Printing LRTee

This part is designed to be printed in either PLA or PETG. When sterilized, either of these materials are likely to be usable in last-resort circumstances.

Printing in PETG

Printing in clear PETG is recommended due to its slightly more flexible nature, toughness, and resistance to elevated temperatures (up to 70C without significant shrinkage/warping).

We've also found that PETG seems to print slightly less air-tight than PLA, but this can be greatly improved by over-extruding. Setting the "extrusion multiplier" to 1.2x (and using the associated STL file that compensates slightly for the increased print size) produces a much more air-tight part.

Printing in PLA

Note that PLA is harder and will shrink more (when heated/sterilized) than PETG. As such, if printed in PLA a sterilization "bath" may be preferred instead of using a low-temp sterilization machine (which seems to still get up to 50C or more) to keep the part from shrinking beyond tolerances for an air-tight fit. If a PLA part will be sterilized (for example, with a low-temp VHP machine), printing at 101-102% is suggested so that the part is properly sized after shrinking.

See the image above for a comparison of shrinkage characteristics along critical dimensions for various annealing temperatures.

Printing Notes

While the parts should print very cleanly, it's good to double check that all fittings are clean and free of extraneous globs of materials to ensure the best connection possible.

The parts should be able to pass the ventilator system's automated "leak test" directly off the printer with no significant post-processing needed.

Infill of 100% should be achieved by using a very high number of perimeters that force smooth, solid printing throughout the build.

Supplying LRTee to Hospitals

If you intend to print LRTee splitters and supply them to local hospitals, we recommend following these steps:

• First, contact the hospital by phone where you intend to supply the parts and see if they are needed/wanted as a last resort.
• Assume you are infected and act accordingly at all times (COVID-19 can be asymptomatic for some people, and protecting hospital staff is critically important). Wash hands and don't handle any more than necessary.
• Use the highest quality PLA or PETG you have. Using pure/uncolored materials is best to limit the addition of other unspecified compounds in the plastic.
• Make a test print. Depending on your printer's setup, you may need to tune settings to get the best print possible.
• Print the associated parts as specified. Note that it takes two (2) splitters for each additional patient, so it's logical to print and supply them in pairs.
• When the parts are finished, try to knock off any burrs, globs, or stringing that could interfere with their operation. You may also be able to gently fit the parts into each other and twist to get a sense for how smoothly the connectors fit.
• Place in a sealable/zip-top plastic bag.
• Print and fill out a form to help the hospital and make certain that you, as a maker trying to help, cannot be held liable (see “LRTee - Hospital Intake Printout.pdf”).
• Place signed and dated form in the bag with the parts and seal.
• Call ahead and schedule a drop off to appropriate medical personnel.