This open bottom "enclosure" is designed to nest on top of the Phecda laser engraver machine.
Intended for a 4" duct fan to attach to the top, to exhaust particulates and smoke, blasted off the work piece by the laser head.

The colored zones in the picture are 250x210mm print bed placeholders. That's how I sized the truss components to fit on the beds, with slot-together junctions, where the print bed sizes overlap. There are indent holes for hex M3 nuts and M3 screws, on the corner pieces, to securely grip the 4" x 20" PET panel pieces, as a wall perimeter. The trussed topper pieces are labeled A-M, and each junction is labeled with a pair of letters, that must match the other side, upon assembly. Under the truss topper, four full 16" x 20" PET sheets are fastened with 180 truss screws, sealing the underside of the truss structure. The 4in duct adapter screws into a PET plastic sheet quadrant, with threaded halves that slot into and attach to, the truss frame.

Parts required to construct (about $31 used, of $57 ordered):
5 quantity, PET plastic planels, 16" x 20" ($30/10qty): https://www.amazon.com/dp/B08KT29YF4/
180 quantity, Truss screws, ~3mm shaft, ~10mm head ($7/100qty): https://www.amazon.com/gp/product/B01MFAIS08/
8 quantity, 5mm OD x 4mm deep, M3 threaded brass inserts ($7/60qty): https://www.amazon.com/dp/B09MCW7ZN5/
16 quantity each, M3x8mm & M3x6mm screws, M3 hex nuts ($7/400qty): https://www.amazon.com/dp/B0CSX4NX7R

Requires one of the thin PET plastic sheets, 16" x 20", cut into four, 4" x 20" pieces.
The sheet plastic, inserts into the two slots on the corner objects. Truss structure corners, use M3 screws into brass inserts.
The plastic sheets edges can be tape sealed, at the seams, with Gorilla crystal clear tape, or packing tape.
Future: redesign some truss pieces, so that none of them need supports, to print properly. Created 2024.