What makes a balancer?

[stark forge]

I am struggling a bit with terminology and it is possible that there are an agreed on definitions in the community.

I've designed this blue print. It takes three inputs and has two outputs. The outputs will receive the same number of items regardless through what combination of inputs they arrive. However when all inputs are filled with the same number of items but different types one can observe that they recieve a different distribution of items. The "fix" would be adding a splitter on the two output lanes.

Blueprint in question.

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

I am interested in descriptive and ideally easily understandable language that i can use to talk about this and differentiates the current design from the one with an extra splitter on the output.

[worldly citrus]

you might find /editor with infinity chests + loaders to be useful for testing things

as for different item types, that can be a bit of a mess with splitters
sometimes they'll fall into patterns and be misleading

a main goal people have is to have equal input draw and equal output

[fallow violet]

theres mainly 3 types of balancers: normal ones, they are guaranteed to balance the belts only when all the inputs and outputs are being used; TU balancers, they will always perfectly balance the belts even when some inputs/outputs get unpligged; lane balancers, they will balance both sides of all the belts

[bright smelt]

lane balancers aren't necessarily TU

[fallow violet]

ok, my book was saying differentely, but i seached and i can confirm what you are saying, ill correct my answer

[stark forge]

What does TU stand for?

[bright smelt]

throughput unlimited
it's when you can throw any combination of inputs and outputs at it, and it'll properly balance without loss of throughput

properly balancing means that the balancer draws equally from all inputs, and supplies equally to all outputs
input/output combination means that some of them are not used, or slowed down
max throughput is obviously at most the lower of sum_of_all_inputs and sum_of_all_outputs

throughput limited balancers will either slow down below min(input, output) or not balance properly

[stark forge]

What does Throughput unlimited mean for compressing designs like 3-2?

[fallow violet]

means if u input 2 belts it wills till balance them

or if u take out one

[bright smelt]

hmm, actually, what I described above would be a UTU balancer. both TU and universal
the TU part applies to compressors as well
compressors don't necessarily balance

[bright smelt]

this one is TL
if you supply the top and mid input, you can draw at most 1 belt out of it

[stark forge]

Are you sure? i think i tried

ah i see what you mean.

imagine i updgragded the splitters one tier

[bright smelt]

Yep, the first splitter those two inputs go through funnels it through one output
You might not see it with only single inserters supplying the inputs

this one should be TU

-# I'm not sure though, it's not designated TU

[stark forge]

However when all inputs are filled with the same number of items but different types one can observe that they recieve a different distribution of items.
Is that property or its opposite named?

[bright smelt]

phflack explained here that these patterns can happen. It's just splitters being splitters.

since we cannot rely on the exact distribution of items (i.e. each active input being equally spread over all outputs), balancers are used to balance belts of the same item only

so if you want to judge whether the output is balanced, you need to measure the item throughput

[stark forge]

I can modify the mechanism (adding a splitter over the outputs) so i can guarantee that property.

[bright smelt]

not without adding additional constraints

[stark forge]

What do your mean by that?

[bright smelt]

this will only work under specific operating conditions
such as having backpressure slowing down the items, or using sparse belts (items have gaps between them)

[stark forge]

This one is Throughput unlimited true or false?

[fallow violet]

false

[bright smelt]

Yeah, it's TL

[stark forge]

I don't see how it is throughput limited.

[fallow violet]

look the 2 belts at the top

they go into one

[stark forge]

Yes, they go into one of a higher tier

[fallow violet]

no?

also it needs to be all the same tier

[stark forge]

Red is higher tier then yellow.

[fallow violet]

cause noone is gonna stick to yellow belts

[fallow violet]

its all red btw

[stark forge]

I just painted over it with yellow here

[bright smelt]

I didn't "see" those yellow arrows at first.
Well, multi-coloured balancers exist, but that pretty much locks it out from being upgraded

[fallow violet]

ye multi colors are usually for bigger balancers

128+

cause u mught need belt weaving

[bright smelt]

The whole thing is red belts though. And you feed it with yellow belts.
I'd say it's mincing words whether the contraption itself is TU or not

[stark forge]

So is defining things 😄

[bright smelt]

I want to disagree, but I'd be in the wrong 🙃
You're never getting to a definite answer for the TL-ness though.

[stark forge]

Question, is a splitter a throughput unlimited 2-2 balancer?

[stark forge]

There is a book on this?

[fallow violet]

theres a full every balancer book

it was saying what they do too

[bright smelt]

Yes, it's a UTU 2-2 balancer
guess how a 1-1 balancer looks like 😛

[spice needle]

Balancer

Raynquist Fall 2025 balancer book
Balancer Mechanics

[bright smelt]

First link is the balancer book, second link a good explanation of the terminology.
The two gifs show the difference between TL and TU

Mandatory reminder that balancers are rarely the best solution.

