What is a CMMS
A CMMS (computerized maintenance management system) is software that holds the asset register, schedules preventive maintenance, tracks work orders and spare parts, and produces maintenance KPIs. It replaces spreadsheets and paper with a single history for every machine.
The difference from a spreadsheet is the link between records: each work order (WO) is tied to an asset, a plan, the parts consumed and the hours spent. That history is what lets you calculate MTTR, PM compliance and cost per machine without retyping data.
Visual map of the work order cycle
The map shows a WO path inside the CMMS, from request to close-out, and the KPIs calculated with this article's example.
CMMS functions
| Function | What it does | Result |
|---|---|---|
| Asset register | Site, line, machine and component tree with tag, manufacturer and criticality | Base for everything else |
| PM schedules | Generates WOs by calendar, by meter (hours, cycles) or by condition | Follow-through on the maintenance plan |
| Work orders | Request, prioritize, schedule, execute and close with labor hours | History per asset |
| Parts and stores | Min/max stock, part reservation on the WO, consumption per machine | Fewer stoppages from missing parts |
| KPIs | MTTR, MTBF, backlog, PM compliance, cost | Decisions based on data |
| Mobile and attachments | Updates from the floor, photos, checklists, sign-off | Less paper and delayed entry |
The work order cycle
- Request: operations or maintenance logs the problem with asset and priority.
- Review and planning: the planner defines tasks, hours, parts and tools.
- Scheduling: the WO goes into the weekly schedule, aligned with the production window.
- Execution: the technician records hours, parts and findings.
- Close-out: failure cause, action taken and downtime are saved.
- Analysis: the data feeds the KPIs and the review of the PM plans.
Close-out with a failure code is the step most often skipped, and it is the one that makes the history useful. Without a recorded cause, the CMMS is just a task list.
Example: one month of KPIs from the CMMS
Fictional example: a crew of 5 technicians (40 hours per week each) closed the month with the data below.
| Monthly data | Value |
|---|---|
| Total WOs | 120 |
| Scheduled PM WOs | 84 |
| PMs completed on time | 78 |
| Corrective WOs | 36 |
| Downtime hours on corrective WOs | 108 h |
| Open WO hours (backlog) | 520 h |
PM compliance = PMs completed on time ÷ PMs scheduled
| KPI | Calculation | Result |
|---|---|---|
| PM compliance | 78 ÷ 84 | 92.9% |
| Planned share | 84 ÷ 120 | 70% |
| MTTR (corrective) | 108 h ÷ 36 | 3.0 h |
| Backlog in weeks | 520 h ÷ (5 × 40 h) | 2.6 weeks |
Reading: 30% of the work is still reactive, and a 2.6-week backlog is acceptable (rule of thumb: 2 to 4 weeks). Six PMs are late, and that is where to look for the cause. See the definitions of MTBF and MTTR to read the numbers correctly.
How to choose a CMMS
Set criteria weights before seeing demos, then score each system from 1 to 5. Fictional example with three candidates:
| Criterion | Weight | System A | System B | System C |
|---|---|---|---|---|
| Ease of use | 25 | 4 | 5 | 3 |
| Mobile app | 20 | 5 | 4 | 3 |
| PM scheduling | 20 | 3 | 4 | 5 |
| Parts and inventory | 15 | 3 | 4 | 5 |
| Reports and KPIs | 10 | 4 | 3 | 5 |
| Total cost (license + rollout) | 10 | 2 | 3 | 4 |
| Weighted score | 100 | 3.65 | 4.05 | 4.00 |
System B: (25×5 + 20×4 + 20×4 + 15×4 + 10×3 + 10×3) ÷ 100 = 4.05. B and C are only 0.05 apart, so the decision goes to a 30-day pilot with real data. Also ask about data import, local-language support and who owns the data if the contract ends.
Rollout in 5 steps
- Clean the register: start with critical assets, one unique tag each. Use the criticality analysis from RCM.
- Standardize codes: job type, priority and failure cause, in short lists.
- Load the plans: PMs per asset, with task, time and parts.
- Run a pilot: one area, 4 to 6 weeks, and adjust the workflow before scaling.
- Train and enforce close-out: a WO closed without hours does not count. Connect it to autonomous maintenance so operators raise requests.
The CMMS supports the planned maintenance pillar of TPM and feeds the availability figure in OEE. To decide what to schedule, see the differences between preventive, predictive and corrective maintenance.
Common mistakes
- Buying the software before defining the process: the system reproduces the existing mess.
- Incomplete register: without an asset hierarchy, there is no reliable cost or history.
- Closing WOs without cause and hours: the KPIs become false.
- OEM plans copied without review: they create excess PM.
- No data owner: assign someone to register quality and a monthly audit.
- Expecting the system to fix things alone: it shows where the problem is, but action is still the team's job.
Frequently asked questions
What does CMMS stand for?
Computerized Maintenance Management System.
What is the difference between CMMS and EAM?
A CMMS focuses on maintenance execution (WOs, PMs, parts). An EAM covers the full asset lifecycle, including purchasing, finance and projects.
Does a CMMS replace a spreadsheet?
Yes, once you have many assets and WOs. For a handful of machines a spreadsheet still works, but it loses history and automatic KPIs.
Which KPIs does a CMMS calculate?
MTTR, MTBF, PM compliance, backlog, planned work percentage and cost per asset. In the example, compliance was 78 ÷ 84 = 92.9%.
How long does implementation take?
It depends on the register. A one-area pilot takes 4 to 6 weeks, and plant-wide rollout usually takes a few months.
Do I need a mobile app?
Not mandatory, but updating the WO at the machine cuts delays and entry errors, and it weighs the most in technician adoption.
Sources
- KARDEC, A.; NASCIF, J. Manutenção: Função Estratégica. Rio de Janeiro: Qualitymark.
- PALMER, D. Maintenance Planning and Scheduling Handbook. New York: McGraw-Hill.
- MOUBRAY, J. Reliability-centred Maintenance. Oxford: Butterworth-Heinemann; New York: Industrial Press.
- NAKAJIMA, S. Introduction to TPM: Total Productive Maintenance. Cambridge: Productivity Press, 1988.
- EN 13306: Maintenance terminology (CEN).
Keep studying: trusted sources and links
- ABRAMAN: Associação Brasileira de Manutenção e Gestão de Ativos (in Portuguese)
- SMRP: Society for Maintenance & Reliability Professionals
- Wikipedia: Maintenance
Save this address: Manufatura Enxuta is your school for lean manufacturing. Come back whenever you need to study, with a complete article, a visual map and trusted sources. Follow one of the learning paths or check the A–Z glossary.
Want to measure what really matters?
Download the free e-book on performance indicators and track the losses in your operation.
Download the e-book
About the author
Lean Manufacturing & Behavioral Management Specialist
Over 20 years in the automotive and metalworking industries (GM and Dana), Lean Manufacturing practitioner since 2006. SENAI instructor and mentor in Brazil’s Brasil Mais Produtivo program, delivering consulting, training and audits for 50+ companies, combining quality, productivity and people development.
