Should the interval follow shots or the calendar?

A: Shots above 9,000 a month, calendar below it, hybrid on the line. The inputs are daily shots and utilisation, not the age of the tool.

What if the mould has no counter?

A: Multiply output by cavities and reconcile at month end. A two-cavity tool doubles the quantity and the result is usually within 3%, close enough to tell whether 25,000 shots has passed.

Can a plant at 30% utilisation keep a calendar plan?

A: Not directly: at 147 shots a day, 25,000 shots take 170 days, so a 60-day window burns 10 h a year in stops the tool never earned. Move the trigger to shots.

How is the 15% overdue line applied?

A: As a share of the node: 28,750 shots at the 25,000 point, 57,500 at 50,000 and 115,000 at 100,000. Past the ceiling the service is logged as missed and the count restarts after it is done.

Who keeps the service history?

A: It follows the tool, not the person. When a mould moves to a subcontractor the 9 fields travel with it, otherwise the receiving plant cannot tell where the next node sits.

Mould Maintenance Interval

Quick answer: Fix the mould maintenance interval in shots, not months: past 9,000 shots a month, service at 25,000 and 100,000 hits, and use dates only as backup.

Shots are the only unit that tracks wear
Converting a calendar into hits
The three service points and the hours they cost
Where 9,000 shots a month becomes the switch line
Running both systems without double-booking
FAQ

1. Shots are the only unit that tracks wear

A press running 14,000 shots a month on a quarterly plan goes 42,000 hits between stops: no inspection in between, and one window that lands wherever the calendar puts it.

A calendar-based mould maintenance plan assumes every month looks like the last. Where peak and slow months differ by 30% or more, that assumption fails both ways: slow months pull the tool early for nothing, fast months let it run 40% past the node, and the extra hits come off the shut height rather than the schedule.

Counting shots removes the guess. Each service point becomes a number the tool earns, and the date only decides whether it arrives next week or next month.

2. Converting a calendar into hits

One figure does the conversion: average shots per day. Two shifts of 20 h, one cavity and a 62 s cycle give about 420 shots a day, or 9,240 a month over 22 working days, which sits almost on the switching line in section 4.

The intervals then become arithmetic. At 420 a day, 25,000 shots arrive in roughly 60 days, 50,000 in 119 and 100,000 in 238. A calendar rounds those to 2, 4 and 8 months, harmless inside 2 days and dangerous once the error passes a fortnight.

Utilisation breaks the conversion, because the 420 baseline assumes 85% uptime. At 35% the press makes 147 shots a day, so 25,000 shots take 170 days while the calendar still opens at 60, buying four pointless stops of 2.5 h, or 10 h a year. At 92% it makes 455 a day and reaches 25,000 in 55, so a 60-day calendar overshoots the node by 2,200 shots, a 9% error. Shorten the calendar to 50 days when the plant is hot; switch the trigger to shots when it is cold.

Mould maintenance planning context: steel moulds with lifting eyes and hose fittings stored along a concrete aisle beneath blue racks and a red crane beam

3. The three service points and the hours they cost

More service points do not make a better plan. Three levels cover routine care on a case tool, and each one added beyond that splits the windows until two stops sit a fortnight apart.

Service point	Calendar equivalent	Downtime booked	Times a year	Merged with
25,000 shots	about 60 days	2.5 h	4	2nd and 4th merged into 50,000
50,000 shots	about 119 days	no separate window	2	follows 25,000 with 1 h added
100,000 shots	about 238 days	6 h	1	same window as annual service
Annual service	365 days	6 h	1	includes the 100,000 point

One tool then books 16 h of planned downtime a year: four stops of 2.5 h at the low level, plus 6 h shared by the 100,000 point and the annual service. That sounds modest until it competes with changeovers, trials and repairs, which is why the work order is released 3 days ahead.

4. Where 9,000 shots a month becomes the switch line

The 9,000 figure is derived, not borrowed. Over 22 working days it means 409 shots a day, about 97% of the 420 baseline. Divide 25,000 by 9,000 and the interval is 2.8 months, which a calendar rounds to 3, a node error near 2,000 shots or 8%. Once that passes 15% the plant has skipped a service, so 9,000 is the ceiling for calendar scheduling, not an optimum.

Schedule	Trigger	Monthly shots	Main cost
By shots	counter reaches a multiple of 25,000	above 9,000	needs a trusted counter and month-end reconciliation
By calendar	fixed week or fixed month	below 9,000	over-serviced in slow months, under-serviced in peak
By order batch	before each production batch	many small batches	batches compete for the same window
Hybrid	shots trigger, calendar backstops	hovering around 9,000	two logs must reconcile

Above the line the calendar error runs one way, so the mould maintenance trigger must be shots. Three ways to read that number, in falling reliability: a PLC count is cleanest but forces reconciliation whenever a tool changes machine; a mechanical counter travels with the mould but leaves no history once reset; with no counter, output times cavities is the only option, usually within 3%.

A hybrid suits plants swinging around 9,000. Both logs must reconcile, or each hides the other's misses.

Mould maintenance planning: an open black wheeled case beside a timber pallet, egg-crate foam in the lid and instruments resting inside

5. Running both systems without double-booking

When a tool carries both plans, one rule settles every conflict: shots win. A date that arrives before the count slides; a count that arrives first releases the work order the same day.

The overdue line is 15% of the node, so a 25,000-shot service reaching 28,750 with no record counts as missed, without waiting for a visible defect. The line gives the crew a signal instead of a judgement call.

Records must support that judgement, which means 9 fields: service date, tool number, machine number, cumulative shots, node serviced, downtime hours, parts replaced, technician and verdict. Cumulative shots and technician get dropped first, and dropping either breaks the trail, one for the check and one for accountability. The annual service shares the 100,000 window, inside 6 h.

Conclusion

A mould maintenance interval is a scheduling decision before it is a maintenance task. The line sits at 9,000 shots a month, the nodes at 25,000, 50,000 and 100,000, the overdue trigger at 15%, and shots take precedence while both plans are live. Write those numbers into the log and the calendar stops competing with the counter. A year above 16 h of downtime usually means a node was booked twice.

This article covers case-side specifications only and does not address any handling, loading or use of the contents.