Plastic Internal Gear – POM/PEEK, M0.15-M2.0, AGMA 13

A plastic internal gear is an internal ring gear whose gear body and tooth form are composed of engineering thermoplastic — an alternative to steel ring gears for applications where the plastic gear's inherent advantages (lower mass, no rust, lower manufacturing cost, self-lubrication, non-magnetic, electrical isolation) outweigh its lower load capacity compared with steel. Plastic pinions are not made of tooth-shaped transmission parts in the traditional machining sense — they are formed directly in the injection moulding process, which allows very complex geometry (stepped shafts, flanges, integrated rack-engagement channels) to be produced in a single moulding operation with no secondary finishing required. This represents a cost saving of 50–90% over metal counterparts in the appropriate size and load range.

Korea Ever-Power's precision plastic internal gears are produced in POM, PA, PPA, PBT, and PEEK — module M0.15 to M2.0, diameter Φ3–Φ120 mm — to meshing grades from DIN 5 through AGMA 13. ISO 9001:2008 / TS16949 certified. ODM and OEM service. Vacuum tray packed. DHL and UPS delivery.

POM (Polyoxymethylene / Delrin)

The most common plastic for precision gear applications. Excellent dimensional stability, low moisture absorption (0.2%), good chemical resistance, self-lubricating, and the best combination of stiffness and toughness among standard gear plastics. POM gears run quietly against steel or nylon pinions without grease in light-to-medium load applications. Typical use: automotive window regulators, HVAC actuators, printer drives, appliance mechanisms.

PA (Nylon — PA6, PA66)

Higher toughness than POM; better wear resistance against metal pinions; absorbs more moisture (1–3%) which can cause dimensional change in humid environments. Glass-filled PA66 (30% GF) provides significantly higher stiffness and load capacity for larger internal ring gears where standard PA's deflection under load would cause interference. Typical use: power tool ring gears, bicycle hub internals, consumer electronics drives.

PPA (Polyphthalamide)

Semi-aromatic polyamide with higher heat resistance than PA66 (HDT 260–280°C at 1.8 MPa, glass-filled). Lower moisture absorption than PA66. Better dimensional stability at elevated temperatures — critical for automotive under-bonnet internal gear drives where ambient temperature can reach 130–150°C. Typical use: automotive transmission actuators, EV motor auxiliary drives, high-temperature industrial controls.

PBT (Polybutylene Terephthalate)

Good dimensional stability, excellent chemical resistance to fuels and lubricants, low moisture absorption. Stiffer than PA at the same wall thickness. Glass-filled PBT provides high stiffness-to-weight ratio. Typical use: automotive fuel system ring gears, electrical connector internal drives, appliance motor drive ring gears where chemical resistance to cleaning agents is required.

PEEK (Polyether Ether Ketone)

The highest-performance engineering thermoplastic for gear applications. Continuous use temperature 250°C; excellent chemical resistance to virtually all solvents and lubricants; radiation resistant; biocompatible (ISO 10993). PEEK internal ring gears approach metal gears in load capacity at significantly lower weight. Typical use: aircraft actuator drives, military equipment, medical implant mechanisms, high-temperature industrial drives.

Material Selection Guide

POM → default choice (best value, best precision). PA → where toughness vs steel pinion matters. GF-PA66 → higher load, larger ring gears. PPA → under-bonnet automotive. PBT → chemical/fuel resistance. PEEK → extreme temperature, aircraft, medical implant. Send the application conditions — temperature, load, chemical environment, accuracy grade — and Korea Ever-Power will confirm the optimal plastic grade for your internal ring gear.

Automotive Systems

POM or PPA internal ring gears M0.5–M1.5 in window regulator planetary drives, seat adjuster mechanisms, HVAC door actuators, and electric parking brake drives. TS16949 certification meets automotive OEM incoming qualification. Vacuum tray packing protects dimensional precision during transit.

Medical Equipment

PEEK internal ring gears M0.3–M1.0 DIN 5–6 in surgical robot joint planetary drives, infusion pump drives, and diagnostic equipment table positioning actuators. PEEK's biocompatibility (ISO 10993), radiation resistance, and autoclave compatibility suit implant-adjacent and sterile-environment medical device applications.

Aircraft and Military

PEEK internal ring gears M0.2–M0.8 AGMA 13 in aircraft instrument planetary drives, satellite mechanism ring gears, and military equipment actuators. Non-magnetic, radiation-resistant, and operating at 250°C continuous — PEEK internal gears replace stainless steel in weight-critical aerospace applications.

Industrial and Mechanical Drives

POM or GF-PA66 internal ring gears M0.5–M2.0 in industrial robot joint planetary stages, printing machine drives, packaging machine actuators, and conveyor system small planetary reducers. The 50–90% cost saving vs metal ring gears at these load levels makes plastic internal gears the economical standard for high-volume industrial drive applications.

Consumer Electronics

POM internal ring gears M0.15–M0.5 in camera lens zoom drive planetary stages, smart watch movement planetary gear sets, and printer paper feed planetary drives. The cost saving over metal at this scale is decisive — POM internal ring gears at M0.15 are too small for metal machining at competitive cost but straightforward in injection moulding.

