Front armrest

[ptashek]

Reviving this thread, as I did go the 3D printed route recently in my W124 and wanted to show it's perfectly viable. Exactly same problem as described - the old plastic core shattered under load due to old age. You can see the prototype stage + final print below.

Due to build volume limitations of my printer I had to split the model into two parts, then put them together with industrial-grade CA glue. The support element was reinforced with three 8mm stainless steel rods.

The new shape also required some small modifications to the foam surround, but none of it can be seen/felt once assembled. Finally, the foam surround was glued back to the new core using trim adhesive.


My time was free as it's one of my other hobbies, modelling took about 8h total + 2x 14h to print partial prototypes for verification, then 37h for the final print, another hour for re-assembly and installation. In total about 800g of PETG filament. Total cost, including energy used, was under 25EUR. Totally worth it!


Prototype of spring support plate


First prototype of the load bearing parts of the core



Final part printing


Final pre-assembly fit check



Foam surround glued back into place



Ready to re-install

[rumb]

Impressive!

[marku]

Yes really impressive. I was determined not to be defeated by mine so cut it all out of the foam. The actual support was in many pieces but it cleaned up and all glued back together with foam and covering back you would not know. So quite please with the result.

[arman]

Amazing work there! 3D printing is so effective and powerful!

[Taha]

Great job. Looks much beter than the original. Just wondering is that possible to make some small parts such as antenna drain plug or first aid kit compartment handle with the 3D printer? Thanks.

[ptashek]

Great job. Looks much beter than the original. Just wondering is that possible to make some small parts such as antenna drain plug or first aid kit compartment handle with the 3D printer? Thanks.

Yes. As long as it's not structural/load bearing or exposed to higher temps on a permanent basis. Some houseld filaments start going soft at 60°C (PLA), others are good to about 80-90°C (PC).

I actually have a prototype model of the handle already.

However for anything that needs to be water/air tight or have close tolerances, a high resolution resin printer is much better, than a filament deposition one. These have their own downsides as the resins are quite toxic and need careful handling and postprocessing.

For load bearing or high temperature parts you're looking at printing with specialist polymers or alloys that household printers are unable to process.

For that you need an SLS/DMLS printer (selective / direct metal laser sintering) - which for example Porsche used to 3D print pistons for a GT3 technology demonstrator engine.

These can cost anywhere from tens of thousands USD (polymers only) to milions (can print titanium, for example).

The technology has reached a point where you can do anything with it, the main limitation being how much money you're willing to throw at the problem.