Clog problems with CR-6 SE

I have been having problems with recurring clogs with my printer after 4-5 hours into a print job.

So far :
I changed my hotend in october,
I changed my extruder 2 weeks ago.
I have changed the Bowden tube and my nozzle.
I have tried 2 brands of filament.
The filament was previously dehumidified with a filament dryer.
print speed 60mm/s
retraction on at 6.5
Have tried Z-hop on and off
extrusion temperature tried between 190 and 210 deg C
somethimes I get the telltale knocking sound
sometimes I check the print to find no filament is coming out as the printer goes back and forth in the air.

What am I missing?

Is retraction too high? sometimes if a print has a lot of retraction in a small area it pumps heat up into where its supposed to be cool and causes a clog of melted filament there

I would run a retraction test, Most Bowden systems I can get away with 3-4mm retraction, direct-drive I am only at .8 to 1.5mm.

What kind of machine are you running?

so bringing it down from 6.5 to 3. Is this what you mean? I could sure give it a shot.

Well Jason, the topic is clog problems with CR6-SE.: … LOL
What is weird is this started around the holidays. I have had no such problem in the year preceding that. Maybe my print project is what is causing this problem…

LOL, sorry my bad, Been looking at a lot of posts today, Trying to play catchup…

But yes, reduce the retractions from 6.5 to 3 and give it a try, Also do the refraction test may be able to get away with less.

I am still somewhat of a noob… how do I perform the retraction test? (feeling quite stupid right now wink-wink)

Sorry, not an issue, Have a look at Teaching techs Calibration GitHub. Link below

This is the one specific to retraction but I recommend for everyone to run through his whole site at least once on one printer to see how one issue can affect another. It’s a could of evenings to run through the whole thing but it’s a good learning experience.

As @Jason suggests, do the retraction test. Every time you retract the filament, yes, you pull the filament out of the nozzle tip so it does string - that’s the main point, but you also bring hot filament up into the Bowden tube. The hot filament starts to warm up the inside of the Bowden tube and so the point at which the solid plastic filament transitions to liquid rises higher and higher. If you retract too much, the filament may still be liquid when it enters the Bowden tube and it solidifies there, sticking to the inside of the tube and creating a clog.

Running your hot end too hot will also do this.

Another key thing to check: is your front fan running at full speed and is there debris blocking the air flow either of the fan itself or on the fins of the heat sink? Without proper cooling, the heat creeps it’s way up into the tube with the same result.

Lastly, the bottom end of the Bowden tubes tend to bake after a while. Every once in a while, when I start getting clogs as you describe, but my fan is clean and running, I take the Bowden tube out and clip off the bottom 1 to 2 cm.

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Simplest things to try are to replace the boden tube with Capricorn tube to prevent the tube burning like Lego said AND do the Luke Hatfield trick on the hotend (as shown on CHEPS you tube page, if the six has a stock Creality hotend). Make sure the tube ends are cut square and that the hotend is assembled right IE: how the nozzle and heat break are tightened up.

So I got the STL file. But do I just print or do I have to enter some numbers in Cura beforehand?

Also :
Am using a Capricorn Teflon tube. Sniped itbowden tube yesterday to make sure…
I have some stringing, yes. Am printing at 60 mm/s with a current temp of 190deg

addendum :
and after 3 hours, extusion blocked…

Which STL file are you referring to? The Teaching Tech Calibration page linked to earlier provides GCode so you can just go ahead and use it.

Have you verified that the fan on the FRONT of the hot end is running at full speed, that there is no debris in the fan, and that the heat sink fins are clean?

A print clogging after 3 hours sounds an awful lot like Heat Creep which is almost always an airflow problem or an overly-hot printing temperature, but you said you are running at 190C, so that just leaves airflow.

Are you certain it is a blockage and not heat creek softening the filament and allowing the extruder gears to chew a notch in the filament rather than feeding it?

So I received a few question and have some news.

Well i do have marks on the filament when I remove it to clean. But I don’t know if there is some amout of teeth marks to be expected or not.

@Legomaniac the STL I am referring to is from the post by Loosenut

The fan at the front and the one at the side were cleaned on monday when I started some steps to rectify. I cleaned as best I can. I don’t have air in a can. I am not convinced as to whether or not it is fucntionnig properly.

I rechecked the bowden tube, changed de clamp in the hot end, used cleaning filament and restarted the print last night at 200deg c and went to bed.

As I write this morning I am at 11hrs, 76% completed and I do have stringing but I am on my way to get a printed part.

Does this bring us closer to the cause of my situation? Is changing the fan the solution ( a somewhat inexpensive one).

Also would like to thank again all you nice people with your suggetions. I live out in the boonies with limited ressources out here. Most of the stuff is ordered online and no tech stores to take the machine in the shop (if such services exist).

Your input is really appreciated

Marks are to be expected. A big notch is not. It still sounds like heat creep. Perhaps a fan but it could also be how throat is arranged to the nozzle and cooling. There is some leeway in how deep the nozzle is and how deep the throat.

Personally I have the throat as shallow into the block as reasonable and the nozzle as deep. This gives the most separation from hot section to cool section. It is easier than a new fan. Although that might help too.

So after 16 hr 12 minutes I got a print done. Here are a front and back view.

So far :
retraction distance from 6.4mm to 3mm
Z-hop disabled (forgot to mention this)
Temperature 205deg (not 200 like I stated previously)

Any suggestions on how to tweek to get rid of some, most or all stringing?

When did I do that???

You were getting less stringy prints before weren’t you? This is PLA?
my recollections is you have printed a number of big miniature landscape parts in the past.

I think your nozzle is worn out.

My experience is brass wears fast. It might improve dramatically if you replace it.

Sorry wrong reference.
The retraction test is actually from here
from the post by Jason. The test is down at the middle of the page.

actually Kitedemon I changed the nozzle twice thinking I might have had a faulty one.

I always had a bit of string depending on what I was printing. Nothin this major. Also the finish of this piece is not as nice as what I use to have before.

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