---
title: "What is a CMMS, and why start it from the machine?"
description: "A CMMS tracks work orders, PM schedules, assets and spare parts. See what it does for a plant, why hand-entered history misleads, and how to judge floor fit."
category: "Maintenance and reliability"
author: "Reliability Engineering Team"
published: "2024-12-03"
updated: "2026-10-20"
source_url: "https://www.iotflows.com/blog/what-is-a-cmms/"
---
> Question: What does a CMMS do for a production plant, and what makes one fit the floor?

## Key takeaways

- A CMMS holds four records: work orders, assets, preventive maintenance schedules and spare parts inventory.
- A work order is the unit of everything in a CMMS, so where work orders start decides how current the system is.
- Work orders opened from machine stops and events carry the real stop time, which hand entry loses.
- In a NIST case study, 93% of 21,107 work orders were closed on a Friday, so their recorded durations did not reflect the work.
- Judge a CMMS by how fast an operator can file a request and how many work orders the machines open on their own.

A CMMS (computerized maintenance management system) is the software where a plant requests, plans, records and reviews maintenance work. For a production plant it does four jobs: it turns machine problems into work orders, brings preventive tasks due, tracks spare parts and keeps each machine's repair history. It fits the floor when work orders start from what the machines report, with the stop time attached, instead of from somebody remembering to file one.

This guide is for maintenance leads and plant managers choosing a CMMS or fixing one nobody uses. It covers what the system holds, where work orders should come from, why hand-entered history misleads, and how to judge fit.

## What is a CMMS?

> **Definition.** **CMMS (computerized maintenance management system)** is software that records maintenance work orders against each machine, brings preventive maintenance due on a calendar or run-time schedule, tracks spare parts, and keeps the repair history that maintenance decisions are made from.

The US Department of Energy’s operations and maintenance guide describes a CMMS as management software that supports managing and tracking maintenance activities. It adds that a CMMS makes no decisions: it gives the maintenance manager the information to make them.[1]

Under every screen, a CMMS holds four records.

| Record | What it holds | Question it answers |
|---|---|---|
| Work orders | One job: machine, people, parts, status | What needs fixing, and who has it? |
| Assets | Machines and components, with manuals | What do we maintain, and where? |
| PM schedules | Recurring tasks by date or run time | What comes due this week? |
| Parts inventory | Stock by location, reorder points | Is the bearing on the shelf? |

Everything else is a view of those four. The backlog is a filtered list of open work orders. A machine’s history is every closed work order that names it. A reorder list is the parts whose stock fell below their reorder point.

### CMMS, MES and machine monitoring

Plants often confuse three systems that answer different questions.

| System | Question it answers | Main record |
|---|---|---|
| Machine monitoring | What are the machines doing? | Run time, stops and part counts |
| CMMS | What needs fixing, with which parts? | Work orders |
| MES | What to make, and how did the run go? | Production orders and quality records |

They meet at one point: a machine stop is a monitoring event, and the repair it needs is a CMMS work order. The side-by-side, with where each sits in ISA-95, is in [machine monitoring vs MES vs CMMS](/compare/machine-monitoring-vs-mes-vs-cmms/).

## What a CMMS does for a production plant

The DOE guide lists the functions a CMMS covers, depending on the system.[1] Here they are with a plant example for each.

| Function | Plant example |
|---|---|
| Work orders by machine and priority | Spindle fault on Haas VF-2 #3, high |
| Searchable work order history | Every repair on Press 4, by date |
| Calendar or run-time PM | Grease the spindle every 500 run hours |
| Labor and cost by machine | Hours and parts spent on Molder 7 |
| Time to close, by component | Median and worst repair on a gearbox |
| Parts inventory with reorder | Reorder V-belts at 4 on the shelf |

Choosing which PM goes on a date and which on run hours is its own decision, covered in [how to choose a maintenance strategy](/blog/maintenance-strategies/).

A large share of that work doesn’t start as a plan. In NIST’s survey of US manufacturers, an average of 45.7% of machinery maintenance was reactive.[3] Each of those jobs starts with a failure that has to reach the CMMS, so where work orders come from decides whether the CMMS is current.

The DOE guide frames the need as a set of questions.[1] Consider a CMMS when you can’t answer these from records:

- When was this machine last serviced, by whom, and what did they find?
- Which work is open right now, and who has it?
- Are you waiting on parts, or carrying stock nobody uses?
- Where are the manual and the lockout procedure for this machine?

You don’t need one yet if one technician does every job on a handful of machines and keeps a log current. Move when a second person needs the same history, or when [PM tasks start slipping](/blog/preventive-maintenance-schedule/#compliance).

> **Check the year on benefit claims**
>
> The DOE guide relays a survey by A.T. Kearney and Industry Week of 558 companies already using a CMMS. They reported an average 20.1% less equipment downtime and a 14.5-month payback.[1] The guide cites the survey from a 1994 CMMS product guide, so treat these as old, self-reported figures, not a forecast for your plant.

