E3D-v6 hotend has poor design for printing 3mm PLA using Bowden extruder?

I tried one original and two chinese E3D v6 hotends, also original Volcano hotend with 0.6mm nozzle. All of them have the same symptom – plastic gets stuck after a while (from several minutes to hours) producing a jam inside the hotend.

My printer has a Bowden 3mm extruder and a heated bed (70°C for PLA).

I tried unsuccessfully (without stable result):
Powering hotend fan from 16V instead of 12V. Hotend radiator is slightly warm to touch.
Putting extremely powerful motor in the extruder (6.5kg·cm).
Oiling the plastic.
Various printing temperatures and speeds.
Various PLA filaments.

Is all-metal design defective for printing PLA? Are there any other options I may try? Are there good hotends guaranteed to print PLA?

I made an experiment – I drilled a hole inside the hotend as shown in red on the picture:


And filled the hole with a piece of Teflon tube.
I’m able to print with this hotend at speeds <30mm/s, but this is not what I want.

I've been doing similar experiments.

The problem I see is that if the soft PLA is retracted back into the heat break, then it can expand on the next unretract and jam against the walls of the metal heat break. Others have used polishing techniques such as this one:
[www.youtube.com]
to make the plastic less likely to stick.


One design that works really well for me is to drill out the heat break till almost right at the end, and insert the teflon tube all the way through the heatsink so that it ends up at the level of the top of the heater block. You are left with 2mm of metal heatbreak, then the nozzle. This has a problem in that you're not supposed to go higher than 250 degrees or so, otherwise it degrades the teflon tube. It does work really well though, no more issues with jamming.

You can see this design if you scroll down here: [www.thingiverse.com]


I've tried various heat breaks with the teflon going down various amounts inside the heatbreak, and the rest of it having a 2mm hole, but it always seems to have this same issue. I tried polishing the inside with a drill bit and polishing compound, but it didn't really seem to do that much. I think the sand idea should work better.


My next experiment will be to use high temperature silicone as a liner inside the heatbreak. This works well on the outside of the heater block and stops plastic sticking to it, so I can't see why it wouldn't work on the inside of the throat.


Good luck, keep us posted on your results.

I used a genuine E3Dv6 to print 3mm PLA and ABS through a bowden tube for quite a while, very successfully. I didn't use any special tricks - normal Gregs-Wade geared extruder with a standard NEMA17 motor feeding the bowden tube, with 12v power. The only problem I had was getting the retract amount correct, and used to get a lot of stringing, but that was to do with the bowden feed. Apart from that - no issues at all.

Now I use the same hot-end (using some new components for the size change) with 1.75mm filament and a direct drive extruder, simply to get over the stringing problem.

It's well worth looking at the E3D website's problem-solving pages - they're very good. E3D Wiki link

Edited 1 time(s). Last edit at 04/27/2017 09:46AM by David J.

David, i tried all advises from the E3D Wiki without any luck Currently this head seems to be a marketing bullshit for me.

Real J-Heads, from [www.hotends.com], are very very good at printing PLA.

Edited 1 time(s). Last edit at 04/27/2017 11:09AM by reifsnyderb.

Quote
Vladimir13
David, i tried all advises from the E3D Wiki without any luck Currently this head seems to be a marketing bullshit for me.

Well, I used this hot-end to print the parts for 2 other printers, without problems. I now run 2 printers, and each has a genuine E3Dv6 hot-end. Both work properly, and only cause me problems when I make a mistake, e.g. switching off the power while there is filament loaded, which means that the cooling fan doesn't keep the heatsink cool and the heat transfers up into the body of the hot-end. This can cause the filament to melt where it shouldn't, resulting in a jam. I now have a routine whereby I withdraw the filament whenever I plan to shut down the printer, and let the hot-end temp drop as far as possible before hitting the off switch.

I suspect that you have a problem with the way you are using it... sorry to be blunt, but that's the way it looks from here.

But real J-heads are also good, if you want to try an alternative - see post above.

Edited 1 time(s). Last edit at 04/27/2017 04:45PM by David J.

I can only speak on using a 3mm Genuine E3d but my jamming issues went away when I followed the following:

Always keep the heatsink fan on when cooling the hotend down past 70deg C. This is VERY important, I think this is what happens (and Tom Salanderer pretty much confirmed this in one of his videos):

On the 3mm version (i've not had this issue with the 1.75 version) the fan on the heatsink keeps the temperature down, especially where the heatbreak meets the heatsink.
this stops the plastic from expanding at the top of the heatbreak when the plastic is not extruding.

If the fan is turned off while still hot the heat creaps up and expands the plastic in the heatbreak, which forms a seal which you pretty much have to drill out!

So, never cut the power until the hotend is back down below 40c

Once I started doing this every time my problems were greatly decreased, I still got the odd jam, but mainly because I think of the damage I did to the heatbreak when drilling it out.

Since switching to genuine E3D 1.75 full & lites I've never had the same issue, So I think its definitely the extra mass of the 2.85mm filament causing the problem.

I assume this doesn't happen on the 1.75 models due to less transient thermal mass and the presence of a ptfe tube.