Hex Hot end, few quick questions...

Hi guys,

So just got around to installing my hex hotend on my taz 4. Installation and wiring went ok. I installed the taz5 firmware from the link at the end of the installation guide. I’ve noticed that the little turbo fan stays on all the time…is that normal?
Also, what is the size of the stock nozzle on the hex? mine says “3” on it, i’m assuming .3mm? I really liked the .35 nozzle size on the budda, anyone know where you can get different nozzle sizes for the hex?

thanks again

The fan on the Hexagon is there to cool the bore so heat doesn’t travel back up and melt your extruder body amongst other things (also to prevent PLA jamming too) and is supposed to be always on.

If you bought the hot end from lulzbot directly, it’s a 0.35mm nozzle. If you got it somewhere else, there are a variety of different possibilities. The one I aquired for my TAZ is a 0.40mm nozzle actually. You can get different nozzles here or other places: http://www.makerfarm.com/index.php/hot-ends/hot-end-parts.html

There is such a thing as a 0.3mm nozzle, you may very well have one of those.

ok thanks, great info…I sorta have to figure out what the nozzle size is though, obviously it’s somewhat important. It was sent to me as a replacement by lulzbot. It has a big 3 on it. Maybe lulzbot admin can chime in here. I’m doing a print with it set to .3mm so I’ll see how that turns out. thanks again for the quick reply.

Ok, so I didn’t even make it through 2 hours of printing without this hotend %$@#! up. And I just replaced my budda snozzle because it just stuffed up.

Now the hex end is jammed and I can’t figure out how to fix it. The filament is jammed in the tube with the brass lining, not the nozzle. I removed the nozzle, broke off a nozzle cleaner tip in it, so that’s trashed, put a new nozzle on (actually had one lying around that fit), I tried to heat it up and reinsert some filament, but the bulk of the abs is stuck in the shaft, above where it heats so I can’t push it or remove it…am I doing something wrong here? Why did this thing jam an hour in, it’s brand new! For plastic to jam in the main shaft, could it be heat creep? it was only on for an hour or two. I’m not liking the fact that I can’t really take apart the hex hot end, I feel helpless to fix it.

You can’t pull the filament out after heating the hotend to extrusion temps? Make sure to open the idler. If pulling the filament put doesn’t work, remove the nozzle heat up the hotend and push the filamemt through.

Could be the hotend not lining up with the extruder. When assembling, it helps to have a piece of filament in the hotend to lineup the extruder… bamboo skewer might be 3mm also.

It’s a 3mm metal tube. if you heat it up to the melt point of ABS, the fillament is coming out. if its not, i’d be inclined to look at the heater core or look for a short. At least verify the operating temperature is being reached with the hexagon. If it’s locked in the barrel, something wierd is going on. The only thing I can think of is if the nozzle was blocked due to overpressure since it was a 0.35mm nozzle trying to print at 0.3mm height off the bed, the fillament melt pushed back up the bore and melted into a ring shape in the slight gap between the brass liner and the lower tube assembly. Heating the hot end up should still make that come free though.

maybe get a pin punch about the size of the bore and insert it from the nozzle side, but try to knock the fillament back from that side towards the top plate?

I have a couple hot ends like this at the repair shop! I am planning to try to unblock them when I get a chance, but I have not figured out what I am going to try to fix them. They are in a really badly plugged state. :cry:

I think/hope support may have an answer to unblocking the throat of the extruder block when they come back Monday. :blush:

If you have not done it yet I would try the process kcchen_00 recommended.

I use a piece of copper beading wire to unblock nozzles with, plus it helps me figure out what size nozzle I have on the extruder. I have a roll of ~.32 MM and ~.29 MM wire. I can see which passes through on the nozzles that only have the ‘3’ on them, since Lulzbot gets custom .35 nozzles and I can find only .30 nozzles. I also need to find some ~.5 MM wire for the new nozzle size.

