Prusa I3 MK3 MK3S Advanced BMG Extruder

Hello, thank you for your interest in this BMG extruder!

Overall, this project can be described as challenging and therefore not well suited for beginners.
From me a big thank you to all developers involved!

update 16.Okt.2019: New add-on - new x-carriage and y-holder using bronze sintered bearing maintenance-free (plain self oil bearing, 8mm x 12mm x 12mm) instead of linear ball bearings (LMU8, 8mm x 15mm x 24mm). Advantage: much quieter because of less vibrations, less weight and maintenance-free (incl. to .zip file).

This extruder is a new alternative to the well known and proven Prusa R3 / R4 / R5 extruders for the Prusa I3 MK3/S 3D printers. The goal is to further improve print quality while enabling good and fast maintenance. Expanding, the extruder includes the Bontech 3:1 gearbox, powered by a lightweight NEMA17 pancake stepper motor to decrease ghosting and ringing. From the use of a larger stepper motor, I advise because of the significantly higher weight from, also would have the motor axis, by 2mm, be shortened to about 18mm in length.
The front of the extruder is divided into upper and lower halves for easy maintenance. To service the hotend, the base can be easily dismantled. With 3 screws from the rear, the stepper motor and the upper part of the front panel are easy to remove. The extruder housing contains no filament sensor. A matching filament sensor is always attached separately to the top of the extruder. Thus, a sensor can be easily changed according to requirements without dismantling the extruder. 3 different sensor housings are currently available. A Chimney for operation with a MMU2S, with a matching door hinge, equipped with a Prusa IR sensor, or a housing for operation with the laser sensor and a ball bearing to prevent false alarms, also with a matching door hinge. A sensor housing for operation with the Prusa IR sensor without the use of an MMU2S is also included to the attached .zip file and is currently available from Bondtech.sa, as well:
https://github.com/BondtechAB/Bondtech_Prusa_i3/tree/master/CAD-Files/MK3s%20Sensor%20Add-On
The extruder is designed for operation with a BEAR X axis. The holder for the X-axis (x-carriage) is made to fit (16T pinion, 20T pulley). If another X-axis or another diameter of the pulley is used, e. g. stock Prusa x-axis, the associated x-carriage is also largely suitable, but lacks access to the mounting screws of the stepper motor.
As an option, a small lamp holder is added for use of, for example:

https://www.amazon.com/Yitee-Keychain-Bright-Ultra-thin-Portable/dp/B00QYNPKU2/ref=sr_1_1

The extruder is fully tested, easy to print and works fine, even with TPU filament, on my Prusa I3 MK3.
Many additional files are included in the attached .zip file.
Since it is a "full-size extruder", as well as the original Bondtech extruder or the Prusa R3 extruder, a changed firmware is necessary if you are using the IR-sensor, e. g.:

https://github.com/BondtechAB/Bondtech_Prusa_i3

or for custom changes and compile, even for 0.9 ° instead of 1.8 ° stepper motors:

https://github.com/guykuo/Prusa-Firmware/tree/0.9-Degree-Stepper-Support

When converting from the existing Prusa R3 / R4 / R5 extruder or a Bondtech (eg K63) extruder, many existing components can continue to be used.
Here is a list of all additionally required but often already existing components:

Hotend, e. g. E3D V6:

https://e3d-online.com/v6-all-metal-hotend

Hotend fan:

https://noctua.at/en/nf-a4x10-5v

Component fan:

https://de.aliexpress.com/item/32963170156.html

Stepper motor:

https://www.omc-stepperonline.com/de/nema-17-42mm-schrittmotor/nema-17-bipolar-1-8deg-13ncm-18-4oz-in-0-7a-2-9v-42x42x25mm-4-drahte.html?mfp=149-schrittwinkel[1.8]
 
https://www.amazon.de/gp/product/B01LESPDCQ/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

1 x knurled screw:

https://www.bondtech.se/en/product/thumbscrew-assembly/
 
1 x gear drive:

https://www.bondtech.se/en/product/shaft-assembly/
 
1 x motor pinion:

https://www.bondtech.se/en/product/motor-gear/
 
2 x ball bearings:

https://www.bondtech.se/en/product/ballbearing-5x8x2-5/
 
1 x axis 3.0 x 32 for the "door hinge":

https://www.bondtech.se/en/product/shafts/

1 x Gear-Kit 1.75/5.0

https://www.bondtech.se/en/product/drivegear-kits/

1 x P.I.N.D.A 2 sample

https://zaribo.com/sensors/59-pinda-2-probe-sensor-3d-printers.html

1 x laser filament sensor:

https://zaribo.com/sensors/94-filament-sensor.html

or 1 x IR filament sensor:

https://zaribo.com/home/171-mk3s-ir-filament-sensor-kit.html

In addition div. M3 bolts and nuts.

A special construction manual for this extruder has not yet been created.
The pictures and parts of the instructions by Bondtech.sa and Prusa Research serve as an assembly aid.

https://www.bondtech.se/en/product/prusa-i3-mk2-5-mk3-extruder-upgrade/
https://support.bondtech.se/c/Prusa
https://support.bondtech.se/Guide/03.+Prusa+i3+MK2.5+-+MK3+Upgrade+Kit+-+Installation/29?lang=en

https://manual.prusa3d.com (E-axis assembly)
https://manual.prusa3d.com/Guide/5.+E-axis+assembly+(textile+sleeve)/822?lang=en

Recommended additional modules (also incl. to the .zip file):

x-axis:
https://www.thingiverse.com/thing:3226689
https://www.thingiverse.com/thing:3716110

Part fan nozzle:
https://www.thingiverse.com/thing:3249344

More photos will follow.
A small video shows the application of the sintered bearings:
https://youtu.be/4Mw2OPnXC-4
This thing is improved if necessary by updates.

Do not forget to change the motor step parameters using an usb terminal or octoprint.
I prefer this g-code values, in this order:

M350 E16; change micro steps from 32 to 16
M92 E415; change steps per unit (mm) from 280 to 415
M500; store changes to the internal eeprom (rambo board).
M503; check the changes.

I like to answer your questions in the comments.

Happy printing :-)

SIE-Maker

post printing, hint:

Check the small set screw (M3 x 2mm) for the gear wheel. The grub screw should not exceed the intended length of 2.00mm. Do you measure higher values, please sand with fine sandpaper on the side to the axis to a max. length of 2.00mm.