Plastic injection molded parts manufactured by industrial gears are becoming more popular as they have some clear advantages over their metallic versions. Following are the key reasons for their use, their **manufacturing process**, and **material properties**:
### **Why Use Plastic Injection Molded Gears?**
1. **Lightweight** – Plastics are considerably lighter in weight than metals, reducing inertia and energy consumption in moving systems.
2. **Corrosion Resistance** – Plastics, unlike metals, resist rust and chemical deterioration, and therefore are ideal for hostile environments.
3. **Low Noise & Vibration** – Plastic gears are quieter due to their dampening properties.
4. **Cost-Effective** – Injection molding facilitates **large-volume production** at lower costs compared to metal gear machining.
5. **Self-Lubricating Options** – Some plastics (e.g., POM, nylon) have inherent lubricity, reducing maintenance needs.
6. **Design Flexibility** – Complex gear geometries (e.g., helical, bevel) can be molded accurately without secondary machining.
7. **Electrical Insulation** – Plastic gears are non-conductive and therefore find application in electronics and medical devices.
### **Manufacturing Process: Injection Molding**
1. **Material Preparation** – Plastic pellets (e.g., POM, nylon, PEEK) are dried (if hygroscopic) and fed into the injection molding machine.
2. **Melting & Injection** – Plastic is melted to a molten state and injected into a **precision mold** at high pressure.
3. **Cooling & Solidification** – The mold is cooled to solidify the plastic into the necessary gear form.
4. **Ejection & Finishing** – The gear is ejected, and a small flash or burrs are trimmed off (if necessary).
5. **Quality Control** – Gears are inspected for dimensional accuracy, strength, and defects (e.g., warping, sink marks).
### **Common Plastic Materials & Their Characteristics**
| **Material** | **Key Properties** | **Typical Applications** |
| **POM (Acetal/Delrin®)** | Stiffness is high, friction is low, wear resistance is excellent | Precision gears, automotive parts |
| **Nylon (PA6, PA66, PA12)** | Abrasion-resistant, tough, good fatigue resistance | Power transmission, conveyor systems |
| **PEEK** | Resistant to high temperature, chemical, strong | Aerospace, medical, high-load gears |
| **Polycarbonate (PC)** | Impact-resistant, transparent (if needed) | Light-duty gears, consumer electronics |
| **UHMW-PE** | Extremely wear-resistant, low friction | Food processing, conveyor gears |
### **Limitations to Consider**
- Lower load-carrying capacity than metal gears (though reinforced plastics can increase strength).
- Thermal expansion may require design changes.
- Not suited for extremely high-temperature applications (unless PEEK or high-performance plastics are utilized).
### **Conclusion**
Plastic injection molded gears perform well in applications where **weight, noise, corrosion resistance, and cost** are significant factors. The advent of **engineering plastics** (i.e., fiber-reinforced grades) has elevated their use in demanding industries like **automotive, medical, and robotics**.
Would you like some material recommendations for your particular gear application?
