Hi, What are the limits for the minimal crafting time?

I have set time to 0.13888 — 180 ore/s in assembly 3, but with the speed modules it unable to compress 360/s (60/s belt x 6). Even with the 4 x speed 3 (+200%) it still just 5.5 x belts 60/s — half of one belt is not moving

There are only vanilla game limitations for most recipes (i didn't implement any limits). Steel smelting admittingly has a little sloppy way to convert decimal number to 0.1 accuracy for display purpose. But if you had CompressedSteelSmeltCost = 0.0001 then:

CompressedSteelSmeltCost = math.floor(CompressedSteelSmeltCost x 10)/10.0
= math.floor(0.0001 x 10)/10.0
= 0.0? ... It might give it a higher minimum limit from the base game.

Recipe values are what they are before affected by speed modules, assembler speed etc which further multiply it.