Introduction: 3D Printed COVID-19 Mask With Gasket (NOW WITH 100% MORE FLANGE!!!)

This Instructable is a stop-gap measure. This is in no way a replacement for proper N95 or N99 masks used in a medical setting. This is a measure that is being taken by makers across the country, possibly the planet, in response to insufficient medical supplies to combat the COVID-19 virus.

I was asked by a local agency to provide backup/emergency masks due to their dwindling supplies. I am using the "Montana Mask" currently distributed by the Billings Clinic Foundation.

I applaud the foundation for their work, but they have not made available step-by-step instructions on how to make these masks and, possibly, more importantly, information on what they are using for gasket material. The gasket is key to creating an effective seal between the face and the hard plastic. Without a proper transition material between the face and mask, the mask is rendered less effective. This would expose the person wearing it to the virus.

The Instructable here covers the assembly of an adult large mask. I have not been assembling many medium-sized masks and only have anecdotal experience with them. I hope to create a sizing chart for these masks in the near future.


3D printer

Filament (I am using PLA)

Computer to operate printer or upload files to SD card

1/4" flat elastic fabric

Weatherseal (I am using MD Auto and Marine Rubber Weatherseal, product number 01025, SKU: 4337401025)

Rubber tool dip

Ruler or tape measure


Small paintbrush

Clamp devices (I am using hemostat and paperclips, you could get away with just paperclips if you don't have the hemostat)


Filter (I am using a MERV-14 rated air purifier filter material, use MERV-13 or higher rated material)

Step 1: Get Your Printer Going!

**Update** I am including an updated filter holder/frame with a flange!

Thanks to, they have helped make a sturdier flange than the brims I have been using.

***Further Update with New Files***

(White mask pictures) I have met with several served agencies and they wanted a more secure way of holding the filter. What I came up with was to add a flange and cross member to the mask itself. That way, when the filter is put in place, it is effectively held from the front and the back. The individual I met to do the fit test said that the flange on the front side of the mask will also help provide a better seal.

(Black mask picture) Since I already have a pile of maks printed, I decided to make a retrofit kit to print and glue to the masks as well as give out to the first responders who already have the mask. I found that a layer of super glue is sufficient for this. If you wanted to make sure it seals, add a layer of plastic dip around the outside of the retrofit plate.

Step 2: Finish Your Print

**Update** This step is no longer necessary if you get the new files located earlier on the Instructable. The flange eliminates the need to print and retain the brim and thus makes finishing much faster.

I added the brim for two reasons. First, it helps the print adhere better to my build plate. Secondly, the brim, on the outside of the filter holder, seems to do a little better job sealing around the filter, so I decided to leave it.

CAREFULLY cut the brim from the inner "windows" of the filter holder. I found that cutting diagonally into the corners and then pushing the trapezoid shapes inward helps them break off easily.

On the mask part, the brim around the filter holder needs to be removed in the same way that the brim was removed from inside the filter holder. The little brim on the outside edge can be peeled off easily or left, your choice.

Step 3: Prep Your Gasket

For the large mask, cut a 16" piece of the weatherseal. I have had approximately 3/4" of material left over to be trimmed at the end. You could get away with using 15.5" pieces and have less waste.

Find the middle of the piece of weatherseal by using the very precise method of "folding it in half." This will help us put the middle of the weatherseal at the bridge of the nosepiece and have the joining seam at the bottom of the mask (under the chin area).

Raise the plastic strip covering the adhesive by pinching the weatherseal. Lift it up slightly and cut with the scissors.

Step 4: Put on the Gasket

Peel off an inch of the adhesive cover and start at the top of the nosepiece. I clamped it down with hemostats to get a good seal.

Continue to peel the adhesive cover off of the weatherseal and firmly press the weatherseal along the inner edge of the mask with approximately 1/8" hanging outside the mask. Continue around the inner edge until you run out of weatherseal. Restart the process back at the nosepiece and work down the opposite side of the mask. When you reach the bottom, trim the excess weatherseal to fit, but leave a small overlap. This ensures that there is no gap in the gasket.

