AM Planetary Carrier

The AM Planetary Carrier is the carrier plate with integrated sun gear for the AM series planetary gearbox. Five planet gears (sold separately) ride on the dowel pins pressed into the carrier plate; those dowel pins protrude out the carrier plate's bottom side to locate and support the planet gears as they orbit the sun gear and ring gear. This carrier assembly — with its pressed-in planet pin dowels and the integral sun gear — is the central structural and kinematic component of the AM planetary gearset. Korea Ever-Power's AM Planetary Carrier is machined from 1117 steel with 15-tooth sun gear at diametral pitch 32, pressure angle 20°, and supplied as a complete ready-to-install carrier assembly.

Korea Ever-Power's AM Planetary Carrier is a compact, precision component: diameter 1-3/8 in. (34.9 mm), length 15/16 in. (23.8 mm), pin diameter 0.125 in. (3.175 mm), weight 0.07 lbs (31.8 g). The combination of the compact dimensions, low weight, and the planetary gearset's high power density makes this carrier component suitable for size-constrained drive applications requiring high reduction ratio and coaxial output.

The Four Components

The AM planetary gearset consists of four major components: the sun gear (the central gear, integrated into the AM carrier plate), the planet gears (five gears riding on the carrier dowel pins, not included), the ring gear (the outer gear with internal teeth that meshes with the planet gears, not included), and the carrier (the AM Carrier Plate, which supports the planet gear shafts and rotates as the planets orbit the sun). The significant difference between this planetary arrangement and ordinary gearsets is that the planets orbit the sun — their shafts are not fixed in space. It is this epicyclic (planet-orbiting) motion that permits the planetary gearset's unique versatility.

The Carrier's Role — Planet Support and Output

The carrier plate is a rigid frame that holds the five planet gear shafts (dowel pins) at equal angular spacing around the sun gear centre. As the planet gears are driven by the sun gear and react against the ring gear, they rotate on their own axes (spin) and also orbit around the sun gear axis (revolve). The carrier plate rotates at the orbital revolution speed of the planet gears — which is slower than the sun gear speed by the planetary reduction ratio. When the carrier is the output element, this slower rotation is the gearset's reduced output speed.

Two Inputs, One Output — The Ratio Equations

The planetary gearset's three elements (sun, ring, carrier) can each be input, output, or fixed ground — giving up to six different ratio combinations from one set of gears. The most common arrangements are: (1) Sun input → Carrier output, Ring fixed: ratio = 1 + Z_ring/Z_sun (speed reduction); (2) Ring input → Carrier output, Sun fixed: ratio = 1 + Z_sun/Z_ring (modest speed reduction); (3) Sun input → Ring output, Carrier fixed: ratio = −Z_ring/Z_sun (speed increase, reversed direction). The negative sign indicates direction reversal in the fixed-carrier arrangement.

Why Five Planet Gears?

The AM carrier uses five planet gears (five dowel pins). Having multiple planets distributes the transmitted torque across multiple tooth contacts simultaneously — each planet carries one-fifth of the total tangential force, reducing the tooth load per planet compared with a single-planet arrangement. The use of five planets gives the AM planetary gearset exceptional load capacity for its compact size (diameter 1-3/8 in., weight 0.07 lbs), while the equal spacing of five planets provides a smooth, balanced force on the sun gear and carrier that minimises vibration and bearing load at the centre.

The 1117 Steel Carrier Plate

The AM carrier plate is machined from AISI 1117 steel — a free-machining resulphurised carbon steel with good machinability and moderate strength. 1117 steel is commonly used for carrier plates, precision shafts, and other components requiring tight dimensional accuracy from machining rather than forging. The 0.125 in. diameter planet pin dowels are pressed into the carrier plate with an interference fit — the press-fit force must be sufficient to prevent the dowels from pulling out under the planet gear radial and tangential forces during operation.

Diametral Pitch 32 — Sun Gear Geometry

Diametral pitch 32 (DP 32) is a fine pitch — the pitch diameter of the 15-tooth sun gear is 15/32 = 0.469 in. (11.9 mm). This fine pitch is appropriate for the AM carrier's compact size (overall diameter 1-3/8 in.) and low load capacity (0.07 lbs weight indicates a light-duty application). At 20° pressure angle (the industry standard for most spur and helical gears), the tooth form provides good tooth strength, adequate contact ratio, and compatibility with standard DP 32 generation tooling.

