Molding Process of Plastic Mold for Infusion Set Drip Chamber
2026-05-28 10:38:19
Plastic Mold
Infusion set drip chamber is a kind of medical thin-walled precision plastic part, mainly made of medical-grade PVC or TPU. As hollow cavity products, drip chambers have complex inner shapes, and strict requirements are put forward on cleanliness, transparency, burr-free surface, no precipitation and consistent dimensions. This article introduces the complete molding process of dedicated molds for drip chambers from raw material pretreatment, mold commissioning, injection parameters, ejection to defect treatment and production management.
1. Raw Material Pretreatment RequirementsMedical soft PVC is the mainstream material for drip chambers, while high-end products adopt food-grade TPU. PVC has low hygroscopicity, but low-temperature air sorting and dedusting are required before production to remove surface impurities. If stored in humid environment, PVC shall be dried at 60~70℃ for 2~3 hours, and the temperature shall not exceed 80℃ to prevent thermal decomposition. TPU has strong hygroscopicity, which needs dehumidification and drying at 80~90℃ for 4~6 hours, with moisture content controlled below 0.02%.
Raw material conveying adopts fully closed pipelines. Production workshops maintain Class 10,000 clean standards to avoid secondary pollution. Recycled materials are completely prohibited to ensure medical safety.
2. Mold Structure and Pre-commissioning Points
Drip chamber molds are mostly multi-cavity symmetrical two-plate molds equipped with hot runner systems to eliminate cold runner waste and ensure uniform feeding of each cavity. Combined cores and side core-pulling mechanisms are designed for hollow structures, matching with precision ejection systems to realize smooth demolding. Corrosion-resistant mirror mold steel is selected, and the surface roughness is controlled within Ra0.02μm to guarantee high transparency.
Venting design is critical. Micro vent grooves with depth of 0.01~0.015mm are opened at parting lines, runner ends and core-pulling positions. Each cavity has independent vent structures. Surrounding cooling water channels ensure uniform mold temperature. Before formal production, commission and check the coordination of mold opening, closing, core pulling and ejection actions to eliminate jamming and scratch.
3. Core Injection Parameter SettingsFor PVC with poor thermal stability, segmented low-temperature barrel temperature is set: 150~160℃ for feeding section, 165~175℃ for middle section and 170~178℃ for nozzle, with the overall temperature below 180℃. The barrel temperature for TPU is set between 190℃ and 210℃. Mold temperature is controlled at 30~45℃ for PVC and 40~60℃ for TPU.
Multi-stage injection is adopted for hollow thin-walled drip chambers. Low pressure and low speed are used for runner filling, medium speed for main cavity filling and slow speed for terminal buffer to prevent core offset and flashes. Multi-stage gradual pressure reduction packing is applied to avoid dents and excessive internal stress. The cooling time is set as 8~12s according to wall thickness. Low back pressure and low screw speed are configured for PVC to reduce shear heat and material decomposition.
4. Ejection, Demolding and Picking ProcessCombined structure of ejector pins and ejector plates is adopted for ejection. Two-stage ejection speed prevents product deformation and whitening. Oil-based release agents are forbidden for medical products. If auxiliary demolding is needed, only a small amount of water-soluble food-grade release agent can be used.
Automatic manipulators with flexible vacuum suction cups are applied for picking to avoid extrusion deformation. Finished products are directly collected into closed clean containers without manual contact. Connected blanks are cut by special precision cutters to ensure smooth and burr-free notches.
5. Common Molding Defects and Solutions
Yellowing and internal black spots are caused by over-high temperature or poor venting, which can be solved by lowering temperature and cleaning vent grooves. Bubbles and foggy surface result from insufficient drying, so extend drying time and appropriately raise mold temperature. Uneven wall thickness is due to core offset, which needs to fasten core structures and optimize injection parameters. Flashes are eliminated by trimming mold gaps and reducing terminal pressure. Deformation and dents can be improved by extending cooling time and adjusting packing parameters.
6. On-site Production Management SpecificationsThe whole production process complies with medical clean standards. Timely dedusting and disinfection are carried out in workshops. Process parameters are fixed and managed. First-piece inspection and batch sampling inspection are implemented for dimensions, appearance and light transmittance. Molds are maintained daily to check core pulling, ejection and sealing parts. Regular cleaning and polishing are conducted to achieve long-term stable production of medical drip chambers.
