Laryngoscopes, as key instruments for observing the structures of the pharynx and larynx in clinical diagnosis and treatment, require their injection molding production to meet both precision manufacturing and medical safety standards. From production environment control to injection molding process optimization and final product quality inspection, every link must comply with the regulations of the medical device industry. The following is an analysis from four dimensions: environment, technology, materials, and quality control.

I. Production Environment Requirements: Cleanliness and Stability Are Both Important

1. Classified Cleanliness Control

The laryngoscope injection molding workshop needs to be classified according to the "Good Manufacturing Practice for Medical Devices." The core area (such as the molding area for the viewing blades) must meet the ISO 7 (Class 10,000) cleanliness standard, that is, the number of suspended particles ≥0.5μm in each cubic meter of air should be ≤352,000, and the number of microorganisms (airborne bacteria) should be ≤10/m³. The auxiliary area (such as the material storage area) can be relaxed to the ISO 8 (Class 100,000) standard, but it needs to be isolated from the clean area through airlocks and pass boxes to prevent cross-contamination.

2. Dynamic Temperature and Humidity Regulation

The production environment temperature should be controlled at 20±2℃, and the humidity should be ≤40% to prevent material moisture absorption, which can lead to dimensional deviations or static electricity attracting dust. For example, polycarbonate (PC) material is prone to water absorption when the humidity is too high, and bubbles may form after injection molding; when the humidity is too low, static electricity may occur, attracting airborne particles. The workshop needs to be equipped with a constant temperature and humidity system and monitor the data in real-time through sensors.

3. Anti-static and Anti-contamination Measures

• Anti-static System: The floor should be made of epoxy self-leveling or anti-static PVC flooring, with a resistance value between 1×10⁵ and 1×10⁹Ω. Operators should wear anti-static hooded suits and gloves and pass through an air shower for dust removal before entering the clean area.
• Contamination Prevention: The equipment layout should follow the "unidirectional flow" principle to avoid reverse material flow leading to contamination. For example, the injection molding machine for the viewing blades and the assembly line should be connected through a buffer room, and the assembly line should be equipped with a laminar flow hood (airflow speed of 0.25-0.5m/s) to ensure local cleanliness.

II. Injection Molding Technology Requirements: Precision and Stability Are the Core

1. Equipment Selection and Precision Control

• All-electric Injection Molding Machine: It adopts a closed-loop servo control system, with an injection pressure fluctuation of ≤±1% and a holding pressure repeatability accuracy of ±0.5MPa, ensuring a product weight difference of <0.1%. For example, KraussMaffei equipment from Germany uses linear guides and ball screws for transmission, with a positioning accuracy of ±0.001mm, avoiding oil contamination from traditional hydraulic systems.
• Mold Manufacturing: The mold tolerance should be controlled at ±0.005mm, and the surface should be mirror-polished (Ra≤0.2μm). Hard chrome plating or diamond-like carbon (DLC) coating can be used to improve wear resistance. The mold should be ultrasonically cleaned and its accuracy re-measured after every 5,000 molding cycles to prevent die release agent residues from causing dimensional deviations.

2. Process Parameter Optimization

• Temperature Control: The barrel temperature should be set according to the material characteristics. For example, the barrel temperature for polyetheretherketone (PEEK) should be controlled at 380-420℃. Too high a temperature can cause material decomposition, while too low a temperature can result in poor fluidity.
• Injection Speed and Pressure: Thin-walled parts such as viewing blades require high-speed injection (speed >500mm/s) to avoid weld lines, combined with multi-stage holding pressure (e.g., three-stage holding pressure, with the pressure gradually decreasing from 80% to 50%) to reduce internal stress.
• Cooling System: The mold should be designed with conformal cooling channels, and the cooling water flow rate should be ≥15L/min to ensure a mold temperature uniformity of ≤±2℃ and prevent product warping.

III. Material Selection and Biological Safety

1. Medical-grade Material Standards

The injection molded parts of laryngoscopes need to be made of materials that meet the ISO 10993 standard, such as polyphenylsulfone (PPSU) and polycarbonate (PC). Taking PPSU as an example, it needs to pass 12 biological safety tests, including cytotoxicity (MTT method), sensitization (skin patch test), and pyrogen (limulus amebocyte lysate test). Its molecular weight distribution should be narrower than 1.8 to ensure batch stability.

2. Raw Material Storage and Use

Raw materials should be stored in a constant temperature and humidity warehouse (temperature 20±2℃, humidity ≤40%). After unpacking, they should be put into use within 8 hours. Each batch of materials should be provided with biological compatibility reports and FDA 510(k) certification documents, and undergo incoming inspection for melt index (MI) and color difference (ΔE≤1).

IV. Quality Inspection and Traceability System

1. Full-process Inspection

• First-piece Inspection: A coordinate measuring machine (CMM) should be used to measure key dimensions (such as the thickness of the viewing blade and the curvature of the lens) at the micrometer level, with a 100% coverage rate for geometric tolerance inspection.
• Online Inspection: A high-speed visual inspection system (2000 frames per second) should be used to identify defects such as weld lines and air holes. Products with a defect area >0.1mm² should be automatically rejected.
• Final Inspection: Accelerated aging tests (e.g., 70℃/168 hours) should be conducted to simulate a 5-year service life, and the product's resistance to disinfection should be verified through gamma ray or ethylene oxide sterilization.

2. Full-lifecycle Traceability

Each injection molded part should be marked with the production batch, mold number, operator information, etc. through laser marking or QR codes to ensure product traceability. Production data should be uploaded to the MES system in real-time, forming an electronic file containing 150 parameters to meet the compliance requirements of FDA 21 CFR Part 11.

Conclusion

The production of laryngoscope injection molding needs to take "precision manufacturing" as the main technical line and "medical safety" as the quality bottom line. From clean workshop environment control to the parameter optimization of all-electric injection molding machines, from the strict selection of medical-grade materials to full-process quality inspection, every link must comply with the ISO 13485 medical device quality management system and China's "Good Manufacturing Practice for Medical Devices." With the increasing demand for minimally invasive and visualization in the medical industry, laryngoscope injection molding technology is developing towards higher precision, higher cleanliness, and higher biological safety, providing more reliable instruments for clinical diagnosis and treatment.