RAMPS 1.3 Case ventilated (Q50760)

Note this was made for the RAMPS 1.3 board. Slight improvements; leveled the board, added powerjacket and repositioned USB hole. Ventilation added, dimensions based on Sepa MFB25B12 12VDC fan http://nl.farnell.com/sepa/mfb25b12/fan-25mm-12vdc/dp/1217961. This case is used for a milling machine with relatively slow stepper speeds, no extruderheater and no heated build platform. The fan is connected to screw terminal D9, with the fan pin assigned to it. Given the fan is quite noisy, I think of adding a thermistor later on and tweak the code so that the Arduino takes care of adaptive cooling. Ventilation efficiency has not been verified with RAMPS driving a RepRap with extruderheater or heated build platform. 2011-08-24 Minor update (pcb space) of the covers 2011-08-25 The obvious showed after the first print: the fan had to be moved up (to get max airflow along the stepper drivers) 2011-08-29 Attached final OpenSCAD and .stl files. 2015-09-14 Added RAMPS 1.3 note 2015-11-06 Connector panel, see https://www.thingiverse.com/thing:1115903