Why do I have (need?) so many idle bots?

[Laie]

I've come to the point where I run subassemblies on bots. Of course, one question I ask myself is "how many bots do I need to run this part of the factory?"

Disclaimer: I do not have one single logistic network spanning the entire map: they're pretty local affairs, while sub-factories are only interconnected by rail.

Now, the only method I'm aware of is to dump ever more bots into the site, until I get to the point where there are idle/available bots in the network. It's quite noticeable that I either have zero bots available, or lots of them. I wonder why this is so?

Aunt google brought me to a benchmark suggesting that I should carefully tailor the number of available bots to the strict minimum. Seeing how I'm not overly UPS conscious elsewhere, I probably shouldn't worry too much about that, though.

[jodokus31]

You also need a lot of roboports. bots waiting for recharging can be quite significant, if too little

[Laie]

You also need a lot of roboports. bots waiting for recharging can be quite significant, if too little

Granted, but a shortage of roboports is relatively easy to diagnose.

[BicycleEater]

My guess would be that in areas without enough bots, there is a backlog of things that need moving (all the buffers are empty), so if you keep adding bots until you have idle bots, you will find that when you do have idle bots, loads of them will suddenly be idle, as previously you were also finishing the backlog up.
This means that you should keep adding them until you have idle bots, then remove them until you only have some idle (I would recommend having a few idle bots anyway, just to avoid peak-load overwhelming them, as this may result in a backlog again, which might not clear by the time the next peak comes).

[quyxkh]

Robot dispatch has to be bone simple. It's ... I haven't done a full investigation, and it's been a while, and I stop short of keeping a notebook, but as I recall, when it sees new jobs queued that aren't immediately taken by robots already in flight, it dispatches one robot per tick for ten ticks, then two per tick for ten ticks, then four, then 8 and so on, until (I'm guessing) it sees jobs being assigned to robots already in flight. So its response to bursty demand, the kind you get with trains, is very likely to overshoot unless you constrain it by only having about as many robots as you really need to get all the jobs done just as the next demand spike hits.

[astroshak]

Robot count for any given subfactory is a tough one, IMO.

I once set up automatic delivery of bots when either logistic or construction bot available was less than 10. I had nowhere NEAR enough roboports; though I had quite a few in that outpost. I eventually went back because it was not producing anything, and found that all of the bots were hanging out waiting their turn to recharge … all (I forget exactly how many) 30-50 thousand of them!

If you are going to set up automatic delivery of bots based on how many there are available … be sure to use combinator logic to set a hard ceiling on the number of bots. That, or use a mod that makes it so they don’t have to recharge (such as Nuclear Robots Reboot).