What I would suggest is that you should keep proper documentation of your design work. Prepare a proper Excel document for this purpose, which includes all the points of discussion with managers and other team members, the design changes made in the previous design, and the design changes that are to be made in the next version of the design. This allows you to have complete knowledge of the life cycle of your designs.

To address a team member taking credit for my CAD design work, I would approach the situation professionally and directly. I’d first have a private conversation with them to clarify any misunderstanding, explaining that the work was my contribution and expressing my expectation for proper acknowledgment. If the situation persists or was intentional, I would bring it to the attention of our supervisor, providing any supporting documentation or files that demonstrate my role in the design. Handling it calmly and with evidence helps maintain professionalism while ensuring credit is given where it’s due.

If you are part of a team, that means the work belongs to the team, since most companies hire teams, it's most likely that the work belongs to the company and not the team at all. If said teammate was promoted to a higher position above the team using work I had absolutely, in a proprietary sense, committed then I would simply hand in my resignation. If you feel strongly that your work is proprietary, belonging to you, then to me that sounds like motivation to start your own business practice. Intellectual property is only as valuable as the value attributed so don't burn yourself out in teams where you are the lead actor believing that some day your hard work and dedication will take you to new heights professionally.

In this situation, I’d start by having a frank conversation with the colleague who took credit for my work. I’d explain how such actions harm both the project and team dynamics, as well as his own growth. I’d seek to understand his motives and, if needed, offer support with any technical challenges. Importantly, I’d make it clear that this is the only warning, emphasizing that if it happened again, I’d have to involve higher management. This approach addresses the immediate issue while maintaining a constructive environment, balancing accountability with empathy and the goal of fostering team cohesion.