Cycle time is the number most CNC shops quote a job on, and the one that most often turns out wrong once the job is running. The definition is simple; the useful part is knowing which pieces of time it includes.
The cycle time formula
Cycle time = Total running time ÷ Parts produced. For a single part, that running time splits into two pieces:
- Cutting time — the tool feeding into material. For one pass it is cut length ÷ feed rate.
- Non-cutting time — rapid moves, tool changes, spindle starts and stops, probing, coolant dwell.
Loading and unloading the part is usually kept out of cycle time and tracked as handling time, so a slow job can be traced to the program or to the operator side, not just “slow”.
A worked example
One shift on one turning machine (illustrative numbers):
Time the machine was running a program
- Value
- 6 h 24 min (384 min)
Parts produced
- Value
- 320
Programmed cycle time from CAM
- Value
- 66 s
| Input | Value |
|---|---|
| Time the machine was running a program | 6 h 24 min (384 min) |
| Parts produced | 320 |
| Programmed cycle time from CAM | 66 s |
Actual cycle time = 384 min × 60 ÷ 320 = 72 s per part — 6 seconds, or about 9%, slower than the program says. Across 320 parts that gap is 32 minutes of running time the quote never accounted for. Try your own numbers in the cycle time calculator.
Programmed vs actual cycle time
The programmed time is an estimate made before the first chip. The actual time is what the machine did — with feed overrides, extra tool changes and stops included. The two drift apart quietly, which is why it pays to measure the actual number per part rather than trust the estimate.
ThingConnect measures it from the controller: each time the part counter goes up, the machine’s running time since the previous part becomes that part’s cycle time. Time the machine sat waiting is not counted, so a long tea break doesn’t make one part look slow. Reports then use the typical (median) cycle, so one odd part doesn’t skew the number either.