Most preventive maintenance programs fail in mold shops. Not because the concept is wrong — maintaining your molds is absolutely critical. But because they are based on time instead of usage. And time-based PM is one of the most expensive mistakes a mold shop can make.
If you are scheduling PMs on a calendar — every three months, every six months, every year — you are leaving some molds over-maintained while others are running past their service window. The mold that is producing five thousand cycles a month accumulates wear at a vastly different rate than the one producing five hundred. A calendar does not see that difference.
Shot-count-based PM is the right approach. Every time a mold runs, it accumulates wear. Erosion on the cavity surface. Guide pin wear. Ejector pin degradation. Cooling line scale buildup. These things do not care about the calendar. They care about cycles. Every single shot against the mold contributes to that wear, and tracking shots gives you an objective measure of when maintenance is actually needed.
Here is how it works in practice. First, you set maintenance thresholds for each mold. Maybe that means a full PM at ten thousand cycles and a major overhaul at twenty-five thousand cycles. Those numbers vary by mold — a high-cavitation mold running high-temperature engineering plastics will hit its thresholds much faster than a simple two-cavity mold running polypropylene.
The system tracks every cycle automatically or through manual entry. When a mold approaches its threshold, the system alerts the maintenance team before it becomes an emergency. Work orders are created with the full mold history attached — last PM notes, recurring issues, parts used, technician observations from previous services.
After the PM is completed, the cycle counter resets for that mold. The maintenance record is updated with what was found and replaced. The next PM schedule is recalculated if the mold has been reconditioned or if a component was upgraded. Everything is documented and connected.
The result is molds that get maintained when they need it — no more, no less. You reduce unnecessary downtime on healthy molds that do not need service yet. You prevent catastrophic failures on worn ones that have exceeded their threshold. And your technicians have full context when they start each job instead of guessing what was done before.
The difference between time-based and usage-based PM is the difference between saying "I think that mold might be due soon" and saying "that mold has eight hundred forty-seven cycles left before it needs service." One approach leaves money and reliability on the table. The other is data-driven and objective.
If your shop is still running on calendar-based PM, the first step is just tracking shot counts. You do not need to overhaul everything overnight. Start with the tracking, let the data accumulate, and watch the pattern emerge. By the time you have three months of shot count data, you will know exactly which molds need more frequent PM and which can safely run longer between service intervals.