3D Printing - Covid mask #2

Crazy time !  Another 3D print of a mask that claim to protect from the virus.

I am kind of skeptical about the feasibility and functionality of such solution, then I did find some people pointing out to a project.




At this time I'm NOT endorsing in any way to use this mask as real solution since too many questions are unanswered !
First of all, here some links to this project and its story.
This mask design apparently is coming from a clinic, the Billings Clinic in Montana.

• Billings doctor interview
• Billings clinic
• Billings STL
• Billings mask source file
• Billings Instructions

Is quite important to state that currently this, and similar projects, need to be considered a way to prolong the life of common surgical masks.

These are NOT TO BE CONSIDERED equivalent to N95 type masks !!!

Let me be repeat that :  

THIS AND SIMILAR PROJECTS ARE  NOT  DESIGNED TO BE  EQUIVALENT TO N95 MASKS !!!!

G-code file preparation

Once downloaded the STL files I did opened with the slicer Cura 3.6.0 on LXDE Ubuntu 18.04.

The project is divided in three parts, so three different STL files are present.

Here the setting I used for the two  STL files in the project:

• Material : Hatchbox white PLA 
• Printer : Ender 3 Pro   (stock but with yellow springs and glass bead)
• Shell :
• Wall thickness : 1 mm
• Wall Line count : 2
• Infill :
• 10
• Cubic
• Material :
• Printing temperature : 200 C
• Build plate temperature : 60 C
• Initial Printing temperature : 205 C
• Initial plate temperater : 65 C
• Enable retraction
• Speed :
• Initial print speed : 35 mm/s
• Print speed : 60 mm/s
• Build Plate adhesion :
• Skirt

The file was then uploaded to OctoPrint for the print.

Instructions

On the Billing website there are instructions about how to prepare the mask.
I copy them here :

Printing the Files 

• Two .stl files need printed per mask and are located at www.LongLiveYourSmile.com
   (don't understand the website above, is not containing any project)

• We suggest PLA material 

• Takes 3 hours and varies printer to printer 

• Designed to be printed without supports 

• Print an array if possible, source file is included if one would like to modify 

• Designed for Adult Large, scale to 90% or less for smaller masks 

Making the Mask 

• Sand around the edge touching face with 200 + sandpaper 

• Fasten elastic cord to the attachments and adjust to desired tension 

• Elastic chord, string, straps, or any variation can be used as ties 

Placing Filter 

• Existing clinical masks can be used as a filter by cutting them into 2.5 in squares, can get 6 filters from one mask 

• Replacement filters can also be ordered from High Tech Filters Shane Rekdal 800-785-6985 or email shane@flowmarkhightech.com 

• Place filter material on the inside of the mask and fasten by pushing holding ring and filter together into space 

Aseptic Technique 

• These masks are reusable, but each person should have their own 

• Masks can be cleaned and disinfected by soap and water as well as disinfectant agents 

• Practice good hygiene by washing hands before and after changing filters and removing mask 

• Clean mask often, change filter often

Results

(the results will be updated as I will be able to run more tests)

The project is composed by 2 files.

• a mask 
• a filter holder

I just had to rotate correctly the filter and the mask to be printed on the correct angle.
Other than that no problem.
About 40 minutes for the filter holder and 3 hours and half for the mask.

Comments

Well, in a way the mask is similar to the previous one I tested.
It takes less time to be printed out and the wearing seems similar.

However I don't like the way the filter need to be attached to the mask.  The filter cap is not guarantee any and sealing, leaving small gaps between the mask and the filter holder.

There are some important questions to answer in this particular application.

1. Is PLA suitable for the application ?
   Specifically :
1. is it safe to breath through it ?
2. Is it possible to disinfect it ?
3. Is it sturdy enough ?
2. What is the best design ?
3. How long can be used ?

PLA (PolyLactic Acid) is generally non toxic  (see Everything You Need To KNow About PLA) so in theory should be OK to have it in contact with the skin and breath through it.

The PLA is considered to be a porous material and thus this could be a problem.
Dirt and thus viruses could enter easily in a pore and be difficult to clean.
However it depends about how to clean it.

Somebody suggest to use a solution of Sodium Hypochlorite (bleach) and water.
It seems a very effective solution against the corona virus (system used by the Italian Red Cross to clean up the ambulances after transporting infect people).
Maybe nebulized or immerse the mask in it and leave for at least an hour.

If the solution is not damaging the mask (melting) and if after it can be cleaned with distilled water (really not good to breath vapors of Sodium Hypochlorite) then the mask should be probably used.

Alternatively to sanitize the mask is probably possible to place it in a small environment filled up with Ozone for few hours.

Another point to be explored is how good the filter operate and thus how to attach the filter to the mask.

Mechanically speaking the mask is sturdy and should last safely for few months at least.

Conclusion

At this time I can not say these masks are to be a viable solution, still too many unanswered questions about the safety of the material and the sealing capability and the air intake and filtration.
Probably I can say that is better than nothing but there is no guarantee they can prevent the virus to enter or exit the mask.
Again, if the choice is between this and nothing, then of course go ahead.

The cost is low enough but it takes anyway about more than 4 hours to print one plus some extra time to prepare the mask and anyway filters are needed, so if you don't have surgical masks then this mask is totally useless.