Stethoscope

This project aims to create a research-validated stethoscope whose plans are available freely and openly. The goal is for the bell to cost ~USD$1-2 to produce, and the rest of the stethoscope to cost approximately the same. You can see the peer-reviewed publication relating to this stethoscope's validation here:

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0193087

Currently, the stethoscope resulting from this project functions as well as the market gold standard, the Littmann Cardiology III.

Bill of Materials

Printed parts:

• 1 stethoscope head (head.stl)
• 2 ear tubes (eartube.stl)
• 1 Y-piece (y_piece.stl)
• 1 Spring (spring.stl)

Other hardware: Some vendors are suggested. See Bill of materials ODS file for more information.

• 40cm - 50cm Silicone 12mm or 13mm OD, 8mm ID

  • 8MM I.D X 12MM O.D NGP60 Clear Translucent Silicone Hose Pipe Tubing (USD$6.95/meter)
  • 8MM I.D X 13MM O.D NGP60 Clear Translucent Silicone Hose Pipe Tubing (USD$7.34/meter)

• 20cm Silicone 6mm or 8mm OD, 4mm ID (cut into 10cm pieces)

  • 4mm ID x 6mm OD
  • 4mm ID x 8mm OD

• Diaphragm: 40mm diameter cut from a report cover with approx 0.35mm plastic sheet

  • Staples 21639 report cover (UPC 718103160223) (USD$8.84)
  • You can cut the diaphragm by hand or with a stamp like this one

• Earbuds: Any large-sized standard earbuds will do.

  • Silicone Earbuds 7 Pairs - Large size

Optional hardware:

• Metal spring for holding ear tubes together

Print Instructions

INFILL MUST BE 100%

All printed parts should be printed with ABS or PLA plastic at 0.2mm layer height, though it is acceptable for the first layer to be 0.3mm.

We print the eartubes and Y-pieces with a brim of 2mm to ensure that none of the parts lift off.

INFILL MUST BE 100%. Otherwise, the stethoscope will not print well.

Assembly Instructions

• Insert silicone into mold and allow to set as per manufacturer instructions.
• Attach the diaphragm (40mm) to the stethoscope head.
• Attach the stethoscope head to the silicone tube.
• Attach the silicone tube to the Y-Piece.
• Attach spring to ear tubes.
• Attach the Y-piece to the ear tubes.
• Attach the ear tubes to the molded earplugs.
• Test the stethoscope as per the validation instructions.

Printing the inserts

The inserts are included in the manual directory. Using 8.5 x 11 (Legal) paper, they can be printed at 8.25" page width with 95% scale for the top print and 90% scale for the bottom print using GIMP.

The top insert is cut at 14.5cm and again at 1cm creating two labels of 13.5cm height. These inserts are printed on adhesive material.

The bottom insert is cut at a width of 20cm with a height cuts at 25cm, 15cm, 13.5cm and 3.5cm creating 10cm x 20cm inserts.

Changing and creating SCAD files

CrystalSCAD and OpenSCAD were used to create all STL files. To recreate the stethoscope head, simply do:

gem install crystalscad
ruby source_files/stethoscope_head/stethoscope_head.rb

The SCAD files output from CrystalSCAD are found in source_files/stethoscope_head/output and are named as follows:

• PrintableStethoscopeHead1Assembly_output.scad - The head
• EarplugMold_output.scad - Earplug mold

Mass Manufacturing

We generally print 3 stethoscopes per plate to ensure that each stethoscope is created out of the same material.

Our serial numbering system consists of two parts. The last number part is the total number of unique stethoscopes created since day 1. All numbers before that dash are spool identifiers involved in that stethoscope. For example,

001-010 would be the tenth stethoscope made with the first spool in our repository. If the first spool makes a total of 15 stethoscopes, then the first stethoscope of the second spool would be 002-016. If the twentieth stethoscope uses plastic from spool 002 and spool 003, it would be 002-003-020.

Other stethoscopes

Others have made 3D printed stethoscopes too. See:

• https://www.youmagine.com/designs/stethoscope-chestpiece

Licensing notes

As per our understanding, hardware is not covered by copyright. However, we present our work under the TAPR OHL license insofar as it applies.