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Guarantee of cavity and core concentricity: The mating surfaces of the cavity and core are processed by slow-feeding wire cutting to ensure their coaxiality ≤ 0.01mm; IT5-grade locating pins are used to fix inserts, ensuring the positional deviation of cores between multiple cavities ≤ 0.005mm, thereby structurally reducing the risk of eccentricity.
Melt flow balance design: A hot runner system (with independent gates for each cavity) is adopted, and runner dimensions are optimized through CAE simulation to ensure the melt filling speed deviation between cavities ≤ 5%; the gate is positioned at the center of the test tube bottom to reduce asymmetric shear force during filling and avoid wall thickness deviation to one side.
Cooling uniformity control: Spiral cooling channels (8-10mm from the cavity surface) are built into cavity inserts, with water temperature control accuracy of ±1℃, ensuring uniform cooling shrinkage of PP material. The wall thickness difference at different positions of a single-cavity test tube ≤ 0.05mm, and the wall thickness deviation between multiple cavities ≤ 0.03mm, ultimately achieving an overall eccentricity ≤ 0.1mm.
Process adaptability of S136 inserts: S136 is quenched and tempered to 48-50HRC, ensuring sufficient hardness (reducing cavity wear after long-term use) while retaining certain toughness (avoiding brittle fracture); its mirror polishing performance (up to Ra ≤ 0.04μm) can reduce the flow resistance of PP melt, preventing uneven filling caused by rough cavity surfaces.
Smooth demolding design: The core adopts a micro-taper design (0.02°-0.05°) combined with nitriding treatment (surface hardness ≥ 650HV) to reduce the friction coefficient between PP and metal; the ejection system uses a combined structure of synchronous ejector pins and ejector plates, with uniform ejection speed (error ≤ 0.02mm/s) to avoid test tube deformation or wall thickness deviation during demolding.
Dead-angle-free cleaning design: Cavities, runners, and insert joints adopt arc transitions (R ≥ 0.5mm) to avoid residual fluid accumulation; the fitting gap of mold parting surfaces ≤ 0.005mm to prevent material overflow and subsequent material accumulation, meeting GMP requirements for clean production of medical devices.
Corrosion resistance and low precipitation: S136 stainless steel has excellent chemical resistance, withstanding corrosion from additives in PP materials and subsequent disinfection processes (such as high-temperature steam, alcohol wiping), and the material itself has no precipitates, avoiding contamination of test tube contents (such as blood, reagents).
The mating surfaces of inserts (such as the guide part between core and cavity) undergo mirror polishing and nitriding treatment, with surface roughness Ra ≤ 0.02μm and friction coefficient ≤ 0.1, reducing wear during mold opening and closing; guide pillars and bushings are made of SUJ2 (fitting gap ≤ 0.003mm) to ensure unchanged positioning accuracy after long-term movement.
Calculated at a daily production of 50,000 pieces, under normal maintenance (cleaning water channels and inspecting ejector pins every 100,000 mold cycles), the cavity size wear ≤ 0.01mm, enabling stable production of ≥ 1,000,000 mold cycles, meeting the mass production requirements of medical consumables.
Inserts adopt a modular design; worn single cavities can be replaced independently without overall disassembly and repair, reducing downtime; the ejection mechanism is equipped with a stroke sensor to monitor ejector pin movement in real-time, avoiding mold damage caused by jamming.
A pressure detection interface is reserved in the cooling water channel to regularly monitor water flow uniformity, preventing uneven cooling (affecting wall thickness accuracy) due to scale blockage.
This medical PP test tube multi-cavity mold achieves stable precision molding with wall thickness eccentricity ≤ 0.1mm through high-precision processing of S136 stainless steel inserts (guaranteeing concentricity and surface quality), balanced design of hot runner and cooling systems (controlling wall thickness eccentricity), hygiene-grade structural optimization (meeting medical safety requirements), and wear-resistant treatment (extending service life). It also features operational characteristics such as easy maintenance, low pollution, and long service life, fully adapting to the strict requirements of medical test tubes for precision, cleanliness, and mass production.
