APPLICATION 01

SATELLITE ATTITUDE
CONTROL DRIVE

Ring gear specification: Ti-6Al-4V aged or 15-5 PH H900, M1–M3, DIN 3–4, MoS₂ ion-beam-deposited coating or sputtered MoS₂ for vacuum operation, zero-outgassing requirement per ASTM E595 (TML ≤ 1.0%, CVCM ≤ 0.1%), qualified for 10⁸ cycles in vacuum (10⁻⁶ Pa) at −60°C to +120°C, 100% dimensional inspection. Satellite attitude control systems use a variety of actuators — reaction wheels (spinning flywheels whose angular momentum provides attitude stabilisation), control moment gyroscopes (CMGs, which tilt a spinning flywheel to produce a gyroscopic torque), and direct-drive attitude thrusters — but all eventually require a precision ring gear in the planetary gear train that couples the brushless DC motor to the wheel or gimbal output. The ring gear in a reaction wheel planetary drive is the highest-cycle component in the entire satellite — at 5,000 RPM motor speed with a 5:1 planetary gear ratio, the ring gear accumulates 2.16 billion tooth contact cycles per year. Over a 15-year satellite design life, the ring gear must sustain 32 billion tooth contact cycles — beyond the commonly cited ISO 6336 material endurance limit (10⁹ cycles), requiring special material qualification at the ultra-long-life regime where material properties below the conventional endurance limit are needed.

APPLICATION 02

UAV FLIGHT
CONTROL ACTUATOR

Ring gear specification: 17-4 PH H900 or 15-5 PH H900, M2–M4, DIN 4–5, PFPE grease lubrication (−55°C to +125°C), ratio 20:1–80:1 (2-stage planetary), backlash ≤ 2 arc-min at the actuator output, mass-optimised hollow ring (minimum wall thickness for the stress requirement). UAV (Unmanned Aerial Vehicle) flight control actuators — the electromechanical drives that move the control surfaces (ailerons, elevators, rudder, flaps) and landing gear doors on military and commercial UAVs — use compact planetary gearboxes with precision ring gears to reduce the high-speed torque of a brushless DC motor to the low-speed, high-torque output needed to move a control surface against aerodynamic load. The ring gear in a UAV actuator must simultaneously meet the precision (backlash ≤ 2 arc-min for control surface position accuracy), temperature (−55°C cold soak before first flight, +125°C in solar heating on the ground), and mass (every gram must be justified against the UAV payload budget) requirements that define flight-quality hardware. Korea Ever-Power UAV actuator ring gears are 100% individually measured (not sample inspection) for profile form error, total pitch deviation, and radial runout before being accepted for flight use — any single gear outside the DIN 4 tolerance band at any measurement point is scrapped, not reworked.

APPLICATION 03

HELICOPTER ROTOR
PITCH ACTUATOR

Ring gear specification: 15-5 PH H900 or 17-4 PH H900, M3–M5, DIN 4–5, aviation mineral oil lubrication (MIL-PRF-23699) in sealed housing, qualification per DO-160 (environmental) and MIL-G-45204 (gear manufacturing), proof load test at 3× rated torque before installation, 100% MPI after heat treatment. Helicopter tail rotor pitch actuators and swashplate actuators for main rotor collective pitch control are among the most demanding aerospace actuator applications — the ring gear must transmit the full rotor pitch control torque (which can be several hundred Newton-metres for a large civil helicopter) while operating in the highly corrosive, vibration-intensive environment of the tail boom or rotor head, where gearbox access for inspection is limited and replacement in the field requires specialised tooling and training. The planetary ring gear in a helicopter pitch actuator is typically a 2-stage design (for the high ratio needed to step down from a 3,000–6,000 RPM brushless DC motor to the slow-speed, high-torque actuator output), with the ring gear as the fixed element (non-rotating ring) in the standard planetary arrangement to maintain a compact cylindrical envelope that fits within the constrained space of a helicopter control system mounting bracket.

We are designing a new satellite antenna pointing mechanism and need a ring gear for a 2-stage planetary drive at M2, 72T. What documentation and testing will Korea Ever-Power provide for a space-qualified component?

