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Bear Extruder 0.7.0-beta MK2.5S MK3S

by pekcitron Jul 1, 2019
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Hi..about to build a full bear, do you know of any remixs of this dual fan that will fit on the bear? theres a bear bmg one in the files but dont think its correct one...cheers steve


Dual Part Cooling Fan Mount / Shroud with Nozzle View for Prusa i3 MK3

There is a BLtouch Version? could you make a model for that too? please?

Not planned yet sorry.

Sir, I am wondering if I can print the fan duct with petg. I don't have abs around now.

Yes you can. Only if you print high temperature filaments (nozzle temp > 280°C) constantly you should consider using ABS or even PC or Nylon for the fan duct

Can the extruder be adapted to use 3mm filament? I'm guessing it's designed for 1.75mm.

I think it should be possible. I am not planning to do it but you can find the Fusion 360 source files are attached.

awesome thanks! probably missed that picture or it's too late into the night for me to understand.

can you please tell me how is the x axis tensioned? on the left or on the right? TIA!

You mean the x-asxis belt? When you sit in front of the printer on the right x-axis end. There are two screws that are attachedto the carriage of the x-axis idler. Check the second picture...

thanks amprint for the help :-)

Hi, I just received the MK3S upgrade form Prusa. Could I just install the original design by Prusa, or is this the correct upgrade? Does this have the new filament sensor?

I have the full bear MK3 now. Which is great!

Don't know what you mean with "correct upgrade" but you can install both versions.
And yes, this version does suppot the new (non laser) filament sensor.

Hi pekcitron !
I'm upgrading my prusa i3 MK2s to MK2.5s with full bear upgrade. And I decided to go with RJ4JP bearing, can you tell me if there will be a version of the bear extruder, compatible with RJ4JP ?

Big Thanks !

Not planned sorry, I tested them and I find they have too much play, including on Igus rods (thus it gets better over time on this one).

I'm planning on continuing to use my MK3 filament sensor ( making it indirect with https://www.thingiverse.com/thing:3464119 )

Do you recommend I use the .6 version of the parts or using .7 and adding the indirect mod on top?


Bear Extruder MK3 Indirect Filament Sensor

I would recommend to use latest version of the extruder, a lot of small improvements have been included. So give a try to this mod (I didn't try it myself).

Pekcitron, thanks a lot for this. A couple of months ago I printed the 0.6.0-alpha MK2.5 MK3 and it went great! So far I had zero issues. I wonder, to upgrade to this version, should I print all parts again? Is there anything I could reuse from the previous version?

Unfortunately, all parts have been improved and we recommend to re-printed them all. However, changes on X ends are intended to improve assembly and you don't necessarily need to update them unless you have problems with the Z axis.

Hi Pekcitron, are the x axis parts compatible with the last extruder of the original Mk2.5s ? Or I need to print also your extruder block?

No the X axis is not compatible with all original extruder. However, Bear extruder is having lots of improvements over the original MK2.5S or MK3S extruder.

Assembled this extruder and x-axis 2 days ago. I must say I am very happy with it and thanks to Pekcitron for this. Whole process and the guide is enjoyable. I do however have a complaint :) When I was inserting the last screw in the x_carriage_back (M3x18) the hex nut in the x_carriage fell inside of the extruder_body (into that funnel). It was totally my mistake as I didn't press the hex nut in as much as I should have. Now I am one screw short but I think it is not effecting my prints in anyway.

I really liked the whole process of putting this together and thank you so much for your continuous effort! I will be looking for updates/upgrades closely :)

Hey deyyo, thank you very much for the kind words and feedback. For the X carriage screw I think I can improve this in the assembly guide to make sure the screws are fully inserted.

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Made and assembled it today, turned out super awesome. I haven't had any issues at all and the 3rd print with the new X-Axis and Extruder is now running absolutely fine on my MK3S.

Thank you for this brilliant design, I had a lot of issues with the stock prusa extruder due to the misaligned path. This design is a lot more intelligent and easier to assemble. It does not require a complete disassembly when changing a wire etc. - and there is a proper tensioner on the X axis belt.

Great Stuff :-)

Thank you for the feedback, very happy you like it!

I just printed out all of the extruder pieces to upgrade my old v0.6 Bear Extruder assembly so I can use the new MK3S style filament sensor. For some reason, my steel ball won't fit inside the pocket of the extruder body at all. The diameter of my steel ball is 7.95mm. Any advice?

Hi, you probably got a wrong steel ball, Prusa is using 7mm steel ball. Does it come from Prusa?

Smashing build, keen to get started but I am confused, the Bear extruder bill of materials under filament sensor parts quotes an 8mm ball. As I would like to construct this from scratch so my Prusa remains in action, I am keen to get the correct size.

That explains it. It did not come directly from Prusa. I'll try to modify the extruder body to fit my slightly bigger steel ball or track down a correctly sized 7mm one. Thanks!

It is now fixed, sorry for the mistake. 7mm is the correct size.

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Is this thing up-to-date? I started printing these parts and noticed that the nozzle fan duct is missing from the zip. So I downloaded everything from the source at https://github.com/gregsaun/bear_extruder_and_x_axis. I reprinted the filament sensor cover from the github STL's and that's when I discovered that the STL's on github are different from the STL's in this thing.

Can you explain the difference please?

Never mind. I see that the thing was updated on July 1 and the new one matches what's on github. I just need to sort through what needs to be updated.

Yes up to date, I just re-uploaded the optional parts zip for a typo ;-) . I keep this in sync with my GitHub.

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what are the perimiters and infill for all parts or do we just follow previous ones?

Thank you for you great work and this update!
I currently have an MK2.5 with the old filament sensor which is working great for me. However I would like to upgrade to this extruder assembly because it has a couple great improvements. Do you see any problems in adjusting this design back to the original laser filament sensor. As far as I have seen only the sensor mount is different. Would love to remix this.

Hi amprint, would love to see a remix for the laser filament. The top of the extruder is almost the same as the previous 0.6.0-alpha that was supporting the laser sensor, so should be pretty easy to remix it. Don't hesitate to ask if you have questions during the remix.

Thanks for your quick response.


Didn't print it yet, but I'll try it as soon as I started upgrade my x-axis

Bear Extruder body 0.7.0-beta MK2.5
by amprint

Awesome thank you! Please keep me in touch how it goes.

Okay, bear extruder MK2.5 style is installed and is working.
I'll post a make as soon as I have made some pictures.

The only "problem" I encountered was that the cables of the laser filament sensor didn't fit into the groove of the extruder back plates. Seems that the cable of the old sensor is bigger (I think it has one wire more) than the new one. I didn't check it yet but maybe the back plates of the 0.6.0 version didn't change and can be reused.
If I have time I'll compare them and add them to my remix.

Thanks again for this great design!