Cargo inventory only partially filled

[srhank]

In one of my stations, the train keeps getting stuck with partial inventory. I do move multiple resources packed in the cargo cars, which is probably a bad idea, but I still don't understand why the inventory is not filling up. As you can see from the picture, there is only 88 steel in one of the slots, there is still some left in the chest, yet the inserters are idle. Posting this in General, as I probably just misunderstand how the logic works.

[Nexarius]

Easy to explain.

Imagine this scenario:
All slots filled but 2
1 slot hat 95 steel the other 95 iron plates.

Inserter picks up 12 iron plates and puts them into the cargo wagon but only 5 fit so it still has 7 in the arm and gets stuck.

[srhank]

Thanks. You are probably correct. I didn't think this was the problem because:
1. I had the problem even before I got stack inserters. I suppose it's still possible if, say, the inserters each pick up an Iron while there is only room for Steel.
2. I thought I saw it happen even with a resource loaded by a dedicated (filter) inserter.
I will pay closer attention to double-check #2.

[5thHorseman]

Thanks. You are probably correct. I didn't think this was the problem because:
1. I had the problem even before I got stack inserters. I suppose it's still possible if, say, the inserters each pick up an Iron while there is only room for Steel.

Even regular inserters get a benefit from some stack size increases.

[Zavian]

Thanks. You are probably correct. I didn't think this was the problem because:
1. I had the problem even before I got stack inserters. I suppose it's still possible if, say, the inserters each pick up an Iron while there is only room for Steel.
2. I thought I saw it happen even with a resource loaded by a dedicated (filter) inserter.
I will pay closer attention to double-check #2.

If there are mixed resources available, the inserter will just grab whatever it likes, which may not match whatever item the partially empty stack in the train needs. If you are going to load mixed resources that way, I recommend dedicated belts and inserters per resource. That way you wont get stuck with a partially full stack, and all the inserters having something else in their hands, or equally bad, something else at the end of the belt preventing more of the needed item from reaching an inserter.

An alternative is to just add a "OR 30 sec" waiting condition to the train.

[Serenity]

Or use filter inserters to pick up from the belt and have dedicated buffer chests for each item

Mixing belts like that is not a good idea though. Usually each lane should only have one kind of item