Stop Guessing. Start Predicting: A Universal Digital Twin for Laser-Based Manufacturing

High power lasers are used for a variety of manufacturing processes on time and length scales that cover many orders of magnitude and on different materials. The variety of processes achievable through laser-material interaction results from numerous coupled, nonlinear physical phenomena. Within this chapter, a universal model is presented that accurately simulates a broad spectrum of processes, including welding, additive manufacturing, cutting, ablation, drilling, and surface structuring, encompassing both continuous wave and ultrashort pulsed lasers and their interaction with various materials. Starting from the fundamental principles of conservation of mass, momentum, and energy, a continuum mechanical framework is introduced that captures the main multiphysical effects.

Physics-based simulations are routinely used to understand and optimize laser-based metal additive manufacturing processes. Across the wide range of model predictive capabilities and computational costs, a lack in understanding of the implications of model choice for simulation accuracy persists. We present the first detailed comparison of results obtained with a one-fluid approach (FLOW-3D) and a two-fluid approach (Mass-of-Fluid model) for the simulation of laser-induced melt pool formation and vaporisation, applied to scenarios ranging from conduction-mode melting to deep-penetration copper welding with different beam shapes.

Laser beam welding has emerged as a powerful tool for manufacturing copper components in electrical vehicles, electronic devices or energy storage, owing to its rapid processing capabilities. Nonetheless, the material's high thermal conductivity and low absorption of infrared light can introduce process instabilities, resulting in defects such as pores. This study employs a hybrid approach that combines in situ synchrotron X-ray imaging with compressible multiphysics process simulation to elucidate pore-forming mechanisms during laser beam welding of copper. The findings show that pore formation is driven by four different mechanisms: bulging, spiking, upwelling waves at the keyhole rear wall and melt pool ejections.

This work bridges the gap between ultrafast electronic excitation and macroscopic material removal in dielectric materials. A comprehensive simulation framework couples free electron generation via multiphoton and avalanche ionization with the subsequent hydrodynamic response of the material, capturing the full chain of events from initial laser absorption through to ablation crater formation. The model is validated against experimental ablation data for glass substrates processed with femtosecond laser pulses.

A new model for compressible multiphase flows involving sharp interfaces and phase change is presented, that uses a variant of the Volume-of-Fluid model to track phases by advecting their respective mass, and is hence called Mass-of-Fluid model. The framework is aimed at predicting the coupled multi-physical phenomena involved in most processes encountered in laser material processing, with the aim of minimizing a priori assumptions on the nature of the process. Emphasis is put on the multiphase fluid flow model, especially on the treatment of compressibility and phase change.

Laser powder bed fusion of metals (PBF-LB/M) is an additive manufacturing technique which has recently been growing in popularity in industrial use cases. However, several challenges persist, including the issue of solidification cracking observed in widely used Ni-based superalloys. Through retrofitting an existing PBF machine with a dual beam system capable of dynamic beam shaping, it is possible to overcome this issue. In this regard we propose a methodology that utilizes a numerical simulation tool to identify optimized parameters. The effectiveness of the found beam shapes was proven in experiments, where crack density was reduced to near-zero.

This study extends an existing comprehensive computational framework to gain insight on hot cracking in the simulation of laser-based additive manufacturing via powder bed fusion. A novel approach to predict hot crack susceptibility based on vapor cavitation, building on a conceptual model akin to the Rappaz-Drezet-Gremaud criterion is introduced. Unlike conventional practices involving ex-situ evaluation of a criterion, the proposed model emerges implicitly from the underlying multiphysical modeling framework.

Intricate dynamics in ultra-short pulse laser ablation of metals necessitate deeper process understanding. This work presents an auspicious contribution in this direction, incorporating a sophisticated three-dimensional finite-volume simulation tool, building upon our previously validated models in continuous-wave laser material processing. Atop the existing multiphysics framework, a two-temperature and a Drude absorption model has been integrated.

This work investigates the rapid formation of high aspect ratio through holes in thin glass substrates using a quasi-continuous wave (QCW) laser approach. By engineering the temporal pulse shape, precise control over the drilling process is achieved, enabling high-quality micro-drilling with minimal thermal damage. The results are supported by multiphysical simulations that capture the coupled dynamics of beam propagation, absorption, and material removal.

Keyhole laser beam welding (LBW) of 304L stainless steel sheets with a gap in between was numerically simulated with a three-dimensional, transient, multi-physical model for laser material processing based on the finite volume method (FVM). The model's ability to reproduce experimental results on a relatively coarse computational mesh within reasonable computing time, so as to serve as process optimization tool, is presented.