Plastic Worm Gears

Plastic worm gears transmit power between shafts at 90° (non-parallel, non-intersecting) with smooth, quiet operation and high speed reduction in a compact single stage — making them the standard gear type for camera auto-focus drives, rearview mirror actuators, water valve actuators, gate drives, and consumer electronics wherever self-locking or high-ratio compact reduction is needed. Korea Ever-Power supplies both the worm (the spiral screw shaft) and the worm wheel (the toothed ring that meshes with the worm) in POM (Polyacetal / TEPCON M90-10) and Nylon, module M0.2–M2.0. The plastic worm gear product range includes worm gear valve drives, worm gear pumps, and linear actuators. Compared with spur gears, plastic worm gears offer significantly quieter operation — the gradual helical tooth contact and the sliding-dominated mesh of the worm-wheel interface produce the lowest noise of any gear type.

Korea Ever-Power's plastic worm gears feature: high efficiency for plastic worm standards; irreversible motion (self-locking) capability at low lead angles; compact design for 90° shaft arrangement; high load capacity relative to physical size; and reduced vibration and noise vs equivalent spur gear drives. Custom per drawing or sample; prototype testing before mould making.

Worm + Wheel Set

Miniature Worm

Custom Worm Sets

Worm (Screw Shaft) Specification

Example Products

Worm and Worm Wheel Geometry

The worm is a shaft with a helical thread cut on it — essentially a screw. The worm wheel is a helical gear with teeth curved to wrap around the worm's thread. As the worm rotates, its thread pushes on the curved teeth of the worm wheel, causing it to rotate about an axis perpendicular to the worm shaft. The number of worm threads (starts) equals the number of teeth the worm wheel advances per worm revolution — a single-start worm advances the wheel by one tooth per revolution, giving a ratio equal to the wheel tooth count.

High Speed Reduction in One Stage

A single plastic worm gear stage can achieve ratios from 5:1 to 100:1 — ratios that require 3–4 spur gear stages to achieve. The ratio equals wheel tooth count / worm thread starts: a 30T wheel with a 1-start worm gives 30:1. This high ratio in a single stage makes worm gears the preferred choice for space-constrained drives where a large reduction must fit in a small housing — exactly the situation in camera drives, rearview mirror actuators, and instrument mechanisms where the worm gear stage fits in millimetres of housing space.

Self-Locking — Irreversible Motion

At low lead angles (the angle of the worm thread), worm gears are self-locking — the output (worm wheel) cannot back-drive the input (worm). This is because the friction force at the worm-wheel mesh, when the load tries to drive the worm backwards, exceeds the tangential force component of the load — the gear train locks in position. Self-locking is a critical property for rearview mirror drives (must hold position without constant power), water valve actuators (must stay closed without power), and gate drives (must not drift). Single-start plastic worm gears are typically self-locking at the friction coefficient of POM (μ ≈ 0.10).

Sliding Contact and Efficiency

The worm gear mesh is dominated by sliding contact (unlike spur and helical gears where rolling contact dominates). The worm thread slides along the worm wheel tooth surface as the worm rotates — producing higher friction losses than spur gears. Plastic worm gear efficiency is typically 30–70% depending on lead angle, friction coefficient, and tooth geometry — compared with 96–99% per stage for spur gears. POM's very low friction coefficient (μ ≈ 0.10) gives plastic worm gears better efficiency than many metal worm gear combinations with standard oil lubrication. The efficiency advantage of single-start plastic worm gears over metal worm gears at low-load applications is well-established in camera and instrument drive design.

90° Shaft Arrangement

The worm gear naturally produces output on a shaft at 90° to the input shaft — without needing bevel gears or additional right-angle conversion stages. In camera pan/tilt, mirror adjustment, and gate actuator designs, this 90° arrangement allows the electric motor to be placed along one axis while the driven shaft rotates about a perpendicular axis — a packaging solution that is difficult to achieve with any other single-stage gear type. The small worm shaft (Ø4–6 mm for M0.4 plastic worm) enables the motor-worm-wheel arrangement to fit in extremely compact housings.

