Making Protective Face Shields with a K40 Laser Cutter - Part 3

Part 1 Part 2

We finally had a chance for the household to go ahead and make some shields.

Cleanliness

This was tricky, I don't have gloves, but do have a face mask each that covers our mouths and noses. So, I would not count these masks as sterile and as such have been careful to pass on that information to recipients.

So we had frequent hand washes and (for what its worth) baby wipes to wipe down the plastic that gets a bit of a dirty residue from the smoke produced during cutting. 

Fortunately the masks are easy to clean.

Finding Recipients

While waiting for the laser cutter to do its thing (about 8 mins / shield) there was plenty of time to open up Google Maps and search on care homes nearby. I emailed (where there was an email address on the website) or otherwise phoned a total of 5 homes within walking distance. 

One asked for 12 on the phone and was very grateful as they had no face shields at all. Another said the same on email (yesterdays delivery). And already we have two more deliveries to make tomorrow to care homes and GP surgeries. There is clearly a huge demand here in the UK.

What Next?

The next step is to find a cheaper source of material than eBay! and find out if there is a better way to distribute.

Although it seems that hospitals are the main focus and care homes and GP surgeries have rather been left to fend for themselves. So I feel that providing them with masks, fits both my small scale of production and a need that if it reduces infections will lighten the hospital load at the front end.

Making Protective Face Shields with a K40 Laser Cutter - Part 2

In part 1 of this post I looked at laser-cutting the plastic band. In this post, we can now attach the clear A4 sheet to the shield.

I used this from eBay with a thickness of 140 micros for the visor, which seems about right.

The A4 clear 'acetate' sheet fits in landscape aspect ratio and is punched with 4 holes. I used one of these:

.. and put one pair of holes in the middle, as you would a normal sheet of paper for a ring-binder. I then carefully put the other holes in at the edges by lining up one side of the hole punch puncher with an existing hole. This is fiddly, so 
Edit: This works fine,  didn't realize that if you push the guide rail on the side most of the way until it says A5 (on ours) punch one set of holes then flip the acetate sheet through 180 degrees and punch again, the holes are in the right places. Try this on paper first to avoid wasting acetate.


I have ordered one of these: which should make all the holes in one go.

The little plastic tabs on the strap fit snugly into the holes and hold the 'acetate' sheet in place.

Review

The inner band holding the head away from the visor works well and prevents misting up. The whole thing was comfortable even wearing glasses. I'm sure its a way from rigorous professional protection equipment, but I think its a lot better than nothing, or just a face mask on its own.

It's also entirely plastic and I would have thought washable. I have three of these now, which we are going to send to medical and carer friends of ours who have expressed an interest.

Now I know its possible on A4, I'm ordering more materials and we'll get cracking. I'll come back with a part 3 on manufacturing cleanly and experiences in donating these.

Other Resources

This all stems from the work here https://community.andmirrors.co.uk/t/covid-19-laser-cut-face-shield/168 and https://www.kitronik.co.uk/blog/kitronik-make-nhs-frontline-ppe-visors/

There are lots of other projects and designs out there and Google will stay a lot more up to date than any list I put here.

Making Protective Face Shields with a K40 Laser Cutter - Part 1

This blog documents my efforts to make protective face masks using a low cost K40 laser cutter using Kitroniks visor design.

The A4 'acetate' sheets for the transparent shielding bit haven't arrived yet, so consider this post a Part 1 , dealing just with making the strap shown below. The clear visor part will come later.

Early indications: Yes, it's feasible - if you have a K40, give it a go.

K40

These laser cutters are very low cost, but only have a small bed (about 330x220mm useable).

Their bed is much too small to take the files that Kitronik designed for their cutters, but if you have a bigger laser cutter then don't mess around with A4 it will be much more efficient to go to the full-size design here.

Design Files

Download the design files for A4 from github here or direct zip download here. The original DXF file was created by Dave at Kitronik and kindly passed on to me by Loraine Underwood, a fellow K40 owner (hers is in bit ATM)

The file A4 face shield band.dxf is the original file from Dave. I use the open source K40 Whisperer to control my K40, and this expects files to be an SVG, with vector cut lines to be in red 0.1mm wide. So the file A4 face shield band k40 whisperer.svg is an SVG version of the original with the lines made suitable for K40 Whisperer. I have also spaced things out a bit, because the K40 can be a bit 'melty' and close together lines can cause problems.

If you make a version of this for the default and highly suspect original K40 software, then please let me know and I'll add it to the repository.

The really nice thing about this design is that it just uses two materials, 0.5mm Polypropylene for the strap material and standard clear A4 OHP acetates (used full size without the need to cut). Whats more everything just clips together, no need for glue or staples.

Material

I bought a few sheets of Polypropylene Plastic Sheets 0.5mm here. It seems to be quite widely available as A4 to try. I now need to wait for a load more. Kitronic also sell this material, but not as A4. However buying some big sheets and cutting them up may work out cheaper.

Eventually you will need the clear 'acetate' sheets to use as a visor - Kitronic recommend this. My sheets haven't arrived yet, they will be discussed in part 2 of this blog.

Cutting Parameters

Your parameters will vary so, please cut a small test piece before wasting material. This was what I found worked best for my K40. Speed for vector cut 15mm, power (set by the knob on the k40) about 50%. My beam seems to diverge at higher powers than that, but I probably don't have the focus right.

The material is quite light, and I have seen people use small magnets in this situation to keep the parts flat to the bed. I didn't use magnets and it worked ok for me. But if yours starts flapping about, you know what to do.

Assembly

Please note that what I am describing here is making the first visor so, I am paying no attention to cleanliness at all. When making these for real, I think it would be sensible to be gloved and masked.

It took me a while to figure out how the pieces fit together, so here's what I learned. I have put numbers on each piece to make it easier to reference the parts.

1. Here's the cut sheet.

There is a bit of singing and in places the plastic had stuck itself together again. But I found it separated from the sheet easily enough.

2. The Pieces Labelled

For your first make, I'd suggest marking each piece like this (a sharpie will do). Or you may just be a lot better at puzzles than me and consider all this unnecessary!

3. Join Pieces 1 and 2

Bend the tabs of piece 1 and push them through the horizontal slots in part 2.

4. Join Pieces 2 and 3

Piece 3 feeds through the two end vertical slots in piece 2 like a belt through a buckle.

5. Join Pieces 1 and 4
Piece 4 fits on to piece 1 in much the same way.

6. Outer Strap
You should now have a long strap.

7. Inner strap
The inner strap is required to keep the clear part away from the wearer's face. Piece 5 accomplishes this by making a bow in the main strap.

Start by joining piece 5 to piece 2 and then to piece 1 using the horizontal slots.

8. Final part
The basic shape is there now, so it just remains to attach the buckle that connects the two ends of the strap together.

Join 4 and 6 together first. These have two positions, presumably for big and small heads. Fine adjustment of size uses piece 3.

My Donation Plans

Making these on a K40 is slow and so I don't expect to be making more than a few hundred of these visors at most. So, personally, we will be donating these to care-workers and other people we know who are desperate for protective wear and not too worried about the quality on the basis that something is better than nothing. I think, I'll leave supplying to the NHS as something for the big players (with big laser cutters) to do. But that's just what I think.

I hope to post part 2 of this tomorrow, if the clear plastic arrives.

Good luck and let me know how it goes.