E36 Cup Holders

A major flaw on E36’s is the absence of cupholders. Instead, BMW preferred to having ashtray’s available to the passengers. There are a few aftermarket options for cupholders, ranging from 75$ to 150$ USD. I decided to take matters into my own hands, to design and fabricate my own. My objectives with the design was holding the average drink size, looking OEM / fitting interior aesthetic, without needing to drill or cut any part, making it fully reversible.

The most difficult part was mapping out the surface of the console to ensure a proper fitting insert. The surface had non-symmetrical fillets, draft angles, and a limited amount of space. To outline the surface, I began getting a rough estimate of the dimensions through my calipers, modelling a 2D sketch of the profile, printing a 1mm thick plate of said sketch, checking the fitment, and iterating until it had a nearly identical 2D profile, both across the horizontal and vertical.

On the console, the ashtray sits in a dip. To simplify, I ignored such dip when designing the cupholders, however, the mounting holes of the ash tray sit within the dip. In order to re-use the expanding rivet, I extruded the mounting hole to sit on the tray which enabled me to effectively re-use the rivet.

For dark interior car parts, which can be exposed to the sun for a long period of time, ASA and ABS are preffered, as opposed to common PLA, since it can sag, deform, and become brittle due to prolonged sun exposure. I went with ASA since it has the best material properties, however the trade off is that it is much harder to print and is sucseptible to warping. To get a succesful print, I pre-heat the bed and chamber to reduce internal stress caused by material shrinkage and added brim to increase contact area between model and build plate. These two steps were most effective on providing a satisfactory print.

I am pleased with the final outcome. The cupholder fits snugly, remains stable, and meets my initial objectives. I believe it matches the interior aesthetic well.