Owners often feel their machines are busy all day. Spindle utilization is the number that checks that feeling, because it counts only the time the spindle is turning.
The formula
Spindle utilization = Spindle running time ÷ Available time × 100.
- Spindle running time — minutes the spindle was turning. Strict versions count only cutting time and leave out air cuts and positioning moves.
- Available time — usually the scheduled shift. Using the full 24 hours instead shows how much capacity is never scheduled at all.
A worked example
One machine over one 8-hour shift (illustrative numbers):
Scheduled shift
- Minutes
- 480
Machine in cycle
- Minutes
- 330
Spindle turning
- Minutes
- 250
| Time | Minutes |
|---|---|
| Scheduled shift | 480 |
| Machine in cycle | 330 |
| Spindle turning | 250 |
Spindle utilization = 250 ÷ 480 = 52%. The machine was in cycle for 69% of the shift, but tool changes, probing and rapid moves inside those cycles took another 80 minutes without the spindle cutting. That gap is a programming and tooling question; the 150 minutes out of cycle is a floor question.
Spindle vs machine utilization
Machine utilization counts the time a machine is running a program. Spindle utilization counts only the time the spindle turns inside that, so it is always the smaller number. Read together, they split lost time into “the machine wasn’t running” and “it was running but not cutting”.
ThingConnect reports in-cycle utilization per machine and shift from the controller, and reads spindle speed and load on every poll, so both sides of that split come from the machine rather than an operator’s log. On controls that expose them, the controller’s own operating and cutting time counters are read too.