Heat creep with Dragonfly BMO and CR10 type hotends

[eugen360]

Hello friends!

Heat creep became my worst nightmare although from 2016 (when I've started 3D printing) I never ever had such problems... 

I did a search on google for this problem and Voron0 builds but it doesn't seem to be the case of others so I'm wondering what is wrong with me? I've build a few printers until now but never had so many problems like with this one...

I have chosen the bowden setup because I like it more (keeping the X gantry as lightweight as possible). So I've started with a CR10 clone hot-end exactly like this one:

 

A very small and cheap Chinese hot-end. After a few small successfully printed parts (mostly test prints) I've tried something larger, I guess it was the spool holder if I remember correctly. The sound of the extruder grinding the filament caught me by surprise first! I thought something blocked the spool from rolling but it wasn't the case... force removing the filament from the heat-block revealed the problem. After a few more tries (printing at 210-220 degrees) all ended in the same situation I've decided to spend a few more money for a "good and shiny" hot-end. So I've bought the Phaetus Dragonfly BMO. Indeed a nice piece of work but... starting a 25 minutes print on 245 degrees with ABS (this filament https://www.formfutura.com/shop/product/titanx-2846) the bed at 85 degrees, after 15 minutes - heat creep! 

I'm lost... !

The 3010 cooling fan IS working normally! 

[eugen360]

I was thinking on modifying the stl files for a 4010 cooling fan (for CR10 and this Dragonfly I had to do it anyway) but... I'm the only one having this problems ?

[atrushing]

29 minutes ago, eugen360 said:

I was thinking on modifying the stl files for a 4010 cooling fan (for CR10 and this Dragonfly I had to do it anyway) but... I'm the only one having this problems ?

This doesn't sound like a good time. I have been using the Dragonfly BMO on multiple printers with just a 5V 3007 hotend fan and can't say I've had any heat creep issues while printing PLA, PET and ABS even with chamber temperatures up to 60 C.

I have had some clogging issues after many hours of printing and certain filaments seem to make it worse. I will usually clean out the clog and then season the nozzle with vegetable or canola oil and that lets me get back to printing.

[eugen360]

3007 at 5V ? I must admit, that's something!

Well, if it's the oil than I'll submerge the hot-end in oil! Just kidding! I have a DIY dust filter for the filament and the sponge is soaked in oil but at the time of this prints I wasn't using it. This ABS roll is brand new...

[atrushing]

Just now, eugen360 said:

3007 at 5V ? I must admit, that's something!

Well, if it's the oil than I'll submerge the hot-end in oil! Just kidding! I have a DIY dust filter for the filament and the sponge is soaked in oil but at the time of this prints I wasn't using it. This ABS roll is brand new...

It does seem odd that this problem would come up so quickly.

Are you sure that the PTFE tube is sitting down as far as possible into the hotend?

[atrushing]

Also, is it a decent quality PTFE tube? And is it a proper bowden tube (2mm I.D.) and not the reverse bowden tube (3mm I.D.)?

Just trying to rule out possible problems..

[eugen360]

I've pushed the tube as hard as I could and as "far" as it goes... I suppose it is in the right position, there is no way to see. Eventually I'll remove it measure with a piece of wire or something the required length and after that making sure the exact length of tube is entering the hot-end. But you consider that in both hot-end cases and after many tube removals and reinsertions it could be this problem?

[eugen360]

Quote

Also, is it a decent quality PTFE tube? And is it a proper bowden tube (2mm I.D.) and not the reverse bowden tube (3mm I.D.)?

It is the exact same quality and dimensions as Prusa printers uses. Actually the tube was taken from a Prusa MMU unit.

[atrushing]

3 minutes ago, eugen360 said:

I've pushed the tube as hard as I could and as "far" as it goes... I suppose it is in the right position, there is no way to see. Eventually I'll remove it measure with a piece of wire or something the required length and after that making sure the exact length of tube is entering the hot-end. But you consider that in both hot-end cases and after many tube removals and reinsertions it could be this problem?

It is possible. Some of the bowden fittings do not allow the PTFE tube to pass through into the hotend. There is a hexagonal hole in the bottom that needs to be drilled out with a 4mm drill to allow pass through. Or you could use a short piece under the bowden fitting that remains in place and the upper tube is the one you can disconnect.

[eugen360]

Hmm, I've sharpened the tube like you sharpen a graphic pencil especially to make sure it will reach the end of it's travel and also to make sure it will match the entering in the body of the hot-end...

[eugen360]

The fitting is the standard ECAS04 used in the Voron builds.

[atrushing]

3 minutes ago, eugen360 said:

The fitting is the standard ECAS04 used in the Voron builds.

Then that shouldn't be the problem. It is the old style bowden fittings that had that issue.

[atrushing]

14 minutes ago, eugen360 said:

Hmm, I've sharpened the tube like you sharpen a graphic pencil especially to make sure it will reach the end of it's travel and also to make sure it will match the entering in the body of the hot-end...

I'm just spitballing here because I am running out of ideas.. If you have sharpened it too thin it might be weak at the end and allowing the filament to bulge out. I normally just nick the edge off with a sharp blade.

 

[eugen360]

Quote

I'm just spitballing here because I am running out of ideas..

 Thank you anyway atrushing! I really appreciate it! 

Quote

it might be weak at the end and allowing the filament to bulge out

But in the area where the tube ends the filament it is not yet melted, still hard, maybe warm a little bit... as it can be seen in your first attachment, it is in the cold part of the hot-end. The problem happens a centimeter or so lower ...

[atrushing]

One more silly question. Is the hotend fan blowing towards or away from the hotend?

[eugen360]

It isn't silly at all  

It is blowing correctly towards the hot-end. Double checked the fan rotation and "wind" direction... 

[atrushing]

And it is a genuine Phaetus Dragonfly?

[eugen360]

Yes, it is!

[atrushing]

It might be worth checking your retraction values. A bowden setup does need extra retraction but maybe the hot plastic is getting pulled too far back up the hotend and causing issues.

[eugen360]

Right now the retraction setting are - 3 mm at the speed of 50 mm/s.

[atrushing]

According to the Andrew Ellis Tuning Guide he suggests:

• Bowden - Start at 1mm @ 30mm/s.
  • The upper limit depends on your bowden length/slack/tolerances.
  • Pressure advance can significantly reduce retraction needed for bowden.

So, it might be worth tuning in your pressure advance too.

Edited December 5, 2022 by atrushing

[eugen360]

Thanks for the extra info. I did a calibration (with the CR10 type) but not with this new one. First time I'll try some oil... let's see what's happening! I will also reduce the retraction. (the tube is ~ 30 cm).

[eugen360]

Hello again!

There's a saying in my part of the world "one drop of oil makes as many as 10 mechanics"... and it really does sometimes! It really looks like the all metal hot-ends need some extra lubrication. As I said above, never had problems like these before but that's because I always used hot-ends with PTFE liners inside. Now it's the first time I switched to all metal and... lesson learned! I'll put on the dust filter with oily sponge in it no matter what!

Yesterday evening I did 3 prints, ~ one hour each at 90 deg. bed and 230 hot-end, ABS with no part-cooling fan, one after the other, no break just the pause of taking the part off and starting the new print job. And NO issues at all! 

I guess... that's it!

Thank you atrushing for your time and help!