COVID Face Shield Remix–3-Post Version of Prusa’s–A 3-Hole Punched Transparency Film

This remix is the first model I’ve ever posted as a fairly new-to-the-game 3D printing+ dude: <1 year since I started this as both an educational tool and then a hobby (obsession). Please forgive me for any newbish screwups.

This remix of the fabulous RC3 version of Mr. Prusa’s COVID Face Shield takes advantage of something I noticed only due to being a long-time teacher.

tldr: the text describes using Overhead Transparency Film for the shield portion on the RC3 as is. Additionally, I have created a 3-post version of the headband, and a few other things. See the breakdown at the bottom.

Or, read this unnecessarily long description of what I did and what motivated that.

Upon reading the initial blog post soon after it was published, I wondered if you could use OHP* Transparency Film as a low-cost, and usually easy to get, substitute for the transparent PETG for the shield part. In fact, I wrote this as a comment, sort of wondering out loud. (See: (https://blog.prusaprinters.org/from-design-to-mass-3d-printing-of-medical-shields-in-three-days/#comment-16201)

After screwing around with it for way too long, I found that it seems** to work well enough as a replacement if you have the transparency film already (like I do–several hundred sheets) or can’t get the other, proper materials as indicated in the release and printing information.

What makes this different and need a remix? Actually you can use the official RC3 parts and just punch holes in the correct places. If I have the time, I’ll post a template and/or measurements for this too. I planned to do that a while back, but when I tried, it seemed to require that I include a .stl file so I left it as an unfinished draft.

However, interestingly, I found that the two outside posts shared, by design or by accident, the same displacement*** as the two outside holes in a typical 3-hole punch device. That means you could remove the center die and use a 3-hole punch to get nearly perfect outside holes. I have made several of these face shields this way (hopefully there are pics of those too attached).

Or, you can be totally extra and redesign it so that there are only 3 holes! Well, I did. And thus this remix.

Soooo, I (amateurishly) added a middle post and removed the other inside ones. There is a whole story behind that if you’re interested, btw. It’s a tale of Woe, Calculus, and Newbicity. This crap is already too long so I’ll skip it for now.

The logic behind this remix was that you could 3-hole punch a million, give or take, of these OHP films fairly quickly and have multiple, disposable and ultimately replaceable shields.

Known Issues/Contemplations:

1. OHP Transparency film is not as durable as 5 mm thick PETG transparent material.
2. They are around 5 mil thick, which is about 0.1 mm.
3. The film’s properties varies wildly by brand and from type to type. I have 3 different kinds, and all have their own pluses and minuses. Note:
   
   a. Some will tear at any crinkle—avoid using.
   
   b. Only 1 of the 3 seemed “totally” transparent. Test. The types I have the most of cause a bit of blurriness, especially for objects at a distance.
4. Using OHPTF as a substitute is probably not good enough in professional settings and/or severe conditions. Okay for the grocery, probably. Not recommended for surgery unless you’re really in a pinch.
5. I have not included any files for the bottom or for the bands.
6. I and these files are not endorsed by any health agency. These mothers could be the worlds best breeding grounds for viri, virii, and/or viruses, et. al.
7. I’m just a guy with some time doing a thing. Mr. Prusa did a good thing. I thought this might help someone somewhere do another thing good-like.

I have included the following stl files:

1. 3-Post/Hole remix of RC3: same thing but two interior posts removed and a new one place in the center. Lines up with a 3-hole punched OHP transparency film.
2. Same, but half as tall: a 50% z-axis reduction version—post sizes are the same, everything else is reduced by 50%, including the text and the band attachment posts.
3. Retaining clips that fit on the full-sized version—to be safe, I designed some clips for the two edge posts/holes. The idea was that this was flimsier and might need it. However, it seems to work well without if the sheet is tightly fit. I include them anyway.
   
   a. There are several versions. I even mirrored them for each side.
   
   b. However, I decided it was asinine to have parts that only fit one a certain side. From my tests, they fit on either side so its not important to have 2 versions, or to even have to have them in the right place.

Hint: curl the transparency film by pulling it down vertically on a solid horizontal surface.

*Overhead Projector
Disclaimer—I know nothing.
the arc length of the curve is the same as the linear displacement of the two outside holes