J-Head Mk 12 High Temperature Development Hello, Development of the new J-Head Mk 12 is going great! After one more round of positive testing, we expect to have it available at [www.hotends.com] Here is a picture of the J-Head Mk 12 heat sink between an e3d and hexagon hot-end. Latest video: [youtu.be] https://reprap.org/forum/read.php?1,824633,824633#msg-824633 Fri, 11 Sep 2026 09:53:48 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?1,824633,827307#msg-827307 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,827307#msg-827307
No pic for release yet. When it's released there will be lots of pics. :)

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jinx
reifsnyderb just wondering if there a picture of the Jhead Mk12 yet
]]> reifsnyderb General Fri, 29 Jun 2018 18:33:10 -0400 https://reprap.org/forum/read.php?1,824633,827271#msg-827271 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,827271#msg-827271 jinx General Fri, 29 Jun 2018 03:59:31 -0400 https://reprap.org/forum/read.php?1,824633,827237#msg-827237 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,827237#msg-827237
Actual print testing with the J-Head 12 is going very well! Even though it's a bowden extruder, 2mm retracts are working fine.

Both ABS and PLA are now printing very nicely.

Printing ABS at 60 mm/sec works fine at 235 degrees and with 2mm retracts. At 125 mm/sec, I increased the temperature to 245 degrees and 3mm retracts. Prints great!

I have just started some serious testing with PLA. Thus far, no problems. Printing at 190 degrees, at 60 mm/sec, and with 2mm retracts works great. I'll up the speed with future prints.

In the near future, testing will commence with much higher speeds.

Brian]]> reifsnyderb General Thu, 28 Jun 2018 16:38:49 -0400 https://reprap.org/forum/read.php?1,824633,826272#msg-826272 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,826272#msg-826272
The bowden tube is made out of 4mm OD/ 2mm ID PTFE tubing. It's the same tubing I use for PTFE liners on J-Head Mk 8's and J-Head 10's.

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dc42
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reifsnyderb
The heat break section is 2mm. I tried 2mm retraction and 4mm retraction. No problems. The bowden tube is about a meter long.

With a 1m Bowden tube, my guess is that none of that 4mm retraction at the extruder will actually reach the hot end. My experience is that you need retraction of almost 1% of the length of the Bowden tube just to take up the filament slack in the tube, before retraction actually happens at the extruder. A little less with high-quality PTFE tube such as Capricorn. So with a 1m Bowden tube I would expect you to need around 10mm to 11mm retraction to ensure that enough retraction occurs at the hot end to avoid leaving blobs at the start of travel moves.
]]> reifsnyderb General Wed, 20 Jun 2018 17:16:00 -0400 https://reprap.org/forum/read.php?1,824633,826267#msg-826267 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,826267#msg-826267
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reifsnyderb
The heat break section is 2mm. I tried 2mm retraction and 4mm retraction. No problems. The bowden tube is about a meter long.

With a 1m Bowden tube, my guess is that none of that 4mm retraction at the extruder will actually reach the hot end. My experience is that you need retraction of almost 1% of the length of the Bowden tube just to take up the filament slack in the tube, before retraction actually happens at the extruder. A little less with high-quality PTFE tube such as Capricorn. So with a 1m Bowden tube I would expect you to need around 10mm to 11mm retraction to ensure that enough retraction occurs at the hot end to avoid leaving blobs at the start of travel moves.]]> dc42 General Wed, 20 Jun 2018 16:52:36 -0400 https://reprap.org/forum/read.php?1,824633,826258#msg-826258 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,826258#msg-826258
Other tests:

Left to sit with PLA in for 30 minutes at 195 degrees without any retraction. No problem.

Left to cool down with PLA in it, no retraction prior to cooldown, heat it back up to 295 degrees and extrude. No problem.

Retract 2mm, at 295 degrees, and wait for 30 minutes. No problems

Retract 4mm, at 295 degrees, and wait for 30 minutes. No problems.

The static test rig is now torn down and I hope to be doing actual print tests this weekend.






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dc42
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reifsnyderb
Static testing continues with the new J-Head. There was only one failure. It failed to jam with PLA. (:D

How much retraction did you use, and what length Bowden tube (if any) does your test setup have?
]]> reifsnyderb General Wed, 20 Jun 2018 15:22:45 -0400 https://reprap.org/forum/read.php?1,824633,826257#msg-826257 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,826257#msg-826257
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reifsnyderb
Static testing continues with the new J-Head. There was only one failure. It failed to jam with PLA. (:D

How much retraction did you use, and what length Bowden tube (if any) does your test setup have?]]> dc42 General Wed, 20 Jun 2018 15:09:32 -0400 https://reprap.org/forum/read.php?1,824633,826247#msg-826247 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,826247#msg-826247 reifsnyderb General Wed, 20 Jun 2018 13:59:14 -0400 https://reprap.org/forum/read.php?1,824633,824798#msg-824798 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824798#msg-824798

