Black Spot Control in White Injection Molded Parts
Black spots in white injection-molded parts have long troubled injection molding factories, significantly impacting the appearance and quality of products.
Raw Material Control
1. Raw Material Procurement and Inspection
Choose High-Quality Suppliers: Select reputable raw material suppliers with strict quality control systems. High-quality suppliers often implement better purification and filtration processes, effectively reducing impurities in the raw materials.
Strict Raw Material Inspection: Establish a robust raw material inspection system to perform random checks on each batch. Inspections should include visual checks (to detect visible impurities) and melt flow index testing (to ensure the raw material’s processability meets requirements and indirectly assess its quality).
2. Raw Material Storage and Handling
Clean Storage Environment: Keep the raw material storage area clean, dry, and well-ventilated. The warehouse floor should ideally use dust-resistant and easy-to-clean materials.
Pre-Treatment of Raw Materials: Dry raw materials before use and screen them with a mesh filter to remove large particles and foreign objects.
Equipment Maintenance
1. Screw and Barrel Maintenance
Regular Inspection and Replacement: Periodically check the condition of the screw and barrel for wear and replace them as needed. It is generally recommended to conduct detailed inspections after producing a certain number of products (e.g., 500,000–1,000,000 cycles, depending on the product and equipment). Replace components such as screws when wear exceeds a certain threshold (e.g., 10–15% of the original size).
Cleaning and Maintenance: Regularly clean the screw and barrel during production. Thoroughly clean them whenever switching between different colors or types of raw materials to prevent cross-contamination.
2. Heating System Maintenance
Calibration of Temperature Control Components: Periodically calibrate heating system components and thermocouples to ensure accurate temperature measurement and control.
Heating System Inspection: Regularly check heating elements for localized damage or short circuits. During daily inspections, observe the appearance of the heating elements for discoloration or deformation. Replace defective elements promptly to prevent localized overheating that could decompose raw materials and cause black spots.
Mold Maintenance
1. Optimization of Venting Systems
Design Reasonable Vent Structures: During the mold design, incorporate sufficient and strategically placed vent slots or holes based on the product’s shape and structure.
Regular Cleaning of Venting Channels: Clean mold venting channels regularly during production to prevent blockages caused by plastic residue or other contaminants. Use compressed air or specialized mold cleaning agents for this purpose.
2. Mold Cleaning
Surface Cleaning: After each injection cycle, clean the mold surface to remove oil stains, and release agent residues, and plastic debris. Use specialized mold cleaners and soft brushes for effective cleaning.
Rust Prevention: For mold materials prone to rust, apply anti-rust oil or use anti-rust packaging materials during storage. Before use, ensure that any rust-preventive materials are thoroughly removed to avoid contamination of the molten plastic.
Environmental Management
1. Workshop Cleaning and Dust Prevention
Floor and Equipment Cleaning: Maintain clean workshop floors by sweeping and mopping regularly to reduce dust. Clean equipment surfaces frequently to prevent dust accumulation. Surround equipment with barriers or protective enclosures to minimize dust dispersion during operation.
2. Personnel Operation Standards
Workwear and Hygiene Management: Operators should wear clean work attire and change into designated clothing and footwear before entering the workshop to prevent external dust and contaminants from entering. Regularly clean work attire to maintain cleanliness.
Operational Training: Provide training for operators on proper injection molding practices, including raw material handling, mold operation, and product retrieval procedures.
