I added a 40mm fan to the RAMPS board to keep the drivers and especially the heat bed transistor cool. The heat sink on the transistor was getting warmer than I liked and I think I was having trouble with the bed getting to temperature. I'm not sure if it was a real problem or not, but since I added the fan, it's been fine.

I didn't design the fan mount. I used this one: http://www.thingiverse.com/thing:49235

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