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Trakyan
I'm having trouble picturing how the heater block, heatbreak and heatsink go together.
]]> reifsnyderb General Wed, 06 Jun 2018 21:23:09 -0400 https://reprap.org/forum/read.php?1,824633,824795#msg-824795 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824795#msg-824795 Trakyan General Wed, 06 Jun 2018 20:41:09 -0400 https://reprap.org/forum/read.php?1,824633,824785#msg-824785 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824785#msg-824785
Best Regards,

Brian



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Trakyan
0.25 mm walls and a set screw to hold it in place? You'd need to be a surgeon to assemble this thing without crushing it. Also, that's a tiny heatsink, how effective is it and what fan will you use to cool it?
]]> reifsnyderb General Wed, 06 Jun 2018 17:47:43 -0400 https://reprap.org/forum/read.php?1,824633,824708#msg-824708 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824708#msg-824708 Trakyan General Wed, 06 Jun 2018 03:45:33 -0400 https://reprap.org/forum/read.php?1,824633,824691#msg-824691 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824691#msg-824691 good luck with it, 0.25 on the heatbreak sounds like some feat on machining.]]> MechaBits General Tue, 05 Jun 2018 18:52:33 -0400 https://reprap.org/forum/read.php?1,824633,824679#msg-824679 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824679#msg-824679
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MechaBits
Ok, Ok $4 [www.ebay.co.uk] must have gone up since i last looked.
]]> reifsnyderb General Tue, 05 Jun 2018 17:18:32 -0400 https://reprap.org/forum/read.php?1,824633,824675#msg-824675 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824675#msg-824675 www.ebay.co.uk] must have gone up since i last looked.]]> MechaBits General Tue, 05 Jun 2018 17:06:24 -0400 https://reprap.org/forum/read.php?1,824633,824673#msg-824673 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824673#msg-824673
The part with the heat break isn't present in these pictures. However, the heat break has a wall thickness of about 0.25mm. So there is very little heat conduction up to the heat sink.


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jinx
will the Mk12 have the grub screws holding the heat break into the heat sink ( think that a nice feature to bring in from the hexagon).

NO heat break! kind of hoping to see a chimera style break in the design
]]> reifsnyderb General Tue, 05 Jun 2018 17:01:36 -0400 https://reprap.org/forum/read.php?1,824633,824672#msg-824672 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824672#msg-824672
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jinx
like that brass work,, but whats the stubby piece next to the threading
]]> reifsnyderb General Tue, 05 Jun 2018 16:59:59 -0400 https://reprap.org/forum/read.php?1,824633,824668#msg-824668 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824668#msg-824668 jinx General Tue, 05 Jun 2018 16:35:49 -0400 https://reprap.org/forum/read.php?1,824633,824667#msg-824667 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824667#msg-824667
NO heat break! kind of hoping to see a chimera style break in the design]]> jinx General Tue, 05 Jun 2018 16:32:56 -0400 https://reprap.org/forum/read.php?1,824633,824665#msg-824665 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824665#msg-824665
leOcWh9.jpg]]> reifsnyderb General Tue, 05 Jun 2018 16:23:40 -0400 https://reprap.org/forum/read.php?1,824633,824659#msg-824659 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824659#msg-824659
The center part is the heat sink. The E3d shown is a real V5 and the Hexagon is real as well. No knock-off parts shown.

Brian



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MechaBits
But a Volcano heatblock is only $1, Looks more like a copy of a cheap chinese copy of your Jhead - 1
]]> reifsnyderb General Tue, 05 Jun 2018 16:00:24 -0400 https://reprap.org/forum/read.php?1,824633,824656#msg-824656 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824656#msg-824656 (I can only see a pic with one hotend)]]> MechaBits General Tue, 05 Jun 2018 15:51:51 -0400 https://reprap.org/forum/read.php?1,824633,824645#msg-824645 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824645#msg-824645
I'll post a picture of the heater block soon.

Best Regards,

Brian





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jinx
BUT,BUT that pic doesn't look like the heat block in the vid? ( appears more like the volcano in the vid )
]]> reifsnyderb General Tue, 05 Jun 2018 13:14:33 -0400 https://reprap.org/forum/read.php?1,824633,824643#msg-824643 Re: J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824643#msg-824643 BUT,BUT that pic doesn't look like the heat block in the vid? ( appears more like the volcano in the vid )]]> jinx General Tue, 05 Jun 2018 12:55:16 -0400 https://reprap.org/forum/read.php?1,824633,824633#msg-824633 J-Head Mk 12 High Temperature Development https://reprap.org/forum/read.php?1,824633,824633#msg-824633
Development of the new J-Head Mk 12 is going great! After one more round of positive testing, we expect to have it available at [www.hotends.com]


Here is a picture of the J-Head Mk 12 heat sink between an e3d and hexagon hot-end.


bA0dqwh.jpg

Latest video:

[youtu.be]]]> reifsnyderb General Tue, 05 Jun 2018 10:48:54 -0400