**Shell injection molded plastic** manufacture involves several important processes, from product design to final inspection. Step-by-step process description is given below:
**1. Design & Mold Making**
- **Product Design**:
- 3D modeling via CAD software including wall thickness, draft angle, ribs, and undercuts for moldability.
- Simulation (e.g., Moldflow) for calculating flow, cooling, and potential defects.
- **Mold Design:**
- Separated into core/cavity, with components including gates (edge, submarine, or hot runner), ejector pins, cooling channels, and vents.
- Material: Hardened steel (high volume) or aluminum (prototypes/low volume).
- **Mold Fabrication:**
- CNC machining, EDM (electrical discharge machining), and polishing to create smooth surface finishes.
**2. Material Preparation**
- **Plastic Selection**:
- Standard resins: **ABS** (strength), **PC** (clarity/heat resistance), **PP** (chemical resistance), or **PC/ABS alloys**.
- Additives: Pigment, UV stabilizers, flame retardants.
- **Drying**
- Hygroscopic materials (e.g., nylon, PC) are dried between 80–120°C to prevent bubbles.
**3. Injection Molding Process**
- **Machine Setup**:
- Clamping force (e.g., 50–300 tons) based on part size.
- Temperature zones: Hopper → Barrel (180–300°C) → Nozzle.
- **Cycle Steps**:
1. **Clamping**: Mold closes under high pressure.
2. **Injection**: Plastis being melted is injected into the cavity (speed/pressure controlled).
3. **Packing**: Extra pressure takes up the place of shrinkage.
4. **Cooling**: Parts solidify (time varies with thickness).
5. **Ejection**: Mold opens; ejector pins force out part.
**4. Post-Processing**
- **Gate Trimming**:
- Manual or automatic sprue/runner remnants removal.
- **Deburring**:
- Removing flash (excess material at parting lines).
- **Surface Finishing**:
- Painting, electroplating, texture etching, or laser marking.
- Secondary operations: Ultrasonic welding for multi-part assemblies.
**5. Quality Control**
- **Dimensional Checks**:
- Calipers, CMM (Coordinate Measuring Machine), or optical scanners.
- **Visual Inspection**:
- Imperfections such as sink marks, weld lines, or color variation.
- **Functional Testing**:
- Drop testing, waterproofing (for enclosure), or assembly fit verification.
**6. Packaging & Shipping**
- **Cleaning**:
- Anti-static processing for electronic parts.
- **Packaging**:
- Special trays, vacuum sealing, or foam boxes to cushion from damage.
**Injection Molding Strengths**
- **Efficiency High**: Fast cycles (seconds to minutes per part).
- **Accuracy**: Accurate tolerances (±0.1–0.5mm).
- **Volume Scalability**: Cost-effective in mass production.
This method is widely applied in **electronic enclosures, auto components, medical equipment**, and consumer goods. If you need information regarding a specific step, let me know! Kama@hwplasticparts.com
