My print volume is only 150mm in the Z axis, so the GramiPhone horn was hard to print. It would have required a lot of support. This is a 150mm tractrix-shaped horn for the GramiPhone.
As uploaded, I had to glue the horn into the GramiPhone stand to make it fit without drooping. If you want to fiddle with it to make it press fit properly, I have also uploaded the python code that I used in FreeCAD to draw the cross section. Maybe a diameter of 4.2mm will work better than 4.1mm. You can use the python code to create a wide variety of horns, like a megaphone or what-have-you. Here is how you use the python:
- Start FreeCAD and open a new Part Design.
- Create a sketch in the YZ plane with no offset and not reverse direction.
- Copy and paste Tractrix.py into the python console. If you can't see the python console choose View|Panels|Python Console.
- Wait a long time for the cross section to draw. When it's finished, there will be a lot of vertical and horizontal constraints. So many that the green drawing will be obscured behind the red constraints.
- Close the drawing.
- Revolve the drawing about the vertical axis 360°.
- Choose the revolution in the Combo View and export it to STL.
N.B. After step 4, you can delete the bulk of the drawing and only keep the top section if you want to test the fit of the horn into the stand.
I printed a skirt and support on the first 10mm. If your printer is really good at overhangs, you may not need support.