[stark forge]

If i have an universal throughput unlimited 3-2 non-balancer and put a UTU 2-2 balacner behind it, do i get a 3-2 UTU?

[bright smelt]

a universal non-balancer? that's a paradox

[stark forge]

Imagine a contraption that if only one input is active, always directs it to the first output no matter the input instead of splitting it between the two outputs as a balancer would but if more than input has items on it, it balances otherwise. I think i could build that using signals.

[bright smelt]

That's a compressor

[stark forge]

Let me rephrase:

i have an universal throughput unlimited 3-2 compressor (unrelated to my design) and put a UTU 2-2 balacner behind it (and the belt types of first output and sexond input match), do i get a 3-2 UTU?

[bright smelt]

i have an universal throughput unlimited 3-2 balancer and put a UTU 2-2 balancer behind it, do i get a 3-2 UTU balancer?
I edited a bit for correctness.
A: You don't need to add anything to get a 3-2 UTU balancer to get a 3-2 UTU balancer

[stark forge]

This is a different question from what i asked.

[bright smelt]

Do you have a specific use case in mind? It seems like you want to build something instead of wanting to learn about balancer stuff.

The question you asked doesn't make that much sense to me. I've never seen compressors being part of balancer notation.

[stark forge]

Well it by itself wouldn't be, but if we put its output through a balancer ... then the entire (in my current understanding) would become a balancer.

[bright smelt]

You can do a 3-3 balancer and the compress it down to 2 belts.

[bright smelt]

no, because compressors never draw evenly. at most you could get an output balancer

(while generally "balancer" means contraptions that balancer both their input and output, it's possible to build contraptions that balancer only either side)

[stark forge]

Thank you 😄

[stark forge]

giggles I am very interested in the state of the art of balancer theory and this thread was created to learn about that

[bright smelt]

well, it is an art

and it shouldn't be pursed other than for its own sake
balancer books exist and most of the time, there's better alternatives than balancers

[stark forge]

I've been thinking about doing an entire balanced Nauvis till rocket launch play through for the fun of puzzling.

[bright smelt]

wdym balanced

[stark forge]

Okay, every building can be thought of as a bunch of sources and drains for streams of items which form a network.

If i have a 30 mining drills which feed 48 smelters the connection between them is fully balanced.

and do that for every build in my play through

[bright smelt]

please no
I mean, you can do whatever you want, but I mentioned twice in this thread that balancers are usually not the optimal solution

[stark forge]

nods But it sounds like a fun puzzle.

I also consider chests/cars fed/drained by the same inserters a balances.

[bright smelt]

The only puzzle would be to find a place for all those balancers.

[stark forge]

This would be a how i do circuits. Fed from the left, has no outputs but those would be attached to the green circuit AMs

actually, let me place the filters. I forgot to set them

[fallow violet]

tf am i seeing

[stark forge]

This is balanced in that, the inserters between two machines exceed the input limits and if there are multiple connections leaving a machine they are symmetric. The two green circuit machines draw from 1:2 balanced iron plate lane and the 3 copper wire machine draw from a 1:3 balanced copper plate lane. The two green circuit machines are fed symmetrically from the 3 copper wire machines.

[fallow violet]

i still dont get the point of doing all that

[stark forge]

It is fed by a lane of iron plates and a lane copper plates from the left.

[fallow violet]

this isnt satisfactory where every input needs to be balanced

[stark forge]

nods

[fallow violet]

like

why

also it makes it hard to tile

[stark forge]

Because i had so much fun puzzling that out.

[fallow violet]

oh thats good then

also the filters arent needed

[stark forge]

They are needed for understanding 😄

[fallow violet]

man i still dont understand how u gonna input from the same belt

they get consumed at different rates

and a machine could grab some then wait

so that would mess it up

[stark forge]

They are in different lanes.

[fallow violet]

ohh nvm

[stark forge]

Like there will be no belt from which inserters feeding different machines draw from in a way which prioritizes one machine over the other in my entire base. That is the goal.

that is the idea.

[fallow violet]

oh ok

[stark forge]

so no Smelter stacks.

No laying down a line of miners along a belt. Since if there was a back pressure, that would result in the miners being blocked unevenly.

Fluids are already balanced as long as there is no pump between them.

Anyhow if i wanna do that i need a solid grasp on balancers and stuff.

[stark forge]

the difference between input balancer and output balancer matches my observations.
I do not understand how general this https://factoriobin.com/post/cgn0od/195 is. The rest of the book i was able to follow but i feel like the comments and discussion it links to show a lot more depth then the book discusses.
Are there other resources you can recommend

[bright smelt]

Where are the output inserters in your puzzle?

