I find the use/idea of scrap generating machines rather silly, how about a machine that process materials to get trace minerals out of them. like stone could have 0.01% of irdium in it . then you process 1000 stone and you get 1 ingot of irdium. you can also get other trace elements iron, tin, copper, uranium etc. maybe even dump all your other ores into it? it could output ingots or special lava? you could also use flux?
I still like the mass fabicator as it is.
Introducing the plasmatron arc furnace! this awsome device is capable of seperating the tiny amounts of valuable trace elements from regular stone and dirt. be warned all you mud hut dwellers this machine is capable of consuming you entire house with in a single tick. that is all the dirt your house is made of if it where in a chest. one very neating function of this machine is that you can use flux (ie. glass, salt) to incress the yield of certian elements/minerals, this will effect how much of the other elements/mineral will be burned off. bewarned using flux in the furnace is know to eat the machines carbon crucible.
((ore_kind(# of stacks = % ))*flux(flux_kind))