Noise — Quieter than Spur Gears

Plastic worm gears are significantly quieter than spur gears at equivalent output torque — the smooth helical sliding of the worm thread against the worm wheel teeth produces no tooth mesh impulse (the primary source of spur gear noise). The contact is continuous and gradual throughout the engagement cycle, and the plastic material's inherent damping further absorbs the small remaining vibrations. The result is near-silent operation — critical for camera drives (audio recording), automotive mirror actuators (interior quietness), and medical equipment (patient environment).

① High Efficiency

POM's very low friction coefficient (μ ≈ 0.10) gives Korea Ever-Power's plastic worm gears higher efficiency than comparable metal worm gears lubricated with standard oils — especially at light loads typical of camera and instrument drives. The TEPCON M90-10 POM formulation used in Korea Ever-Power's miniature worm gears is specifically optimised for tribological performance in worm gear applications, providing consistently low friction over the life of the gear.

② Irreversible Motion

Single-start plastic worm gears are self-locking — the output shaft cannot back-drive the motor when power is removed. This irreversible motion property eliminates the need for a separate braking mechanism in positional drives such as rearview mirror adjusters, valve actuators, and gate mechanisms — the worm gear itself holds the position without power. This simplifies the drive circuit and reduces the bill of materials for the actuator mechanism.

③ Compact Design

The worm gear's 90° shaft arrangement and high single-stage ratio (up to 100:1) in a compact package make it ideal where the motor must be oriented along one axis and the output along a perpendicular axis with minimal overall dimensions. An M0.4 plastic worm (Ø4–6 mm × 6–10 mm length) with a 30T worm wheel achieves 30:1 in a housing that a spur gear train of equivalent ratio would require 10–15× more volume.

④ High Load Capacity

Despite the plastic material, worm gears have high load capacity relative to their physical size — because the line contact between the worm thread and the worm wheel tooth distributes the load over a larger contact area than spur gear tooth contact at the same module. This contact geometry gives worm gears higher surface durability (resistance to pitting) than spur gears of the same module, compensating partially for the lower material strength of plastic compared with steel.

⑤ Reduced Vibration and Noise

The continuous sliding contact of the worm-wheel mesh produces essentially zero tooth mesh frequency vibration — unlike spur or helical gears that produce impulse loading at each tooth engagement. Combined with POM's inherent damping (loss factor significantly higher than steel), plastic worm gears are the quietest plastic gear type for the 90° shaft arrangement. Typical operating noise for a Korea Ever-Power M0.4 plastic worm set: 25–30 dB(A) at 0.5 m — below the threshold of awareness in quiet consumer environments.

IP Cameras and Monitors

M0.4 plastic worm set (30T wheel + 1T worm, TEPCON M90-10, total 0.75 g) in IP camera pan/tilt head drives and monitor tilt drives. The self-locking property holds the camera angle without power; the near-silent operation suits indoor surveillance in quiet spaces; the 30:1 ratio matches the small stepper motor to the pan/tilt speed requirement in a housing only slightly larger than the motor itself.

Automotive Rearview Mirror Actuators

M0.4 RH single-start POM worm (1T, 0.22 g) in automotive exterior mirror adjustment gearboxes. The micro worm shaft fits in the mirror housing's compact actuator pocket; the single-start self-locking property keeps the mirror in position without power drain from the motor; POM's resistance to automotive temperature cycling (−40°C to +85°C) maintains dimensional stability for accurate mirror positioning across seasons.

Water Valve Drives

Gear screw and screw nut sets (ODM specification) in motorised water valve actuators for HVAC zone control, irrigation system valves, and water treatment shut-off valves. The worm gear's self-locking property ensures the valve stays in its last commanded position when power fails — a critical safety requirement for water system valves. POM's chemical resistance to water and common water treatment chemicals (chlorine, fluoride) ensures long service life in these wet environments.

