Optimized Dual Chamber Whistle

This is a whistle with a small bed footprint (41 x 6 mm) that can be printed very efficiently - about 2 minutes and 1.15 grams of PLA per whistle. The model's internal geometry contains tiny gaps to force the Arachne perimeter generator to minimize the length and number of paths, with much of the whistle body being printable in just two or three lines per layer.

The whistle reaches >105 dB(A) (measured at ~30 cm) with little effort.

Print time estimates

The following per-whistle print times are slicer estimates with the stock profile (modified per the printing instructions) with PLA filament on a plate of 10 whistles. I do not own any of these printers, these numbers are for reference only. You can probably go a lot faster than this with some tuning.

• Prusa MK4S (HF0.4, SPEED): 2 min 18 sec

• Prusa CORE One (HF0.4, SPEED): 2 min 12 sec

• Bambu A1 (Standard): 2 min 10 sec

• Bambu H2S (High Flow, Standard): 2 min 0 sec

Printing Instructions

Tested with PrusaSlicer, OrcaSlicer, and Bambu Studio with a 0.4 mm nozzle. 0.5 and 0.6 mm nozzles might also work (but I haven't had the time to test them, please let me know if you manage to get them to work). The STL is provided in the suggested printing orientation.

This design does not leave much room for error. Make sure your printer and filament are tuned properly (flow rate, pressure advance, retraction, etc) and that your filament is dry (brand new filament is often soaking wet). Filaments with low layer adhesion (such as matte and silk PLA) may need to be printed hotter and/or slower. For ABS/ASA, a warm enclosed chamber is required for layer adhesion. (This will be extremely printer-dependent, but on a printer with a short melt zone and a "low speed" PLA, you may need to raise the temperature as high as 260°C if you are printing at a decently high speed. However, at a certain point, layer adhesion will suffer due to polymer degradation.)

Feel free to adjust the settings, these are provided as a starting point that I have tested. Please let me know if you find any improvements or have issues with your specific setup.

Ensure the following settings are set (you may need to enable showing advanced/expert settings):

• Layer height: 0.3 mm

• First layer height: 0.3 mm

• Wall generator/Perimeter generator: Arachne

  • Minimum wall width/Minimum perimeter width: 80% (smaller values may be needed for wider nozzles)

• Wall loops: 2

• Slice gap closing radius: 0 mm

• Precise wall(†): Off

• X-Y hole compensation(*): Off

• X-Y contour compensation(*): Off

• Only one wall on top surfaces(*): Off

• Only one wall on first layer(*): Off

• Thick bridges: Off

• Extrusion rate smoothing/Max volumetric slope: as appropriate for your printer

• Retract on layer change: On

• Wipe while retracting: adjust as needed

• Wipe distance: adjust as needed

• Z-hop/Lift: disable if needed

(*) OrcaSlicer/Bambu Studio only
(†) OrcaSlicer only

Create the following height range modifiers:

• 0.9-4.8 mm

  • Outer wall/External perimeters: 0.73 mm (this is not a typo)

  • Inner wall/Perimeters: 0.73 mm

  • For filaments with low layer adhesion, reduce outer wall speed

• 4.8-5.2 mm

  • Layer height: 0.2 mm

  • Wall loops/Perimeters: 1

• 5.2-5.8 mm

  • Top surface pattern: Concentric (this is to prevent air from leaking between the chambers)

• 5.8-9.7 mm

  • Outer wall: 0.73 mm

  • Inner wall: 0.73 mm

  • For filaments with low layer adhesion, reduce outer wall speed

• 9.7-10.1 mm

  • Layer height: 0.2 mm

  • Wall loops/Perimeters: 1

Infill direction

For faster printing, change these settings too to make the infill run in the long direction.

OrcaSlicer

• Internal solid infill pattern: Rectilinear

• Solid infill rotation template: 90

PrusaSlicer

• Fill angle: 90°

• Solid fill pattern: Aligned Rectilinear

Height modifiers:

• 10.1-10.4 mm

  • Fill angle: 0°

• 10.7-11 mm

  • Fill angle: 0°

Bambu Studio

• Internal solid infill pattern: Aligned Rectilinear

• Infill direction: 90°

Height modifiers:

• 10.7-11 mm

  • Infill direction: 0°

Verifying Slicer Results

The resulting slice should look like this:

Ensure the bridges are appearing as intended:

The following outputs indicate incorrect slicer settings:

Revision History

• v1.3 (2026-03-22): improved printing reliability of upper chamber

• v1.2 (2026-02-22): more tweaks for reliability; updated printing instructions

• v1.1 (2026-02-22): slightly tweaked internal geometry for more reliable results at higher printing speeds

• v1.0 (2026-02-22): Initial release