stainless steel on a 316 L base plate. The thermo mechanical analysis is solved in two dimensions under plane stress assumption. Nonetheless, the metal addition is taking into account in this numerical analysis. An increment of material is added at each time step. This numerical approach allows reducing the computational time. The temperature and residual stress fields are computed at each time step. Two patterns of deposition strategy are also investigated. It is shown that the longitudinal stress varies mainly along the vertical axis. A sample with 5 overlaid layers has been scanned with neutron diffraction technique in order to measure the final residual stresses. Both numerical and measured residual stresses are in good agreement. The Aster finite element software is employed for the numerical analysi

Transient behaviour of deposition of liquid metal droplets on a solid substrate

International audienceThis paper investigates the mechanisms that contribute to the spreading of liquid metal macro-drop deposited during Stationary Pulsed Gas Metal Arc Welding on an initially cold solid workpiece. Surface tension and inertial effects take an important part in the behaviour of the liquid metal macro-drop, but in this configuration the influence of energetic effects can also be significant. The experimental results are discussed in the light of dimensional analysis in order to appreciate the influence of the process parameters and the physical mechanisms involved on the spreading of a macro-drop. A law is established to model forced non-isothermal spreading