Tuesday, April 21, 2020

COVID-19 Printing Projects

People all over the country are printing stuff for healthcare workers to help make up for shortages of PPE even though we have the GREATEST healthcare system in the WORLD! 
I have been doing some printing with a bunch of people from the Milwaukee Makerspace.

Bias Tape Folders

First it was bias tape folders for people sewing face masks. People were printing a design from Thingiverse.  I loaded up the bed and printed 50 of them in one go.  It took something like 20 hours. The design was excessively solid- like you could drive a tank over it.  Unfortunately I didn't keep any photos of them printing.

The original bias tape folder design from Thingiverse.  This is used to fold thin strips of cloth so it can be sewn to the edges of masks. It will never have any real mechanical force applied, yet the walls are 2 mm or so thick.

I redesigned it using the basic dimensions I pulled from the STL file on Thingiverse (why don't people post the CAD files?).  The new design used much less plastic and printed much faster because most of it is just 1.2 mm thick perimeters, so 3 passes with a 0.4 mm nozzle.  I printed a couple batches of 77 parts at a time, about 12 hours per batch.

My bias tape folder design.

The new design is more than solid enough to do the job of folding strips of cloth and will easily withstand being stepped on, though I can't say the same about the foot doing the stepping!

77 at a time.  I probably could have bumped it up to a 9 x 13 array.


Next was earsavers for people who wear the masks with elastic ear loops. I know from experience that those things can get pretty uncomfortable. 

Earsaver in use.

I printed a dozen of the preferred design from Thingiverse and it took 2 hours and 28 minutes. I managed to break a couple of them when I tried to pry them off the bed. Looking at the design and the way they print I decided to see if there was a better design out there, so I checked all the remixes on Thingiverse and didn't see anything I liked. 

The Thingiverse design for earsavers.  I can fit 12 on the bed at one time.

It was time for another redesign. There were numerous problems with the original design. It was too thick and inflexible (that's why they broke while I was taking them off the bed), there were many areas where the extruder has to lay down infill, which takes much too long, and there were too many sharp corners, all of which slows down printing.

Come on people!  We're trying to use a slow process (3D printing) to mass produce stuff as quickly as possible. You have to think in terms of how the slicer and printer work to minimize print time.  The forces applied to an earsaver by the elastic ear loops in just a few 10s of grams.  It doesn't need to be thick to do its job, and it's better for wearer comfort if the thing is flexible, and that means thin. If you want it to print fast, you want perimeters only. That means the structure of the print should be a small whole number multiple of the line width. Infill takes a long time, so eliminate it!

I designed the new earsavers so that everything would be a perimeter. I copied the gross dimensions and shape from the original STL file. The ribs are 2.4 mm wide, so 6 passes of a 0.4 mm nozzle at perimeter speed, and no infill. They print in only three, 0.25 mm layers using about 1 g of filament each, and 12 of them print in about 37 minutes (at 150 mm/sec).

Earsavers from Mark Rehorst on Vimeo.

The new design earsavers print in <1/2 the time and use much less filament, and come off the bed without breaking. They flex easily so are more comfortable to wear than the original design.

Here are the Fusion360 CAD files for my bias tape folder and earsaver designs.  You can DL the CAD files or just export STLs.

For anyone building a 3D printer, notice the location of the prints and the skirt in the photo above. You really can print literally edge to edge on the bed without autotramming and auto zeroing if you build the printer right.


  1. Hey Mark, here in Beautiful British Columbia more than six hundred 3D enthusiasts self-organized ad-hoc to pump out ear savers and face shields, see https://www.bcc3d.ca. The ear saver design we're using is a bit heavier than yours but still much lighter than your first example. Keep up the good work!

    1. Thanks! I'll check out your earsaver design. There's always room for improvement!

  2. Hi Mark!

    Got here from Hackaday :) In case you're looking for a way to increase your bias tape maker yield, I've been able to nearly double my tiny printer's capacity by printing every other bias tape maker upside down and packing them closely together.


    Keep up the great work!