The gasket tends to peel where the cheekbones meet the mask. I added two large paperclips to hold the gasket in place as I finish the seal.

Step 5: Finish the Seal

The adhesive on the weatherseal will not stand up to repeated use. Add a coating of rubber tool dip to the outside of the mask where the weatherseal and PLA meet. This improves durability.

Pay special attention to where the two ends of the weatherseal meet at the bottom of the mask. Apply rubber along the entire area where the two ends meet.

Let dry for 30 minutes and then remove the hemostat and paperclips. Apply a second layer and let dry.

For quality control, shine a light along the inner edge of the gasket and look for any tiny gaps, especially along the seam where the two ends meet.

Alternatively, if this mask is for your personal use, you could put the mask on, hold your palm flat against the filter hole, and breathe in. Any sounds of air moving across the gasket will mean the seal has a problem.

Step 6: Add Your Elastic

Cut two 18" pieces of the flat elastic fabric. You may only need 16" but since I am distributing these, I wanted to give the receiving person the ability to trim the bands to fit them.

Thread the elastic through the holes in the side of the mask. Once they are sized to the wearer, tie the elastic in whatever manner you choose and trim the excess elastic.

Step 7: Install Your Filter

Note, I am using a coffee filter for the demonstration, as I am waiting for my filter material to arrive. A coffee filter might be fine if you are working with sawdust or some other large particles. If you are giving this mask to a first responder or medical professional, please DO NOT use t-shirt, bandana, coffee filters, or other unsuitable materials! Source out a filter that will provide an appropriate level of protection!

The Billings Clinic Foundation suggests that existing clinical masks can be used as a filter by cutting them into 2.5" squares. A person can get 6 filters from one mask, thus extending the current supply.

I will be using a MERV-14 rated air filter which is cut into 2.5" squares.


After delivering the first batch of masks, the method putting the filter in from the front worked 90% of the time. The gasket was so effective that when the user was breathing very heavily, the pressure displaced the filter.

If you add the filter from the back, still having the finished side pointing toward the user's mouth. This method will keep the filter in place even with heavy breathing.

Step 8: Wear It With Pride

To attain a proper seal, your face should be clean-shaven. I am not a first responder, so I am still a little partial to keeping my scruff around as long as I can. But if it comes down to staying healthy or keeping the facial hair, I will shave.

That being said, the gasket still provides a fairly good seal around my short facial hair. I would still recommend only using these in a serious fashion with a clean shave.

The Billings Clinic Foundation recommends to change the filter and wash the mask with soap and water between each use.


PLA mask may be slightly adjusted to improve fit and seal for each user! Using a hair dryer on a low-medium setting, you can gently heat the plastic and press lightly on the plastic to change its form. I have also seen that dipping in very hot water can get similar results.

Things to keep in mind:

1. Do not overheat the plastic

2. Do not apply heat directly to the gasket material

3. Take it slowly as not to damage the mask

4. Redo the Quality Control step by sealing the hole for the filter with mask on your face. Breathe in to see if the seal has improved

5. If you hear air leaking, run your fingers along the edge where your face meets the gasket, a change in sound may show you where a leak may be and further heating and pressing may be needed

6. Also perform an air leak check by running your fingers along the area you heated and formed. This will check to see if there is any delaminating between the layers of the plastic

Step 9: Future Considerations

If you are printing one for yourself, congrats, you are now covered.

If you are now turning your wife's craft room into a small cottage industry and making a dozen or two of these per day to distribute, you might want to look at sterilization.

I am distributing these to my served agencies with each mask inside a quart-sized baggie. I am putting each baggie under my 200 watt UV light for half an hour.

Is this method perfect? Probably not.

Will it kill all germs and bacteria? Probably.

Will it keep one person from sneezing and infecting a box of 30 masks in one go? Yes.