Why startup after a shutdown is critical
During an extended stop, changes can happen that are not visible at a glance: component contraction from ambient temperature, surface oxidation, sediment in cooling circuits or loss of lubrication in moving parts.
Restarting the production cycle without checking these conditions can lead to rejected first parts, accumulated damage to wear components or, in severe cases, damage to the mold from a cold start without proper preheating.
Visual inspection before mounting the mold
Before mounting the mold in the machine, check for surface corrosion, moisture, storage residue, the condition of the shut-off surfaces and any loose or missing elements that may have been noted at the last service.
Compare the current condition with the record from the last production run or the last maintenance, to identify any change that occurred during storage.
Checking the cooling system before startup
Confirm that the cooling circuits are free of sediment blockages, that the connections do not leak and that flow reaches the specified rate before starting to preheat the mold.
A partially blocked circuit after a long stop can go unnoticed for several cycles, creating thermal variation that affects cooling time and the dimensional quality of the first parts.
Mounting and cycling a cold mold right away can create severe differential thermal stress, especially in hardened steel molds. Follow the specified preheating curve.
Moving parts and lubrication
Check the free travel of ejectors, slides and guided elements. Long periods without use can harden lubricant or let in moisture that promotes surface corrosion on guides and bushings.
Cycle the ejection system manually, if the design allows it, before the first automatic cycle, to confirm there is no binding that could damage the mechanism under the force of a production cycle.
Adjusting process settings on restart
The process settings documented in the last production run are the starting point, not a guarantee. Ambient temperature, the material lot and the initial thermal state of the mold may require minor adjustments for the first parts.
The first parts after restart should be treated as setup parts, not conforming production, until dimensional and cosmetic stability is confirmed over consecutive cycles.
Startup checklist
☐ Check corrosion and moisture
☐ Compare with the last record
☐ Confirm all elements are present
☐ Check shut-off surface condition
☐ Check circuits for blockages
☐ Confirm there are no leaks
☐ Validate the specified flow rate
☐ Follow the preheating curve
☐ Check ejector travel
☐ Review lubrication of guides and bushings
☐ Cycle ejection manually
☐ Confirm there is no binding
☐ Treat first parts as setup
☐ Confirm dimensional stability
☐ Validate appearance over consecutive cycles
☐ Document the adjustments made
Common questions.
How long a stop counts as extended enough to need this checklist?
It depends on the material molded and the storage conditions, but as a general reference any stop longer than a few weeks, or with exposure to moisture or ambient temperature changes, justifies this full check.
Can the first startup parts be sold as normal production?
They should not be treated as conforming until dimensional and cosmetic stability is confirmed over consecutive cycles. They should be identified and segregated as setup parts during startup.
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