Korea Ever-Power’s standard documentation and testing package for satellite planetary ring gears: (1) Material certification (EN 10204 Type 3.2 for space applications): mill certificate for the Ti-6Al-4V or PH stainless billet, confirming alloy composition to AMS 4928 (Ti-6Al-4V) or AMS 5659 (15-5 PH), mechanical properties (UTS, yield, elongation, reduction of area) from a companion test piece cut from the same forging or billet as the gear blank, and heat treatment record. Type 3.2 certification is independently witnessed by a third-party inspection body, which most satellite prime contractors require. (2) 100% individual dimensional inspection report: every aerospace ring gear is measured individually on the CMM — not by sample inspection. The report covers profile form error at 6 teeth equally spaced around the ring, total pitch deviation, radial runout, bore diameter and roundness, face parallelism, and thread or flange mounting feature dimensions. (3) MoS₂ coating process record and coupon test report: for vacuum-service gears, the ion-beam-deposited MoS₂ coating thickness (measured on a companion coupon) and adhesion (scratch test per ASTM C1624) are documented for each coating batch. (4) ASTM E595 outgassing test report: for satellite use, confirming TML ≤ 1.0% and CVCM ≤ 0.1% — all materials (gear alloy, dry film coating, any adhesive or sealant) must individually pass this test. Korea Ever-Power maintains current ASTM E595 test data for all aerospace gear materials and coatings used in standard production. (5) Qualification test protocol (if required by the satellite prime): for new designs, Korea Ever-Power can design and conduct a component-level qualification test programme — typically 10⁷ cycles at rated torque in a vacuum chamber at the specified thermal range, with dimensional inspection before and after to confirm the gear remains within specification after the simulated service life. The qualification test is conducted at Korea Ever-Power’s facilities or at a third-party test laboratory as specified by the customer’s quality plan.

Why does titanium ring gear tooth contact fatigue life require a different design approach than steel, and what safety factor should we use for a 15-year satellite design life?

Titanium alloys present two specific contact fatigue behaviour differences from steel that require modification of the standard ISO 6336 gear design approach: (1) No clearly defined endurance limit: steels (including carburized 20CrMnTi) have a well-defined contact fatigue endurance limit (σ_H,lim) — the contact stress below which fatigue cracks do not initiate, confirmed by test data plateauing beyond 10⁷–10⁹ cycles. Titanium alloys (including Ti-6Al-4V) do not have a clear endurance limit — the S-N curve (stress vs cycles to failure) continues to slope downward well beyond 10⁸ cycles, meaning the allowable contact stress must continue to be reduced as the design life increases beyond 10⁸ cycles. For a satellite ring gear accumulating 3 × 10¹⁰ contact cycles over 15 years, the allowable contact stress at this cycle count is determined from extrapolated test data (typically at 30–50% of the conventional 10⁷ cycle allowable stress), not from the endurance limit. (2) Fretting susceptibility: titanium gears in contact are prone to fretting at the tooth contact zone under the micro-slip motion that occurs at each mesh cycle — the fretting produces a local titanium oxide abrasion product (TiO₂) that acts as an abrasive at the contact zone, accelerating wear. The MoS₂ dry film on the gear tooth surface prevents titanium-to-titanium fretting by interposing the low-shear-strength MoS₂ layer between the contact surfaces. Design approach for 15-year satellite life: Korea Ever-Power uses an extended S-N curve for Ti-6Al-4V (derived from available literature data at cycle counts up to 10¹⁰) combined with a contact fatigue safety factor S_H ≥ 1.8 at the 15-year cycle count — significantly higher than the S_H ≥ 1.2 used for industrial ring gears at conventional cycle counts. The higher safety factor compensates for the uncertainty in the extrapolated S-N data beyond the test database’s upper cycle limit and for the potential for fretting damage accumulation over the satellite’s lifetime.

What is Korea Ever-Power’s minimum order quantity and lead time for aerospace prototype ring gears, and can the same specification be supplied for flight hardware production?

Aerospace prototype and flight production supply parameters: Prototype (engineering model / qualification model): minimum 2 pieces (to provide one spare for test); lead time 28–45 days from drawing approval, depending on material availability and DIN class. DIN 4 internal Ti-6Al-4V ring gears have a longer lead time than DIN 5 steel due to the CBN internal grinding setup time and the temperature conditioning required for dimensional stability. Flight hardware production (low-rate initial production, LRIP): minimum 5 pieces per order; lead time 35–55 days from drawing confirmation. Flight hardware is manufactured under a separate production plan that requires all tooling, fixturing, and process parameters to be locked (no changes without formal deviation or engineering change order) — this process lock is the key difference between prototype and flight production manufacture. Documentation level: prototype hardware can be supplied with the full dimensional inspection report without the third-party witnessed Type 3.2 material certificate (substituting Type 3.1); flight hardware requires Type 3.2 as standard. Qualification data support: Korea Ever-Power retains manufacturing process records (heat treatment charts, CBN grinding programme parameters, coating batch records, individual measurement data) for 20 years for all flight hardware production — enabling post-flight anomaly investigation and providing the design heritage data needed for future upgrades or re-orders. Enquiries for aerospace ring gear prototypes should include the drawing (or equivalent dimensional specification), material and heat treatment specification, quality class, MoS₂ or other coating requirement, and the acceptance test requirements — Korea Ever-Power responds with a technical review and quotation within 5 working days.

Spur Gears

Ti · PH stainless · DIN 3–5 · space

Helical Gears

Aerospace reducer · DIN 4 · low noise

베벨 기어

Ti-6Al-4V · 15-5 PH · angle drive

Worm Gears

Self-lock actuator · antenna Az/El

Ring Gears

Aerospace · satellite · DIN 3–5 · Ti

Planetary Gears

Reaction wheel · actuator · Ti · DIN 4

Plastic Gears

PEEK · low-outgas · sensor gear