In the effort to fight COVID-19, the precious plastic community and the rest of the open-source/DIY people are trying to find smart ways of producing PPE. We have noticed that in many countries face shields (visors) are one of the lacking equipment and people are desperately trying to produce them. Most solutions rely on 3D printing which is precise but very slow. In plastic production, extrusion is the fastest. We have decided to use the standard precious plastic extruder (v.3) to offer this novel design of the shield mask.
We have reviewed the standards for making face shields and the recommendations of doctors to design our model. Of course we have been very inspired by many efforts all over the world that tried to find solutions. We have focused on the Badger shield first as it was the first validated DIY solution we found and it is now mass produced by Ford. It has also measurements which we used. We also used the only extruded Precious Plastic solution from Menor Plastic which includes a video tutorial. And we of course used ideas from 3D printing designs that offered solution on using standard A4 overheads, principally this one and the “Prusa” shield. That have been validated by hospitals
Our designs tries to ameliorate several things:
- using less plastic possible to produce faster.
- Being most comfortable with a clear gap between face and screen
- have a better, secure and adjustable attachment
How to make a face shield from basic elements and the extrusion machine
Face shields are critically lacking in many countries affected by COVID-19. You need up to 22 per patient. We need a DIY way of making these and making these fast. Remember that face shields are only a complement to googles and masks and are meant to reduce the viral charge. Notice that we have a simpler tutorial on Precious Plastic community website.
Make a die to attach to the extruder
The die needs to have a relatively large entry and a tapering end. The best is to have some bars to cool down a bit the plastic and funnel it towards the exit. The outside plates are only 1mm apart. You can also do it without die by stretching the plastic straigth from the nozzle but it is even more complicated to control the thickness and elasticity of the future band.
Extrude the stripe
This is a delicate part and needs improvement as you need to pull the plastic out so that the thickness and flow is even. First the die is preheated, cleaned and lubricated in the oven at 165︒C. You need to initialise the flow by heating up the nozzle. We made a video of the struggle when the die is cold.
Because of changes in the thickness and rate of cooling your stripe might twist We heat it up back with the hot air gun and pass it inside our metal mangle. This will straighten the band. Don’t expect miracles, you will keep the concave shape. To circumvent this problem we are building a conveyor belt that stretches and flatten the plastic die. With the conveyor belt, the plastic stripe is slick and doesn’t wiggle. You can roll it around a barrel to give it the right shape before cutting. overall at the moment we have 5% loss on the stripe length due to quality changes. The quality changes due to overheating of the rollers or change in the plastic extrusion rate. Discarded plastic is shredded and extruded again.
Based on the work on the Badger Shield, we can see that ideally the contact with the head should be 13″/ 33 cm. Since we want air to flow between the face and the screen to avoid fogging, we make a 44 cm stripe.
Here we have used HDPE from ocean plastic. We regularly recover large quantities of it on the local beaches. We recommend HDPE as it is easier to source, as a low temperature to melt and release very few fumes. Our extrusion machine is set at 140︒C at nozzle and 135︒ in the barrel.
stripe hand pulled Stripe wriggling, needs to pass into the roller press (metal mangle) High quality stripe coming out of the conveyor belt Roll the stripe around a barrel to shape it and count how much you made! 20+ metres of high quality stripe of HDPE
Punch holes for the attachment
The best for the attachment is an elastic band for clothes but we didn’t have any so made with a rope like in the example of Menor Plastic . However to avoid making knots and for an easy attachment you can simply punch a set of holes A square wood chisel size 10 is perfect for that. You have to make 3 sets of 2 holes and one set of 3 holes at one end (could be two if you use rope).
You can also use a leather work oval punch for a better and faster finish. Ideally you have an Arbor press to attach your hole punch but here we used the drill press. Please follow our little tutorial video below.
Lace the plastic band
Follow the right order for comfort, according to drawing The 2-hole design allows to tighten at any size of head quickly. The third hole design is to pass the elastic band in a very secure latch.
Knot to attach the head band
Staple or clip the screen
Staple the screen
The advantage is that it is fast and quick to secure. The disadvantage is that you cannot sterilise and reuse your screen.
Try to centre the screen with your attachment then staple from one end over a piece of wood, the sharp legs of the stable outward. Then lift by leveraging with a blade between the screen and the wood. 3 staples suffice one on each end and one in the middle, going progressively from one side to the other. Keep the staples open until the screen is really tight on the plastic stripe you extruded. You can repunch the screen to adjust if needed. Then close the staples with your fingers or a piece of metal.
Punch the screen with A4 perforator
Instead of stapling you can also use car clips with a tree profile or even easier to source, 6 mm wall plug holes. Ideally you can use a 4 holes A4 punch perforator. Or you can use a heavy duty punch such as the ones for leather or metal work or if you are quite careful a wood drill of 5mm. If you manually choose the spacing you need to have at least a hole on each side and one in the middle. Clips can be through the holes, their tips pointing outward. To attach a wall plug, you need to force the plug through the plastic stripe towards the inside of the mask so that the rounded bit is close to you. It will be hard as it is slightly more than 5 mm but will secure the plug inside the plastic stripe. Then you cut the head of the wall plug so that you can keep the diameter to its minimum. You can then place the screen in. If you work outside and you are worried that the screen might fall, you can open the plug as on the second picture. To be 100% secure with the fixation, you need to put the screen on the inside so that the clip squeezes it onto the plastic stripe.
face shield v3 with car clips
The plastic sheets can be sourced from acetate overhead (>0.25 mm), a cut soda bottle or from a lamination machine (we laminated two ends together, as proposed by some Belgian doctors). The visor takes on most of the designs of approved PPE with a minimum of resource and should be working as expected. Some shields close the top of the screen towards the head. It is not recommanded as it will make the screen foggy and potentially make you sweat and put fluids in contact with your mouth or eyes. If you want to put to close the screen, you need to build a respirator system with it. In addition, you need to wear a mask and ideally googles to protect from the entry points of the virus. Your mask needs to be as dry as possible to reduce the viral charge.