Here is a design for a cloth + filter mask.
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Most of the world is at a “better than nothing” stage on PPE. Cloth masks filter about 50% of the particles and can be cleaned to be reused, so lot of people are pushing to make those. I’ve tried a couple of 3D printed face masks posted online. Each are multiple pieces, take 2-4 hours total print, porous surface, and potential holes from print errors.
I think 3D printing holds better solutions. Medical grade may be beyond the troops working at home, but clean, disinfected parts are possible.
My current thought is to make a small flat printed frame that can be formed with a heat gun. Cut and place a sheet of 3M HVAC filter in the frame, and secure with elastic bands. Depending on form fit, possibly adding a rubber rim with Sugru or some cut rubber tubing.
Though there’s more post processing, it should get the prints down to 20 minutes and use 15 g instead of 100g of filament. Also bending into shape nixes most of the standard Z-axis weakness of FDM. The design still needs a lot of work. I’ll post progress pictures later.
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The design still needs outside fabric securing and a jig for heat forming, but the proof of concept kind of works.
Pros:
Mask without sewing
Mass production: Shorter print time/ less filament than other 3D masks
Full filter coverage (not relying on print integrity)
Cons:
Printed plastic is single use
Single unit: printing mask and jig will take as long as other mask prints
My Net:
Sewn masks with a non-woven cloth insert beat this out, because they can be washed and reused.
What do you think? Is it worth pushing this design further?
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I applaud your ingenuity, @MerganMcfergan. I think it’s a goid start, and can be revised to make it better.
The advantage of the most recent sewing design is a pocket where nurses, etc. have been putting coffee filters, hepa filters, and whatever they can get their hands on. The version you made seems like a single layer of cloth, and isn’t reusable.
It’s a good first draft. How do you think it can be modified to match the advantages of the cloth designs?
Hi again. Thanks to Pearce & hon1nbo for the directions.
My particular interest is to develop a field engineered complete ventalator system using readily available components. Hope to use the DMS open design culture, even though the space is closed.
Seems it should be easily built in a clean shop and then sterilized as easily as a piece of commercial kitchen equipment. Then would publish plans and build a few hundred & give them to hospitals. I think the FDA piece must be handled properly, Think that will be possible, but it doesn’t matter until there are actual devices. BTW, these devices can be made simple because they could be used for simple and direct cases, leaving the legacy machines to handle the complicated cases.
Personally, have been studying these machines for a few hours. Below I ask any qualified member to contribute a couple of off-the-top-of-their-head numbers.
- Looks to me like a simple 2 stroke engine.
- Need the mixture to be at right pressure, temperature, humidity, flow.
- Need to be able to clear unwanted fluid from the exhaust side.
Somebody: numbers please. Just 2 questions here:
- For a “typical” (sorry I don’t know a better word) use case, at what temp(), pressure(), humidity(_____) to deliver volume(_) what number of times per minute().
- The exhaust cycle should start(patient controlled or timed) seconds() after the end of the intake and should be at a max negative pressure of ().
With the answer to these questions the device can be sized and power requirements determined. I think the values will allow for the build of tabletop unit. If the intake is mostly the atmosphere, then perhaps a floor standing plenum could feed several individual units the right conditions. Got any takers? Somebody that knows a typical range of these valuers please throw them in on a 1st pass level! Thanks.
Thanks @Holliday! My note was really a long winded vote for hand sewn masks. I provided details of my attempt hoping to spur someone else’s innovation.
Regarding filter material, I have the filter wrapped around a large ring and pushed through the smaller mask hole. The securing system on the front could handle your choice of 2-4 filter layers. I just stopped the testing at one layer of fabric, because single use can’t beat washable/reusable.
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I’ve printed a sample of all the face shield STLs that could fit my printer, but I think this lady’s hand made version is a much efficient for time and materials: https://www.youtube.com/watch?v=5PMYPAuA5Fo
Material supplies on Amazon are getting short, but there was still plenty to get a small production run.
Digging through that North Texas Mask Makers group, there are a lot of medical professionals actively working to get these goods. https://www.facebook.com/groups/519935795386447/
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Is anyone making/needing the Prusa shields?
If we modify the shield size very slightly then we could use over head projector slides, of which I have hundreds !!! (8.5"x11")
I would really like to do what I can, but so far I have not been able to find a good place to determine if these are needed in the DFW area, nor how to contact anyone to try to make it happen.
Is anyone at DMS actively working with health organizations on actually getting home manufactured face shields?
Regards,
Steve
Harbor freight still has the metal mesh face shields (for wood activities) you could tape the transparency to it, literally.
Cheap, no, but reasonable, and the have good reviews for the annual spring lawn cleanups
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2 depends on which mode the ventilator is in and is only slightly more complicated than can be summarized in a single question.
source: https://simulation.health.ufl.edu/technology-development/open-source-ventilator-project/
I’m making these:
And created this bottom support for it:
Uses standard 8.5”x11” transparency sheets as the shield, and the holes are spaced for a 3-hole paper punch. Downside is that only one set will fit on my Prusa’s bed and they are taking 69 minutes per set to print.
(Using paper instead of a transparency sheet for better viewing of the parts. Original part is in grey, my addition is in blue.)
I can print 15+ a day. I’ve sent off 4 to a nursing friend of mine on the “front lines” in Austin. He has approval from his management to use them. Awaiting feedback on the first batch while I continue to print more.
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Thanks benemorius. I have a “kind of” functioning system that can follow a set of user controlled rules. I’ll add to it today and can send you a video of it working. Can we talk? If yes, please call me. Chuck McCoy 214-394-5832
Hello SteveDC. My business partner has and is organizing to do exactly that. We have about a dozen printers at the office now and are seeking to crowd source more print hours. Give me a call if you’d like to engage. Chuck McCoy 214-394-5832
So, my high school robotics team have managed to focus in on a plan and a design they are going to produce.
They have managed to establish contacts and ‘clients’ and we have started producing shields based on the Columbia University design (https://studio.cul.columbia.edu/face-shield/)
If anyone is interested in the Woodrow Wilson effort, or even possibly donating either printer time, money or supplies, you can read a little bit about it here…
https://www.therobocats.com/covid-19-face-shields
Steve
Excellent work!