    1. That's a great idea! I can probably get close to 200 of them on the bed that way. Thanks!

    2. Sure thing! The only downside is the now 40+ hour print time LOL.

      I tested mine out slowly - can I print one upside down, then one up and one down, etc. Obviously bed adhesion is important, because I've had one loose bias maker take out two neighbors.

      For what it's worth, my delta can print these about 1.5-2mm apart as long as I keep the speed down to 50 mm/s or so.

      Good luck!

  3. how about some flexible nose pieces?

    1. Nose pieces for what? You'll have to be more specific...

  4. Hey Mark,Thank you for the explanation of why and how to get rid of the infill for the ear savers. I had been printing a version of the popular design and reduced it to 3 layers, similar to you. It is strong enough for sure. I delivered 40 pieces to nurses at a local hospital. I gave them some with a hair comb and some without. Overwhelmingly, the girls wanted the hair comb version and in fact asked me for more. The boys wanted the regular version. So I took your design and added some 'tines', making their width a multiple of 0.4. Now I have a fast print plus the design feature that is being asked for. Here is a screenshot: https://photos.app.goo.gl/5jWNtnyrQYXmshqP7. Should I put the remix somewhere? I don't think you posted to thingiverse did you?

    1. Looks good! I didn't post on thingiverse, but it would be a good idea to put it somewhere that others can get to it.

    2. Hey are you gonna post the comb version please so I can print some of those too
      PS what material are you guys printing these in

  5. Hey Mark,

    I really like the design and appreciate the speed and efficiency at which you can push these out. Can you submit this to the NIH? I've been using the NIH one that you posted first and while I appreciate efficiency, I also like the fact that any hospital administrator can point to that review and say look at least someone has blessed this and not ban their nurses from using it.

    https://3dprint.nih.gov/discover/3dpx-013410 is the link for the initial version and I've been doing this on a site here https://opearsaver.com/ where I've worked with others and we've delivered several hundred across the country so far.

    I'd love to switch to your design because it would be much faster and cheaper to build, but I won't without someone giving it top cover.

    1. Thanks, but I wouldn't know who to submit it to at the NIH.

    2. You sign up for an account at 3dprint.nih.gov and post the STLs to the COVID-19 collection; they are reviewing community submissions for being appropriate to use in a clinical setting.

    3. I love this ear saver design. I packed 16 on a 330mmx330mm bed, and I'm fairly certain with more work I could fit more. I've confirmed that 14 can fit in a 285x285 space with room to spare.

      I posted the STL along with the 16-way layout I came up with exported as a single STL at https://forum.makerforums.info/t/improved-design-for-3d-printing-ear-savers/80095/2

    4. Submitted to NIH: https://3dprint.nih.gov/discover/3dpx-014026
      I managed to fit 15 of them on a 300x300 bed plate. It's a lot easier to do in CAD than to try to do it in PrusaSlicer!
      Here's 15 of them arranged on a 300x300 bed:https://drive.google.com/open?id=1h7kHyv5BGDMXvat4yr_P-Gp5sRGCfujw
      Here's a single piece: https://drive.google.com/open?id=1bYHcXgWYJe2UXc73xeKmbaWK6uGflRFj

  6. I manage broke the ear saver at the branch split. Is it possible that
    1) make the whole think smooth finish,
    2) reinforce the split area
    These will enable for easy to clean, and stronger.

    1. I would not have expected anyone to clean and reuse these. They are more of a use and throw away type part. You could always make them a little thicker if you need more strength- just scale the Z axis in the slicer to increase thickness. I print them in ABS and they're pretty tough. PETG would probably be good, too.

  7. A nurse in my neighborhood said that they are wearing scrub caps, so hair tangling isn’t an issue for them. After trying the first set I printed, she asked for me to print them slightly thicker because they were damaging the ear loops of the masks they are sterilizing and re-using. Scaling Z only by 200% makes them five layers with 0.3mm layers, so I’m trying that for her next. She says that she expects the thicker ear savers to be gentler on the mask loops. This way they are definitely strong enough to disinfect and re-use. I'm printing them in PETG now, which should survive wash-and-reuse fine.

    1. I use ABS- I didn't know anyone would be trying to reuse them- I figured they were use once and throw away.


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