Magnets for Collaborative Robots (Cobots): Requirements, Grades, and Supplier Selection

N48SH and N50H are the dominant grades for cobot joint motors. N48SH (45–48 MGOe BHmax, 150°C continuous rating) is preferred where the motor sees sustained load and elevated internal temperatures. N50H (50 MGOe BHmax, 120°C rating) is acceptable for cooler-running joints where the higher flux density is worth the lower thermal margin. Both should be GBD-processed in 2026 to insulate against heavy rare earth price volatility.

Cobots run at very low speeds for precision positioning and at high speeds for rapid moves between positions. The motor controller relies on consistent torque output across the entire speed range, which requires consistent magnet flux. ID tolerance ±0.02mm controls the air gap between magnet and stator (a 0.1mm air-gap variation causes 5–10% torque variation). Ring-to-ring flux variance under 1% ensures every motor in the cobot fleet behaves the same — critical for control software that cannot afford per-motor tuning at scale.

Backdrivability is the ability for a human to push the cobot arm and have the motors yield smoothly without resistance. It is essential for safe human-robot interaction and for hand-guided teaching. Magnet contribution to backdrivability comes through cogging torque — the residual torque ripple from the interaction between magnet poles and stator teeth. Smooth sinusoidal flux from radial multi-pole rings minimizes cogging; the trapezoidal flux from segmented arc assemblies makes backdrivability noticeably worse.

Often yes. Cobot joint motors and humanoid robot joint motors share the same fundamental requirements: high torque density, low cogging, thermal stability under sustained load. Both gravitate toward radial multi-pole rings in N45SH or N48SH grade. Humanoid robots typically push torque density harder (more peak torque per kg) and need more aggressive thermal margin, but the overall magnet specification overlaps significantly.

2–3 weeks for 50–100 piece prototype batches is the qualifying standard for any supplier serving the robotics industry. Suppliers requiring 6–8 weeks for prototypes are not operationally suited to modern cobot product development cycles. First production lots typically take 6–10 weeks including tooling, qualification, and any export licensing. Ongoing production runs 8–12 week lead time including MOFCOM licensing for SH grades.

The SH and UH grade magnets used in cobot joint motors contain dysprosium and/or terbium, which puts them under China's April 2025 MOFCOM export licensing regime. Commercial robotics applications including cobots are routinely approved with proper end-use documentation; license timelines run 6–10 weeks under normal conditions. Use a supplier with in-house licensing capability to avoid the additional delay of routing through a trading company.

A standard 6-axis cobot contains six joint actuators, each built around a single radial multi-pole sintered NdFeB ring as the rotor magnet — so roughly 6 high-torque joint magnets per arm. Smaller stepper or servo magnets in the gripper, end-effector, and any wrist roll/pitch DOFs typically add another 1–4 magnets depending on the gripper design. Total NdFeB content per cobot is usually 0.4–1.2 kg, scaling with payload class. A 5 kg payload cobot sits at the lower end of that range; a 20 kg payload cobot sits near the top.

It already has, indirectly. NdPr blended oxide moved from approximately USD 53/kg in January 2026 to roughly USD 135/kg by late April — a ~155% YTD jump. For a typical 6-axis cobot carrying ~0.8 kg of NdFeB, raw-material cost alone moved from roughly USD 40 per arm to roughly USD 100 per arm. The specification response has been to lock in GBD-processed grades (which cut heavy rare earth content 50–70% at equal performance) and to renegotiate any Q1 2026 quotes with 90-day price-locks. The grade itself rarely changes — the supply contract terms do.