I started with a wooden platform made out thin hardboard on top of MDF. Then I built the upper part of the enclosure out of plexiglass and aluminum channel. I purchased the plexi and aluminum channel from Lowes. The aluminum channel is 1/16" x 3/4" x 3/4". I bolted the whole thing together with #8-32 screws. The build chamber dimensions are 15"H x 20"W x 22"D.
I 3D printed some screw down feet for my Printrbot so it doesn't move around inside the cabinet. You can download the design for the feet here: http://www.thingiverse.com/thing:724909
The whole front of the enclosure is a hinged door. Magnetic door catches keep the door closed.
The top of the cabinet is also hinged and can be opened.
My Printrbot has a heated print bed so it uses an ATX power supply from a computer. It has a bunch of extra wires that aren't used by the printer so I made a hollow area underneath to hide all the extra wires.
I made a spool holder out of a 6" Lazy Susan bearing and a piece of plywood. I put a 3/8" carriage bolt in the center of the spool holder turnable which is used to secure the filament spool to the holder. I used some #6-32 stand-offs and #6-32 screws with the heads cutoff to allow the turntable to sit an inch above the lid so it can rotate. This also allows the turntable to be lifted off when the top lid needs to be opened.
Then I designed a knob and cone that secures the filament spool to the turntable. You can download the design here: http://www.thingiverse.com/thing:829930
Here is a more detailed shot showing the path of the filament into the cabinet. I drilled a .25" hole in the top panel.
Next I added LED light strips around the top of the cabinet to light up the inside. The strips are power by +12vdc so I was able to hook them up to the Printrbot ATX power supply. The lights turn on when the printer is powered up.
Here is the printer in action inside the cabinet:
There one thing I'm still working on. I put an exhaust fan in the upper right corner of the back wall of the cabinet. I don't want the cabinet to get too hot inside but I also don't want the fan to run all the time or run at full speed so I'm designing a small circuit that controls the fan speed based on the temperature inside the cabinet.
I mounted my OctoPrint print server running on a Raspberry Pi to the side of the cabinet. I also added a 20x4 character LCD display that shows useful info about the printer.