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.

Earsavers

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.