Preventive, predictive and corrective are not the same
Preventive maintenance is carried out before failure, at a frequency defined by use, time or criticality. Predictive maintenance uses condition signals to decide when to intervene. Corrective maintenance responds to a loss of function or damage that has already happened.
In practice, a mature program combines all three: basic periodic tasks, condition-based inspections and a controlled process for handling unexpected failures.
Setting the right frequency
There is no universal interval. Frequency depends on the number of cycles, the material processed, storage conditions, available water and steam, temperature, how aggressive the process is, mold complexity and the consequences of a stoppage.
Use the history to adjust the interval. If a component shows repeated wear before the scheduled service, either the plan should change or the cause that accelerates its deterioration should be investigated.
Inspection before disassembly
The condition on arrival holds evidence that can be lost during cleaning or disassembly. Before working on the mold, record its identification, general condition, contamination, residue, leaks, missing parts, connections, impacts and areas with visible wear.
Where possible, document the symptoms reported by production and the conditions in which they appear. Photos with location and scale make future interventions easier to compare.
Do not clean away the evidence before recording the as-received condition and relating it to the reported symptom.
Functional surfaces and geometry
Look for impacts, cracks, deformation, material loss, corrosion, unusual marks and residue build-up. Shut-off, sealing, contact and forming areas deserve special attention.
A cosmetic repair can hide a mechanical cause. When there is abnormal contact or fracture, alignment, interference, mounting, closing sequence and load distribution should be evaluated before blaming only the damaged component.
Thermal systems and fluid lines
Inspect tubing, coils, fittings, seals, connections and channels. Look for leaks, blockages, crushed lines, corrosion, previous repairs and areas exposed to bending or vibration.
Pressure or flow tests should follow defined procedures and conditions compatible with the design. Record the medium used, pressure, duration, acceptance criterion and result.
Isolate energy sources and fluids before working on the mold. Tests should be carried out by competent personnel with defined limits and protective equipment.
Moving and guiding components
Check guides, bushings, pillars, ejectors, springs, cylinders and mechanisms. They should move as intended, without binding, abnormal play, interference marks or contamination that blocks their travel.
A sticking guide is not always solved with more force. First determine whether there is residue, corrosion, deformation, misalignment or surface damage.
Filling, venting and ejection
Check fill guns, nozzles, vents, filters and ejection elements. Material build-up, oxidation or contamination can change filling, heat transfer and part release.
Missing, blocked or improvised components must be recorded. Before removing a stuck part, assess the risk of damage and agree on the scope of the intervention.
Documentation and closing criteria
The report should separate the as-received condition, findings, diagnosis, work performed, spare parts used, tests and recommendations. It should also distinguish the preventive scope from additional repairs found during inspection.
Closing requires verifiable criteria: correct movement, no leaks, dimensional condition where applicable, complete accessories and documentation delivered. The resulting history makes it possible to spot recurring issues and plan spare parts.
Basic maintenance checklist
☐ Confirm mold, revision and scope
☐ Record as-received condition
☐ Apply lockout and energy isolation
☐ Define disassembly and test risks
☐ Check shut-offs, surfaces and functional geometry
☐ Inspect guides, bushings and moving parts
☐ Look for cracks, deformation, corrosion and wear
☐ Verify fasteners, fixings and accessories
☐ Check filling and fill guns
☐ Clean and verify vents
☐ Inspect circuits and connections
☐ Verify ejection and travel
☐ Run the agreed tests
☐ Record results and evidence
☐ List open items and recommendations
☐ Update history and next service
Common questions.
How often should a mold be serviced?
The frequency should be set according to cycles, process conditions, criticality and history. A fixed interval that ignores these variables may turn out to be insufficient or unnecessary.
What should a maintenance report include?
At a minimum: identification, as-received condition, findings, diagnosis, work performed, spare parts, tests, results, open items, recommendations and responsible people.
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