## Where work orders come from

> **Definition.** **Work order** is one unit of maintenance work on one machine: what needs doing, who does it, which parts it uses, when it is due and what status it is in, from the moment it is opened until the work is signed off.

A CMMS is only as current as its [work orders](/docs/get-started/glossary/#work-order). A work order can start in six ways, and each one fits a different kind of work.

| Origin | Starts when | Fits |
|---|---|---|
| A planner | Someone fills in the form | Rebuilds, projects, one-off jobs |
| An operator request | An operator reports a problem | Leaks, noises, loose guards |
| A classified stop | A stop gets a maintenance reason | Breakdowns, tool crashes |
| A machine event | Shock, health or heat crosses a limit | Faults with one obvious response |
| A meter | Run hours or parts reach a trigger | Wear that follows use |
| A recurrence | A date comes due | Inspections owed on a date |

Pick the origin by who knows first. The machine knows first about a stop, a shock or its run hours. An operator knows first about a leak or a smell. A planner knows first about a rebuild.

The DOE guide gives the machine-first pattern for an air filter. A pressure sensor reports when the filter needs changing, the CMMS opens the work order on that need instead of every three months, and the filter comes out of stock with a reorder if needed.[1] The same logic works for a spindle, a die or a mold.

> **Which machine events should open work orders?**
>
> Open a work order automatically for events with one obvious maintenance response: a shock above the crash threshold, a bearing health score past its limit, a motor over temperature. Keep a machine stopping or a sensor going offline as alerts only. They fire on every changeover, jam and network drop, and a backlog full of them hides the real work.

The difference shows most on a night shift. On paper, a tool crash at 22:12 becomes a work order the next morning, with a start time somebody guesses. From the machine, the stop is on record to the second and the work order carries it.

Figure: Two timelines for one tool crash at 22:12. The paper path runs through the operator, the supervisor and a note to day shift, reaching a work order at 06:40. The machine path records the stop at 22:12:04 and opens the work order at 22:15.

*The same night-shift tool crash, reported by hand and from the machine. Sample data.*

RNPSA, a mining equipment manufacturer in Matehuala, Mexico, describes its old path the same way: an operator told the shift supervisor, who wrote a note, which the next shift supervisor read before calling maintenance. Now the operator who classifies a stop opens the work order in the same step, and RNPSA halved its maintenance response time.

> Continuous vibration monitoring gave us eyes we never had before. We can see tool crashes that would have been invisible, identify the exact moment and severity, and pull historical data to understand what went wrong. Add in Maintain, and suddenly operations and maintenance aren't working in silos, we're collaborating on the same data in real-time. That's transformed how we manage these critical machines.
>
> Miguel Silva, Systems Engineer, RNPSA ([story](https://www.iotflows.com/customers/rnpsa/))

## Why hand-entered maintenance history misleads

A CMMS computes response time, repair time and backlog age from timestamps. When people type those timestamps after the fact, every report built on them inherits the error.

NIST researchers studied ten years (2009 to 2019) of HVAC work orders from a mixed laboratory and office site. Work orders opened across the whole working week, between 13% and 24% on each weekday. Yet 19,597 of 21,107, about 93%, were closed on a Friday.[2]

Figure: Paired bars by weekday. Work orders opened at 22%, 24%, 21%, 19% and 13% from Monday to Friday, while 93% were closed on Friday and 3% or less on any other day.

*Work orders opened all week and closed in Friday batches. Data from NIST’s HVAC case study.*

The closings fell on only 520 days in ten years, about one close-out a week. The authors conclude that the closing dates almost certainly don’t match when the work finished, so durations computed from them can’t be trusted.[2] The dataset also lacked the timestamps needed for time to dispatch, one of the measures the authors ranked most important.[2]

The site was a building, not a production line, but the cause transfers. The authors note that maintenance staff type work orders by hand, often under time pressure, into systems that fit their needs poorly.[2] Here is what a Friday batch does to mean repair time on a hypothetical CNC cell.

#### Worked example: Five repairs, closed in one Friday batch

- Five breakdowns are logged at Monday 09:00, Tuesday 14:00, Wednesday 08:00, Thursday 11:00 and Friday 07:00.
- The technician closes all five at Friday 16:00.
- The machines’ stop logs show each repair took 40, 90, 25, 60 and 35 minutes from stop to running again.

From the CMMS dates, the five repairs take 103, 74, 56, 29 and 9 hours: 271 hours in all, or 54.2 hours each. From the stop logs, they take 250 minutes in all, or 50 minutes each.

**Result:** The batch-closed history overstates mean repair time about 65 times: 54.2 h against 50 min.

Take the start of a breakdown from the machine’s stop and its end from when the machine ran again. Then a late close-out changes the paperwork, not the repair time. That needs stop reasons that tell a breakdown from a changeover, which is what [downtime reason codes](/blog/downtime-reason-codes/) are for.

