Gears material selection shapes performance, durability, and cost-efficiency. Two engineering thermoplastics, POM vs Nylon are the most popular gear materils due to their robust properties and versatility. Both materials offer distinct advantages. How to choose injection molding material for gears? After reading the article, you will have a more inform selection.
Material Requirements for Injection Molded Gears
Injection molding gears operate under demanding conditions. The material used must fulfill several fundamental criteria to ensure reliable and efficient gear performance:
Wear Resistance: Gears undergo continuous meshing and sliding contact, causing frictional wear. Materials must resist abrasion and surface wear to maintain gear tooth integrity over time.
Dimensional Stability (Shrinkage Rate): Precision is critical for gears to maintain accurate tooth geometry and meshing. Materials must exhibit low shrinkage (typically 2-3.5% for POM, higher for nylon) and resist deformation under temperature and humidity changes.
Low Friction: A low coefficient of friction minimizes energy loss, wear, and heat generation, enhancing gear efficiency.
Low Noise: Gears should operate quietly, especially in noise-sensitive applications like office equipment or consumer products. Materials that dampen vibration and reduce operational noise are preferred.
Strength: Gears require high tensile and fatigue strength to withstand cyclic loads and torque without cracking or deforming.
Moisture Absorption: Materials with low moisture absorption maintain dimensional stability in humid environments, preventing swelling or warping that could disrupt gear alignment.
Key Characteristics of POM and Nylon
POM (Polyoxymethylene)
POM, also known as acetal, is a highly crystalline engineering thermoplastic renowned for its excellent mechanical properties and dimensional stability. Common materials for polyoxymethylene injection molding.
- Low Friction: POM boasts a coefficient of friction of 0.2-0.3, offering excellent self-lubrication. This reduces wear and energy loss in sliding applications like gears.
- Wear Resistance: With a Rockwell hardness of R125, POM exhibits up to five times better abrasion resistance than nylon, ensuring durability under continuous operation.
- Dimensional Stability: POM’s low moisture absorption (0.2-0.5%) and shrinkage rate (2-3.5%) make it highly stable, even in humid or chemically aggressive environments.
- Strength: POM offers high tensile strength (60-70 MPa) and superior fatigue resistance, ideal for gears subjected to cyclic loading.
- UV Sensitive: POM is sensitive to UV radiation, which can degrade its properties, and it becomes brittle at low temperatures (below -40°C).
Nylon (Polyamide)
Nylon, or polyamide (e.g., Nylon 6, Nylon 66, Nylon 46), is another semi-crystalline thermoplastic known for its toughness and flexibility. Available in various grades. Common materials for nylon injection molding service
- Wear Resistance: Nylon has good wear resistance (Rockwell R115-120), especially when reinforced or modified, Nylon performs well under sliding conditions.
- Self-Lubricating Properties:: Nylon offers decent self-lubrication, reducing the need for external lubricants.
- Higher Moisture Absorption: Nylon’s higher moisture absorption (up to 3% or more) causes swelling, which can compromise gear precision in humid conditions.
- Strength: Nylon excels in impact resistance and tensile strength, making it suitable for high-torque applications.
- Noise Reduction: Nylon’s elasticity provides excellent vibration damping, reducing noise in gear systems.
- Lower Dimensional Stability: Due to moisture uptake and higher shrinkage rates, Nylon gears may require post-processing or design compensation.
- Limitations: High moisture absorption and lower fatigue strength limit its suitability for precision-critical or high-cycle applications.
POM vs. Nylon: Performance in Injection-Molded Gears
When comparing pom vs nylon for injection molded gears, it’s essential to evaluate their performance across key parameters relevant to gear function. The following table provides a concise comparison of how each material performs in the context of injection-molded gears.
| Property | POM | Nylon |
|---|---|---|
| Wear Resistance | Superior (Rockwell R125, up to 5x better than nylon). Ideal for high-speed gears. | Good (Rockwell R115-120), but wears faster without reinforcements. |
| Dimensional Stability | Excellent (0.2-0.5% moisture absorption, 2-3.5% shrinkage). Maintains precision in humid environments. | Moderate (up to 3%+ moisture absorption). Swelling affects gear alignment. |
| Low Friction | Very low coefficient (0.2-0.3). Self-lubricating, reduces wear and energy loss. | Higher friction than POM. Requires additives for comparable performance. |
| Low Noise | Moderate. Less effective at vibration damping, leading to more noise. | Excellent. Superior elasticity reduces noise in consumer applications. |
| Strength | High tensile strength (60-70 MPa), excellent fatigue resistance for cyclic loads. | High impact resistance, good for high-torque applications, but lower fatigue strength. |
| Moisture Absorption | Minimal (0.2-0.5%). Stable in wet conditions, no drying needed. | High (3%+). Requires drying or environmental controls for stability. |
| Processing | Easier to mold with tight tolerances (±0.005 mm). Suits precision gears. | Flexible for complex shapes, but less precise (±0.02 mm). |
Material Modification and Enhancement for Gear Applications
Both POM vs Nylon can be enhanced through additives to meet specific gear requirements, expanding their applicability.
POM Enhancements:
- Glass Fiber Reinforcement: Increases tensile strength and stiffness, reducing creep under load. This is ideal for high-stress gears but may slightly increase friction.
- PTFE or Graphite Additives: Further lowers the friction coefficient, enhancing performance in high-speed or precision gears.
- UV Stabilizers: Improve resistance to UV degradation, though this is less critical for indoor gear applications.
Nylon Enhancements:
- Glass or Carbon Fiber: Boosts strength, thermal stability, and rigidity, making nylon competitive with POM in high-load applications. However, fibers may increase friction.
- Aramid Fibers: Enhance wear resistance at low loads, though they may fail under high stress.
- Lubricants or Heat Stabilizers: Reduce friction and heat buildup, but excessive additives can compromise mechanical properties.
Modifications must balance performance gains with potential trade-offs. For example, glass-filled nylon improves strength but may increase friction, negating its noise-reduction advantage. POM modifications typically preserve its low-friction edge while enhancing durability.
POM vs Nylon – Which Should You Choose for Your Gear Project?
The choice between Nylon vs POM hinges on the specific demands of your gear application. POM excels in applications demanding high precision, low friction, and reliable performance in humid or chemically exposed environments. Its superior wear resistance, dimensional stability, and fatigue strength make it the preferred choice for automotive gears, precision machinery, and sliding components. However, its UV sensitivity and brittleness at low temperatures must be considered. Conversely, Nylon is ideal for applications prioritizing impact resistance, noise reduction, and cost-effectiveness under moderate loads. Its vibration-damping properties suit consumer products and noise-sensitive industrial systems, but its higher moisture absorption necessitates reinforcements and environmental controls to ensure stability.
Cooperate with Jiangzhi
For optimal results, prototype both POM vs. Nylon under real-world conditions to evaluate wear, noise, and stability. At Jiangzhi, we specialize in providing customized POM and Nylon solutions tailored to your gear project’s specifications. Our professional team of engineers offers material modification services, including glass fiber reinforcement and low-friction additives, to optimize performance for your application. Whether you need high-precision POM gears or noise-reducing nylon components, we can deliver cost-effective, high-quality solutions that meet your budget and performance requirements. Contact Jiangzhi today to explore our custom plastic processing and material enhancement services.
