Towards Near-Net-Shape: : Increased Understanding of Deformations and Pre-Compensation for DED-LB/W by Simulation

Sammanfattning

Directed Energy Deposition using a laser beam and wire feedstock (DED-LB/w) is an effective additive manufacturing (AM) technique for creating near-net-shape stocks, especially in aerospace applications. However, the process is susceptible to deformations caused by thermal distortions and residual stresses, which limit its wider adoption. This study aims to increase the understanding of deformation behaviour for boss features and substrates by simulating the DED-LB/w build process, exploring pre-compensation strategies to improve dimensional accuracy, and evaluating the capabilities and limitations of Simufact Welding 2023.3 for these objectives. Simulations were performed using Ti-6Al-4V (Ti64) as the substrate and feedstock material in two configurations: plate and drum substrate, with different boss lengths and key process variables (KPVs). A two full factorial Design of Experiments (DoE) was conducted to screen for essential factors and their interactions, including parameter, substrate thickness, interpass time, dwell time, and boss length. Additionally, three build strategies and pre-compensation techniques were examined to minimise deviations from the nominal geometry. Results show that increased substrate thickness, lower interpass time, and dwell time lead to significantly less distortion. Proposed pre-compensation workflows decreased surface deviation by up to 88%, with most cases remaining within an overbuild tolerance of 2 mm. Builds should be done one boss at a time, minimising deformation but at the cost of higher interpass temperature and lower mechanical properties. The study provides insights into statistical process development with simulation and highlights the importance of substrate geometry, cooling time, and build strategy in achieving near-net shape stocks.