The mini mill control box has very little cooling. First I drilled some holes in the sides but that still has the printed circuit board getting quite warm in the summer in Arizona. I had this 120vac fan and some filter material left over from an old vacuum cleaner I was using on my table saw. To put this to use I used a hole saw to cut a 2.75 round hole in the back cover of the mini mill control box. Drilled 4 mounting holes for the fan and wired it internally to the 120 vac switch I had previously installed for the circular led light. I always turn the light on when working on the mill so it was just a matter of a couple of splices to pick up the power for the fan. I was not too concerned with the motor since it has a rather nice heat sink built on and not enclosed so it has some airflow.
Hopefully it will keep the control board cool. The fan pressurizes the enclosure. Should keep all the chips out.