TL;DR

Mold cooling failure causes heat check cracks in the containers. Check the cooling air flow to the affected section and inspect the mold cooling passages for blockage before replacing the molds.

What you might see

containers showing heat check cracks at the base
mold surface temperature above the cooling setpoint
mold cooling air flow below the specified rate
elevated container defect rate correlated to one section

Likely causes

Tap to mark as ruled out

Cooling air duct to the affected section partially blocked by scale or debris
Mold cooling hole deposits from mineral scale reducing airflow through the mold body
Cooling air supply pressure below the minimum for the current section speed
Section cooling valve failed to open fully

Required tools

Cooling air flow meter
Descaling agent for mold cooling passages
Mold handling tools
LOTO kit

Safety first

Blank and blow molds retain significant heat from the forming process. Use heat-resistant gloves and allow cooling before handling.
High-pressure cooling air supply. Bleed the circuit before opening any fitting.

Procedure

6 steps · ~45 min

1
Stop the section and lock out the gob delivery.
2
Measure the cooling air flow to the section at the supply manifold. Compare to the specified minimum for this mold type.[1]
3
Inspect the cooling air duct to the section for debris or scale blockage.[1]
4
Remove the blank and blow molds and inspect the cooling holes for scale deposits. Clean with the approved descaling agent.
5
Check the section cooling valve position and actuator. Confirm the valve opens fully on the cooling command.
6
After cleaning and restoring flow, restart the section and monitor container base condition for the next 200 containers.

Sources

Bucher Emhart Glass Bucher Emhart NIS / FlexIS IS (Individual Section) Machine general technical documentation, Bucher Emhart Glass
General IS machine mold cooling system maintenance procedures (general)

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