Food Processing Equipment

POM or FDA-compliant PA internal ring gears in food processing machine planetary drives where metal gears would require oil lubrication (contamination risk) and rust protection. POM's self-lubrication eliminates grease in the food contact zone; its non-rusting property suits the washdown environment where steel gears corrode between production runs.

Why are plastic internal gears 50–90% cheaper than metal?

The cost difference comes from the manufacturing process. A metal internal ring gear requires: raw material (steel bar or forging), CNC turning of the OD and bore, internal gear shaping (slow, tool-limited by bore space), heat treatment, surface treatment, and dimensional inspection — typically 5–7 operations. An injection-moulded plastic internal ring gear requires: mould tooling amortised over the batch, and a single injection moulding cycle (30–90 seconds per part) — 1 operation. Once the mould is made, the marginal cost per plastic ring gear is the material cost plus the moulding cycle time, with no heat treatment, no surface treatment, and no secondary machining required.

How can plastic internal gears achieve AGMA 13 / DIN 5 accuracy?

Injection-moulded plastic gears can achieve higher dimensional accuracy than is generally expected because the mould is machined to extremely tight tolerances (±0.005 mm on tooth profile) and the injection moulding process fills the mould cavity consistently under controlled pressure, temperature, and cooling parameters. The resulting plastic gear inherits the mould's tooth profile accuracy. POM's low shrinkage (1.5–2.0%) is the reason it achieves the best accuracy among standard gear plastics — the dimensional change from the mould dimension to the finished part is small and predictable. At fine pitch (M0.15–M0.5), plastic moulding actually achieves better tooth surface quality than metal machining at the same pitch.

What are the interference conditions for plastic internal ring gears?

Plastic internal gears can be used with the same-module spur gears (metal or plastic), depending on the number of teeth combination. It is necessary to check for involute interference, trochoid interference, and trimming interference for the specific tooth count combination chosen. For standard tooth number combinations, Korea Ever-Power's "Technical Information of Internal Gears" section provides the usable tooth count combinations at standard module and pressure angle. For non-standard combinations, Korea Ever-Power's engineering team will check the interference condition and confirm feasibility before production.

Are stock plastic internal ring gears available for immediate delivery?

Yes — Korea Ever-Power maintains stock of Module 1 plastic internal ring gears in the 20–140 teeth range in standard POM material. These stock gears are available for immediate delivery by DHL or UPS and are vacuum tray packed to protect the tooth profile in transit. For other modules (M0.15–M2.0), custom order production is available — sample lead time and production lead time confirmed on enquiry. For custom geometry (stepped shaft, integrated rack channel, non-standard mounting features), ODM service covers design and mould production from the customer's application requirement. Contact our team with the module, tooth count, and material to check stock availability.

"We design automotive window regulator mechanisms and switched from metal to Korea Ever-Power's POM internal ring gears M1.0 DIN 6. Noise at our acoustic test reduced by 4 dB(A) compared with the metal equivalent — significant for a component installed in the passenger door. TS16949 certification accepted at our OEM supplier qualification. DHL delivery. Vacuum tray packaging maintained the gear profile precision at our incoming measurement."

Kim Ji-soo  |  Automotive Mechanism Design Engineer, Incheon Automotive Systems Co.  ·  Q1 2026

"We develop surgical robot joint drives and specified PEEK plastic internal ring gears M0.5 AGMA 13 for MRI-compatible wrist joints. Non-magnetic confirmed (no response to 0–3T MRI field), autoclave compatible (134°C 50 cycles without dimensional change), and ISO 10993 biocompatible. Korea Ever-Power is the only supplier we found who produces PEEK internal ring gears at M0.5 to AGMA 13 accuracy."

Lee Min-jeong  |  Surgical Robot Mechanism Engineer, Gyeonggi Medical Robotics Co.  ·  Q4 2025

"We manufacture food processing conveyors and use POM internal ring gears from Korea Ever-Power in our planetary drive units. No grease required — POM self-lubrication confirmed adequate for our 8-hour production run cycle at our belt speed and tension specification. ISO 9001:2008 certification accepted at our food safety supplier audit. Zero corrosion issues in the washdown environment after 2 years of production."

Park Sung-min  |  Food Processing Equipment Engineer, Busan Food Systems Co.  ·  Q2 2026

"We import plastic internal ring gears Module 1 (stock range, 20–140 teeth, POM) for distribution to industrial machinery manufacturers. The stock availability with DHL delivery means our customers can get parts in 3–4 days instead of the 20-day sample lead time for custom plastic gears. Vacuum tray packaging maintained the AGMA 12 profile accuracy confirmed at our distributor's incoming gear measurement check."

Choi Byeong-hoon  |  Precision Gear Distribution Manager, Daejeon Precision Components Co.  ·  Q3 2025

"We design camera lens zoom drives and needed POM internal ring gears M0.2 DIN 5 — a combination that no metal machining supplier could quote competitively. Korea Ever-Power's injection moulding in POM at M0.2 DIN 5 gave us a 73% cost saving versus the best machined metal quotation. Tooth profile accuracy confirmed on our optical gear analyzer — within DIN 5 on all 10 sample gears."

Yoon Hyeon-kyu  |  Optical System Mechanism Engineer, Ulsan Precision Optics Co.  ·  Q1 2025