In medical injection molding production, due to the stringent requirements for precision, cleanliness, and biocompatibility of medical devices, any faults in the injection molding process can directly impact product quality or even patient safety. Below, we summarize common issues and solutions in medical injection molding from four key dimensions: raw materials, molds, equipment, and processes.

I. Raw Material-Related Issues

1. Inadequate Biocompatibility of Raw Materials
   • Fault Symptoms: Surface precipitation, abnormal coloration, or failure in chemical testing.
   • Root Causes: Unqualified suppliers, misuse of raw materials, excessive additives.
   • Solutions: Strictly audit supplier qualifications (e.g., ISO 13485 certification), store medical-grade materials separately, avoid mixing with industrial-grade materials, and regularly test additive content.
2. Insufficient Cleanliness of Raw Materials
   • Fault Symptoms: Black spots or fibrous impurities on or inside products, posing infection risks.
   • Root Causes: Substandard storage conditions, inadequately cleaned recycled materials, contamination in the feeding system.
   • Solutions: Store materials in cleanrooms, clean recycled materials via ultrasonic cleaning + high-temperature sterilization, and install high-efficiency filters at the feeding port.

II. Mold-Related Issues

1. Micro-Pore Contamination in Molds
   • Fault Symptoms: Tiny pores on product surfaces, increasing bacterial growth risks.
   • Root Causes: Biofilm formation in mold cooling channels, long-term neglect of mold cleaning.
   • Solutions: Regularly clean cooling channels with bio-enzymatic detergents, wipe molds with medical-grade alcohol after each use, and store them sealed.
2. Poor Sealing at Mold Parting Lines
   • Fault Symptoms: Flash edges on products, requiring secondary processing to meet medical edge-free requirements.
   • Root Causes: Worn parting lines, insufficient clamping force, uneven mold temperature.
   • Solutions: Polish parting lines regularly, calibrate clamping force with high-precision clamping detectors, and optimize the mold temperature control system.

III. Injection Molding Machine-Related Issues

1. Insufficient Cleanliness of Injection Molding Machines
   • Fault Symptoms: Oil stains or metal debris on product surfaces, leading to cleanliness test failures.
   • Root Causes: Prolonged neglect of machine cleaning, hydraulic system leaks, metal wear on screws.
   • Solutions: Clean the machine interior daily before production, replace hydraulic oil and filters regularly, and use lead-free screw materials.
2. Unstable Metering Accuracy
   • Fault Symptoms: Weight fluctuations exceeding ±0.5% in the same batch, affecting the consistency of liquid filling volumes.
   • Root Causes: Unstable back pressure, screw wear, uneven raw material density.
   • Solutions: Install online weighing systems for real-time monitoring, regularly calibrate back pressure sensors, and use high-density, homogeneous raw materials.

IV. Process Parameter-Related Issues

1. Excessive Internal Stress in Products
   • Fault Symptoms: Increased brittleness, prone to cracking during sterilization (e.g., ethylene oxide) or transportation.
   • Root Causes: Prolonged holding time, large mold temperature gradients, insufficient raw material drying.
   • Solutions: Optimize holding pressure curves, use mold temperature controllers for ±1°C accuracy, and dry raw materials to a moisture content of ≤0.02%.
2. Insufficient Sterilization Compatibility
   • Fault Symptoms: Deformation or dimensional deviations in products after high-temperature, high-pressure sterilization.
   • Root Causes: Low glass transition temperature (Tg) of raw materials, uneven mold cooling.
   • Solutions: Select high-Tg medical-grade raw materials (e.g., PPSU, PEEK), and use spiral cooling channel designs in molds to enhance temperature uniformity.

V. Special Issues for Medical Products

1. Inconsistency in Multi-Cavity Mold Products
   • Fault Symptoms: Dimensional deviations exceeding 0.1mm between different cavities of the same mold, affecting assembly precision.
   • Root Causes: Poor runner balance design, uneven hot runner temperatures.
   • Solutions: Optimize runners using CAE simulation, add independent temperature control zones to hot runner systems, and regularly calibrate thermocouples.
2. Excessive Haze in Transparent Medical Products
   • Fault Symptoms: Insufficient light transmittance in products like catheters or lenses, affecting visual inspection or optical functions.
   • Root Causes: Raw material degradation, mold surface scratches, excessive injection speed.
   • Solutions: Reduce barrel temperature by 5–10°C, apply hard chrome plating to mold surfaces to prevent scratches, and control injection speed in stages.

Summary

Medical injection molding must strictly adhere to regulations such as ISO 13485 and FDA standards. Fault troubleshooting requires integrating materials science, mold engineering, and cleanroom technologies. Enterprises should establish standardized operating procedures (SOPs), regularly train operators, and introduce inline inspection equipment (e.g., vision inspection systems, laser thickness gauges) to achieve zero-defect production.

Dongguan Yize Mold Co., Ltd. specializes in medical injection molding, offering end-to-end solutions from medical-grade raw material validation, cleanroom mold development, precision injection molding, to sterilization packaging, helping clients pass CE and FDA certifications. Contact us for inquiries: +86 13302615729 (WeChat/WhatsApp same number).