Altotrombone Bell

A while back I was trying to determine how well you could 3D print a brass instrument. 
I settled on printing a trombone as it was the instrument I was most familiar with and for simplicity, as this would be the first proper design I ended up making in CAD. 
I took a photo of the original bell and some measurements for dimensions, with which I made a copy of its internal geometry. I also made some alternative geometries.

The results were quite interesting. While there was a slight loss in the efficiency of the bell, seemingly due to absorption by the less dense walls, the quality and clarity of the sound were barely impacted. 

It turns out that most of the sound made by the instrument is just made by resonance in the air, not the material, and while in some notes there was definitely detectable resonance in the original metal bell, most actually had the metal hardly swinging at all. 

This behavior can actually be described and simulated over a derived version of the Webster-Equasion, however, this is a little out of the reach of this description. 

I sadly don't have any recordings of the instrument left, and I have since given away the alto trombone. I did not end up printing a slide for it, as I found the mechanics to be finicky at best and even with lots of lubricant it wasn't great for playing. 

I plan to at some point pick up this project again, maybe to even print a full-size bell once I acquire a bigger printer.

This was printed at 0.15mm layer height from white polyterra PLA. I had some issues with structural integrity (as such the pieces of tape), however the sealing was not an issue. The different pieces were glued together with CA glue.

I don't think this will be interesting to reprint to people, but maybe the story was interesting enough to get your attention.

I may search for the measurements I took if interest arises.