Robotics and Automation

AM Planetary Carrier assemblies in compact robot joint drives, servo motor gearboxes, and precision positioning stages. The planetary gearset's coaxial input-output arrangement (input and output on the same axis), high reduction ratio per stage (5:1 to 12:1), and compact dimensions suit the confined envelope of robot arm joint housings where maximum torque density per unit volume is the primary design driver.

Precision Instrument Drives

AM planetary carrier-based gear sets in precision instrument drives, laboratory equipment, and scientific measurement systems. The DP 32 pitch and 15-tooth sun gear at 1-3/8 in. carrier diameter represents a fine-pitch, compact planetary suitable for low-load, high-precision applications where the planetary gearset's low backlash and coaxial output are essential.

Electric Motor Gearboxes

AM planetary gearsets as the reduction stage in compact electric motor gearboxes — stepping down the high speed of small DC or BLDC motors (3,000–10,000 RPM) to the lower speed required by the driven mechanism. The planetary gearset's coaxial output makes it ideal for in-line motor-gearbox combinations where the output shaft aligns with the motor shaft axis, simplifying installation in space-constrained machine designs.

Replacement and Repair

AM Planetary Carrier replacements for worn or damaged carrier plates in existing AM planetary gearbox assemblies. The carrier plate — with its pressed-in dowel pins and integral sun gear — is the component most likely to require replacement in a worn planetary gearset, as the dowel pins are subject to bending fatigue from the cyclic planet gear loads. Korea Ever-Power's carrier plate replicates the original AM gearbox carrier dimensions exactly for direct replacement fitment.

Are the planet gears included with the AM Planetary Carrier?

No — the five planet gears are not included with the AM Planetary Carrier. The carrier plate (with pressed-in dowel pins and integral 15-tooth sun gear) is supplied as a complete carrier assembly; the five planet gears ride on the dowel pins and must be ordered separately. The ring gear is also a separate component. Contact Korea Ever-Power to order the planet gears and ring gear to complete your AM planetary gearset.

What is 1117 steel and why is it used for the carrier plate?

AISI 1117 is a free-machining resulphurised carbon steel — the sulphur additions improve machinability by producing sulfide inclusions that act as chip-breakers during turning and milling operations, allowing faster machining speeds, better surface finish, and longer tool life compared with plain carbon steel. For the AM carrier plate, which requires tight dimensional accuracy on the dowel pin bores (interference fit), sun gear tooth form, and overall carrier dimensions, 1117 steel's excellent machinability makes it the standard material choice. Tensile strength: approximately 490 MPa (as-machined); can be case-hardened for higher surface hardness if required.

Can Korea Ever-Power supply custom planetary carrier plates for other planetary gearbox types?

Yes — Korea Ever-Power manufactures custom planetary carrier plates for any planetary gearbox configuration: different sun gear tooth count, diametral pitch, pressure angle, number of planet pins, pin diameter, and overall carrier dimensions. Provide the drawing (DWG, STEP, PDF) or a sample carrier plate for measurement and quotation. Korea Ever-Power's planetary carrier production covers a wide range of sizes from compact instrument drives (similar to the AM carrier) through large industrial planetary gearbox carriers. Contact Korea Ever-Power with your specification.

"We build compact servo motor gearboxes for robotics and source the AM Planetary Carrier assemblies from Korea Ever-Power. Dowel pin press-fit force measured: 420–460 N across 12 units — consistent interference fit. Sun gear tooth thickness checked on optical comparator: within ±0.003 in. of nominal. Planet gears (sourced separately) mount and spin freely on the dowel pins with correct end clearance. Carrier plate face flatness: 0.0008 in. — within our assembly spec."

Kim Jun-ho  |  Servo Gearbox Design Engineer, Incheon Precision Drive Systems Co.  ·  Q1 2026

"We repair AM planetary gearboxes used in laboratory automation equipment and purchase replacement carrier plate assemblies from Korea Ever-Power. Dimensional match to original AM carrier: OD 1.375 in. ±0.001 in., dowel pin location ±0.002 in. — direct drop-in fitment confirmed on 8 gearbox repairs. Weight matches original (0.07 lbs) — no dynamic balance issues noted on our spin test. Korea Ever-Power is now our preferred AM planetary carrier supplier for all repair work."

Lee Chan-woo  |  Lab Equipment Repair Engineer, Gyeonggi Precision Instruments Service Co.  ·  Q4 2025