Prusa i3 Bear Half Upgrade v1.0

Prusa i3 Bear Half Upgrade v1.0

This is an aluminum frame conversion for the Prusa i3 MK2, MK2s and MK2.5.

Josef PRŮŠA has created numerous of incredible 3D printers and its Prusa i3 MK2/MK2s/MK2.5 is capable of very impressive print quality for a very low price. A huge thanks to him and all its team!

Unfortunately, the frame is the weakest point of the machine. It is very difficult to square, it is not rigid enough on the Z axis and finally the frame might move a bit when you do some maintenance. A very good project has solved those problems by using 3030 extrusion aluminum : Prusa 3030 Haribo Edition.

Why another conversion build?

• To reduce the number of parts to update from Prusa i3 MK2/MK2s/MK2.5 kit (no need to print a new RAMBo cover nor change any cable, rods or firmware from the original Prusa i3 MK2/MK2s/MK2.5)
• Use more aluminum and less printed parts to build the frame (3D printed parts can crack if tighten too strongly, they are less reliable, less precise and might cost more)
• Use Openbuilds hardware:
  • To have a single high quality platform of multitude compatible hardware parts (extrusion, plates, brackets, low profile screws...)
  • V shape gives more possibilities to orientate the printed part (45° angle is more than manageable, with T-Slots you might need to add support)
  • Open source
  • Easy to square and build
  • Worldwide shipping plus several other shops selling these parts
  • Powerful community
  • Easily customizable
• Limited number of measurements needed during the build phase (and no need for a calliper bigger than 150mm)
• Fully open source by providing STL files, STEP files and Autodesk Fusion 360 project file

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Bill of materials
Here is the list of all needed files : bom

Modify the original aluminum frame
With this upgrade you will need to drill the original frame of your Prusa i3 MK2, MK2s or MK2.5.

I have made a 3D printed part to help you place the holes accurately. You can double check the positions with this PDF.

As you will see in the bill of material, the recommended drill bit is a 5.3mm.

If you break the frame, you can send an email to Prusa support to get a new one. You will find few in the Chinese market as well.

If you have access to a CNC machine, you can use this DXF.

Getting Openbuilds V-Slots
The length of V-Slots are detailed here.

On-line shops
Here is a list of Openbuilds stores.

Pre-cut
In the list above you will find indication about pre-cut V-Slots for each shops. If a store in your country does not sell pre-cut V-Slots, try to send an email.

Machine cut
The best way to cut V-Slots is to use a mitre saw with special aluminum blade and lubricant.

Another way is to use a circular saw but you will need a cross-cut sled. As well as for mitre saw, a special aluminum blade and lubricant are necessary.

Hand cut
You can hand cut them accurately using a jig (it just takes more time and effort). I have build one, all details are here : V-Slot Hand Cutting Jig by pekcitron

Tapping
You will need to tap one side (two holes) of 195mm and 110mm V-Slots (8 holes in total)

Manual and assembly instructions
Check the manual here.

Current status
Build doc

Links

• All project data and sources are available on my github : github.com/gregsaun/prusa_i3_bear_upgrade
• Openbuilds build page
• Openbuilds forum page
• Thingiverse page

Sources
Here are a list of sources I used to build this project :

• Prusa : Prusa3D - 3D Printers from Josef Prusa
• Prusa 3030 Haribo Edition : GitHub - PrusaMK2Users/3030_Haribo_Edition: Aluminum extrusion conversion for the Original Prusa i3 MK2
• Openbuilds : Build List | OpenBuilds

Huge thanks to these projects, without them this project can not exist!