TECHNICAL SUPPORT
Published 2026-04-04
A 20g microservowith a metal case is a compact rotary actuator weighing approximately 20 grams, featuring a housing made of aluminum or other metal alloys instead of plastic. This design combines small size with enhanced durability, heat dissipation, and torque consistency. Theseservos are commonly used in robotics, RC vehicles, small CNC machines, and camera gimbals where space is limited but reliability under load is critical.
Unlike standard plastic-cased micro servos that may crack or deform under repeated stress or elevated temperatures, the metal case provides structural rigidity and helps wick heat away from internal components. This guide covers everything you need to know—specifications, real-world performance, common applications, and how to choose the right model for your project—without referencing any specific brand or company.
When evaluating a 20g metal-case micro servo, focus on these six core parameters. All values below represent typical ranges found in standard commercially available units.
Critical note:The “20g” designation refers to total servo weight, not torque or size. Always verify that your power supply can deliver sufficient current (typically 300–800 mA per servo at stall) to avoid voltage drops or brownouts.
A hobbyist built a 4-DOF robotic arm using standard 9g plastic-case servos. After 30 minutes of lifting a 150g payload, the servos overheated, and the cases near the shoulder joint cracked due to repeated stress. Switching to 20g metal-case servos (same voltage and signal) solved both issues. The metal case dissipated heat, and the rigid housing prevented flex under load, allowing continuous operation for over 2 hours without failure.
An RC enthusiast noticed that after upgrading to larger wheels, the plastic-case steering servo would stall on rocky inclines. The case would flex, causing intermittent loss of steering. Replacing it with a 20g metal-case servo provided two improvements: the metal case eliminated flex, and the internal metal gears (standard in metal-case models) handled the impact loads from rock crawling. The result was consistent steering even when the wheels were wedged against rocks.
A videographer building a lightweight 2-axis gimbal for a GoPro initially used plastic-case micro servos. Vibrations from the drone’s motors caused the servo cases to resonate, introducing micro-jitter in the footage. After switching to metal-case servos of the same weight class, the added mass damping and rigid mounting reduced high-frequency vibrations, producing smooth footage. The metal case also provided better heat sinking during long flights.
These cases illustrate a consistent pattern:if your application involves sustained load, vibration, heat, or physical impacts, a metal-case 20g micro servo is not a luxury—it is a requirement.
Small robotic arms (3–5 DOF):Use metal-case servos at base and shoulder joints; plastic-case may suffice for wrist/gripper if loads are light.
RC cars (1/18 to 1/16 scale):Steering servo benefits most from metal case and metal gears; throttle servo has lower stress.
Micro drones with camera tilt:Metal case reduces jello effect from vibrations.
Educational mechatronics kits:Ideal for student projects where repeated crashes and overloads occur.
Automated feeders or small actuators:Metal case prevents creep under constant holding torque.
Follow this step-by-step decision process:
Step 1 – Calculate required torque
Measure the load (in grams) and the distance from servo horn pivot to load center (in cm). Torque (kg·cm) = (load in kg) × (distance in cm). Add 30–50% safety margin. Example: A 200g load at 4 cm needs 0.2 × 4 = 0.8 kg·cm minimum. With 50% margin: 1.2 kg·cm. Most 20g metal servos provide 2.0–3.5 kg·cm, which is sufficient.
Step 2 – Determine speed needs
For steering or flapping mechanisms, look for ≤0.10 sec/60°. For slow positioning (camera pan, gripper), 0.12–0.15 sec/60° is acceptable.
Step 3 – Check voltage compatibility
If using a 5V Arduino or 4.8V NiMH pack, almost all servos work. For 2S LiPo (7.4V nominal), verify the servo is rated for 6.0–7.4V. Many 20g metal servos have a “high voltage” version (up to 8.4V) that provides higher torque.
Step 4 – Examine mounting pattern
Standard micro servo mounting holes are 27 mm apart center-to-center with M2 screws. Some metal cases use M2.5 or have counterbores. Check your bracket’s hole spacing before purchasing.
Step 5 – Verify spline type and horn compatibility
Most 20g micro servos use a 25-tooth spline (Futaba pattern) or 21-tooth (JR pattern). Metal-case servos often include a set of metal horns. Plastic horns may strip under high torque; use included metal horns for critical applications.
1. Power supply rules: Never power a 20g metal servo directly from a microcontroller’s 5V pin (e.g., Arduino). Use a separate BEC or battery capable of 1A continuous per servo. Brownouts cause resets.
2. Signal wire: Connect to PWM-capable pin (usually yellow or white wire). Red is V+, brown/black is ground.
3. Current testing: Before final assembly, measure stall current with a multimeter. If it exceeds your power supply rating, reduce load or add a capacitor (1000 µF) across power leads.
4. Heat management: Metal cases get warm under continuous operation—this is normal, as the case acts as a heatsink. If surface temperature exceeds 65°C (149°F),reduce duty cycle or add passive cooling.
5. Mounting screws: Use thread-locker (e.g., Loctite 242) on metal-to-metal screw joints, as vibrations loosen them over time.
Every 50 operating hours: Check screws on servo horn and mounting bracket. Re-tighten if necessary.
After a crash or overload: Manually rotate the horn through full range. If you feel grinding or uneven resistance, internal gears may be damaged. Replace gears (many metal-case servos have replaceable gear sets).
Cleaning: Use compressed air to remove debris from output shaft area. Do not use oil or grease externally—it attracts dust.
Storage: Keep in dry environment. Metal cases can corrode in high humidity; a light coat of corrosion inhibitor on bare metal surfaces (avoiding seams) helps.
A 20g micro servo with a metal case directly addresses the three weakest points of plastic-case servos: mechanical flex, heat buildup, andimpact resistance. Real-world examples from robot arms, RC cars, and camera gimbals confirm that switching to a metal case eliminates common failures like cracked housings, overheating, and jitter—without increasing weight beyond 20 grams.
Actionable recommendations for your next build:
1. Always use a metal-case servo for any joint or actuator that will experience more than 10 minutes of continuous operation or any load exceeding 100g at a 3 cm arm.
2. Keep plastic-case servos only for ultra-light, intermittent, or purely educational testing where failure is acceptable.
3. Verify torque and voltage using the step-by-step selection process before purchasing—do not rely on product titles alone.
4. Install with a separate power supply and metal horn to unlock the full durability that the metal case enables.
By following this guide, you ensure that your project benefits from the structural and thermal advantages of a metal-case 20g micro servo, resulting in longer life, consistent performance, and fewer field failures.
Update Time：2026-04-04
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