24 Common Rubber Vulcanization Defects and Their Solutions

1. Incomplete Filling of Rubber Products(Symptom: The rubber body is incomplete and not fully filled)Causes:

• Inaccurate compounding/weighing of rubber compound.

• Poor flowability of the rubber compound.

• Improper placement of the rubber compound in the mold.

• Clogged injection holes.

• Flash/Overflow (excess material escaping the cavity).

• Insufficient injection pressure.

• Sudden power failure before injection/transfer is completed.

• Actual material dosage does not match the process requirements.

• Uneven preheating of the rubber compound in the injection machine.

• Different process parameters used for the same product on different machines.

• Injection holes are too small.

2. Rubber-to-Metal Debonding(Symptom: The rubber body separates from the metal insert; poor adhesion)Causes:

• Insufficient surface preparation: Oil and grease on the metal insert surface are not cleaned properly before applying the adhesive.

• Adhesive failure:

• The topcoat or primer is not completely dry.

• Storage time of the adhesive has expired.

• Sudden power failure after mold closing but before injection starts.

• Unqualified/defective adhesive used.

• The metal insert is kept in the high-temperature mold for too long.

• Surface contamination of the adhesive-coated insert:

• Dust pollution due to lack of dust-proof measures.

• Contamination by mold-release agents.

• Oil pollution from equipment maintenance when the insert was not removed.

• Workers not changing to clean gloves when loading the inserts.

• Other process issues:

• Adhesive on the insert surface is too thick or has accumulated.

• Mold temperature is too high or too low.

• Poor mold sealing (flash gap).

• Injection holes are too large.

• Secondary processing/machining.

3. Rubber Product Ragging/Edge Tearing(Symptom: Wrinkles, delamination, and other defects appear at the parting line of the mold cavity)Causes:

• Mold temperature is too high.

• Unreasonable distance of the tear trim grooves on the tear-trimming mold.

• Improper venting.