Turn work into printer-hours
Start with slicer estimates for complete cycles, including supports and any setup that keeps a printer occupied. A single printer-hour is useful only when the machine can actually run the job; separate incompatible materials, nozzles, or build volumes rather than pooling them.
Place long and short jobs deliberately
Long jobs can cover unattended periods, while short jobs are useful when someone is available to clear plates and restart quickly. Avoid a schedule that finishes every plate at the same inconvenient time. The calendar should reflect when a person can unload, inspect, and start the next cycle.
Protect the deadline with real buffers
Night operation, material changes, failed first layers, and reprints create risk even when the arithmetic looks comfortable. Reserve capacity for expected failures and leave a deadline buffer instead of treating every available hour as committed output.
Subtract maintenance before judging utilization
Planned maintenance is not idle time. Remove it from the period first, then compare productive print hours with net available hours. If utilization is low, investigate queue release, changeover, labor coverage, and blocked work before adding another printer.