What a preventive maintenance schedule is
A preventive maintenance schedule is a rule that tells your system when a defined maintenance task is due on a specific asset — before it fails, not after. It is defined per asset or per equipment group and carries three things: a trigger (what makes it fall due), a frequency (how often), and a checklist or task template (what to do). When the schedule falls due, the software auto-generates a PM work order, so the job never depends on someone remembering it.
That is the whole point. PM usually slips not because teams doubt it matters, but because the due-date lived on a wall planner or in one person's head while firefighting won the day. A schedule inside a CMMS turns "we should service that compressor sometime" into a dated, owned, alerted work order that chases itself.
Calendar-based vs usage/meter-based triggers
Every PM schedule is fired by one of two triggers, and choosing the right one is the single most important decision you make. A calendar trigger fires every N days, weeks or months regardless of how hard the asset worked. A usage or meter trigger fires every N running hours, cycles, strokes or kilometres, so a machine that ran double shifts is serviced twice as often as one that sat idle.
| Trigger | Best for | Example | Watch-outs |
|---|---|---|---|
| Calendar Every N days / weeks / months |
Assets that degrade with time, and anything with a statutory or audit date — lubrication, filter changes, safety checks, calibration recalls. | Monthly greasing of a conveyor; quarterly HVAC service; annual DG-set statutory inspection. | Over-services a machine that barely ran, and under-services one on triple shifts — time does not know how hard the asset worked. |
| Usage / meter Every N hours / cycles / km |
Assets whose wear tracks how much they run — motors, spindles, compressors, hydraulic presses, DG sets, vehicles. | Compressor oil every 2,000 running hours; press service every 500,000 strokes; forklift check every 250 hours. | Needs a reliable meter reading — from a runtime counter or a logged entry. No reading, no trigger, so reading discipline matters. |
The meter basis — running hours, cycles, strokes or km — is not invented per schedule; it comes from the asset register, where each asset records how its usage is counted. That keeps the trigger honest and consistent across every schedule on that machine.
How to build a PM schedule, step by step
Building a schedule that survives contact with a busy shop floor follows a repeatable sequence. The first half is planning; the second half is what the software does automatically once the schedule is live.
Steps 1 to 6 you do once per asset or group; steps 7 to 9 repeat for the life of the machine with no re-entry. Three notes make the difference between a schedule that holds and one that decays:
- Criticality first. Rank each asset by the damage its failure does — to output, safety and cost. Criticality from the register is what justifies a tighter interval on the machines that matter and a looser one on those that do not.
- Make the checklist measurable. "Check bearing" is weak; "record bearing temperature (°C)" is strong. A checklist that captures a measured value turns PM into early-warning data, not a tick-box.
- Let not-OK escalate. When a checklist item comes back not-OK, it should be able to spawn a corrective ticket then and there — the whole reason for inspecting is to catch the failure before it becomes a breakdown.
For the checklist itself — what to put on it and how to structure OK / not-OK / measured-value items — see the preventive maintenance checklist guide.
How to choose the right frequency
Trigger tells you what makes PM due; frequency tells you how often. Four inputs set it, and the good news is you rarely start from a blank page.
- OEM manual. The manufacturer's recommended interval is your baseline — oil every 2,000 hours, filters every 3 months. Start there; it reflects the design.
- Criticality. A machine whose failure stops the line earns a tighter interval than the manual's minimum; a spare, non-critical unit can be relaxed toward run-to-failure.
- Failure & downtime history. If an asset keeps failing before its next PM, the interval is too long. History tells you where the manual is wrong for your conditions.
- Duty cycle. A press on three shifts in a dusty foundry wears faster than one on a single clean shift. Match the interval to real load — which is exactly what a meter trigger does automatically.
The practical method: start at the OEM interval, adjust once for criticality and duty cycle, then review against breakdown history every few months. A schedule is a living number — tighten it when failures appear inside the interval, relax it when an asset proves reliable, using downtime and MTTR/MTBF trends as your evidence.
Worked examples — CNC, compressor, DG set, forklift
Concrete beats abstract. Here is how four common assets are typically scheduled. Intervals are illustrative starting points — always temper them with your OEM manual and your own history.
| Asset | Trigger | Typical interval | Key tasks |
|---|---|---|---|
| CNC machine | Calendar + running hours | Monthly check + every ~500 running hours | Way lubrication, coolant level & concentration, spindle temperature, axis backlash, filter clean, chuck & hydraulics inspection. |
| Air compressor | Running hours | Oil ~2,000 h; air/oil filter ~2,000–4,000 h | Oil change, air & oil filter, separator element, belt tension, drain traps, check pressure & temperature. |
| DG set | Running hours + statutory calendar | Oil ~250–500 h; annual statutory inspection | Engine oil & filter, coolant, fuel filter, battery, load test, exhaust & emission check for statutory compliance. |
| Warehouse forklift | Running hours / km | Service every ~250 hours | Hydraulic oil & filters, brakes, tyres, mast chains, battery/electrolyte or fuel system, safety-device check. |
Notice the pattern: compressor and forklift are pure usage assets; the CNC is a hybrid (some tasks by clock, some by hours); and the DG set is hybrid for a different reason — statutory dates force a calendar element on top of usage-based servicing. Most plants end up with a mix.
