Bondtech BMG Extended Filament Guide

A remix of the official Bondtech filament guide that mounts inside the Bondtech BMG extruder. The official filament guide is for sale, with an STL for free download, on the Bondtech website (1).

My design is shown next to the official version in one of the photos. It still mounts within the extruder, but extends the filament entry out beyond the cable chain (2) and below the custom cable mount I designed for my Ender 3 Pro (3). With the side mount spool holder (4) and official Bondtech mount that reorients the stepper motor (5) it provides a good filament entry angle, protects the filament from snagging on the cable chain, and protects the cable chain from abrasion by filament. I made variants with the bore the same size as the original (2.2 mm) as well as slightly larger (2.3 mm and 2.4 mm), to account for the horizontal expansion characteristics of various printers.

1. Bondtech Filament Guide
2. Ender 3 Cable Chain
3. Ender 3 Cable Chain Mount for Bondtech Extruder
4. Ender 3 Pro Side Mounted Spool Holder
5. Bondtech Kit with Mount for Ender 3

Print Settings

Printer Brand: Creality

Printer: Ender 3 Pro

Rafts: No

Supports: No

Resolution: 0.2

Infill: 60% cubic

Filament: eSun PLA+ Purple

The length of this part, and assuming a side-mounted spool holder, means that at high Z any filament snags would apply a lot of downward torque. I printed with absolute overkill of 4* 0.4 mm walls and 60% cubic infill to ensure that it is strong enough to hold up to any abuse. Depending on your printer, you may need to account for horizontal expansion in your slicer to ensure that the guide fits properly within the extruder, then pick the bore that fits your filament. Also remember that you need to get the filament out again, and filament coming back from the hotend can have lumps that might get stuck! I use -0.1 mm expansion and the 2.4 mm bore and everything fits perfectly.