Of course, you will not want to have any PLA printed parts inside the heated enclosure. :(
Aluminum machined parts would work.
I would think it better to have a movable air "lid" that the extruder pokes through (two layers of fanfold papers in opposite directions with long slit in the middle sort of idea -- though that one is patented).
Then keep everything but the bottom of the extruder and the print outside of the heated area. This might be much easier to accomplish on a Wally design.
Aluminum machined parts would work.
I would think it better to have a movable air "lid" that the extruder pokes through (two layers of fanfold papers in opposite directions with long slit in the middle sort of idea -- though that one is patented).
Then keep everything but the bottom of the extruder and the print outside of the heated area. This might be much easier to accomplish on a Wally design.