This is a variant of my other Duet WiFi enclosure. This one will also take the Duet WiFi and the new Duex expansion boards in a single enclosure. It is untried because at the time of writing, the Duex expansion boards have not been released. It should work though.
The Duet WiFi and Duex expansion boards are designed to be fitted back to back. This enclosure design will accept then one above the other, as if they were joined at the Vin connector but then opened up like a book. The enclosure will accept two 80mm fans fitted internally which will blow air on to the back of he boards as is recommended. The fans exhaust through outlets in the top and bottom of the case.
There is room to run cables around the outside of the boards and of course, all the terminals on both boards will be easily accessible. I designed it to fit my printer with cables entering from the left and mounting holes in the base. The cable entry slots are shorter in the middle to allow for a ribbon cable to connect the two boards. there is a cut out in the top to allow easy access to the micro SD card and reset buttons.
I've included the OpenScad file so feel free to adapt it to suit your own needs.
Warning. This thing is 290mm x 140mm so will need a biggish printer bed. If your bed is smaller. then you could achieve the same result bu making two of my other enclosures and fitting them back to back.
Second Warning. You may need a longer Ribbon cable to join the two boards together.