Closed Time
What is the difference between closed time and setup time?
Setup time is the broader period when the machine is not cutting due to preparation, while closed time is the narrower state where access is blocked or the process is held closed. Closed time is one component of setup or waiting time.
How does closed time affect CNC throughput?
Closed time increases the non-productive portion of elapsed time. Since machining time depends on cut length, feed, passes, RPM, and setup/tool-change time, any additional closed interval lowers parts-per-hour even if the toolpath is unchanged.
What shop data should be tracked if closed time is causing losses?
Track door-open/door-closed durations, clamp-close to unclamp time, pallet change intervals, tool-change counts, program-run time, and setup duration separately. Separating these from productive cycle time is necessary for bottleneck analysis.
Closed time on a shop floor is the non-open duration of a process window, when a machine or operation is not available for loading or access because the process is in a closed state. In CNC machining, it includes periods of enclosure, clamping, guarding, or waiting for the machine to reopen, directly adding to non-cutting time and reducing throughput.
In CNC machining, closed time directly impacts throughput as it accumulates during non-cutting states like automatic machining, probing, or pallet changes. Operators monitor door-closed durations and clamp-close intervals to identify hidden delays that aren't captured in cycle time. For millwork and edgebanding, closed time refers to the period after glue application or edge engagement when the assembly must remain under pressure until the bond stabilizes; premature opening can cause glue-starved joints or dimensional spring-back. On the shop floor, supervisors treat closed time as a separate bucket for loss analysis, distinct from setup time or programmed cutting time. This separation is critical in high-mix CNC cells where frequent fixture swaps and inspection cycles create large hidden losses. Tracking these intervals allows precise bottleneck identification and better job quoting, as every extra second of closed time extends total manufacturing lead time.
Confusing closed time with cycle time: Cycle time covers active cutting, but closed time includes loading, clamping, and waiting. Mixing them leads to underquoted jobs and misread utilization data.
Treating door-closed or clamp-closed time as free time: Every extra second waiting for access adds to total lead time. In high-mix CNC cells, frequent setups accumulate into hidden throughput losses.
Releasing a clamped or bonded assembly before the closed state is complete: Opening the press or unclamping early causes edge lift, misalignment, or weak bond lines. Follow specific dwell requirements for adhesive and material.