Shop-Floor Defect Atlas & Troubleshooting Matrix

Blisters / Air Pockets in Skim Coat

Calendering

Visual Symptoms Trapped air pockets or bubbles forming between the fabric cords and the rubber skim layer.

Root Causes Roll temperatures too high causing premature localized scorch, or trapped air during calendar nip pass.

Corrective Actions Optimize calendar roll temperature controllers and reduce roll speed to allow air escape before nip entry.

Blisters Caused by Entrapped Air

Extrusion

Visual Symptoms Large gas pockets trapped internally inside thick extruded profiles like channel sections or solid cores.

Root Causes Inadequate feeding pressure, air trapped between wrap-around layers, or insufficient vacuum venting in barrel.

Corrective Actions Adjust barrel vacuum port suction, optimize feed screw geometry, and ensure clean compound feeding.

Compound Scorching (Pre-vulcanization)

Mixing

Visual Symptoms Stiff, lumpy, or partially cured stock coming out of the internal mixer or mill; low plasticity.

Root Causes Excessive dump temperature, incorrect accelerator loading, prolonged mixing time, or delayed cooling water circulation.

Corrective Actions Lower cooling tower water temperature, check batch temperature sensors, verify accelerator weigh scales, and shorten mixing cycle.

Compound Scorching (Pre-vulcanization)

Mixing

Visual Symptoms Stiff, lumpy, or partially cured stock coming out of the internal mixer or mill; low plasticity and high Mooney.

Root Causes Excessive dump temperature, incorrect accelerator loading, prolonged mixing time, or delayed cooling water circulation.

Corrective Actions Lower cooling tower water temperature, check batch temperature sensors, verify accelerator weigh scales, and shorten mixing cycle times.

Shop-Floor Defect Atlas & Troubleshooting Matrix

Blisters / Air Pockets in Skim Coat

Blisters Caused by Entrapped Air

Compound Scorching (Pre-vulcanization)

Compound Scorching (Pre-vulcanization)

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