Calendar- or Time-based
These kinds of preventive maintenance are completed at regular or scheduled intervals. While all equipment should have PM, regularly checking equipment critical to production will help decrease breakdowns.
A motor-pool may have required maintenance every 4 months. This is a great example of calendar- or time-based PM.
Usage-based
The other type of PM is usage-based, where a machine’s statistics are used to determine corrective actions. Usage statistics can include cycle counts, runtime, miles/kilometers traveled, or hours, among others.
Rounds, where technicians check on the usage statistics of machines, is a kind of PM. Depending on measurements and usage readings gathered in rounds, maintenance may be scheduled.