<p dir="ltr">This study investigated the effects of single-stage and multi-stage (two, three, or four) mandrel cold-forming processes on stainless steel U-shaped, thin-walled profiles, with a particular focus on their impact on stress. These profiles, commonly used as metal expansion joints (also known as compensators or bellows), are essential components in industries such as aerospace, energy, and piping systems. The need for these joints to absorb thermal expansion and mechanical movement while maintaining structural integrity makes precise forming processes critical. In particular, the investigation examined the effects of incrementally increasing the number of forming stages, from one to four, on profile geometry, with particular emphasis on thickness variation, consistency, and stress distribution. Profile geometry and thickness were assessed using three-dimensional scanning, a coordinate measuring machine, and ultrasonic thickness measuring techniques. While these methods have limitations, they provide valuable insights into the formed profiles. Increasing the number of forming stages up to four reduced thickness variation by up to 5%, producing profiles that were more closely aligned with the theoretical design specifications. Stress, a crucial factor in the long-term performance of metal expansion joints, was also reduced by increasing the number of forming stages by up to 6% with four stages. Further reductions in stress and thickness variation could be achieved with more than four stages, though the improvements became less significant. A formula was developed to determine the minimum number of forming stages (N_min) required for thin-walled U-profiles. Depending on the application, additional stages beyond N_min improved profile accuracy and further reduced stress, offering manufacturers flexibility in meeting performance requirements.</p>