Cycle Time
Cycle time in CNC machining is the total elapsed time to complete one part or manufacturing cycle. It includes cutting, rapid movements, tool changes, loading/unloading, probing, inspection, and all non-cutting actions, not just spindle-on time. Machining time is the actual cutting duration, while cycle time encompasses all auxiliary losses and handling.
In an active CNC mill or turning cell, cycle time is the benchmark for predicting part completion from start to finish. Supervisors use it to balance the cell, set takt time, and identify bottlenecks in programming, fixturing, or material handling. CAM software typically estimates cutting time as toolpath length divided by feed rate, then adds rapid traverses, tool changes, probing cycles, load/unload, inspection, and a portion of setup allocation to produce a realistic production number. For quoting and scheduling, experienced shops add a buffer because actual cycle time almost always exceeds pure CAM estimates due to non-cutting motion, part handling, and operator intervention. This same concept applies in millwork and edgebanding: one board through the machine cell includes feed speed, cutter changes, glue and trim stations, and manual handling. Rework or end-trim corrections further increase true cycle time.
Is cycle time the same as machining time?
No. Machining time is the actual cutting duration; cycle time is the full time for one part or one process cycle, including non-cutting and handling activities such as rapids, tool changes, load/unload, and inspection.
What is the basic formula for CNC cycle time?
A common shop-floor model is Cycle Time = Cutting Time + Rapid Time + Tool Change Time + Load/Unload Time + Inspection Time + Setup Allocation.
Why does the real cycle time exceed CAM time?
CAM estimates often omit or simplify rapid traverses, tool changes, probing, operator interaction, and part transfer, all of which contribute to the executed cycle time on the machine.