K40 extraction fan upgrade

A common complaint about most of the K40 laser cutter/engraver machines sold on eBay and [Amazon](https://amzn.com/B01AJGFS7Y) is that the fan is basically useless. They are correct. The provided fan doesn't mount correctly to the machine, leaves large air gaps, and doesn't even move a decent amount of air.

Instead of throwing the fan out, I decided to take it apart and found, much to my surprise, that the fan motor is _**actually of decent quality**_! So, based solely on the provided motor, I decided that I could salvage it by creating an enclosure for it with new fan blades to use as a fume extraction solution.

I use this fan at the end of my exhaust system so that air is being _sucked_ away from the laser, not pushed. This creates negative pressure inside the exhaust duct so that if there are any leaks it will be sucking air in from the workspace, and not pushing fumes out into the workspace.

[Performance video](https://youtu.be/O1QlIzjmHG4)