The term "pull marks" or "streaking" on rubber products refers to surface defects resembling scratches or lines. These issues can arise due to various reasons, outlined below along with corresponding solutions:
Cause Analysis
Mold Issues
- Mold Surface Damage: Scratches or dents in the mold transfer onto the product during demolding.
- Inadequate Cleaning: Residues such as dirt or leftover release agent are pressed into the product during molding.
- Poor Ventilation: Insufficient mold ventilation allows gas turbulence between the mold and rubber during vulcanization, causing streaks.
Manufacturing Process
- Improper Curing Temperatures: Both excessively high or low temperatures can disrupt the rubber's flow, affecting surface smoothness.
- Uneven Pressures: Unequal pressure distribution across the mold results in indentation marks.
- Misuse of Release Agents: Too much or too little release agent can degrade surface finish, with excess causing sliding marks and insufficient amounts leading to sticking.
Material Factors
- Uneven Mixing: Poor dispersion of fillers, plasticizers, etc., can lead to localized concentrations forming streaks.
- Incorrect Compound Hardness: Unsuitable compound hardness for processing conditions leads to poor flow and molding properties.
Improper Handling
- Insertion or Removal Techniques: Rough handling during mold insertion or removal can scratch the product.
Solutions
Mold Maintenance and Improvement
- Regularly inspect and repair mold surfaces, maintaining cleanliness.
- Optimize mold ventilation to ensure efficient gas escape.
Process Adjustment
- Precisely regulate curing temperatures and pressures according to material specifications and product needs.
- Fine-tune the application of release agents for optimal results.
Material Handling Optimization
- Ensure thorough mixing of materials, especially even dispersion of additives and fillers.
- Adjust compound formulas for the right balance of hardness and flowability.
Operator Training
- Enhance operator training, emphasizing proper handling techniques to avoid physical damage during product placement and extraction.
Addressing these causes with targeted measures significantly reduces the occurrence of pull marks on rubber products, enhancing overall product quality.
