I had produced about a thousand of tin, iron and copper, but they were not upgrading. Now that you mentioned that I might have actually needed alloy for that, which I wasn't producing atm, it makes sense. So yeah, probably a bell to change some sprites.
I can't provide a screenshot anymore, but what I've been doing - I was using a hub/array method. That is - a single conveyor belt is going around all of my drills, and comes to a furnace hub. There it splits with 3 layers of splitters into 27 threads, and after that they all come back on a single line, which goes elsewhere, splitting in 2 lines, which go to collector hub and seller hub of the same principle. And all that brilliant design didn't work, because furnaces were almost empty. I believe, splitters work on a tick system, same as furnaces, and furnaces have a whole lot less that 27 ticks to do their thing, which means that such splitter can never fill the demand of furnaces, as it is not transfering items asap. So, I had to split my drill lines into 3 independent ones, removing the front splitter, which started to actually fill the queues past the second and third layers of splitters, but now I realised, that the output is not working, as the single line collecting all the smelted bars just can't make it. Finally, I just had to remove all of that, and slap in a seller/collector/seller/collector right after each furnace, to make it both work smoothly and sell/collect about a half of each item I produced. But ultimately, the whole idea of hubs was just destroyed, as they are simply not working. Current best strat is simply make a 5 item line near each resuorce, which is: drill, conveyor, furnace, conveyor, seller/collector. Which is really not that elegant, and probably not what the game is supposed to be.
I like the game, though) It has so little tools and resources, but you can really unfold it by using your imagination and creativity. That's how Minecraft started back in the days)