Micro Gearbox Selection Guide – How to Choose Gear Material

The influence of Gear material on the performance of micro gearbox In the application of micro gearboxes, the choice of gear material determines performance, lifespan,…

The influence of Gear material on the performance of micro gearbox

In the application of micro gearboxes, the choice of gear material determines performance, lifespan, and reliability. If the wrong material is selected, the gearbox may experience rapid wear, excessive noise, or poor operational performance.

Is there a “Best” gear material?

This is one of the most common questions our customers ask. SGMADA’s answer is: there is no such thing as a “best gear material”, but rather, the gear material that is best suited to your application.

To find the best gear material (best material for gearbox gears), a balance must be struck between key factors such as load capacity, manufacturing cost, and operating environment. Different applications require different gear material properties, so the “Best” gear material is one that is custom-tailored to your specific needs.

In this article, we will share SGMADA’s 20 years of experience with gear materials, helping you find the best gear material for your application.

Common material classification and characteristics of micro gearbox gears

In the design of micro gearboxes at SGMADA, we have used alloy gears and plastic gears. After 20 years of gear design experience, we have summarized the characteristics of the following gear materials.

plastic gear collection — *Plastic Gear*

Metal Alloy Gears

Metal alloys are typically used for micro gears that need to withstand high loads, wear, or harsh environments. These materials offer superior strength and durability。

Material	Density(g/cm³)	Tensile Strength(MPa)	Hardness(HRC)	Corrosion resistance
Copper alloys	8.5-8.9	300-1000	20-40	✅✅✅
Iron alloys	7.2-7.8	250-600	20-55	✅
Tool steel alloys	7.8-8.0	600-1200	50-62	❌
Aluminum alloys	2.7-2.9	200-500	10-30	✅✅✅

Non-Metal Materials

Non-metal gears are mainly made of plastic. These gear materials are used to make miniature gears that require low noise or are cost-effective.

Material	Density (g/cm³)	Tensile Strength (MPa)	Hardness (HRC)	Corrosion Resistance
POM (Polyoxymethylene)	1.41 – 1.43	60 – 100	80 – 90	✅✅✅
PS (Polystyrene)	1.04	40 – 70	70 – 85	✅✅
Nylon (Polyamide)	1.13 – 1.15	70 – 90	70 – 80	✅✅✅
Bakelite (Electro Wood)	1.3	30 – 60	50 – 60	✅

Gear

SGMADA processes a variety of gear materials according to three main manufacturing methods:

1. Gear Hobbing

Materials: Steel alloys, Aluminum alloys
- Steel alloys are strong, durable, and ideal for high-load, high-precision gears.
- Aluminum alloys are lightweight, easy to machine.

2. Powder Metallurgy

Materials: Iron-based alloys
- Iron-based alloys are cost-effective and provide excellent wear resistance.

3. Plastic Injection Molding

Materials: Nylon (PA), Polycarbonate (PC)
- Nylon (PA) has great self-lubricating properties, low friction, and high wear resistance.
- Polycarbonate (PC) offers high impact resistance and strength, suitable for gears in electronics and consumer applications.

5 Key Factors in Choosing Gear Materials

There are many factors to consider when choosing gear materials. As experts in the field of micro gears, SGMADA recommends that you consider the following 5 factors when choosing gear materials.

1. Gear Load Strength

The load strength of a gear determines its durability and reliability in a specific application. If the gear is underloaded, it will cause gear deformation, noise and vibration in the mechanical system.

Material	Gear Strength	Impact Resistance
Plastic (e.g., POM)	❌	✔️✔️
Bakelite	❌	❌
Nylon	✔️	✔️✔️
Steel Alloys	✔️✔️	✔️✔️✔️
Iron Alloys	✔️	✔️✔️

2. Temperature Adaptability

Temperature adaptability refers to a material’s ability to maintain its mechanical properties under varying temperature conditions. For gear design, it is crucial to consider both the heat generated during gear operation and the surrounding ambient temperature in which the gearbox operates.

When gears are exposed to temperatures outside their optimal range, several issues can arise:

Reduced Strength: At high temperatures, materials can lose their hardness and strength, leading to deformation or breakage under load.
Cryogenic Brittleness: In extremely cold conditions, certain materials become brittle and may crack or fracture easily under stress.
Increased Friction and Wear: Higher temperatures cause materials to expand, increasing friction and accelerating wear, while colder temperatures can lead to contraction, affecting the fit and operation.

