1. Introduction
2. Features
3. Compatibility
4. Printed parts
5. Print settings
6. Bill of materials
7. Manual
8. Optional parts
9. Community
10. Images
11. Source
12. Support my work
13. Thank you
14. License
15. Credit and inspiration

The BearExxa (Bear extruder and X axis) is an alternative extruder and X axis for Prusa i3 printer and is designed to improve print quality, reliability and ease of maintenance. It is following the Bear Upgrade project but also compatible with Original Prusa's MK2(S) and MK3(S) frames.

The Bear X axis also supports alternative extruders such as Bondtech Prusa Upgrade, E3D Hemera and vertigo235's extruders.

All parts are available under the GPLv3 open source license. You can download STL, CAD files (Autodesk Fusion 360) or STEP files. Feel free to fork and share!

⚠️ The Bear X axis is NOT compatible with stock Prusa extruder!

• Simple and precise belt tensioning system
• Stiffer X axis design to reduce ringing
• Easier Z bearings installation thanks to clamping system
• Optimized belt path for smoother movements
• Easy access to belt and extruder cables
• Improved X axis bearing alignment
• Kinematic constraint to self-center the X stepper
• Optional: Support for alternative extruders
• Optional: Compatible with E3D Gates idlers

• Better heat management to reduce inconsistency, clogs and heatcreap (also check these recommended hotend fans)
• Stiffer extruder thanks to a uni-body structure
• Easier installation and removal of E3D v6 hotend
• Efficient part cooling
• Self-centering of extruder motor and Bondtech gears
• Reduced risk of extruder blob
• Reliable filament sensor (based on MK2.5S/MK3S sensor)
• Perfectly aligned filament path
• Reduced extruder and Bondtech gear vibrations
• Reduced wear and noise of print fan thanks to a vertical assembly
• Optional: Compatible with MMU2S thanks to the work of vertigo235

The Bear X axis is also compatible with several alternative extruders. See optional parts to get all the information and files for those alternative extruders.

• E3D Hemera
• Bondtech Prusa Upgrade extruder
• Bear extruder for MMU2S by vertigo235
• Gear box for Bear extruder by vertigo235
• Bear Extruder BLTouch Mount by vertigo235

Due to a different belt path, the Bear X axis and extruders are matched to each other and cannot be used separately. As a unit, they are compatible with both Original Prusa frames and Bear Upgrade frames.

• The Bear extruder version supports the new IR filament sensor introduced with the latest Original Prusa MK2.5S/MK3S extruder.
• The Bear extruder version is compatible with original Prusa firmware for daily use. However, (XY)Z calibration and selftest require a dedicated firmware for these steps only.
• MK2.5 (non-S) and MK3 (non-S) are compatible with this Bear extruder version with the exception of the filament sensor.

In an effort to lengthen the Z axis, the original Prusa MK2.5S/MK3S hotend was raised by about 6mm. This placement increases the ambient temperature around heatbreak and heatblock which could lead to print quality and reliability issues. We have decided to not lengthen the Z axis in order to provide best printing experience. Because of this difference with the original Prusa extruder, we provide a customized firmware to pass Selftest and (XY)Z Calibration. Except for these steps, the original Prusa firmware is completely compatible with our extruder.

The firmware is available here: https://github.com/bear-lab-3d/Prusa-Firmware/releases/

Download links for the Bear extruder and X axis (BearExxa) :

• BearExxa MK2.5S : bear_extruder_x_axis_mk2.5s.zip
• BearExxa MK3S : bear_extruder_x_axis_mk3s.zip
• Sources : bear_extruder_x_axis_source.zip

You can also download them via Thingiverse: thingiverse.com/thing:4362586

If you are looking for alternative extruders printed parts, please check the section Optional parts below.

The parts have been designed and tested with the parameters below and it is important to follow them to avoid issues like part cracking, bad bridging, not enough stiffness or wrong tolerances.

Read the print settings here.

Read the BOM here.

The manual contains bill of materials (BOM), print settings and assembly instructions.

Read the manual on guides.bear-lab.com 📖

Here is a list of optional parts designed for the Bear extruder and X axis (BearExxa).

You can also find optional parts made by the community at guides.bear-lab.com/Wiki/community_optional_parts.

Here are the places were the Bear project is the most active. Do not hesitate to ask if you have a question :

• Facebook group : facebook.com/groups/PrusaBearUpgrade
• Discord server of "The 602 Wasteland" community : discordapp.com/invite/hYUjSnW
• Twitter : @gregoiresaunier
• GitHub : github.com/gregsaun

Pictures from Flobler and Grégoire Saunier

All source files in Fusion 360 and STEP format can be download here.

The Bear project is only possible thanks its supporters, you can participate via


patreon.com/gregsaun


paypal.me/gregsaun

You can also send me a tip via Thingiverse if you prefer.

Massive thank you in advance ❤️

First of all, massive thank you to Adrian Bowyer for having invented RepRap.

Thank you to all my Patreon's

Thank you to David Ogles, Flobler, Jason from LDO Motors, Matthew Humphrey, Nathan Denkin, Orlando from All3DMakers, Saiz, Sleene, Termlimit, Vertigo235 for helping me in developing the Bear project.

Thank you to all that have sent me a tip on Thingiverse and PayPal.

Thank you to everybody from Facebook group and The 602 Wasteland community.

Thank you for having purchased a kit from an official distributor.

Thank you to all official distributors for taking care of the kits and customers.

Thank you Jason from LDO Motors for the quality manufacturing and relationship.

Thank you Openbuilds for your hardware, community and state of mind.

Thank you for making the community alive with all your comments, issues, pull requests, optional parts, make, pictures, etc.

This repository and all its files are licensed under the GPLv3 license. Here is a quick summary; for more details please check the LICENSE file.

What you can do:

• Modify
• Distribute
• Private, commercial and patent use

What you must do:

• Include copyright notice
• Include a copy of the license
• Share source files
• Use the same license (GPLv3)
• Document changes applied

• RepRap : https://reprap.org
• Prusa : http://www.prusa3d.com
• Vecko Kojchevski for the help on some details of the X end clamps, X carriage and PTFE cutter : https://www.thingiverse.com/vekoj/designs
• Arnaud Rousseau for "his X-Ends clamped MK3 (Zaribo)" : https://www.thingiverse.com/thing:2964026
• Prusa i3 Solidworks parts from jzkmath : https://github.com/jzkmath/Original-Prusa-i3
• Prusa MK2/S X-Carriage Adjustable Tensioner by Jon Madden : https://www.thingiverse.com/thing:2770019
• Jan Imrich from Kurzy Kocour maker space for all his hard work on inconsistency issue
• The 602 Wasteland Discord community for their precious knowledge and advice
• RH_Dreambox and Robrps for his nozzle fan duct designs
• Joel from Bondtech for having pushed me to pursue the filament sensor idea

Massive thanks to these projects, without them this project cannot exist!