6 Thermal Expansion Effects on Servo Accuracy

Precision is everything when it comes to servo-driven systems. From robotic arms to CNC machinery, servos depend on exact positioning to deliver repeatable, accurate motion. But even in tightly controlled environments, one invisible factor can quietly throw performance off target: thermal expansion.

As components heat up during operation, metals and other materials expand — sometimes by only thousandths of an inch. Yet in systems that rely on micron-level accuracy, even that small change can distort alignment. Here are six ways thermal expansion impacts servo accuracy — and how to counter them.

1. Expansion of shafts and bearings

Servo shafts and bearings expand as temperatures rise, changing alignment between the rotor and stator. This subtle distortion increases friction and affects torque output, causing the servo to draw more current and operate less efficiently. Over time, these effects lead to wear and reduced positioning accuracy.

Prevention tip: Maintain consistent ambient temperatures around servo motors, and allow time for warm-up before calibration or high-precision tasks.

2. Encoder drift and feedback errors

Encoders provide critical feedback to the servo controller. As their housings and mounting surfaces expand or contract, the gap between encoder disks and sensors can shift — even slightly — introducing feedback errors. This drift can accumulate over time, causing servos to “hunt” for position or lose repeatability.

Prevention tip: Use temperature-compensated encoders and verify mounting alignment periodically during maintenance cycles.

3. Gearbox tolerance changes

Gearboxes transmit motion between servo motors and driven loads. Thermal expansion within gears and housings can change backlash and alter the load path. In precision systems, these changes lead to torque ripple and inconsistent motion control.

Prevention tip: Choose gearboxes designed with thermal expansion tolerances in mind, and avoid extended overload conditions that cause heat buildup.

4. Mounting frame distortion

As servo mounts and machine frames heat up, they expand unevenly, particularly when different materials are used together (like aluminum frames and steel mounts). Misalignment between the servo and driven load can cause angular error or vibration, degrading accuracy.

Prevention tip: Use uniform materials for mounting assemblies whenever possible and include expansion joints or compliant couplings to absorb thermal movement.

5. Changes in cable resistance

Servo control and feedback cables expand and contract with temperature, altering electrical resistance. This change can affect signal strength or timing, especially in analog feedback systems. At higher currents, added resistance also contributes to voltage drop and signal distortion.

Prevention tip: Route cables away from high-heat sources, use shielded wiring, and inspect connectors regularly for corrosion or fatigue.

6. Bearing lubrication breakdown

Heat doesn’t just expand metal; it thins and degrades lubrication. In servo bearings, insufficient lubrication increases friction and accelerates wear, both of which reduce accuracy and motor life.

Prevention tip: Follow manufacturer lubrication intervals, and use lubricants rated for the servo’s operating temperature range.

Staying precise under pressure

Thermal expansion is inevitable, but its effects on servo accuracy are manageable. By designing systems with temperature in mind and following preventive maintenance practices, manufacturers can minimize distortion, extend component life, and preserve precision.

Even the smallest temperature fluctuations can make a big difference in motion control performance. Paying attention to alignment, materials, and environmental stability helps ensure servo systems perform with the accuracy they were built for, cycle after cycle.