QU-BU Extruder Improvements

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Re: QU-BU Extruder Improvements

Postby tmccafferty » Wed Jan 16, 2013 3:35 am

brnrd wrote:For 1.75 mm feed, you don't really need any gears with a NEMA 17 motor. I don't even use gears with 3 mm feed with the 0.35 mm J-head and I can extrude ABS up to 150 mm/min or faster with it. That's in terms of the 3 mm feed.


Bart, what configuration are you running the J-head? Is it on an ORD BOT?
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Re: QU-BU Extruder Improvements

Postby gyrogearloose » Tue Jan 22, 2013 2:39 am

There are MK2 J-head hotends for sale on ebay for $52US incl. shipment:
www.ebay.com/itm/New-RepRap-3D-Printer- ... 43b324a431
I have just ordered one to try.
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Re: QU-BU Extruder Improvements

Postby bdring » Tue Jan 22, 2013 3:58 am

Bart, what configuration are you running the J-head? Is it on an ORD BOT?


I am running a fairly stock QU_BD hot end and am pretty happy with it. I thermal epoxy the thermister and don't use their screw for the thermister leads. I am not super happy with the pointy nozzle, but it works.
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Re: QU-BU Extruder Improvements

Postby bloomingtonmike » Tue Jan 22, 2013 4:05 am

What brand thermal epoxy do you recommend?
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Re: QU-BU Extruder Improvements

Postby brnrd » Wed Jan 23, 2013 2:17 am

gyrogearloose wrote:There are MK2 J-head hotends for sale on ebay for $52US incl. shipment:
http://www.ebay.com/itm/New-RepRap-3D-P ... 43b324a431
I have just ordered one to try.


I'm sorry that I didn't read this sooner. That's an old version of the J-Head which is missing the cooling vents and it probably won't perform as well as the latest version which is the Mk V. The Mk V requires so little force that I can push a 3 mm ABS feed at 230C up to 150 mm/min and more through a 0.35 mm nozzle with a direct drive NEMA17 extruder. I recommend ordering the J-head directly from the designer at hotends.com. His prices are not much higher than that e-bay price. He's usually reachable at the reprap irc channel and by e-mail.
Last edited by brnrd on Wed Jan 23, 2013 2:22 am, edited 1 time in total.
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Re: QU-BU Extruder Improvements

Postby brnrd » Wed Jan 23, 2013 2:20 am

tmccafferty wrote:
brnrd wrote:For 1.75 mm feed, you don't really need any gears with a NEMA 17 motor. I don't even use gears with 3 mm feed with the 0.35 mm J-head and I can extrude ABS up to 150 mm/min or faster with it. That's in terms of the 3 mm feed.


Bart, what configuration are you running the J-head? Is it on an ORD BOT?


I think you might have meant that question for me. The J-Head I'm using is a Mk V-BV, which is the latest version, from hotends.com. I use it on a Mendel, Prusa2 and a Hadron. It doesn't really make a difference what printer it's on. I'm using Marlin which allows one to autotune the PID parameters. This is critical to avoid large temperature overshoots which can damage the PEEK thermal insulator.
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Thermal Epoxy

Postby bdring » Wed Jan 23, 2013 2:54 am

What brand thermal epoxy do you recommend?


I had some Arctic Silver Aluminum epoxy from Fry's I bought a while ago to glue heatsinks on Pololus. It dries hard in about an hour.
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Re: QU-BU Extruder Improvements

Postby tmccafferty » Wed Jan 23, 2013 5:12 am

brnrd wrote:
tmccafferty wrote:
brnrd wrote:For 1.75 mm feed, you don't really need any gears with a NEMA 17 motor. I don't even use gears with 3 mm feed with the 0.35 mm J-head and I can extrude ABS up to 150 mm/min or faster with it. That's in terms of the 3 mm feed.


Bart, what configuration are you running the J-head? Is it on an ORD BOT?


I think you might have meant that question for me. The J-Head I'm using is a Mk V-BV, which is the latest version, from hotends.com. I use it on a Mendel, Prusa2 and a Hadron. It doesn't really make a difference what printer it's on. I'm using Marlin which allows one to autotune the PID parameters. This is critical to avoid large temperature overshoots which can damage the PEEK thermal insulator.


Brnd, what is the rest of the extruder that you are using with the j-head on the Hadron? I am having fits with the qu-bd. I have done Bering mods and that helped tremendously with drive force and I printed good for about 10 minutes. Then the extrusion got very fine and I couldn't even push the pla through the nozzle by hand. I think the heat had backed up the tube. I don't have enough experience yet to know much about diagnosing it. Would love to get something that would work reliably.
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Re: QU-BU Extruder Improvements

Postby brnrd » Wed Jan 23, 2013 3:43 pm

tmccafferty wrote:
brnrd wrote:
tmccafferty wrote:Brnd, what is the rest of the extruder that you are using with the j-head on the Hadron? I am having fits with the qu-bd. I have done Bering mods and that helped tremendously with drive force and I printed good for about 10 minutes. Then the extrusion got very fine and I couldn't even push the pla through the nozzle by hand. I think the heat had backed up the tube. I don't have enough experience yet to know much about diagnosing it. Would love to get something that would work reliably.


I'm using a newer version of this extruder (http://www.thingiverse.com/thing:21728). It works well for ABS but I've only used it occasionally with PLA and I think air cooling needs to be improved for that. I've improved the fan mount but I'm still not satisfied with it. So, I'm going to try other ideas.

It sounds like your problem is with the hot end and not the extruder. It should be easy to design a piece that would mount the J-Head on the lower two mounting holes of the motor to work with bdring's extruder mod.
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Re: QU-BU Extruder Improvements

Postby tmccafferty » Thu Jan 24, 2013 3:29 am

Is the purpose of the fan to keep the tube from getting hot between the actual tip and the extruder? If that's the only purpose, what about wrapping the hot end shaft with small copper tubing and use one of the closed loop heat exchangers like are used to cool CPUs? It doesn't seem like the fan is in a position to do much good to the shaft.
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