Bondtech i3 MK3 BMG Style Geared Extruder



I saw the new upgrade from bondtech for the i3 and liked the idea of putting it on my Axis One machine but wanted to make a few tweaks for my own preferences and simplify it slightly to make it easier to print.

This led me to design a simpler version of the housing’s which would allow me to make any changes i needed. I removed a lot of the hex features from the original. Used the Hex designs on the front to create cutouts for airflow and modified the fixings to use square nuts and threaded inserts. I changed the position of the threaded inserts and added additional to replace the hex nuts.

Modified the cable paths and tie wrap holes for easier printing, and thickened up some sections to print better.

Modified how the front and rear clamp together, now you can remove the front cover along with the stepper motor without having to remove the complete assembly from the carriage.

The extruder assembly should fit any i3 carriage hole fixing the same as Prusa’s upto the new MK3S which is different.

I also created versions for

No filament Sensor – NFS
Laser Filament Sensor – LFS
Optical Filament Sensor – OFS

Both the laser and new optical sensor are designed for the original Prusa parts.

To get the parts for the OFS model i found it easier just to buy the upgrade kit from Prusa for £17.49.

Designed for 1.75mm filament same as original.

Extruder ESteps will need to be changed to 415.0

Original extruder can be found here:

Original Bondtech BMG i3

Hopefully you may find it useful.



I have provided Affiliate links to the items i used but you can get them anywhere you please.

1 Off each of the below items :

BMG Thumb Screw – Aliexpress
BMG Big Gear + Shaft – Aliexpress
BMG Pinion Gear – Aliexpress
M3x32mm Steel Pin – Aliexpress
Collet Clip – Aliexpress
13Ncm Nema 17 Pancake Motor – Aliexpress
Pinda Probe v2 – Aliexpress
5015 Blower – Aliexpress
4010 Blower – Aliexpress
E3D V6 – Aliexpress

2 Off each of the below items :

MR85ZZ ( W627-5 ) Bearings – Aliexpress
Neodymium Magnet 8x1mm ( or 8×1.4mm ) – Aliexpress

Fasteners :

M3 Square Nut – Aliexpress
M3 Brass Inserts – Aliexpress

2 x Hex Nuts
6 x M3 Threaded Insert
4 x M3 Square Nut
1 x M3 x 8mm Cap Head
10 x M3 x 12mm Cap Head
1 x M3 x 16mm Cap Head
2 x M3 x 20mm Cap Head
3 x M3 x 25mm Cap Head
1 x M3 x 30mm Cap Head
1 x M2 x 8mm Cap Head

For the Bondtech gears you have the Original gears from Bondtech which would be the preferred option.

Bondtech Original 1.75mm Gears

But as always there are now clones available which may also work.

Bondtech Clone 1.75mm Gears

you could also just buy a complete clone extruder assembly to use for parts.

BMG Extruder

The choice is yours but it is always preferable to support the actual original designers and developers of a product. But the choice is yours.

Enjoy :-)

Print Settings.

Printed in Real Filament Black PETG purchased from Amazon.

imageBondtech i3 MK3 BMG Style Geared Extruder

Nozzle : 0.4mm
Layer Height : 0.2mm

Print Temp : 245°C
Bed Temp : 80°C
Print Speed : 50mm/s

Top Layers : 6
Bottom Layers : 4
Perimeters : 3

Infill : 30%

Printed on Buildtack.

Download Links.


Thingiverse – thing:3488996

MyMiniFactory –

YouMagine –

Pinshape –

Copyright Licence.


Bondtech i3 MK3 BMG Style Geared Extrudercopyright-bycopyright-nccopyright-sa




This design has a [Creative Commons Attribution Non-Commercial Share Alike](Creative Commons Attribution Non-Commercial Share Alike) license, which means that you can print, remix, and use this model with design credit to bobblejot, but if you want to sell something then you should ask first, at


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