The setup combines three concepts:
- smart furnaces (copper, iron, steel)
passive splitter sorting of 3 resources
passive overflow buffer that controls the smart furnaces
OverviewEach horizontal line of smart furnaces is set to either copper, iron, or steel production by a circuit suggested by none other than XKnight.
The furnaces are ordered in pairs with the left half used for steel production. Both are used for Iron/Copper production, but often the left one will be backed up with Iron plates. Nevertheless this is very compact and simple with no combinators and 10x3 tiles per steel production. Only setups with logistics bots are smaller.
The mixed production is sorted by the passive splitter sorting system. I use a modified version of the magic splitter sorter of XKnightviewtopic.php?f=18&t=19114&start=10#p122988 with a throughput of a full belt. The first magic splitter splits into copper and iron/steel and the second splits iron and steel. This is configured by dropping that resource between the first two splitters. One requirement with this sorting system is that the output never backs up. The cool thing is that the passive overflow buffer behind the sorting prevents exactly that. If the production is higher than the consumption the overflow buffer (warehouse mod) gets filled. If the it reaches the defined limit (10k here) the smart furnaces stop production of that resource. If the belt is empty the splitter are stacked in a way that only 1/32th of the items reach the buffer.
The throughput is limited by the used belt and shared between the three resources. So 40 items/s or 2400 items/min with blue belts. To increase it you need faster belts (bobs mod) or multiple sorting and buffer systems.
The ratio of copper / iron / steel furnaces is controlled by the relative fill level of the three warehouses in steps of 5%. So with 2000 copper and 1000 iron missing 65% furnaces working on copper and 35% on iron.
magic splitters After I understood the basics it was surprisingly easy to play with these. Basically you switch the left output belt on and off by the specific resource on each north facing belts between right between the two splitters.
circuits I had to add a delay when a furnace swtiches to steel to make sure every furnace is empty. Otherwise the fast inserter gets priority over the smart inserter. Funny thing, if the furnace is build on a chunk boarder the fast inserter might have priority always. If you look closely in one row of furnaces I had to place the smart inserters one tile north.