The power box is not the issue causing filament to melt. the motor is getting too hot for PLA, PLA started melting at around 60 degree C. If the ambient temperature inside the machine plus the heat from motor push the filament over that point, It can melt inside the bondtech housing. ABS, Nylon, and PC are high temperature filaments, They won't have this problem as their glass temperature is around 100 degree C. You can't make any of your printer parts out of PLA either, they will deform over time. Simply adding some air flow onto the stepper motor, cools it off enough so this is avoided.
my part, which I posted on thingiverse, extends out the mini board mounting plate to add in a mount socket for another part that you can attach a 35mm fan too.
As far as the part goes, I need to redesign it from the current design. I've been following principles located on this site,
http://www.overclockers.com/waterblock- ... -drawings/currently the 3D printed part has a pipe going through it.
Due to the size, the design is probably going to have to be changed to a solid block with a hole drilled through the center with allen bolts sealing both ends. It will so need taps in on the upper and lower ends to allow for fittings to be put in place. currently they sell fittings for G 1/4 inch. also the mounting system I designed for the board requires a hole in each corner. to screw it into place.