How can qualified plastic products be produced?

Producing qualified plastic products requires strict management throughout the entire process, from raw material selection and process design to production control and quality inspection.

Here are the key processes and operational highlights summarized by Kingsjeng based on years of production experience and customer service insights.

I. Correct Raw Material Selection and Pretreatment   
1. Material Selection  
(1)Based on Product Use: Choose appropriate plastic types (e.g., PE, PP, ABS, PC), focusing on their physical properties (strength, heat resistance, toughness), chemical properties (corrosion resistance, food safety), and processing characteristics (melt index, shrinkage rate).  
(2)Supplier Evaluation: Prioritize suppliers with complete qualifications and request material certification reports (e.g., RoHS, FDA), avoiding recycled or mixed materials that may cause unstable performance.  

2. Raw Material Inspection  
(1)Visual Inspection: Particles should be uniform, free of impurities, and without discoloration.  
(2)Performance Testing: Test melt index, moisture content (e.g., nylon must be dried to moisture content <0.1%), thermal stability, etc. Unqualified materials must be returned or scrapped.  

3. Pretreatment  
(1)Drying: Hygroscopic materials (e.g., PA, PC) must be pre-dried to avoid bubbles or degradation during molding.  
(2)Color Matching and Modification: When using master-batches or additives (e.g., flame retardants, toughening agents), ensure uniform dispersion through mixing equipment (e.g., high-speed mixers).  

II. Sound Mold Design and Manufacturing  
1. Mold Structure Design  
(1)Gate Design: Select gate types (e.g., sub-gate, fan gate) based on material fluidity to avoid weld lines, sink marks, and other defects.  
(2)Cooling System: Reasonably arrange cooling channels to ensure uniform mold temperature, shorten the molding cycle, and reduce deformation (e.g., thin-walled parts require rapid cooling).  
(3)Ventilation System: Install vent slots or vent pins to prevent air trapping, which can cause scorching or incomplete filling.  
2. Mold Material and Processing Precision  
(1)Material Selection: Use corrosion-resistant and high-strength steel (e.g., H13, S136), with surface polishing or coating (e.g., nitriding treatment) to improve wear resistance and product surface quality.  
(2)Processing Precision: Control dimensional tolerances within ±0.01mm, and ensure the roughness of parting surfaces, cores, and cavities meets product requirements (e.g., mirror polishing Ra ≤0.05μm).  
3. Mold Trial and Debugging  
Record process parameters (temperature, pressure, time) during the first mold trial. Inspect the first-piece dimensions, appearance (e.g., flash, sink marks), and performance, then adjust the mold (e.g., repair, optimize gate design) based on results. 

III. Production Equipment and Process Parameter Control  
1. Equipment Selection and Debugging  
(1)Injection Molding Machine Matching: Select an appropriate machine based on material melt volume, ensuring screw speed and back pressure match material characteristics (e.g., low speed for PVC to prevent degradation).  
(2)Temperature Control:  
A.Barrel Temperature: Slightly higher than the material’s melting point to avoid thermal decomposition (e.g., ABS barrel temperature: 180–230°C).  
B.Mold Temperature: Affects product crystallinity and surface gloss (e.g., PE mold temperature: 30–50°C; PC mold temperature: 80–120°C).  
(3)Pressure Control:  
A.Injection Pressure: Adjust based on product thickness (high pressure: 80–150MPa for thin-walled parts; low pressure: 50–100MPa for thick-walled parts).  
B.Holding Pressure: Prevent sink marks, typically 60–80% of injection pressure.  
(4)Cooling Time: Calculate based on product thickness to ensure complete internal curing and avoid ejection deformation.  

2. Production Process Monitoring  
(1)First-Piece Inspection: Confirm the first piece is qualified before each batch and fill out the First-Piece Inspection Report.  
(2)Patrol Inspection System: Inspect product appearance (flash, color difference, sink marks), dimensions (using calipers, projectors), and equipment operation (e.g., temperature fluctuations, hydraulic oil leaks) every hour.  
(3)Abnormality Handling: Stop the machine immediately for debugging if parameter fluctuations or defects are found, trace the produced products, and isolate non-conforming items.  

IV. Quality Inspection and Control 
1. Inspection Standards and Tools  
(1)Visual Inspection: Check for flash, bubbles, sink marks, and weld lines under light intensity ≥800Lux; inspectors must be trained.  
(2)Dimensional Inspection: Use coordinate measuring machines (CMM) and profile projectors to check critical dimensions, ensuring tolerances meet drawings (e.g., ±0.1mm).  
(3)Performance Testing:  
A.Physical Properties: Tensile strength (GB/T 1040), impact strength (GB/T 1843), heat deflection temperature (GB/T 1634).  
B.Chemical Properties: Solvent resistance, migration tests for food-contact materials (e.g., GB 4806.1).  
2. Sampling Plan  
- Adopt GB/T 2828.1 standard, determine sample size based on batch quantity, and set AQL (Acceptable Quality Limit) as ≤4.0 for appearance defects and ≤1.5 for dimensional defects.  

3. Non-Conforming Product Management  
(1)Labeling: Mark non-conforming products with red labels and store them in isolation.  
(2)Disposal: Re-workable products (e.g., flash trimming) must be reinspected; non-reworkable items should be scrapped and reasons recorded (e.g., mold wear, process errors).

V. Production Environment and Personnel Management 
1. Environmental Control  
(1)Temperature and Humidity: Control workshop temperature at 23±2°C and humidity at 45–65%RH for precision products to avoid material moisture absorption or dimensional changes due to thermal expansion/contraction.  
(2)Cleanliness: Regularly clean equipment and floors to prevent dust contamination of raw materials or molds; food-grade products must be produced in dust-free workshops.  

2. Personnel Training  
(1)Operation Training: New employees must pass assessments on equipment operation and process parameter setting, and master common defect handling (e.g., adjusting holding pressure to resolve sink marks).  
(2)Quality Awareness: Regularly conduct training on QC Seven Tools (e.g., Pareto chart, cause-and-effect diagram) to reinforce the mindset of "not producing or transferring non-conforming products."  

VI. Continuous Improvement and Maintenance 
1. Mold Maintenance  
(1)Regularly clean molds (e.g., use copper brushes to remove residual plastic), inspect wear on cores and cavities, and perform comprehensive maintenance monthly with anti-rust coating.  
(2)Record mold usage cycles, conduct flaw detection when reaching the service life (e.g., 500,000 cycles), and promptly replace vulnerable parts (e.g., ejector pins, sprue bushings).  

2. Process Optimization  
(1)Analyze quality data through PDCA cycles, identify potential risks using FMEA (Failure Mode and Effects Analysis) (e.g., insufficient mold ventilation), and implement preventive measures (e.g., adding vent slots).  
(2)Introduce automated equipment (e.g., robotic part removal, visual inspection systems) to reduce human error and improve stability.  

VII. Compliance and Certification 
1.Regulatory Compliance: Products must meet national standards (e.g., GB/T 17037) or international standards (e.g., ISO 9001); export products require CE, UL, and other certifications.  
2.Traceability System: Establish production records (raw material batch numbers, process parameters, inspection results) to ensure products can be traced to raw material batches and production timestamps. 

Conclusion

Producing qualified plastic products relies on the synergistic effect of “materials-molds-process management” with a core focus on prevention and process control. Through standardized operation,refined management, and continuous improvement,full-chain quality control from raw materials to finished products can be achieved.  

As a professional manufacturer and service provider specializing in customized injection molds and plastic products, Kingsjeng is consistently dedicated to continuous improvement and striving to continuously meet customer requirements and ensure customer satisfaction.