Calendar vs usage — a decision guide
When it is not obvious, this is how to decide which trigger wins — and when to run both.
Hybrid schedules are common and worth the small extra setup: they protect a critical asset from both failure modes without over-servicing on either axis.
Calibration as a PM schedule
Calibration is preventive maintenance in disguise. A gauge, instrument or measuring device has a validity period, and when it expires the instrument must be recalled and recalibrated before it can be trusted again — which is functionally a calendar-based PM schedule with a due recall. The trigger is the calibration-due date, the checklist is the calibration procedure, and closing the job resets the next due date exactly as any other PM does.
For plants running ISO 9001 or IATF 16949 systems, a missed calibration recall is an audit finding, so treating gauges as scheduled assets — with the same auto-generated ticket and alert as a machine PM — closes a real compliance gap. The full workflow is covered in the gauge calibration management guide.
Keeping schedules alive: alerts, PM-due dashboard, compliance
A schedule that no one sees is a schedule that slips. Three mechanisms keep PM from quietly dying:
- Alerts that reach people. When a schedule falls due, the planner gets an email, SMS or WhatsApp alert — so action does not depend on someone opening the software to check.
- A PM-due dashboard. One screen showing what is due, due soon and overdue, per asset and per team, so nothing hides. Overdue PM is visible, not forgotten.
- PM compliance — planned vs done. The one number that tells you whether the system is working: of the PM raised this month, how much was completed on time. Track it and PM stops losing to firefighting.
Still tracking PM due-dates on a wall planner or a spreadsheet tab?
We can show you a live PM-due dashboard, an auto-generated work order with its checklist, and email/SMS/WhatsApp alerts — in 30 minutes, on your own assets.
How Fast Maintenance implements it
Fast Maintenance Software is a working implementation of everything above, built by Improsys in Pune on the shared Fast Suite platform and available cloud or on-premise. The schedule you designed on paper becomes a self-running loop:
Because it runs on the shared platform, the same deployment serves manufacturers of every kind across India and worldwide — MSME plants and larger ISO/IATF-audited operations alike — with transparent INR pricing. See maintenance software pricing, or start from the CMMS pillar guide for the full picture.
Frequently asked questions
What is a preventive maintenance schedule?
A preventive maintenance schedule is a rule that tells the system when a defined maintenance task is due on a specific asset. It is set per asset or per equipment group and triggered either by the calendar (every N days, weeks or months) or by usage (every N running hours, cycles, strokes or km). Each schedule carries a checklist, and when it falls due the software auto-generates a PM work order so the job never depends on someone remembering it.
Calendar-based vs usage-based PM — which should I use?
Use calendar triggers for assets that degrade with time or must meet statutory dates — lubrication, filters, safety checks and calibration recalls. Use usage or meter triggers for assets whose wear tracks running hours, cycles, strokes or km — compressors, CNC spindles and DG sets. Many critical assets need both: a hybrid schedule where whichever comes first, calendar or meter, raises the PM ticket.
How often should preventive maintenance be done?
Frequency comes from four inputs: the OEM manual's recommended intervals, the asset's criticality in your register, its failure and downtime history, and its real duty cycle. Start with the manufacturer interval, then tighten it for critical or hard-run assets and relax it for lightly used ones. Review the interval as breakdown history and PM findings accumulate so it reflects reality, not the brochure.
How does the software know when PM is due?
Each schedule stores its trigger — a calendar interval, or a meter basis taken from the asset register. Fast Maintenance checks these continuously; when a schedule falls due it auto-generates a PM ticket, lists it on the PM-due dashboard, and pushes email, SMS or WhatsApp alerts to the planner. On close, the next due date is recalculated from the calendar interval or the latest meter reading.
What is a good PM schedule for a CNC machine, compressor and DG set?
A CNC machine typically runs a monthly calendar check plus a running-hours schedule for spindle and lubrication tasks. An air compressor is best driven by running hours — oil, filters and belts by meter. A DG set combines running hours for oil and filter changes with a statutory calendar check. Fast Maintenance runs calendar and meter triggers together, whichever falls due first.