What Processes Are Included in The Complete Production Flow of China Injection Processing
China injection processing is a continuous multi-process manufacturing flow from raw material preparation to finished product delivery. The control level of each link directly affects the appearance, dimensional accuracy and long-term stability of plastic parts. Negligence in any process may easily induce defects such as silver streaks, sink marks, deformation and cracking, affecting final delivery quality.
Raw Material Preprocessing
After raw materials arrive at the factory and unpacking, first conduct raw material appearance inspection to check plastic pellets for caking, impurities, color difference and moisture. Isolate batches that fail inspection in a timely manner. Perform drying procedures according to material properties to remove moisture absorbed by raw materials. Excessive moisture will gasify at high melting temperature and form silver streaks and bubbles on the product surface, seriously damaging product quality. For products needing color matching, add color masterbatch, toughening additives and other auxiliary materials according to proportion, put into mixing equipment for full stirring and mixing, and stand still after mixing to avoid batch color difference caused by uneven dispersion of color masterbatch. For highly hygroscopic materials, keep heat preservation after drying to reduce water absorption from air again.
Mold Installation and Commissioning
Use overhead crane to hoist the mold between injection mold platens, align the locating ring and fasten the mold with pressing plates. Connect cooling water circuits, oil circuits and ejection sensing lines. After pipeline connection, pass cooling water to test and check leakage at pipeline joints, fasten and replace sealing parts in time if leakage is found. Then manually test mold opening and closing action, inspect slides, lifters, ejector pins and other moving parts one by one to confirm smooth movement without jamming or collision interference. Combine product drawings and material shrinkage rate to initially set barrel temperature, injection pressure, cooling time and other basic process parameters to get ready for trial molding.
Trial Injection and Process Optimization
Start trial injection after equipment preheating. Produce samples in small batches. Technicians take out samples to visually inspect surface for weld lines, flash, sink marks and other appearance defects, and measure key assembly dimensions with calipers and micrometers. Gradually adjust barrel segmented temperature, injection speed, packing pressure and cooling duration according to actual sample status. Compare samples in multiple rounds of repeated debugging until sample appearance and dimensions fully meet drawing and customer standards. After stable parameters, solidify complete molding process form as execution basis for subsequent mass production. Record problems occurring in trial molding and corresponding adjustment schemes for later traceability.
Mass Injection Molding
In formal mass production, the equipment automatically circulates according to solidified processes, sequentially performing mold closing, injection, packing, cooling, mold opening and product ejection. During production, operators regularly inspect equipment running noise, material temperature and mold temperature, continuously sample and inspect product appearance and observe mold status to handle sudden abnormalities timely. Keep production records, register production batch, output, abnormality occurrence time and handling mode to realize full traceability of product production. When raw material batches change, re-verify in small batches to confirm no quality fluctuation of products before continuous production.
Post-processing of Products
After product ejection, first remove gates and runner materials and clean flash burrs generated at parting surfaces. Many engineering plastics retain internal molding stress after molding, which is easy to crack during use or assembly. Tempering heat preservation treatment is required to release internal stress of plastic parts. High-gloss products go through polishing process. Slight warpage of structural parts can be corrected by shaping. For products requiring bonding and spraying, add oil and dust removal on the surface to guarantee adhesion of subsequent surface processing.
Product Inspection and Testing
Carry out inspection work according to established inspection specifications. Basic inspection includes appearance check, key dimension measurement and assembly matching verification. For functional plastic parts, add special performance tests such as tensile strength, impact resistance, sealing and high-low temperature cycle. Inspectors separate qualified products and non-conforming products. Non-conforming products are marked and isolated separately. Record defect types in detail and feed back to process and mold posts to analyze root causes of defects and formulate improvement measures to reduce repeated occurrence of similar nonconformities. Inspection records are saved with batches to meet customer quality verification requirements.
Packing and Warehousing
Clean surface dust and debris of qualified products, pack according to order specifications. Mark outside packages with product model, production batch, quantity and production date. Transfer packed products to warehouse for storage by zones, do moisture-proof protection, and input inventory account synchronously waiting for order delivery. Control packaging pressure in packing link to avoid deformation of thin-wall products under compression.
Production Completion and Mold Maintenance
After order production, empty residual raw materials in barrel and clean barrel to prevent material degradation under long-time high temperature. Close water and oil circuits before mold disassembly, take apart the mold, wipe and clean residual oil and material debris on cavity surface. Inspect wear status of cavity, inserts and guide parts. Spray anti-rust agent evenly after confirming no damage, close the mold. Transfer the mold to designated position in mold warehouse for storage, power off equipment, clean production site and complete 5S arrangement. Record mold wear status when warehousing to evaluate before next production and reduce mold failure in subsequent mold opening.
