Blood glucose meters are classified as in vitro diagnostic medical devices. Their outer housings come into direct contact with human skin and testing surroundings, making sterile design an essential factor to secure product safety, prevent cross contamination and satisfy relevant medical specifications. As critical tools for plastic forming, molds need comprehensive sterile design covering material selection, structural layout, precision machining, cleanliness management, sterilization compatibility and whole-cycle traceability. All designs shall conform to ISO 13485 and YY/T 0033 standards, keeping finished housings sterile and stable throughout production, application and disinfection processes.
1. Sterility and Biocompatibility Standards of Mold MaterialsQualified mold materials serve as the fundamental guarantee of sterile performance. The selected materials must resist corrosion and rust, allow easy cleaning and produce no harmful precipitation, so as to restrain microbial reproduction and chemical leakage. Cavity and core components adopt 316L medical stainless steel, which holds superior endurance against acid, alkali and common disinfectants. It can endure EO sterilization, gamma radiation and repeated wiping with 75% alcohol without releasing metal impurities. Moving parts including guide pins, ejector pins and sliding blocks are made of S136 stainless steel with DLC coating, featuring low friction, high wear resistance and stable demolding effect. Common carbon steel is banned from usage to avoid rust debris polluting products. All raw materials shall pass cytotoxicity and skin irritation tests under ISO 10993, ensuring no toxic substances escape when touching molten medical plastics like PP, PC and PC/ABS blends.
2. Core Layout Rules for Sterile Mold StructureMold construction abides by the design concepts of no cleaning dead ends, anti-fouling and smooth air discharge. Optimizations are implemented on parting surface, gating system, cooling pipeline, exhaust channel and demolding mechanism to cut off hidden contamination sources. Flat and smooth parting surfaces are applied with assembly clearance controlled below 0.01mm to avoid flash and dirt buildup. Round corners above 0.5mm are designed on housing edges to reduce scratch risks and clean blind spots. Deep slits and narrow grooves that trap contaminants are strictly avoided.
Closed hot runner systems are applied to replace traditional cold runners, minimizing residual material and pollution chances. Hidden gates are arranged on invisible inner positions to prevent burr contamination. Runner inner walls are finely polished to reduce melt residue and bacterial attachment. Cooling pipelines are arranged evenly with reasonable spacing, maintaining balanced mold temperature and reducing deformed gaps that gather dirt. Vent grooves are set at melt filling terminals to exhaust trapped air rapidly, preventing burnt spots and enclosed microbial living spaces. Ejector components are assembled with precise matching gaps, avoiding plastic residue accumulation inside fitting seams.
3. Precision Machining and Surface Purification TreatmentHigh-precision manufacturing and smooth surface treatment effectively eliminate tiny gaps where microbes adhere. Key forming parts are processed with tolerance within ±0.005mm to keep consistent product dimensions and reduce irregular gaps. Cavity and core surfaces are polished to Ra≤0.2μm, removing micro pits and scratches. Smooth surfaces greatly lower microbial adhesion difficulty and simplify daily disinfection work.
All mold assembly work is carried out in ISO Class 7 clean workshops. Staff wear sterile protective suits and gloves, and adopt dust-free tools to assemble components, stopping external particles from invading mold interiors. After assembly, tightness inspection is conducted to guarantee sealed mold structure and isolate outside pollutants. Polished parts go through ultrasonic cleaning and vacuum drying to fully wipe off metal scraps and polishing agent leftovers.
4. Clean Workshop Operation and Daily Mold ManagementMolding production must be conducted in standardized clean workshops reaching ISO Class 7 cleanliness level. Constant air circulation and regular ozone disinfection keep suspended particles and settling bacteria within qualified ranges. Indoor temperature and humidity stay stable to suppress mold and bacterial breeding. Operators follow strict dressing codes and avoid direct touch with mold forming surfaces. Raw plastic materials are stored in sealed containers to block dust and foreign impurities.
No conventional release agents are permitted during production to avoid chemical residue pollution. Special non-precipitation coating can be used for auxiliary demolding when necessary. Molds are stored in sealed dust-proof areas with constant temperature and humidity conditions. Regular maintenance and ultrasonic cleaning are arranged after fixed production batches to clear residual plastic scraps and tiny wear debris. Damaged sealing parts and aging coatings get timely replacement to sustain stable sterile performance.
5. Structural Design Compatible with Sterilization ProcessesFinished blood glucose meter housings need to adapt to mainstream medical sterilization methods, so mold design shall reserve proper shrinkage compensation according to different disinfection modes. Cavity sizes are adjusted based on shrinkage rates caused by EO sterilization and gamma radiation, preventing dimensional failure after disinfection. Mold materials and surface coatings maintain stable physical properties under repeated sterilization without aging or peeling off.
Mold structure is optimized to reduce closed blind cavities, enabling sterilizing gas and radiation to cover all housing surfaces thoroughly. Reasonable structural design balances sterile protection and practical usage performance of final products.
6. Compliance Inspection and Traceability ManagementAll mold design documents and production records comply with ISO 13485 quality management requirements. Core components are marked with exclusive identification codes to record material batches, machining parameters and maintenance history, realizing full-process quality traceability. Before formal delivery, molds undergo strict sterile detection, particle inspection and biocompatibility recheck. Qualified verification reports are required before putting molds into mass production. Timely design adjustment can be made to match updated medical regulations, maintaining long-term compliance of sterile molded products.
