How full storage can hide a production bottleneck

Start with the depot that emptied

Look at the machines that slowed down and check each material feeding them. One input depot will often be empty or falling while the others remain full. That tells you which material to follow first.

A full depot can hide the problem after the factory has been idle. The machines at the end may consume 120 items/min while the earlier machines only make 80. The depot supplies the difference until it empties, so the shortage does not appear right away.

Watch the depot for more than a few minutes. A brief dip can come from a Fire Wave or an uneven delivery. A level that keeps falling while the factory runs means that material is being used faster than it arrives.

Follow the missing material backward

Go to the machines that make the missing material. If their output storage is full, they are making enough and the problem is between them and the machines that need it. Check the rail, its merges, and the receiving depot.

If those machines are waiting for an input, follow that input to the previous group of machines. Repeat the same check there. You are looking for the first place where material stops arriving quickly enough.

If the machines are running continuously but still make too little, count them and check the recipe they are using. A V1 and V2 recipe for the same item can have different output rates and different input needs.

Shared materials are easy to miss. Two parts of the factory may both draw Electronics, Sulphuric Acid, or another component from the same production area. Count both uses when you decide whether that area is large enough.

Check the required rates in the calculator

Open the Production Calculator for the item made by the machines that slowed down. Set the number of machines you built, or enter the items/min you want. Expand the production chain to see how much of every input is required.

Compare those numbers with the machines already in the factory. If the calculator says the line needs two Electronics furnaces and you built one, you have found a clear shortage. If the machine count is correct, check whether its own inputs and rail deliveries match the required items/min.

The full-chain summary combines repeated uses of the same material. This helps when several branches rely on one shared component. It also shows whether fixing the current shortage will place more demand on another part of the factory.

Fix the first place that falls short

Add a machine when production is too low. Add extraction when the source material is too low. Split or reroute a rail when enough material is being made but does not reach the next part of the factory.

After the change, run the factory again with little stored material and watch the same depot. If its level stops falling, that shortage is fixed. If another depot begins to empty, follow the same process from that material.

Do not add machines just because the line stopped once during a Fire Wave. A short interruption is different from a depot that drains every time the factory runs. If you deliberately want storage to cover a known shortage, use the separate storage-buffer guide to check how long it will last and how long it needs to refill.