For the singularity cards you need such vast amounts of imersite, I'm adding speed beacons as much as I can for the quarry drills, and it's barely enough. (And also efficiency modules for lower biter aggro of course.)

However I think I'm hitting the 60 per second limit. I'm at 250% mining bonus by now, I add 9 Speed3 modules and the info box says it's mining at 42.5/s, which with the productivity bonus should be 148.75 imersite per second? But it can't even fill a 90/s belt. The productions stats says it's doing 4.5k/min which is 75/s, so about half of what I expect.

I don't really understand how this limit works and before Krastorio2 I don't think I've ever even come close. I don't really mind if the drill isn't running at the full speed since I don't suppose anything can be done about that. But at which speed bonus do I start losing productivity ticks? So that the quarry drill no longer runs at +250% productivity but effectively a lower value?

My imersite mines run out way faster than I expected so I think I'm already well over the limit but don't quite understand the math to see what speed I can set for each productivity bonus. I haven't found any places that explain this, since I guess normally you don't really speed up drills all that much.

Am I right in thinking that the maximum speed before I lose productivity ticks is 60/250% = 24? Because at that point there will be 60 productivity ticks per second? If so I'm going to need way more imersite mines... but at least they will not waste anything.

Oh, I just saw that imersite has mining_time = 2, so that would explain the factor of two I was off. That surprised me though because the quarry drill can only be used on imersite, so it seems like it should just have mining_time = 1 and the quarry drill be half as fast instead. (Never understood why the vanilla ores and drills were set up like that too, seems unnecessarily counterintuitive.)

But I'd still like an answer to the rest of my question, how fast can I make the quarry drill before I lose productivity (if that ever happens)?

Factorio runs at 60 update per second and for each update, only something once can be crafted/mined so the limit is pretty much 60 per second for one quarry, yeah.

Thanks for the response! So it's just limited to 60 imersite per second, and if I get more mining productivity the drill just slows down more and more? And I don't lose productivity gains because the productivity would tick faster than the engine can do?

Alright, did some testing in the editor with this.

I made a quarry drill at +1500% speed, i.e. stated mining speed 160/s. With a mining bonus of 370% right now, I manually ticked the engine sixty times, so exactly one second has passed in game.

It put 376 imersite in the output box. That's exactly 160/2 + 160/2*3.7 = 80+296. The imersite cave abundance reduced by exactly 80.

So we can conclude that drills aren't limited by the 60/s limitation and higher speeds scale normally, and that the mining bonus also works normally even at these speeds. In other words: make your quarry drills as fast as you want!