150mm tractrix horn for GramiPhone

thingiverse

My print volume is only 150mm in the Z axis, so the GramiPhone horn was difficult to print because it would have required extensive support structures. This is a 150mm tractrix-shaped horn for the GramiPhone. As uploaded, I had to attach the horn to the GramiPhone stand with glue to make it fit properly without sagging. If you want to experiment with making it press fit perfectly, I 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, such as a megaphone or something similar. Here is how you use the Python: Start FreeCAD and open a new Part Design document. Create a sketch in the YZ plane with no offset and not reversed direction. Copy and paste Tractrix.py into the Python console. If you can't see the Python console, choose View|Panels|Python Console. Wait for a long time for the cross section to draw. When it's finished, there will be many vertical and horizontal constraints. So many that the green drawing will be obscured behind the red constraints. Close the drawing. Revolve the drawing around the vertical axis 360 degrees. Choose the revolution in the Combo View and export it to STL. Note: After step four, you can delete most of the drawing and only keep the top section if you want to test the fit of the horn into the stand. Print Settings: Printer Brand: RepRap Printer: Prusa i3 ZRIB Rafts: No Supports: Yes Resolution: 0.3 mm Infill: 30% Notes: I printed a skirt and support on the first 10mm. If your printer is really good at overhangs, you may not need any support structures.