RSW-AI-three-layered – Methodology for Parameterizing 3-Sheet Joints in Resistance Welding Using Artificial Intelligence

The »RSW-AI-three-layered« research project standardizes the parameterization of three-sheet joints in resistance spot welding (RSW) and uses AI to derive suitable welding parameters for new combinations. This digital tool significantly reduces the effort required to determine the welding range, particularly when unknown material combinations are introduced.

This is particularly relevant for small and medium-sized enterprises (SMEs) in the automotive industry. These companies are under growing pressure to reduce vehicle weight, for example by using high-strength steels with thin sheet thicknesses. Such combinations present new challenges for the welding process.

From simulation to AI model

© Fraunhofer IPK / Larissa Klassen
Resistance Spot Welding Cell at Fraunhofer IPK

First, the welding process for a three-sheet joint is investigated both experimentally and numerically. The numerical simulations expand the data space by introducing additional process variations and, at the same time, provide insights into the welding process that would not be possible through experimentation alone.

Based on this process data, an initial machine learning (ML) model is developed that predicts the formation of the weld bead (the load-bearing weld joint). The algorithm predicts the lower current limit at which the required weld spot diameter is achieved. A second model predicts the upper current limit at which spatter begins to occur. It takes into account thermoelectric processes and physical boundary conditions.

Four requirements are central to model development:

  • Robustness: The model responds to real-world process influences in the production environment without overinterpreting them.
  • Generalizability: It can be used on different production lines and with various materials.
  • Data Security: Since the model processes real production data, it is protected against external attacks.
  • Local Operation: The model runs locally, so no data leaves the company.

Finally, all the findings are integrated into a prototype component and demonstrated.

Activities of Fraunhofer IPK

Fraunhofer IPK is responsible for defining the data format, designing and performing the FE simulation, and developing the AI models for predicting the parameter window.

The design of the simulation models is based on many years of experience in the numerical simulation of welding processes. The expertise gained from previous projects (such as those on spatter prevention in resistance spot welding or defect detection in the laser DED process) enables the AI models to be designed to meet specific needs.