Does a J-Head Really Need an Aluminium Groove Mount?

Hello Everyone,

I've started installing a J-Head hot end, and I'm wondering if it really needs the thick aluminium groove mount? Does the plastic style work just as well, or does the aluminium act as a heat sink to such a degree that it improves reliablity with PLA for example?

I've actually fabricated one nice aluminium groove mount, I just wonder if I should just print up an ABS version for the next machine...

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Yvan

Singularity Machine

I made a wood grove mount from 70's wall panneling extras for my original Prusa when I got my J-head.

It works like a charm.

I also use the two screw mount for my Wallace version of the Eckstruder. No problems there.

I suspect the ABS grove mount plates would work just as well.

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Komb'
Glankonian Protoforms

For a long time people have been selling laser cut plywood and acrylic mounts for the J-Head. They seem to work.

I always use ABS mounts for JHeads. Works perfectly fine. Even with an aluminum mounting plate you would most likely still need a fan for printing with PLA.

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I think it's safe to say that current thinking is to use a fan on most hot ends for most materials. You certainly see them a lot more than you don't ....

The PEEK material in the J-Head is not a chunk of tool steel. It melts and you can easily get a hot end warm enough to melt one. There are *lots* of pictures / threads from people who have done this. It's a fine hot end and lots of people get excellent results from them, just make sure you don't run the hot end so hot it melts. Depending on who you talk to that's somewhere in the 230 to 240C range with a fan. With out a fan it's a "that depends" sort of thing (somewhere lower, but how much lower ..). If the bottom of the plastic is at / below 230, the top end will be well below that, regardless of cooling. With a fan it should be at room temperature.

If you do run a fan - shut off the hot end *before* you unplug the power. Let it cool down to something rational before you stop the fan turning. You *probably* would never see an issue just puling the plug, safer to wait the 90 seconds ....

Thanks for the feedback everyone! LOL about the 70's paneling, I've used that stuff for all manner of things!

I was trying to figure out what to do. The aluminium groove mount is time consuming to fabricate, but I don't want to skimp on something critical. I will try an ABS version for the next batch of machines.

With these machines I have to stick with aluminium, because I'm fitting a J-Head under a Wade style extruder on a Prusa i3 set up for use with PLA. So far I'm experimenting with this fan duct on the prototype. I've added a hole about 7 by 15 mm to cool the PEEK J-Head body, but I might make it a bit larger.

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Yvan

Singularity Machine

The fan for PLA is to cool the printed PLA, not the hot end. It is pointed at the print. Some hot ends, particularly all-metal, use a fan blowing over the heat sink to keep the heat from traveling up towards the extruder. You would still need a fan blowing on the print if you use PLA. Direct drive extruders also use a fan blowing on the stepper to keep it cool.

I've never had a fan blowing on my J-head hotends and they have always worked great. The PEEK does not conduct heat very well which is why it is used. One of my printers has an acrylic mount and the other wood. No problems with either.

Cheers,

KDog

I've printed many kilos of ABS, mostly on all metal hot ends, so this PLA thing is new to me. I've been getting conflicting info about whether or not to cool the PEEK J-Head body. Possibly this is from people printing with ABS which needs a slightly higher temp.

With PLA, there seems to be an issue where the PLA plugs up above the melt zone and the extruder strips the filament.

Quote
KDog
The fan for PLA is to cool the printed PLA, not the hot end. It is pointed at the print. Some hot ends, particularly all-metal, use a fan blowing over the heat sink to keep the heat from traveling up towards the extruder. You would still need a fan blowing on the print if you use PLA. Direct drive extruders also use a fan blowing on the stepper to keep it cool.

I've never had a fan blowing on my J-head hotends and they have always worked great. The PEEK does not conduct heat very well which is why it is used. One of my printers has an acrylic mount and the other wood. No problems with either.

Cheers,

KDog

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Yvan

Singularity Machine

Some ABS filaments have recomended temperatures around 250-260C. Other ABS filaments have recomended ranges of 210-230C. If you have the "hot" ABS, it's not going to work well with a J-Head.

Where do you find these "hot" ABS filaments? I'll admit, I've only printed Ultimachine filament, but I've never heard of anyone printing ABS above 240C. Certainly not 250-260. Does "hot" ABS require hotter HBP temperatures, or offer higher glass-transition temps? What is the advantage to using "hot" ABS filament? I'm in the process of converting to an E3D 1.75mm hotend, so I'd like to know if there are any advantages to using ABS filament that would otherwise be unsuitable for my J-head. I would've already been using the E3D if not for the fact that all the filament I have is 3mm. I'd like to use up as much of my 3mm filament as possible before switching.

If you take a look at the Afina line of printers, their filament all is set up for a 260C hot end. It's all ABS. There are a number of places that have glow in the dark or other odd color stuff that list 250C numbers for standard printing (and lower temps for the rest of their stuff). I'm by no means trying to sell anybody on hot filament. I'm only trying to point out that there is no one temp range for all ABS out there.

At some point the Eckertech guys had some higher temp. ABS, I don't know where they obtained it from. I've got a couple of their all metal hot ends, so those are the ones I used for anything on the hot side like nylon.

The J-Head is on a machine without a heated bed, so it would be for PLA only at the moment.

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Yvan

Singularity Machine