Makes · Ender 3 Pro

Branca

What happens when GPT Astra designs a new extruder for my Ender 3 Pro?

I gave GPT Astra one job: design a new extruder for my Ender 3 Pro. Could it actually pull it off?

Printables
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Free · STL, STEP + editable Fusion file · GNU GPL v3

YouTube What Happens When GPT Astra Upgrades an Ender 3 Pro?

A new body and arm. Your hardware.

A new body and idler arm for the stock extruder.

Branca exploded view: white printed body, bushing and spring carrier, blue idler arm, and the stock Ender 3 Pro motor, gear, idler, spring and screws
Exploded to assembled: the printed parts around the stock Ender 3 Pro hardware.

Branca R59 replaces the plastic body and idler arm of the Ender 3 Pro’s stock single-gear extruder with printed parts.

It keeps the original motor, brass drive gear, 624U grooved idler, spring and screws. The only things you add are two M4 heat-set inserts and two push-fit collets with clips.

Designed with GPT Astra

A fully parametric Autodesk Fusion design, modeled by AI.

Branca R59 assembled on the stock NEMA 17 motor: white body, blue idler arm
Branca R59, assembled on the stock motor.

GPT Astra modeled Branca as a fully parametric design in Autodesk Fusion, with Codex working through my Fusion MCP.

GPT Astra and I revised the spring, checked interference, worked out how the parts go together and gave the shape a Gaudí-inspired Modernisme feel. Branca came out of that back-and-forth.

Driving Fusion through PC control was cumbersome, so I built a Fusion MCP with Codex along the way. See what the Fusion MCP can do →

The four parts

STL and STEP, already oriented for printing.

PartColorPrint orientation
01_bodyWhiteMounting face down
02_idler_armBlueBroad outer top down, manual supports
03_pivot_bushingWhiteFlange down
04_spring_carrierWhiteClosed rear face down

Print settings

  • PETG
  • 4 walls
  • 30% gyroid
  • 5 top / 5 bottom layers
  • Manual supports (idler arm only)

Print one of each. Don’t scale a part to fix one fit; it changes the mounting pitch too.

Branca printed parts together: white body and blue idler arm
The printed parts together: white body, blue idler arm.

Hardware

Almost everything comes off the extruder you already have.

Reused from one stock Ender 3 Pro extruder

  • NEMA 17 motor
  • Brass drive gear with grub screws
  • 624U grooved idler
  • Spring
  • M3x18 pivot screw
  • M3x10 motor screws (2 pan, 1 countersunk)
  • M4x8 axle screw
  • M4x12 adjuster screw
  • M3x10 rivnut
  • PTFE tube

Added

  • 2× Ruthex RX-M4Sx4.0 short heat-set inserts
  • 2× 4 mm PTFE collets with retaining clips

The full list with notes is in BOM.csv, in the download.

Blue idler arm with a double-shear fork around the stock 624U idler
Double-shear idler fork around the stock 624U idler and M4x8 screw.
Section view of the tensioner: stock spring, M4 adjuster screw, heat-set insert and printed spring carrier
Tensioner section: stock spring and M4 adjuster, heat-set insert, printed spring carrier and reused rivnut support.

What’s in the download

Everything to print it, build it and change it.

  • STL and STEP for each of the four parts (mm, already oriented for printing)
  • Editable Fusion file (BRANCA_R59.f3d)
  • Printing and assembly guide (PDF)
  • BOM, hardware reuse notes and print settings
  • License and attribution files
Printables

Make one.

Print it, post it, remix it and make it better. The files are free on Printables.

Download on Printables
YouTubeWatch the build

Licensed under GNU GPL v3. Stock hardware reference geometry comes from Creality’s official Ender-3 CAD (GPLv3); the notice is included.

Branca assembled on the Ender 3 Pro extruder motor