BMW Z3 Seatbelt Retainer
Below is a walk through the process of creating replacement parts for a customer’s BMW Z3. The customer had recently purchased the vehicle and the seatbelt retainer was completely missing on one side, while only half of the original piece was present on the other. Check out the process of recreating these pieces from the partial stock part, with some customer-requested design changes!
A render of the final model created for the replacement seatbelt retainers
The customer-provided original part was incomplete. It had broken near the middle, so one of the two “tabs” that holds the seatbelt inline with the curvature of the seat shoulder was missing.
The stock part has studs that go through the seat upholstery and into a backing plate inside the seat. To replace these stock parts you need to replace this back plate as well, which is a time-consuming job.
To make the replacement easier, the customer requested a flat bottom face, so the new parts could be adhered to the seat, rather than needing to use a backing plate like the original.
To match the original part as much as possible, the replacement part is curved in all 3 coordinate directions. While this ensures a OEM-like fit, it also adds complexity for printing, due to the lack of a flat surface to orient on the print bed.
Sometimes with projects like this, a handful of test prints are necessary to get the best quality for the final product. With parts that are small enough, I find prototyping like this to be the most effective way to dial in print profiles.
The setup above ended up consistenly producing the highest quality. Using the AMS with the Bambu Labs P1S, this was printed in PETG with PLA for the supports. PLA and PETG don’t bond to one another, so they are perfect to use as support for difficult geometries, because you can reduce the z-distance between the supports and the part to help improve the bottom-surface finish.
The customer was happy with the final product and was able to stick these seatbelt retainers to the seats using a marine & automotive upholstery adhesive! Although the original replica replacement parts are available and relatively inexpensive, the time saved with the mounting process for these made the 3D printed options preferable for the customer. If you have a similar type of project and are interested in hearing about potential options that use 3D printing, reach out on social media, through email, or through a custom project request!
