Solutions to Gloss Defects on ABS Injection-molded Products

Gloss defects—local highlights, uneven reflection or bright spots—are common in ABS injection molding, seriously undermining product aesthetics and market acceptance. Root causes lie in mold conditions, molding processes, raw material properties and product structural design. Addressing this issue requires targeted optimization based on actual production and defect origins. This paper analyzes core causes, provides practical solutions and prevention measures, and incorporates industry-recognized key data for on-site guidance.

I. Core Causes of Gloss Defects

Abnormal Mold Surface Conditions

The mold cavity directly replicates onto the product surface. Uneven roughness, residual oil or mold release agent can cause highlights. Excessive local polishing reduces melt flow resistance, leading to gloss marks. Scratches or burrs on the cavity may also trigger abnormal local reflection.

Deviations in Molding Process Parameters

Mismatched parameters are a major cause. Overly high melt temperature causes material degradation, producing low-molecular-weight substances that migrate to the surface and form a glossy layer. High injection speed intensifies shear heat, leading to uneven gloss. Insufficient holding pressure or time fails to compensate for shrinkage, resulting in sink marks with gloss defects.

Improper Raw Material Properties and Pre-treatment

Excessive lubricants or plasticizers migrate to the surface, forming a shiny film. High moisture content causes gas vaporization; bubble rupture leaves glossy marks. Impurities or excessive recycled materials lead to uneven plasticization and local gloss issues.

Unreasonable Product Structural Design

Excessive wall thickness variation causes uneven cooling, with thick areas prone to shrinkage-induced gloss. Sharp corners without fillets cause melt eddies and stress concentration, forming bright spots. Complex structures like deep grooves may hinder melt flow, triggering gloss defects.

II. Targeted Solutions

Mold Condition Optimization

Uniformly polish the cavity to ensure consistent roughness and avoid over-polishing. Use dedicated cleaners to remove oil and mold release agent, and reduce agent usage later. Repair scratches and burrs with oilstones for a smooth surface. Optimize gate position and quantity to achieve uniform melt filling.

Molding Process Parameter Adjustment

Control ABS melt temperature at 200-230℃ to reduce degradation. Lower injection speed by 10%-20% and adopt a slow-fast-slow segmented mode to avoid melt impact. Set holding pressure at 60%-70% of injection pressure and extend holding time to 1.5 times the wall thickness for sufficient compensation. Prolong cooling time and demold only when the surface temperature drops below 60℃ to reduce gloss differences.

Raw Material Optimization and Pre-treatment

Select ABS with proper additive ratios and limit recycled materials to 20% or less. Dry raw materials at 80-90℃ for 2-3 hours to ensure moisture content ≤ 0.2%. Add small amounts of inorganic fillers if lubricants are excessive, to inhibit migration. Avoid mixing different ABS grades to prevent compatibility issues.

Product Structural Design Improvement

Optimize wall thickness to ensure variation ≤ 15%. Add transition fillets at corners to reduce flow resistance and stress concentration. Simplify complex surface structures and avoid deep grooves or sharp edges. For strict appearance requirements, add overflow grooves in gloss-prone areas to absorb low-molecular-weight substances and impurities.

III. Prevention and Control Measures

Establish regular mold maintenance; clean and inspect cavity roughness every 30,000-50,000 cycles. Formulate standardized process parameter tables and avoid arbitrary adjustments. Conduct incoming inspections on raw material moisture and additives, rejecting unqualified materials. Perform mold flow analysis during new product development to optimize mold and product structures in advance. Conduct regular on-site product checks and adjust parameters promptly upon detecting gloss defects to avoid batch non-conformities.

Summary

Solving gloss defects on ABS injection-molded products follows the logic of root cause investigation, targeted treatment and full-process control, focusing on four key aspects: mold, process, raw material and structure. In production, first identify causes through inspection and process review, then prioritize adjusting parameters and mold conditions for cost-effective results. Optimize raw materials and structure when necessary. Establishing standardized maintenance and inspection mechanisms can effectively reduce defect recurrence and ensure stable product quality and appearance consistency.