i dont know if anyone has posted this before...but i found pictures plans for a diy blast cabinet..
blast cabinet

That looks interesting and very easy to make!
Personaly I would make some minor modifications.
First I would make the bottom "V" shaped or even just angled down towards the front, so that the blasting media collected and could then be just pushed back down into bucket. Most would slide back into bucket by itself.
Secondly, I would fit a bayonet fitting inside the cabinet so that the airhose didn't need to pass through any grommets.
Thirdly I would feed the suction pipe straight into bucket. Again no grommets for hoses to pass through.

You could do without the extractor system. If so just mount the big air filter onto the outside of cabinet.

Ain't that what life is all about, modifying and adapting?
Good link!

I agree about the V shaped bottom, I did this on mine, but its best in a upturned pyramid with a 4" outlet into a big bucket shape. Then run the sand hose into the bottom of the bucket shape. My "V" is 45degrees,. but is not enough to get it all to fall back into the bottom.

I used an old Hoover to extract the air through a Sponge ti-wrapped over the exit pipe.

Also Get the replacement "tear off" glass shields from Machine Mart spares, as the Glass / perspex window will be opaque in a matter of weeks. They are not expensive. Sitck on inside the window, and rip off when its opaque and replace.
These are only available from machine Mart SPARES place not the shops.
Get the replacement indow covers first... than make the window to fit I didnt

Be sure you get the air exits well filtered as you dont want to get lung damage.

mine is 700mm Cube.
You want some good snap latches on the door as the pressure builds up insider the cabinet as you blast. hence a good air vent and filtration is useful.

There thats my 2d worth.