Laser welding cell design for an industrial application: from 3D modelling to virtual validation

The present thesis addresses the preliminary design of a laser welding cell for busbars in lithium-ion battery packs used in electric vehicles. The work focuses on the conceptual and functional design, aiming to define a company’s standard station that has to be modular, flexible and customizable. The main topic of this project is the preliminary study of the digital twin and virtual commissioning methods, in fact, after the three-dimensional modelling phase, the digital model of the laser welding cell is developed using software Siemens Tecnomatix Process Simulate. The principal advantage of these approaches is the possibility of cycle time evaluation, especially in complex automated line cases. The simulation software used in this work has many suitable functions that help with the layout definition, such as the collision check and the reachability test for the robot path. The laser welding line results from an initial study about batteries and laser welding techniques, followed by a state-of-the-art analysis and market research to identify existing systems available for busbar applications; hence, the cell is designed taking into account different possible technological solutions and layout configurations, considering the pros and cons of each. Once the key features of the machine are defined, each component is modelled in Inventor and the complete station is then converted to the format required by the simulation software: all the objects are classified into specific categories that allow functionalities, special tools and operations based on their intended functions. The kinematic design, for each resource where applicable, allows the model to be animated by defining movements, specifying joint types between links, revolute or prismatic, imposing motion limits and setting speed and acceleration. The operations are determinate that means path planning for the robot and parts flow. The work cycle is built using Cyclic Event Evaluation (CEE) mode: the work sequence is cyclic and governed by the succession of operations defined in the Gantt diagram and controlled by transition conditions. The system is not connected to any controller yet. The code for the PLC is written and checked. It manages the input-output signals that the simulator will share with the digital model and runs the logic flow of operations. The thesis is a preliminary study of the application of the powerful digital twin technique in an industrial context.