There are two things:
- the speed ramp up time (which @3DGG mentioned), I have it set to 3 seconds, but everyone can pick a value they like.
- the “warm-up” of the spindle when initially turning it on for the day: I used to ignore that, but after discussing this here with folks (I’ll try and find that thread), I now have the habit of running a 10-minute spindle warm-up routine macro, that incrementally increases speed from 1000RPM to 24000RPM, staying 60seconds at each intermediate step : this will ensure that the bearings take their sweet time to heat-up, the grease to flow where it needs to flow, and more generally the spindle to reach its operating temperature, especially when it’s cold in the shop. The precision will only be better (but I would not go as far as calling it mandatory)
EDIT: Here’s the discussion I was referring to, and here’s my daily spindle warmup macro.