How to change amount of preloaded resources into lab or assembler?

[Dixi]

Industrial Revolution mod, Quantum Labs stops a lot because inserters do not start inserting until one or zero resources left inside. At that time lab consume resources faster then new arrives, so it stops, until new stack is loaded.
I'm not sure, since it's less noticeable, but in some other modded buildings same situation happens.

Is it possible to define somewhere amount of resources that can be preloaded or must be loaded into a lab or assembler?
Or it's defined by recipe only?

I do not exactly understand why it happens with Quantum labs in IR, since majority of assemblers getting enough resources when supplied by fast enough inserters.

I've searched forums about similar questions but found only reference to same IR lab problem, but it's already archived and can't be viewed.

[Deadlock989]

This is arguably a design flaw in IR that may be addressed in a future version of the mod if there is one. You can get quantum labs working without interruption with vanilla stack inserters, even if they are beaconed with speed modules, but it requires one of a set of specific set-ups, and most likely completed stack inserter bonus research as well. Another workaround is to use loaders instead of inserters.

To answer the modding question, the reason labs behave differently to assemblers is that it is possible to define an overload multiplier property in recipes that affects the amount of "extra" ingredients inserters will load into assembling machines and furnaces that use the recipes, but labs don't use recipes so you can't do anything like that for science. There is no equivalent property for entities, only specific recipes.

[Dixi]

You can get quantum labs working without interruption with vanilla stack inserters, even if they are beaconed with speed modules, but it requires one of a set of specific set-ups, and most likely completed stack inserter bonus research as well. Another workaround is to use loaders instead of inserters.

Thanks for an answer!
I made some tests. To surprise me, it's not the type of inserters matter. As long as inserter supplying more then one type of pots it lags. Taking pots from belt with 2 colors, or taking all pots from a chest makes lab stop a lot. Stack inserter cause more delays compared to a blue one.
As soon as I setup 7 different belts or boxes, each with own inserter, everything works fine. Even blue inserter is enough.

[Deadlock989]

I made some tests. To surprise me, it's not the type of inserters matter. As long as inserter supplying more then one type of pots it lags. Taking pots from belt with 2 colors, or taking all pots from a chest makes lab stop a lot. Stack inserter cause more delays compared to a blue one.
As soon as I setup 7 different belts or boxes, each with own inserter, everything works fine. Even blue inserter is enough.

There is nothing surprising to me here. Inserters can only hold one kind of item stack at a time. Even in vanilla, a post-rocket technology needs six or seven kinds of science pack to advance in progress. If the lab were burning one of each kind of pack per second, your single inserter would need to be able to complete at least 7 full rotate-and-grab actions per second to fulfil that demand. Yes, even regular inserters can move more than one pack at once, but unless that "hand size" is itself 7 or more, one of the pack types would always run out before the inserter has completed a full cycle. But even that wouldn't work, because there is nothing to force an inserter to round-robin evenly between the 7 types anyway - so if the red stack in the lab drops below a threshold before your space stack has been topped up, too bad, the inserter might go back and replenish the red stack again anyhow. Given that research speed bonuses applies to all labs (it can't be restricted to specific lab entities) and that the quantum lab in IR 1.0.12 is already 8x the speed of a regular vanilla lab before any modules/beacons, you simply can't use one inserter to supply them any more. This is partly why the labs are a 7x7 entity with a perimeter contact of up to 28 tiles accessible to inserters.

There are various other set-ups that work even with module bonuses, and all of them work around that limitation that comes from trying to use the vanilla early-game one-inserter-per-lab set-up writ large. Is it a fun puzzle to solve? No, not really, which is why I said it's arguably a design flaw in the mod.