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New printed parts - extruder version R3 (B7)

Jul 14, 2018 9:59 am

UPDATE 4:
New parts C1/R4 for the MK3S/MK2.5S/MMU2S are out! More here: general-discussion-announcements-and-re ... 27888.html

UPDATE 3:
New plastic parts B7 are out, more in this post:[/b]
general-discussion-announcements-and-re ... 25616.html

UPDATE 2:
There is a brand new guide to upgrade your assembled MK3/MK2.5 from R2 (B6) to R3 (B7) parts.
MK3: https://manual.prusa3d.com/c/Upgrading_ ... _R3_on_MK3
MK2.5: https://manual.prusa3d.com/c/Upgrading_ ... 3_on_MK2.5

UPDATE:
New R3 parts are already part of the MK3 and MK2.5 assembly guide. See chapter 5 for more details. A special guide for R2 to R3 upgrade will come soon ;)


Hi guys,
there are new printed parts for the Original Prusa i3 MK3 and MK2.5. This time we've made changes to the extruder design. The main focus was on better airflow and improved cooling. A small improvement goes to printing the flexible filaments. On the GitHub the parts will be labelled R3, same parts are printed on our farm with the label B7.

The theory behind the updated parts:
Air itself behaves like any other fluid and any obstacle in its way causes turbulence and slows the air flow down. Slower flow of the air results in a smaller amount of air pushed through the extruder over time thus limits the effectiveness of the cooling. In other words, the more air you are able to push through the extruder, if needed, the better. Looking at the extruder design (version B2/R6) we've found two areas, where further improvement was possible.

Starting with the extruder body and cover, both parts previously had a grill, which was slowing down the air flow from the Noctua fan. New parts are without the grill, air flow is increased and as a result, cooling capabilities are improved. Moreover, the extruder cover has a new inlet, which is sucking in additional air for cooling the heatsink. A similar technique is used in car design, where is the main air inlet often coupled with additional ones. (Side note: Sadly, the purchase of Dodge Demon with extra air intake through headlight to demonstrate this feature, was declined :D)

Extruder body and cover were further updated with increasing the space for the extruder motor cable on the extruder body and removing the arm supporting the fan on the extruder cover, which is no longer needed.

The difference in temperatures of hotend (heatsink area) between old and new parts:
MK3stockVSupdated.jpg
MK3stockVSupdated.jpg (110.04 KiB) Viewed 58615 times
New_MK3_extruder_body_B7.jpg
New_MK3_extruder_body_B7.jpg (155.84 KiB) Viewed 48721 times
Old vs new extruder body
New_MK3_extruder_cover_B7.jpg
New_MK3_extruder_cover_B7.jpg (148.67 KiB) Viewed 48721 times
Old vs new extruder cover


Apart from cooling the filament, we focused on cooling of the printed object. With the MK2/S the fan-nozzle was unidirectional and printed object was cooled down from the front. On the MK3 we wanted to improve the design of the fan-nozzle so the air flows more around the object. Overhangs facing away from the fan were printed better, however, those facing towards the fan couldn't be as steep as on the MK2/S. Our developers went back to the drawing boards and tested countless designs to improve the fan-nozzle including those from the community and big thumbs up to everyone, who designed his own fan-nozzle and shared it!
MK3_fan_nozzle_new_B7.jpg
MK3_fan_nozzle_new_B7.jpg (131.43 KiB) Viewed 62011 times
Old vs new fan nozzle

The final design is quite different from the MK3's initial version. The major change is in the fan inlet, which is now inclined. The new design enables a much smoother flow of the air in the fan-nozzle and improves the air distribution around the printed object.
MK3_new_fan_assembly_B7.jpg
MK3_new_fan_assembly_B7.jpg (133.83 KiB) Viewed 62010 times

Based on the user feedback, we've changed the design of the extruder body for printing with the flexible materials. The area surrounding the Bondtech gears is now tighter and preventing the Flex to slip away.


Recap of the changes:

Extruder-body (extruder-body-v2.stl)
- removed grill in the area of heatsink
- slight polish to the surface around heatsink
- improvements for printing from Flex
- recommended print material PETG or ABS
- black color only

Extruder-cover (extruder-cover-v2.stl)
- removed grill in the area of heatsink
- slight polish to the surface around heatsink
- new inlet for additional air
- recommended print material PETG or ABS
- black color recommended

Fan-nozzle (nozzle-fan-45deg.stl + nozzle-fan-45deg-support.stl)
- complete redesign
- increased air flow
- inclined fan
- new support for the fan
- recommended print material ABS only
- orange or black color

Parts (STLs) are available here:
https://www.prusa3d.com/download-printa ... ts-stl-mk3
new parts are in the zip file together with other MK3 STLs


Recommended print settings:
- Use latest available Slic3r PE
- Layer height 0.2 mm
- Infill GRID 20%
- Temperatures and speed are set according to the filament profile (PETG or ABS)

Compatible printers:
- Original Prusa i3 MK3
- Original Prusa i3 MK2.5

Questions are welcomed below ;)
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lucas.c3
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Re: New printed parts - version R3/B7

Jul 17, 2018 9:43 pm

If i print this in orange will I have issues with fillament sensor?

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nikolai.r
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Re: New printed parts - version R3/B7

Jul 17, 2018 10:11 pm

How many perimeters are recommended?

chris.n6
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Re: New printed parts - version R3/B7

Jul 17, 2018 10:31 pm

I'd suggest, for anyone printing in high temp materials, print the fan shroud in PC.
ABS and Pet-g droop when the temps are high. PC does not.

mmazurek
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Re: New printed parts - version R3/B7

Jul 17, 2018 10:33 pm

I can't seem to access the second two parts. (shroud and angled bracket)

The extruder parts were available to download.

The drawings and images of the parts show up, but I'm not seeing how to download them.

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moojuiceuk
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Re: New printed parts - version R3/B7

Jul 17, 2018 10:39 pm

Me too - cant see a download button for the STL files for the nozzle-fan-45deg-support.stl & nozzle-fan-45deg.stl files, unless I'm doing something dumb here?! :?

ben.t7
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Re: New printed parts - version R3/B7

Jul 17, 2018 10:46 pm

I had issues as well and after looking like a idiot in support chat if right click on the raw button and select save as you should be able to download the stl.

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moojuiceuk
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Re: New printed parts - version R3/B7

Jul 17, 2018 10:54 pm

Ahh.. Proof I should get some sleep before even thinking about this upgrade!

mmazurek
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Re: New printed parts - version R3/B7

Jul 17, 2018 10:58 pm

Yeah, I would have never have got that.
Especially after downloading the two other files with an obvious button.

Thanks for posting that.

ben.t7
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Re: New printed parts - version R3/B7

Jul 17, 2018 11:02 pm

Trust me I blindly figured it out after looking like a idiot in chat with Shane for a half hour going I can't get it to download and him telling me to save target as. I wonder if there is any special assembly instructions for these new parts or if the original install steps will work.

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