I posted this to a different thread but it may be more useful here:
I made a dust cover with a shop vacuum hose port for my NRG plans thickness sander.
My machine has a 11" long and 9" diameter Hard Maple platen. About all that was available in the 1970's was 9x11 sheet paper backed sanding medium.
The shape of the sawdust funnel is a five sided box without a lid. The sides extend down to the pillow blocks to hold the cover high enough not to block the drum.
To make your own:
Measure the dimensions of the five pieces
Glue three layers of Amazon box quality corrugated cardboard with a generous and complete layer of PVA glue. (use weight for a tight close bond). This will make a thick side for each of the five pieces.
Enforce on the inside each of the eight right angle box seams with 1/4"x1/4" sticks that are as long as it takes to - I cut mine from a Pine 2x4.
PVA bond them.
Cut a hole in the middle of the top that is vac house diameter. Fix a vac hose socket over the hole.

The vac hose socket is fixed at the hole using screws going thru the cardboard and into pieces of 1/4"x1/4" Pine glued to the underside of the top piece.
I covered the outside with a lot of duct tape. Easier to clean The 4 vertical sticks make good legs going down to the pillow blocks.
The hose weight will shift the dust funnel box if not planned against. I use bungee cords on the hose that are attached to a sky hook (my peg board tool holder).
A cyclone trap between the sander and the vac saves having to clean the vac filter every 10 minutes. The sawdust is fine and of a huge volume.
A remote radio control on-off for the vac is also good to have.