Now, let’s explore the temperature adaptability of five common gear materials:

3. Gear Noise

The generation of gear noise is closely related to factors such as material friction, lubrication characteristics and material hardness. At the same time, we must also consider the machining accuracy of the gear.

Noise Sources and Influencing Factors

Friction: Noise can arise during gear meshing due to rough or uneven contact surfaces, or insufficient lubrication. The higher the friction, the more likely noise will be generated.
Self-lubricating Properties: Materials with self-lubricating properties help minimize friction during meshing, resulting in reduced noise levels. These materials reduce the need for external lubrication, further lowering noise.
Hardness: Harder materials tend to increase friction and produce more noise, while softer materials reduce friction, leading to quieter operation.
Precision: The manufacturing accuracy of the gears plays a significant role in noise levels. Higher precision ensures better gear meshing, minimizing noise caused by misalignment or uneven wear.

Material	Self-Lubricating	Friction	Noise Performance	Lubrication Requirement
Plastic (POM)	Yes	Low	✅ Excellent	Minimal
Bakelite	No	Moderate	✅ Good	Requires external lubricant
Nylon (PA)	Yes	Low	✅ Excellent	Minimal
Steel Alloys	No	High	❌ Poor	Requires extensive lubrication
Iron Alloys	No	Moderate	✅ Good	Requires lubrication

Please note: This material analysis table is based solely on the properties of the gear materials. The overall noise level of the gearbox depends on various factors, including gear material, manufacturing precision, gear strength, and the gear meshing alignment.

4. Gearbox Gear Cost

When choosing gear materials, cost is a key factor. The price and processing difficulty of different materials will directly affect the cost-effectiveness of the product. The following is a comparative analysis of the cost and processing fees of common gear materials.

Characteristic	Plastic (POM)	Nylon (PA66)	Bakelite	Iron Alloys	Steel Alloys
Material Cost	Medium	High	Low	Medium	High
Processing Method	Injection Molding, CNC Cutting	Injection Molding, CNC Cutting	Compression Molding, CNC Cutting	Casting, CNC Cutting	Casting, CNC Cutting
Processing Cost	Low	Medium	High	High	High
Batch Production Cost	Low	Medium	High	High	High
Unit Cost	Low	Medium	High	High	High

5. Gearbox gear machining accuracy

The processing accuracy of gears depends on the material and the method used to manufacture them. Here’s a simplified comparison of the accuracy limitations for different materials and their processing methods:

Material	Processing Method	Accuracy Range
Plastic (POM)	Injection Molding, CNC Cutting	High precision (±0.05mm)
Nylon (PA66)	Injection Molding, CNC Cutting	High precision (±0.05mm)
Bakelite	Compression Molding, CNC Cutting	Moderate precision (±0.1mm)
Iron Alloys	Casting, CNC Cutting	Moderate precision (±0.1mm)
Steel Alloys	Casting, CNC Cutting	Low to Moderate precision (±0.2mm)

Gear Material Recommendations for Different Applications

The selection of gear materials requires both theoretical knowledge and practical experience. At SGMADA, we combine 20 years of expertise in micro gearbox design with in-depth material science to guide you in choosing the right gear material for each application.

⚙️ High Strength & Durability

🔻 Best Material: Steel Alloys, Iron Alloys
🔻 Applications: Power tools
🔻 Why?: High tensile strength, wear resistance, and long lifespan
🔻Processing: Hobbing, CNC Cutting, Powder Metallurgy

⚙️ High Precision & Performance

🔻 Best Material: Plastic (POM, Nylon), Steel Alloys
🔻 Applications: Robotics, medical equipment
🔻 Why?: High precision, low friction, and excellent dimensional stability
🔻 Processing: Injection Molding, Hobbing

⚙️ Low Noise & Smooth Operation

🔻 Best Material: Plastic (POM, Nylon)
🔻 Applications: Household appliances
🔻 Why?: Self-lubricating, low noise, and lightweight
🔻 Processing: Injection Molding

⚙️ Cost-Effective Mass Production

🔻 Best Material: Powder Metallurgy (Iron Alloys)
🔻 Applications: Industrial equipment, budget-friendly consumer products
🔻 Why?: Lower material cost, efficient for large-scale production
🔻 Processing: Powder Metallurgy

How to Find Your “Best Gear Material”

🔍 Gear Material Selection Process

✅ Define Requirements → Identify key factors such as load, precision, noise level, and cost.
✅ Match Material Properties → Compare materials based on strength, durability, and processing feasibility.
✅ Validate Cost & Manufacturing → Ensure the selected material meets budget and production constraints.