## What makes a CMMS fit the floor

A CMMS fits the floor when the people and machines closest to a problem can put it on record in seconds. Check these in a trial, on your own machines.

| Criterion | Ask the vendor, then test it |
|---|---|
| Work orders from stops | Does a classified stop open one? |
| Work orders from signals | Which events and meters open one? |
| Requests from the floor | How fast can an operator file one? |
| Usage meters | Machine-counted, or typed in? |
| Parts tied to the job | Does a job hold its parts? |
| Pricing | Can every operator log in? |

The last row matters more than it looks. Per-user pricing pushes plants to ration logins, and an operator with no login files no requests. The problem then travels by word of mouth, as on the paper path above.

The DOE guide names the common ways a CMMS fails: the wrong system for the site, too little training for the staff who enter data, and no commitment to implement it and keep using it. It adds that feature overload is a common complaint, and that most successful installations have a champion who keeps people using it.[1]

Choose a standalone CMMS when most of your work is facilities and building upkeep, or when your machines already report stops into a system you will connect. Choose a CMMS built on machine monitoring when breakdowns and wear on production machines drive most of the work, because the stop, the run hours and the part count are already recorded.

## Start maintenance from the machine with IoTFlows

IoTFlows Maintain is a CMMS built on machine monitoring. A work order is its only object: a request, a planned job and a preventive schedule are the same record with different fields filled in.

Work orders open from [five places](/docs/maintain/overview/#origins): by hand, from a classified stop, from a machine event rule on health, shock or temperature, from a meter, or from an operator’s request in the job runner or on a phone. A [meter](/docs/maintain/meters/) counts runtime hours or parts, emails at 85% and opens the work order at 100%.

A work order holds the parts it needs in Inventory, and marking it Done [moves the stock](/docs/inventory/how-work-orders-move-stock/). As of October 2026, [Maintain](/platform/maintain/) starts at $500 a month with unlimited users, on top of machine monitoring. Device plans are on the [pricing page](/pricing/).

## Roll out a CMMS your floor will use

1. **Load the machines that matter first.** Rank machines by what an hour of downtime costs, using [how to calculate the cost of downtime](/blog/cost-of-downtime/). Enter the top 10 with their manuals, lockout procedures and critical spares.
2. **Agree which stop reasons mean maintenance.** Mark the reasons that need a technician, such as tool crash, hydraulic leak and spindle fault, apart from changeovers and material waits.
3. **Give every operator a way to request work.** Put the request one step from the machine: on the operator screen, the job screen or a phone. Ask for a photo instead of a long description.
4. **Move recurring tasks in, and meter the wear items.** Enter each calendar PM as a recurrence. Move tasks on parts that wear with use to run hours or part counts, as in [usage-based maintenance](/blog/usage-based-maintenance/).
5. **Turn on machine-opened work orders one type at a time.** Start with shock events on CNC machines or health alerts on your most critical motor. Add the next type once the team triages the first within a shift.
6. **Read the history every month.** Count closings by weekday. If most work orders close on one day, your durations are batch close-outs, and repair times should come from the machine’s stops instead.

## Questions

### What is the difference between a CMMS and an EAM system?

A CMMS manages maintenance work: work orders, preventive schedules, spare parts and repair history. An EAM (enterprise asset management) system covers the whole life of an asset across sites, adding purchasing, depreciation and replacement planning to the maintenance work. A single plant that needs work orders and parts control needs a CMMS. A company planning capital spending across many sites looks at EAM.

### Can a spreadsheet do the job of a CMMS?

For one technician and a handful of machines, a shared spreadsheet can hold the work list and the service dates. It breaks when several people edit it at once, when preventive tasks need to come due on run hours, and when parts must be held for a job. It also records only what someone types, so its history inherits every late and missing entry.

### Who should be able to create work orders?

Anyone who sees the problem first. Operators file requests at the machine, technicians open follow-up work, and planners write the scheduled jobs. A planner then reviews new requests, sets the priority and assigns them. Limiting work order creation to the maintenance office means every problem waits for somebody to walk over and report it.

### What is the difference between a work request and a work order?

A work request is a report that a machine needs attention, filed by whoever sees the problem first, often an operator. A work order is the job maintenance agrees to do, with an assignee, a priority, parts and a due date. Some systems keep the two as separate records. Others treat a request as a work order with fewer fields filled in, which a planner completes.

## Sources

1. [Operations & Maintenance Best Practices: A Guide to Achieving Operational Efficiency, Release 3.0 (PNNL-19634), Chapter 4](https://www.osti.gov/servlets/purl/1034595), Pacific Northwest National Laboratory for the US Department of Energy, accessed Oct 16, 2026
2. [The Impact of Data Quality on Maintenance Work Order Analysis: A Case Study in HVAC Work Durations](https://papers.phmsociety.org/index.php/phme/article/download/2814/1781), National Institute of Standards and Technology (Conte, Bolland, Phan, Brundage, Sexton), PHM Society European Conference 2021, accessed Oct 16, 2026
3. [Economics of Manufacturing Machinery Maintenance: A Survey and Analysis of U.S. Costs and Benefits (NIST AMS 100-34)](https://nvlpubs.nist.gov/nistpubs/ams/NIST.AMS.100-34.pdf), National Institute of Standards and Technology, accessed Oct 16, 2026