Worm Gear Pumps

Plastic worm and wheel gear sets in miniature gear pumps for chemical metering, food dispensing, and laboratory dosing. The worm pump's smooth, low-pulsation flow characteristic (from the continuous worm thread engagement) suits precision dosing applications. POM and Nylon's chemical resistance eliminates metallic contamination risk in food and pharmaceutical fluid contact applications.

Antenna and Satellite Dish Drives

Plastic worm gear drives in small satellite dish azimuth and elevation actuators, antenna rotators, and solar panel tracking drives. The self-locking worm gear holds the antenna or panel in the commanded position without power — essential for battery-powered or intermittently powered outdoor installations. UV-stabilised POM provides long outdoor service life without material degradation.

Home Automation and Blinds

Plastic worm gear drives in motorised window blind, roller shutter, and curtain track actuators. The worm gear's self-locking holds the blind at the set height without power; the near-silent operation is essential in bedroom environments; and the compact 90° arrangement allows the motor and gear drive to fit within the slim profile of the blind mechanism housing.

What does "self-locking" mean for a plastic worm gear, and when is it important?

Self-locking means the worm wheel cannot back-drive the worm — if a load is applied to the output shaft trying to reverse the position, the gear train locks rather than rotating back. This occurs when the worm lead angle is less than the friction angle (arctan μ). For POM with μ ≈ 0.10, the friction angle ≈ 5.7°; single-start worms at the small diameters (Ø4–6 mm) used in Korea Ever-Power's miniature plastic worm gears typically have lead angles of 2°–4° — well within the self-locking zone. Self-locking is important for all positional drives (mirrors, valves, antennas, blinds) where the position must be maintained without continuous motor power.

What is TEPCON M90-10 POM used in Korea Ever-Power's plastic worm gears?

TEPCON M90-10 is a tribologically-optimised POM (polyacetal copolymer) formulation specifically developed for gear and sliding applications — the designation M90 indicates high melt strength for consistent injection moulding, and the 10 designation refers to the PTFE (polytetrafluoroethylene) additive level that further reduces the already-low friction coefficient of base POM. The PTFE additive reduces the worm-wheel sliding friction to approximately μ ≈ 0.06–0.08 — lower than standard POM — improving worm gear efficiency and reducing tooth surface temperature at higher loads.

Can Korea Ever-Power supply both the worm and the worm wheel as a matched set?

Yes — Korea Ever-Power supplies matched plastic worm gear sets (worm + wheel) as standard products (e.g., M0.4 × 30T + 1T) and custom sets per drawing. Supplying matched sets ensures that the worm thread lead angle, normal module, and pressure angle are geometrically consistent between worm and wheel — mismatched sets from different suppliers produce incorrect mesh geometry and accelerated tooth wear. Contact Korea Ever-Power with your ratio, torque, and speed requirements to select the correct matched set.

"We produce network cameras and source M0.4 TEPCON POM worm sets (30T + 1T) from Korea Ever-Power for our pan/tilt heads. Self-locking confirmed: held position after 50,000 on/off cycles with zero creep detected. Noise at 0.3 m: 24 dB(A) — below our 28 dB(A) acoustic spec. Back-drive test: 0.5 N·m applied to wheel shaft — worm shaft did not rotate. Dimensional check: gear centre distance within ±0.015 mm of specification. Matched set quality confirmed by our gear roll test."

Kim Ji-young  |  Camera Mechanism Engineer, Incheon Vision Systems Co.  ·  Q2 2026

"We design motorised window blind systems and switched to Korea Ever-Power POM worm gear sets from our previous metal worm supplier. Noise reduction: 8 dB(A) at standard operating speed — now below the detection threshold in a quiet bedroom (background 35 dB(A)). Weight reduction: 4.1 g → 0.8 g per drive unit (metal → plastic). Self-locking confirmed at −20°C and +60°C: no blind drift at either temperature extreme. Cost saving: 67% per unit."

Lee Seong-min  |  Smart Home Automation Engineer, Gyeonggi Home Systems Co.  ·  Q4 2025