For some reason some of my inserters some times skip picking up resources.
I've tried to record this, but then all of a sudden they pick up resources every time they can...
I've only noticed this with assembling machines, but the input stacks aren't full and nor are the output stacks. Yet the inserter will notice ingredients coming down the belt and skip them.

I've made a recording of this happening with Science pack 2 not being inserted in labs while researching Toolbelt, which requires Science pack 2. We can see that the labs aren't active, so it's not due to it being full.

My installation is up to the latest Steam version without any mods.

Any ideas what might be causing this?

Potential problems that aren't occuring:
- I'm using yellow belts, this is the slowest belt in the game.
- It's happening with straight belts, no corners involved.

What might be the case:
- The belts are nearly empty, it feels very inefficient to have full belts by design. Like the different parts of the factory aren't properly tuned.

2 Answers 2


This can also occur when you aren't fully meeting your power requirements. Low power makes some items operate slower, this could be happening with your inserters.


Normal inserters have problems picking up items from:

  • Fast belts, especially if not full.
  • Inner corner off a bent as it has a smaller surface to pick from ergo less time to.

So you can:

  • Use faster inserters.
  • Use slower belts.
  • Ensure that the belts are full.
  • 9
    Also, ensure that your inserters are fully powered. Underpowered machines work slower, in case of inserters that means that they might not move fast enough to grab item from the belt. Sep 12, 2018 at 11:25
  • 3
    He edits the question to emphasize that this isn't the issue, then marks it as correct? Sep 12, 2018 at 17:05
  • 1
    Also they'll only load items into a building if that building doesn't already have some. If a lab already has several science pack 2 then it will not insert more. While seemingly obvious, I've often had this confusion when a different type of science pack is not reaching all of my labs. When you ramp up production of some science packs it can disrupt Science Pack 1s without you expecting it to.
    – NibblyPig
    Sep 14, 2018 at 12:00
  • To add to @SLC, science packs only get inserted into labs that need that type of pack for the current running research. Apr 15, 2019 at 10:48

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