Also, yes, this is entirely unnecessary.

[stark forge]

As i mentined it didn't add them, they could go into different places depending on how i arrange them as part of a larger whole

And i am fully aware that it is unnecessary. I rather discorver my own weird to play on settings that suit me then to aspire to copy or learn some meta. I am not asking for a blueprint on balancers. I want to puzzle that out myself but also respect the prior art and theory others have come up with before.

[stark forge]

Any by wanting to challenging myself with a balanced build i am not insisting to use fit belt balancers all over the place.

[bright smelt]

waterfalls would also result in a balanced build, for a slightly different definition of balanced
anyway, do as you must

[stark forge]

@languid temple Can i reach out to you about FactorioSAT?

I would be interested in the theory/modeling behind it

[languid temple]

Sure, though it's more of a "how do I place this splitter network onto a grid" rather than a tool for creating a balancers from nothing

[stark forge]

That is perfectly interesting too.

May you accept my friend request or you DM me?

[stark forge]

I feel like FactorioSAT is out of scope for this topic/conversation.

[coarse haven]

Aside from the throughput limited/unlimited distinction, there's also the input-balanced/output-balanced/universal balancer(input and output balanced) distinction

[stark forge]

Is there any relationship between those categories?

[bright smelt]

"universal" would be a subsection of the overlap only.

a balancer that is balancing both input and output is just a balancer

only when you can throw any combination if inputs and outputs at it, while still maintaining balance, is it a universal balancer

https://wiki.factorio.com/Balancer_mechanics

[coarse haven]

That wiki page doesn't mention input balanced or output balanced balancers

If it's input balanced then it's sort of half-universal in that any number of inputs will be used evenly

eg. an input balanced 8-8 balancer also functions as any n-8 balancer where n<=8

Honestly maybe the wiki needs an edit, I'm not sure how much detail is warranted though given that you could probably write a whole book on balancers.

[bright smelt]

that is not what universal means, even if applied to one "side" of a balancer

[coarse haven]

What does universal mean then? I thought it meant a balancer that can also work as any n-m balancer where n<=inputs and m<=outputs.

[bright smelt]

Yes, but it doesn't follow from being input balanced and output balanced alone, which is what the venn diagram suggests.

A universal balancer guarantees balance no matter what, but possibly at the loss of throughput.
A throughput unlimited balancer guarantees throughput, but possibly at the loss of balance.

[coarse haven]

I still don't understand why not

lets say you have an 8-8 balancer

if it's input balanced it also works as any n-8 balancer

if it's output balanced it also works as any 8-m balancer

if it's a universal balancer it also works as any n-m balancer

is that not correct?

[bright smelt]

No. In the general case, a certain combination of inputs or outputs may break the balance. Only the special case of universal balancers guarantees it.

Many balancers fail to balance properly once an output backs up or if an output is not used
the first sentence of the universal balancer paragraph in the wiki

Which means that your 8-8 may stop being input balanced if you only use 7 outputs. Unless it's a universal 8-8 balancer.

[vague iron]

That's correct, but input balanced + output balanced is not the same as being a universal balancer
if, however, you were to put an input balanced balancer down and then hook up the outputs of that input balancer to an output balanced balancer, then you'd get a universal balancer (even if the input balanced and output balanced balancers were the same balancer)

[coarse haven]

I feel stupid because I still have no idea what the difference is. What would an input balanced and output balanced but not universal balancer behave like?

[vague iron]

It would be able to act as an input balanced balancer if you don't connect all the inputs, or as an output balanced balancer if you don't connect all the outputs, but not (always) both at the same time - that is, if you don't connect all the inputs and you don't connect all the outputs, then the balancer wouldn't (always) behave like either an output balanced or an input balanced balancer.

[coarse haven]

Ahh I get it now

Feels a bit like semantics since "can do both at once" feels like what an intersection on a venn diagram would mean in my head but I guess it's an important distinction

Especially since you could easily confuse the two when designing a balancer

[bright smelt]

I don't think you get it now. The universal attribute applies to both the input side, and the output side. (or the contraption as a whole)

[bright smelt]

A non-universal balancer does not guarantee balance.
I have written that three times before, in different ways.

[coarse haven]

The distinction seems to be:

Balancers that balance if you're missing inputs OR missing outputs (but not both)
Balancers that balance even when missing both inputs and outputs (truly universal)

The confusion lies in the fact that when I said "both input and output balanced" I meant the second option (universal). I overlooked that the first option is arguably "both" by some definitions.

So in my head you were basically saying "just because it's a universal balancer doesn't mean it's a universal balancer" over and over again, thus my confusion

[bright smelt]

yeah that doesn't make much sense