I. Definition

Precision injection molding is an advanced process using injection - molding machines to produce plastic products. It can control product dimensional accuracy within 0.01 - 0.001mm, far more precise than conventional injection molding. For example, in high - end electronics, components need micron - level accuracy for proper functioning.

II. Characteristics

1. High Dimensional Accuracy: Product dimensional deviations are usually within 0.03mm. In automotive fuel injection system parts, small deviations can affect engine performance.

2. High Geometric Accuracy: Shape and position tolerances like flatness, perpendicularity, and coaxiality are strictly controlled. In optical instrument lens holders, small errors can degrade imaging quality.

3. Good Surface Quality: Products have high surface finish with no obvious defects. This is vital for products like high - end phone cases, enhancing aesthetics and user experience.

4. Strong Performance Stability: Mechanical and physical properties remain stable across batches and environments. Medical syringes must maintain stable performance for safety.

III. Key Influencing Factors

1. Materials: Plastic shrinkage, including thermal, elastic, plastic, post - shrinkage, and aging shrinkage, affects precision. Crystalline resins' shrinkage is influenced by mold temperature, while orientation shrinkage relates to injection pressure and speed.

2. Molds: High - quality steel like NAK80 and 718H is used. Fewer cavities, short and smooth runners are preferred. Mold dimensional, positioning, and parting - surface accuracies determine product precision, with mold tolerances usually within 1/3 of product tolerances.

3. Equipment: Precision injection molding machines with closed - loop control of injection pressure, speed, temperature, and metering are needed. All - electric injection molding machines offer better control and accuracy.

4. Process: Multi - stage injection and precise mold temperature control are key. Injection parameters are adjusted according to product shape and size. Mold temperature is controlled within ±1℃ for uniform cooling.

5. Environment: Temperature, humidity, and dimensional creep in the usage environment can affect product precision. Suitable materials and processes are chosen to ensure stability.

IV. Process Requirements

1. Equipment: Injection pressure ≥25MPa, injection speed ≥300mm/s, mold opening/closing position accuracy ≤0.03mm/≤0.01mm, injection position accuracy ≤0.03mm, tie - rod force balance ≤1%, pre - plasticizing position accuracy ≤0.03mm, template balance ≤0.03mm (zero clamping force)/≤0.005mm (max clamping force), and barrel/screw temperature control accuracy ≤±0.5℃.

2. Mold Design: Design reasonable cavity layouts and runner systems for uniform filling. Set up proper cooling systems for even temperature distribution. Use high - precision parts and advanced manufacturing processes.

3. Molding Process Parameters: Control injection volume precisely. Set appropriate holding pressure and time to compensate for shrinkage. Keep mold temperature within ±1℃.

V. Application Fields

1. Aerospace: Light - weight and high - precision parts, like aircraft interiors, are made using this technology for better fuel efficiency and environmental adaptability.

2. Automotive: Critical parts such as sensor housings, dashboards, and gears require high precision for reliable vehicle operation.

3. Precision Instruments: Optical instrument housings and microscope components demand high accuracy for proper function.

4. Medical: Products like catheters, syringes, and dentures need high precision and safety to meet medical standards.

5. Electronics and Communication: Miniaturized and high - performance products like phone cases and chip packages are produced with precision injection molding.