Domestic appliance plastic injection molded shells are widespread due to their toughness, inexpensiveness, and simplicity of design. Below is an overview of their **production process, materials, and features**:
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### **1. Production Process (Injection Molding)**
Plastic shell production involves the following several main steps:
#### **Step 1: Mold Design**
- A close tolerance mold (usually steel or aluminum) is developed from the 3D model of the appliance.
- The mold has cavities, cooling channels, and ejection mechanisms.
#### **Step 2: Material Preparation**
- Hygroscopic plastic pellets (e.g., ABS, PP, PS) are dried and charged into the injection molding machine.
#### **Step 3: Injection & Melting**
- Plastic pellets are melted in the barrel (heated to 200–300°C, depending on material).
- Molten plastic is injected at high pressure (500–1500 bar) into the mold cavity.
#### **Step 4: Solidification & Cooling
- The plastic is solidified into the desired shape by cooling the mold (with water passages).
- Cooling time depends on thickness (approximately 10–60 seconds).
#### **Step 5: Ejection & Finishing**
- Ejector pins push out the part as the mold opens.
- Post-processing like trimming, deburring, surface treatment (like painting or adding texture) can be done.
#### **Step 6: Quality Inspection**
- Dimensional checks, stress tests, and visual checks for quality.
### **2. Common Materials Used**
The choice of material is based on the appliance's needs (strength, thermal resistance, appearance, etc.):
| **Material** | **Properties** | **Typical Applications** |
|-------------|--------------|------------------------|
| **ABS** (Acrylonitrile Butadiene Styrene) | High impact strength, smooth finish, paintable | Refrigerator side walls, vacuum cleaner shrouds, kitchen appliances |
| **PP** (Polypropylene) | Chemical & moisture resistance, lightweight, flexibility | Dishwasher components, laundry equipment components
| **PS** (Polystyrene) | Rigid, economical, glossy finish | Small appliance casings, cosmetic caps |
| **PC** (Polycarbonate) | Tough, heat & UV stable | Blender containers, microwave parts |
| **PC/ABS Blend** | Marries strength (PC) & processability (ABS) | Power tool casings, high-end appliances |
| **HIPS** (High-Impact Polystyrene) | Low-cost, easy to mold, impact-stabilized | TV back panels, small appliance shells |
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### **3. Important Features of Injection Molded Shells**
- **High Precision & Consistency**: Complex geometries with tight tolerances (±0.1mm).
- **Smooth/Textured Surfaces**: Can be glossy, matte, or textured (e.g., soft-touch coatings).
- **Lightweight & Durable**: Resistant to impact, heat, and chemicals.
- **Cost-Effective**: Mass production reduces per-unit cost.
- **Design Flexibility**: Allows for integrated features (snap fits, ribs, hinges).
- **Recyclability**: Many thermoplastics can be recycled (e.g., PP, ABS).
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### **4. Applications in Household Appliances**
- **Large Appliances**: Front panels of washing machines, doors of refrigerators.
- **Small Appliances**: Blenders, coffee makers, hair dryers.
- **Electronics**: TV bezels, remote control housings.
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### **Conclusion**
Shells made from plastic injection molding are the ideal solution for household appliances due to being **versatile, long-lasting, and cost-effective**. The mold design and materials used significantly affect performance as well as looks.
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