Picture unrelated to question; built for style, not functionality. I've learned that the most efficient (and boring) platform design is a spear.
I think of all the planets, I like Fulgora the least. I have tried two or three approaches to dealing with the sushi belts of parts; my biggest issue is the monomanical logic of inserters, which -- given a storage chest of a dozen different items, seem to get stuck on one item for extended periods. For instance, unloading a train of random stuff, I'll get 15 inserters all pulling out gears for several minutes, ignoring everything else in the chests. It's frustrating beyond belief, so I think I'm not looking at this the right way.
The biggest issue is buffering. I'll get nothing but gears for a few hours, but then they'll dry up and I'll get nothing but low density structure for a few hours and almost no gears. If I were paranoid, I'd think the devs did this on purpose to maximize jamming.
What I'm going to try next is building a train system with per-item trains, or maybe cars, and see if that helps. Transport raw to an island, recycle it, and load up trains with product and send them to a big factory island. I suspect it's simply going to get jammed up at the recycling center and I won't be any further ahead, but maybe I can mitigate that by just having one, really long train that stops every 12 cars and every series of 12 cars has each car containing a single item.
I don't know. Fulgora just feels stupid, or makes me feel stupid. How do you folks handle Fulgora?
Update edit
I completely redesigned everything on Fulgora, and it doesn't get jammed, and I'm only having to "throw away" steel (the plate, not the girders; I'm not sure why the game calls "girders" "plate", but whatever).
My solution, as it is, is based on the suggestion of having a recycling plant rather than recycling at the miners. I'm using trains: I mine ore into trains and ship it to a recycling island, where the output is filtered into train cars - one type per car. I run the trains full of product to wherever I have factories set up, and pull specific items needed there. I avoid sushi belts and sushi boxcars; my production islands are consequently much simpler, and as yet I'm not having to waste product.
I will point out that I initially used recyclers to reduce the amounts out items, but found I had to keep changing what I was recycling because what was overflowing kept changing, and by recycling I was regularly running out of items; this, again, is related to whatever the RNG is doing to me. Honestly, I have a mind to actually keep a counter, because it appears as if I'll get a run of copper coil, where it's the dominant item mined for dozens of minutes, then it'll be blue chips, and so on, cycling through each of the items. It swamps me with one thing that I can't even manage with belt weaving, then suddenly that'll dry up and I'll get only a trickle of that thing for the next couple of hours. I've frequently had launches completely stop because I had to recycle one component to built rocket parts, and then it dries up and I have to built an assembler to produce the product until the RNG deems me worthy to have it start being a mined item again. If the cycle happened over a period of less than hours, I'd record it. Although, the fact that the inserters (almost) all get stuck on the same item pulling from sushi boxes, I could easily show. If I, of anyone else, cared enough.
In any case, with trains and enough storage boxes I have it set up to weather the droughts and floods of specific items, and am assuming either it's coded this way on purpose, or only doing it on my machine because I don't hear anyone else complaining about it.
I was recycling directly from the miners, and then dumping everything into trains, shipping them to an island where I'd sort everything onto belts and into a factory complex. So offloading from the trains, I'd get sushi boxes, and for some reason, every inserter pulling from those boxes onto the belt that fed into the filter sorter set-up collectively selects the same item out of the sushi boxes for minutes at a time. So: given 18 sushi boxes off a train, (almost) every inserter would choose to pull (e.g.) blue chips for several minutes. Then they'd all start grabbing iron plate, and do that for several minutes. It's like a really broken RNG for item selection, or else it's not random at all and just works through some sequence - and they nearly all do it in lockstep.
The end result is that my sort filter field would get jammed up with something. Low density plastic. Red chips. Whatever. I'd clear it, and come back and it'd be jammed up on something else. So I sat and babysat it one day and noticed that inserter behavior. They'd start out looking random, but given long enough and they'd sync to the same item, and then stay on that item for long enough that the sushi belt would be all gears. Or fuel, or coils.
If I'm not mistaken, inserters will always take from either the first or last occupied slot in a container that matches their filters. I'm not in front of my PC so I can't check, but I'm fairly certain it's not random at all. From your description of your setup (miners -> recyclers -> train) I suspect the "randomness" you're seeing is due to how the train wagon gets filled up by the recycler output - which is itself definitely random.
As another comment says, you'll need to use filters to have the inserters do a "balanced pull". If you want maximum throughput then you'll need to wire up some combinators to dynamically adjust the filters over time. If you don't care about achieving max throughput and just want to be sure you don't clog up the unloading, you only need to spread out the ten-ish scrap recycling outputs across the filters for the 6/12 inserters that interact with a given train wagon.
Huh. That makes sense.
I spent yesterday completely redesigning my Fulgora base, so I'm not having that issue anymore, but if I ever need to use sushi belts again I'll keep that in mind. It gets to be a lot of circuitry, which I avoid because at a certain complexity it disincentives changing anything, at least for me.
I get enough debugging in my day job; I don't need to be doing it in my play time, too :-)
I feel you w.r.t. debugging :-)
Thankfully there's always the "brute-force" approach to the rescue; scale up and/or ship in whatever you need from a planet where it's cheap(er).
I've used that! I had a flood of low density, so for a while I was shipping it to other planets, buffering especially on Aquilo. Then it tapered off so much I couldn't launch rockets on Fulgora. ¯\(ツ)/¯
With a redesigned pipeline, I'm in a better place; Fulgora still is hundreds of quality yellow chests and dozens of tanks for buffering, but it isn't getting jammed up anymore.