So I tried all the by the book methods to get it unclogged but nothing worked. I took it off the machine, took the whole hot end apart, removed heater, thermistor, and nozzle, everything until I just had the bare block with the plastic jammed in the main throat. My nozzle was actually fine, but it was the plastic in the main block that was literally glassed in. I ended up taking a torch with map gas and heated it until the ABS bubbled, I then had a scmall Philips screw driver that fit the 3mm diameter hole almost perfectly and I worked and pushed the plastic ABS out from the top through the bottom (nozzle end)…even with heat it was thick and goory and clinged all along the sided of the brass shaft. Have no idea how it got so jammed in there but obviously it was probably heated somehow, ie where it’s supposed to stay solid and cool, where the heatsink and fan are, it turned molten and just compressed and compressed.
Anyway, after I got most of out, I let it soak in acetone overnight to remove any remaining plastic, then blew it out with compressed air in the morning. It looks good as new. I put everything back together and put some antiseize on the threads for the nozzle. Also, I changed nozzles with some 4mm I had ordered from 3d industries.


Fired up the printer, tested for flow and all was good. So far I’m a few hours into the print with no issues. But I’m still worried about heat creep. Although since it works now, it basically means there was a problem with the original nozzle, maybe it got clogged and heat creeped up due to the plastic not flowing through, then it glassed everything in higher up.

NOW…this brings me to my next issue and I hope researchers can chime in here because I’m asking myself, is the Hex Hot end really a good or optimized design to begin with, are we to believe that a tiny heatsink and a micro fan can keep a 300 degree heater at bay???

Isn’t the whole crucial aspect of a Hot end to have a very sharp transition between Solid and Molten state, ie a really sharp melt zone and a very separate cooled zone to keep the upper part of the filament in a solid state to help push it along? I’ve attached two pictures illustrating this, couldn’t you increase the size of the heat sink and add a very large heatsink or insulator to act as a break so heat can’t creep back up? I’m just surprised at the current designs of hotends and I’m wondering why they’re not designed like this, unless I’m missing something… Also, I’m not a fan of relying on a fan for keeping the cool zone maintained, no pun intended. To me, it’s overcomplicated and an area for failure. Would it not be possible to do it passively with a large enough heat sink or insulator, like the budda does? I might try to experiment with a few designs but I want to know if anyone has tried this already…will save me some time and money.

You’re new to the hexagon, huh? :slight_smile:

A lot of different solution have been shared to increase cooling of the heataink. A lot of them are on Thingiverse… search TAZ. I particularly like the design from Wolfie for a 30/40mm fan on the opposite side of the fan duct. It’s only one of many to help reduce heat creep.

Could also try pointing the blower down a bit to get the cooling closer to the first heatsink fin and heat break where its truly needed as you point out.

These solutions were developed primarily for issues with PLA… ABS is usually fine. You may need to turn the idler thumbscrews a few more times for more pressure and therefore more force to feed the filament. Are you noticing any extra filament shavings in the extruder? When you pull the filament can you recognize teeth marks from the hobbed bolt?

BTW if you’re using pure force to remove a cold nozzle, you’re most likely damaging the brass and the threads will eventually shear off in the heat block. Heat up the hotend to 165C+ and the nozzle should come off with wrenches by hand. I think it’s the aluminum heat block expanding to “release” the nozzle.

Yes, new to it for sure. Just installed it yesterday and it jammed…but now that I cleaned it, it’s been printing all day, 8+ hours. But here’s the thing, I changed the nozzle with a .4mm one I had as a spare that I got from 3dindustries.com. Looks like that did the trick, so the nozzle that came with it from lulzbot was probably shoddy. I think what happened was something blocked it, it ran blocked for a little while and compressed all the plastic into the upper throat, it probably heat creeped a bit also so it really glazed over in the main throat.

lol. Yes, I know how to remove the nozzle. I’ learned the hard way with the budda schnozzle aluminum nozzles but even then, they still welded to the aluminum heatblock, I’m hoping the nozzles on the hex are easier to swap out, I put antisieze grease on it this time.

