Description

Prusa Set PG Assembly + PG Ring — Nextruder Planetary Gear Replacement

This is the OEM replacement planetary gear (PG) assembly and matching PG ring for the Prusa Nextruder — the internal gear mechanism that drives filament feeding through the extruder. If your Nextruder is slipping, grinding filament, feeding inconsistently, or making unusual mechanical noises, worn planetary gear components are a likely cause.

Replace Both Parts Together

Important: Both the PG assembly and PG ring must be replaced together. These two components are designed to work as a matched pair inside the Nextruder’s gear mechanism — replacing only one part can result in improper meshing, uneven wear, and unreliable feeding performance. This set includes both parts to ensure correct fit and function.

What the Planetary Gear System Does

The Nextruder uses a planetary gearbox to provide high-torque, precise filament feeding — smaller and more compact than a direct-drive gear reduction while delivering strong grip force on the filament. The PG assembly and PG ring work together inside this gearbox to translate motor rotation into controlled, consistent filament movement.

When to Replace

Filament slipping or grinding marks appearing on the filament surface, clicking or grinding noises from the extruder during printing, inconsistent extrusion despite correct settings and dry filament, reduced grip force causing under-extrusion on longer or more resistant prints, and visible wear or damage to the gear teeth after extended use or heavy filament volume.

These symptoms typically develop gradually over hundreds of print hours as the gear teeth wear from repeated engagement.

What’s Included

PG-Ring × 1
PG assembly × 1

Compatibility

Prusa MK3.9 / MK3.9S
Prusa MK4 / MK4S
Prusa XL
Prusa CORE One / CORE One+
Prusa CORE One L

Not compatible with the MK3/MK3S/MK3S+, MK3.5/MK3.5S, or Prusa MINI/MINI+.

Installation

Refer to the Prusa Knowledge Base repair manual for your specific printer model at help.prusa3d.com. This is an internal Nextruder gearbox repair — follow the disassembly and reassembly instructions carefully, ensuring correct orientation and meshing of the new gear components.