Customized Montana Mask

This is a remix of the Montana Mask. See https://www.billingsclinic.com/foundation/ for the original design or further background informaiton.

Credit for original design belongs to Billings Clinic Neurosurgeon, Dusty Richardson, MD, in collaboration with Billings-area dentist Spencer Zaugg, DDS and his son Colton. If you want to order the filter material mentioned in the link, I have included the Filter Order Form from Flowmark/HighTech.

By many reports, a common problem with masks like this is the fit to the face. This original design used a scan of one of the designers face and there is a suggestion in the write up on scaling the model up or down to get a good fit.

My daughter is a UW-Madison senior in Biomedical Engineering working a co-op rotation at a company producing ventilators. Her lab is taking many precautions, but she asked me to print some masks for her V&V team. I am an Electrical Engineer and I have worked projects using the Intel RealSense Depth Cameras. (inexpensive and readily available.) My wife is a NP and had practical concerns about known problems with the face seal and comfort.

This thing is a customized version for a better fit to the face. The two improvements are splitting the mask body into two pieces so the piece in contact with the face can be printed with softer flexible filament(TPU) and providing a body that can be intersected with a 3D face scan.

My goal is to face scan multiple people and use the scans to create custom masks with improved fit and comfort.

Print Settings

Printer:

jjt MakerSlide

Rafts:

No

Supports:

Yes

Resolution:

0.3

Infill:

35%

Filament: Overture PETG/TPU

Notes:

MontanaMaskFilter.stl and Montana_Mask_Split_Filter_piece.stl should be printed in whatever hard filament you normally use. (PETG/ABS/PLA).

Don't bother printing the other included parts. The JJT TPU part is custom for my face, not yours! Instead, get a 3D scan of your own face and follow directions to create a custom fit, then print in TPU.

Post-Printing

Filter part of the mask.

I printed the filter part of the mask in PETG with the filter down. I did not do a great design job replacing the strap holders so this part should be printed with support.

Face part of the mask (TPU or flexible filament)

This was my first TPU print. I needed to reduce my print flow to 90% or it would jam after a few layers. I also turned off retraction. I have some stringing, but I'm more concerned with functionality than aesthetics. I also switched to a larger nozzle diameter (0.6mm) for taller layers and faster print time.

How I Designed This

Improvement 1) Split the design into a hard and soft pieces.

I split the original design and printed the portion containing the filter in PETG. The original strap holders didn't make the split. I added some small cylinders on the lip to aid in lining up the PETG and TPU parts. This split is useful for keeping one size for the filter piece and custom sizes for the face.

In the F360 file, I have included the original split. The piece that touches the face could be designed to lock to the mask and be printed in flexible filament (TPU). Instead, I created a part that can be intersected for a custom fit.

Improvement 2) Modifying the face interface using a 3D scan

Instead of relying on a one size fits all or generic scaling of the part in contact with the face, I used a 3D scan and intersected that with the TPU part.

This required multiple steps:

Step 1. 3D Scan

I used the itSeez3d application from https://itseez3d.com/ with an Intel D415 depth camera. ($150). The free download only includes three free exports, so be careful. You can do multiple scans but only three exports. There are multiple ways to get a 3D scan. The $79 Intel SR305 should also work for this application.

You only need to scan the portion of the face that interfaces with the mask.

Step 2. Mesh Reduction

I brought the itSeez3d exported .ply file into MeshMixer and did some plane cuts to keep just the face. I also needed to convert to solid and reduce the Mesh to approx 10,000 triangles which is a F360 limitation. F360 also gets confused if the mesh isn't a solid. Finally, I exported to .obj.

All of these steps are covered in various YouTube videos. I also used MeshLab at some point but I don't think that was necessary.

Mesh Mixer - import of original scan.

Mesh Mixer - after plane cuts, solid fill, reduced triangles.

Step 3. Use Fusion 360 to create your custom face fit.

Open the attached .f3d file. Import your own custom .obj face mesh. If the mesh imports as multiple meshes, go back into MeshMixer and do some work to get a single solid mesh. Fusion 360 can not work with surfaces, you want to import a single mesh that can be converted to a solid body. Turn off Design History, convert to Mesh to BRep. If F360 chokes on the conversion you are probably over the 10,000 triangle limit. Go back into MeshMixer and reduce. Now you have a tool body that can cut the "TPU mask part".

Move your face body relative to the TPU mask body to match how you want it to fit your face.

When the mask and face are in the desired position relative to each other, use the "TPU mask part" as the Target Body and your face as the Tool Body in a cut operation. I like to check the New component option and Keep Tools. This will create the TPU piece you want to print. Depending on your computer speed this may take a while.

F360 Cutting the TPU piece with custom face

Work in progress Notes

1. Design the "standard" face interface to lock to the filter piece so it can be printed in TPU or resized to better fit if a 3d scan is not available.
2. Better work flow for the 3d scan. Current method works, but takes a bunch of time.
3. Improve the locking interface between the two pieces.
4. Improve the strap holders so the support isn't required.
5. Clean up the F360 file.
6. Obtain a "standard" mask and create a TPU adapter.

Misc Notes

The TPU filament you get from Amazon is not going to be medical grade. Having acknowledged that, TPU is a good choice.

http://www.medicaldevice-developments.com/features/featureplastic-to-smile-about---thermoplastic-polyurethane-4454777/

The filter material order from Flowmark/HighTech was $17.50/50 filters plus shipping. I will update when these arrive. When I called Weds AM, Brenda said she had a backlog of 400 emails to work through.

I have heard stories about local nurses that can't get a standard mask to fit their faces. It would be interesting to get some used/sterilized masks and create custom TPU adapters for providers that don't fit the standard masks. There is no excuse for a poorly fitting mask in this day and age.