Ok, didn’t know there were solutions for the heat creep issue. But what I’m sort of saying is that, is it not possible to dissipate the heat with a heatsink or insulator alone? without a fan, like the budda does? It would just be that much less complicated.

Might try this one eventually, apparently works well…


I also think I’m going to get into the habit of doing regular preventative maintenance and cleaning of the nozzle, something I havn’t been doing. I wonder how well that cleaning filament works also…

Oh you mean this one…


Ya it’s awesome, I just don’t want to have to reprint the back panel part, I just want a quick fix.

Any of those should work… The added air flow seems to help quite a bit. With that said, I haven’t had issues with the mini-blower. I only print ABS.

Regarding the nozzle quality… I’ve got a bunch of nozzles from MakerFarm in .4,.5 and the .3 along with the one original which came on the hex. I think the general machining process of the nozzles may weaken the interior first layer. Then when heated and cooled, that layer or parts of the layer flake off in the nozzle. Removing, soaking in acetone and a good dental pick seems to rid the flake of brass. I’ve had a clog with each of the nozzles. After the first cleaning they’ve been fine. FWIW, I printed with the OEM nozzle the longest without a clog.

A backup nozzle is always good to have on hand… If one clogs, remove, attach the fresh one, start printing then soak and clean the old nozzle…

Also wanted to mention that LB recommends a bit higher temps with the hexagon as well as a little more tension in the idler. Without the PTFE tube, it can get sticky in the hotend.

All good to know… yes, there’s definitely something going on with the nozzles. Good to know that you had success after cleaning them, there’s this old trick for cleaning seat valves in carburators (which basically look exactly like the inside of a nozzle). you take a q-tip and some metal cleaner, put the q tip in a drill and clean the inside of the cavity until it’s mirror shiny…you could probably do that to the shaft aswell since it looks like it’s a brass insert also. I might try this as a preventative measure on some of the nozzles I ordered.

My fan shroud for the Hex Hotend was made just for the TAZ 4 with the hexagon upgrade http://www.thingiverse.com/thing:845113 only the shroud has to be printed and is holds a 40mm fan. Have had mine installed and running for almost 2 months now with no issues yet and the fan I used pushed 8X as much air as the tiny original one.

Yes, nice work. If I have problems in the future, I’m going to use your mod for sure.

But what I’m saying, is a fan even necessary in the first place? What about just some reworking of the heat sink?

It’s a Mass question. You could definitly make a passive cooling hot end if you added sufficient cooling fins, but it would be heavier and therefore theoretically slower and potentially slightly less accurate (due to microscopic elastic rebound of the belt when changing directions). A fan could cool the same amount with less mass, theoretically leading to faster printing speeds. Same reason you don’t see very many water cooled hotends except for the 4 barrel units like the Kracken

Right, I get that, just wondering if anyone has actually experimented with it…you could make a larger heat sink with larger fins for little cost in weight at the sizes we’re talking about, the effects of the extra mass would be negligible, we’re not talking about adding a pound of weight, would probably amount to only a few more grams. Or maybe there would be other method of design that helps to passively cool it. Anyway, it’s working now so I guess why mess with it :slight_smile:

The E3D V6 Lite took this approach. It has lower temp capabilities and omits the fan. I read somewhere that the heat sink was slightly different.

Ya that’s interesting. I have a hunch that things get exponential as the degrees go up, so maybe that’s why we’re not seeing this done with a hot end that can do 300 degrees. Maybe the heat sink required for that would just end up being too large afterall.

Who knows, I have a lot of aluminum lying around, might just experiment at some point. An all metal hot end is seriously the simplest concept in the world from a mechanical standpoint. They’re WAY overpriced IMO. I could probably build one x times better for x less cost. So stay tuned.