When the production schedule leaves no time for PM

You fit planned maintenance into a full production schedule by booking each PM as a job on its machine, with its own duration, so it takes capacity the way an order does. Then time each task to a stop the schedule already has, such as a changeover or a weekend, price every deferral before you grant it, and agree in advance who decides when a PM and an order want the same hours.

This guide is for maintenance leads and plant managers whose PM list keeps losing to the order book. Building the task list itself is covered in how to build a preventive maintenance schedule.

Why does PM keep getting bumped?#

PM gets bumped because the production schedule treats the machine as always available. Capacity is the shift hours, every one of them is open to orders, and the PM lives in another system with no hours on the machine’s lane.

For example, a Haas VF-2 on two 8-hour shifts has 80 hours a week. The planner loads 72 hours of orders and 4.5 hours of changeovers, a 95.6% load that looks efficient. The 4-hour way-lube and filter service due Wednesday has nowhere to go: the 3.5 hours left are Friday’s last hours, half an hour short and two days late.

PM only becomes planned downtime once it holds hours on the schedule. Log the PM stop under a planned reason, as the planned downtime entry describes, so it stays out of your unplanned losses.

Three habits keep the machine always available on paper:

• Two calendars. Orders sit in the schedule and PM sits in the maintenance system, and nobody lays one over the other.
• No durations. A PM with no hours on it can’t be reserved, even by a planner who wants to.
• Loads near 100%. A machine planned to its last hour has no room for anything that wasn’t on the plan. Loading each machine below its planned hours explains why queues explode past about 85%.

Book PM as a job on the machine#

Book each PM as a job on the machine it stops, with a duration and a date, before any orders are loaded. The schedule then subtracts its hours the same way it subtracts a changeover.

On the VF-2, 80 − 4 − 4.5 leaves 71.5 hours, so the 72 hours of orders no longer fit. The schedule shows half an hour of overload at the end of Friday, a week ahead, instead of a skipped PM on Wednesday. Half an hour is a decision you can make: trim an order, move one to a twin machine, or book the PM beside a changeover.

1. Create the PM as a job on its machine

   Title it so the floor can read it: PM: way lube and filters, CNC-04. Put it on the machine, never on a department or a cell.

2. Give it the full time on the machine

   Count lockout, the work, restart and a first-part check. A 3-hour service with 30 minutes to lock out and 30 minutes to warm up and check the first part holds the machine for 4 hours.

3. Place it inside its window

   Maintenance gives every PM a window, such as 3 days either side of the due date for a 4-week task. Book the job on a slot inside it.

4. Pin it before orders are loaded

   Fix its date so re-sequencing and rush orders move around it, not through it. A PM that floats with the orders ends up after all of them.

5. Load orders into the hours that are left

   Load the week against the hours open to orders. Any overload now appears as a late order you can see and price.

Put PM where the machine already stops#

The cheapest hour for PM is one the machine is already stopped for. Booked beside Wednesday’s 1.5-hour changeover, the 4-hour service overlaps it, so it costs 2.5 hours of order time instead of 4, and the 72 hours of orders fit with 1 hour to spare.

To use changeovers, you need to know how long they really run. Measuring changeover time gives you the figure to book against.

Let a usage meter open the window#

A calendar PM lands wherever the calendar says. A usage-based PM is due after a set number of run hours or parts, and an early warning before that point turns the due date into a window you can fit to the schedule.

Size the warning so the window always spans at least one natural stop. Warning early enough to stage the job shows how to work out the lead time from daily usage.

Altium Packaging runs a wear part on counts this way. Its Slide Knife is inspected every 100,000 bottles: the team gets an email as it gets close, and at 100,000 the inspection opens as a work order on its own.

What does deferring a PM cost?#

Deferring a PM doesn’t save its hours. It moves them into a later week, which is usually just as full, and adds the risk that the failure the task prevents arrives first.

Plants that lean on reactive maintenance pay for it in production time. In a NIST survey of 71 US manufacturing establishments, the half that relied most on reactive maintenance, 69% of their maintenance on average, lost 10.38% of planned production time to unplanned downtime. The half that relied least, at 22% reactive, lost 4.91%.^[1]

That second half also spent more on maintenance: 2.9 cents per dollar shipped against 1.6.^[1] PM isn’t free. It trades maintenance hours for production time, and each deferral is a bet on that trade.

You rarely know that chance, but you do know the task’s as-found record. A task whose last service found the part worn near its limit fails the test. One that found the part like new three services running passes it, once. Put your own hourly figure in from pricing an hour of downtime.

Who decides when PM and an order collide?#

Maintenance decides whether a PM can move and how far. The planner decides where it goes inside that limit, and the plant manager decides only when someone wants to go past it.

Write the rule down before the first collision, so nobody negotiates it on a Wednesday afternoon with a truck waiting.

A regulation-dated task has no window. OSHA requires each mechanical power press it covers to be inspected and tested at least once a week for the condition of its clutch/brake mechanism, antirepeat feature and single-stroke mechanism, with an exception for presses that meet the standard’s control-reliability and brake-monitoring requirements.^[2]

Run PM and production on one schedule#

In IoTFlows, Maintain and the Production Scheduler work on the same machines the sensors monitor. Maintain holds each PM as a recurring work order or a meter that emails at 85% and opens the work order at 100%, and its Calendar view shows the backlog by due date.

In the Production Scheduler, book the stop as a task on that machine with its time estimate, and choose Lock scheduling so the optimizer plans orders around it. The Schedule issues list flags any order double-booked against it, and a Simulation shows what moving the PM does to overdue work before you commit.

Run a weekly PM and schedule review#

Collisions shrink when maintenance and planning meet before the week is released, not after it starts. Hold a 30-minute review each Thursday, with the maintenance lead and the planner, before next week’s schedule goes to the floor.

1. Pull the next two weeks of PM

   List every calendar PM due in the next two weeks and every meter past its 85% warning, with each task’s hours on the machine.

2. Match each PM to a natural stop

   Find a changeover, an unscheduled shift or a weekend inside each window. Book the PM beside it, or on its own slot when there is none.

3. Book and pin before orders load

   Put every PM on the schedule as a job with its duration, and fix its date. Then let the planner load orders into what is left.

4. Settle collisions with the written rule

   Apply the decision table to every clash. Anything past its window goes to the plant manager in the same meeting, not by email next week.

5. Review last week’s misses

   Give each missed PM a cause: no slot booked, bumped by an order, part missing or estimate too short. When “bumped by an order” shows up every week, the load target is too high.

Track PM compliance from the same list, counting a late PM as a miss. The first month shows which machines have no natural stops and which PM estimates are wrong, and both are fixed on the schedule, not on the shop floor.