N95 masks don't require 3D printers, they require melt-blown fabric. My girlfriend and I are chemical engineers, and took a look at the process that turns bulk, cheap, and widely available plastic (PE, PP, PC, etc) into melt blown fabric. She noted that it looked pretty nasty to her, and she wouldn't want to be involved with the startup for a new plant, and we regularly work with pretty nasty chemicals in large quantities. I was less hesitant, thinking it doesn't look that awful but I tend to be far less risk-averse. With proper safety precautions I think I'd be fine with it, but both of us feel that companies are extremely likely to fail at fully protecting the workers near the equipment from hazards. Here's an example of the machinery required: https://www.youtube.com/watch?v=897yTI6wXWY

You need a lot of capital for a melt-blown fabric facility, and some specialized engineers. China and Taiwan managed to build new facilities of huge size very quickly - it can be done, but apparently much harder for the large American conglomerates to get off the ground as quickly. https://www.wfuv.org/content/covid-19-has-caused-shortage-fa...

If you can get >$10 million together, and a very dedicated and specialized team of engineers, plant operators, machinists, and businesspeople - you might be able to finish your factory before 3M's Rhode Island and Arizona plants, if you start right now. But you won't do it in a distributed way with a bunch of people with 3D printers.

However, it seems there's evidence that non N95 masks have some efficacy. Just regular old cotton clothing cloth. You could start an MLM/Amway/Mary-Kay/Avon/Vemma/Younique style thing to get out-of-work people to make these at home and sell them to friends and family.

Sinopec decided on Feb 24 to built a melt-blown fabric plant https://www.youtube.com/watch?v=p9lchhBE7cE. It was operating on March 6. It took them 10-12 days to build, from scratch, a facility to produce 1.2 million N95 masks per day. One of my links above shows another facility built in 11+ days making 200,000 N95 masks per day.

At the start of the outbreak, Taiwan could product 100,000 N95 masks per day, but have built over 60 production lines, and now make enough melt blown fabric to product over 20 million N95 masks per day. Notably, Taiwan had a HUGE stockpile of masks, so even though making 100,000 masks per day wasn't enough for their population, they had enough in storage to last them while they built up their capacity. Now they make enough to send tons of masks the the USA every week.

USA (3M) decided to build melt-blown fabric facilities around March 23: https://www.powderbulksolids.com/news/Honeywell-Expands-N95-... and to a much smaller capacity. And none of the new lines in the USA are up and running yet. "Before the onset of the COVID-19 pandemic, 3M was manufacturing about 50 million masks per month" ... "In its continuing effort to help meet demand, 3M says it is working to double its global N95 mask production numbers once again to 200 million units monthly." But they think that will take another YEAR to accomplish. Only 35 million N95 masks are currently made in the USA, by 3M or others. https://www.nasdaq.com/articles/n95-mask-production-wont-mee...

Ideally, each citizen would have a new N95 mask for every day. We'll get to 1 mask per citizen per month, sometime around a year from now.