Arc Segment Magnets for Industrial Servo Motor Upgrade

Problem

A US servo motor manufacturer wanted to upgrade from ferrite to NdFeB magnets to increase torque density without changing the motor housing dimensions. The challenge: NdFeB arc segments required tighter tolerances (±0.05 mm on arc geometry) than their ferrite supplier could guarantee, and the magnets needed to operate at sustained temperatures up to 120°C.

Solution

We coordinated with a Ganzhou factory specializing in arc segment production for motor applications. The factory uses precision wire-cutting and surface grinding to achieve the required arc geometry tolerances.

Key steps:

• Sample iteration 1: Validated grade (N45H) and basic dimensions
• Sample iteration 2: Refined arc radius and pole face flatness
• Sample iteration 3: Confirmed coating adhesion and thermal cycling stability
• Production release after third sample approval

Specifications

• Material: NdFeB (N45H)
• Shape: Arc segment (60° span)
• Dimensions: OD 52 mm, ID 42 mm, length 30 mm
• Tolerance: ±0.05 mm on arc faces, ±0.03 mm on length
• Coating: NiCuNi
• Magnetization: Radial through thickness
• Operating temperature: Up to 120°C continuous
• Volume: 2,400 pcs/quarter (4 magnets per motor × 600 motors)

Results

• Torque density increased by 35% compared to ferrite version.
• Motor assembly weight reduced by 22%.
• Three sample iterations completed within 5 weeks total.
• Production lead time stabilized at 3 weeks per batch.

Next Steps

Share your motor cross-section drawing with target torque specs. We will recommend the optimal grade and confirm arc geometry feasibility with the factory.