Update 29/04/2020 I have uploaded the basic sketch of the mask for use in fusion360. This is just the basic simple sketch.

31/03/2020 If you are looking for a hard shell design I have this one. It can be printed in both PLA and TPU combined. https://www.thingiverse.com/thing:4243998

17/03/2020 - 5 The different sized nose pieces were not a good option. I spent some time and came up with a small and large version, depending on which size mask you choose. The holes of these should be a little easier to fit over the pegs. Bending them is easy if you place them between your fingers and place the centre under some running hot water straight from the tap. As it softens just squeeze the two sides together to the desired spacing. You can make them tight as they will spread apart.

17/03/2020 - 4 I uploaded a slightly altered valve (Valve v3) that is a little thicker and a slightly larger diameter. I find that this model prints a little better than the original and provides a slightly better overlap. I will leave the older version in case it works better for some users.

17/03/2020 - 3 I didn't like how the nose clip was fitting so I made several different versions based on length. These go from 34mm to 46mm. Select the size that fits best for your face/nose. These can be bent by heating the PLA with a hair dryer or placing the part in hot water for a short while. Sorry but they will need to be flipped over for printing.

17/03/2020 - 2 I have just uploaded a small version of the mask and a small nose piece. Sorry but I don't have anyone to test this on. It uses the same cartridge parts and valves. Please leave comments so I know what I have to do to fix these.

17/03/2020 - 1 If you are having difficulty snapping the mask together please read the comments where I have provided a couple of suggestions. I have uploaded a 2nd version of the original cartridge (Cartridge V2) where I have added a chamfer to the inside diameter. Hopefully this will make it fit the mask part easier. I have not test printed this yet so I am leaving the original Cartridge file available for download until I do.

16/03/2020 I have uploaded a newer mask replacement that has a reinforced connector edge as well as a better folding design. The snap portion will close with less of a gap at the bottom as well as in the middle of the ridge. It also has slightly higher nose posts to allow the PLA nose clip to fit a bit better. I have also included a flat style filter cartridge that works better if you are using a flat piece of filter cut in a circle as your filter. This piece can be printed in PLA or TPU.

If you print 2 valve separator per vent, a valve can be connected to one of the separators and the two can be sandwiched to produce a movement area for the valve. Place these units into the openings so one is the revers of the other to provide an inlet and outlet valve. The plain separator can be inserted to hold the filter in place in the canister and the whole unit then slips over the valves on the mask.

Summary I have never printed in TPU on my AnyCubic Predator and wanted some model to give it a try. I spotted the Flexible Mask by iczfirz and thought that something useful would be a good option. It was also a good choice as it is quite a large print area (about 200x200) and had some thin surface areas as well as a little height to check for stringing and some parts that required after print assembly.

I found it printed out very well but with my limited sewing skill's I found it difficult to put together. I ended up with a sloppy sewing job which I ended up tearing out and then used glue instead. This worked better for me but was still a little awkward.

I decided I would try and make some alterations to the design which would make it easier for me to assemble. My model presses together and requires no sewing. It is printed out of TPU except for the nose clamp which needs to be a harder plastic so it can be bent to pinch the bridge of the nose. The design is also a little larger to fit my face and has slots for elastic or strings to be used to fasten the mask to the face. Printed straps could be used (I did not include a design) but I decided that it was faster and easier just to use something else. The slot area has been reinforced slightly to allow for other attachment methods.

The filter caps can be filled with whatever filtering material you have available. I do not profess to know anything about which materials to use so you would need to research this. I have included ingress and egress valves with the design that press into place and slide into the face openings. Obviously they need to be placed in opposite directions for them to work properly. If you are using a material that needs to be kept away from the valve there is an additional separator that can be inserted above the valve and will keep the filter material away from the valve. Not knowing anything about theses masks, I am not even sure if a valve is needed. The mask should work as a basic filtering system without the valves and just relying on the filter material.

Note: on further reading I have discovered that the valve is really only necessary on the outlet as a way to help make breathing a little easier and to try and decrease the moisture, and that valves are not really a necessity at all. In this case I may redesign the model to take this into account.

If you prefer you can print 4 valve separators (2 for each side) and use them to sandwich the valve between them. In this case the valve gets connected to one of the separators and the other is placed on the valve movement side to create a space that allows the valve to open and close freely. The double unit is then inserted into the mask opening and pushed to the bottom. The filter material is then inserted and the cover is installed over this.

The parts for a complete mask would then be:

• 1 x filter mask (TPU)
• 1 x filter mask nose (PLA)
• 2 x valve (TPU)
• 4 x valve separator (TPU or PLA) Choose style depending on filter used
• 2 x cartridge (TPU or PLA) or
• 2 x flat cartridge (TPU or PLA)

Additional materials needed: fastener strap material Filter material sealing material for main seam

The main seam, because it is a press fit, leaves some small gaps that should be closed off. Some stitching could be used for this or other material such as some flexible sealant or other glue material. If you have a method to apply a heated bead of TPU that may also work as a good sealant. If none of these are available, taping or fastening a filter material to the inside of the seam would also work. I am looking at a better notching of the pattern to see if I can decrease the bulge/bend effect. It might also work to soften the TPU with a little heat to try and reform it after it has been snapped together.

This is not a medical device but could potentially decrease the amount of airborne contaminants that a wearer would breath in or expel.

Please feel free to comment about any issues you see with the design.

Thanks again to iczfirz for his original design and inspiration.