Ultimaker s5 with 0.4mm CC nozzle stops extruding nylon 6 CF filament after a few hours of printing

[madest 0]

Hello all, I recently got my hands on a CC nozzle along with some nylon 6 CF composite filament from Polymaker (PA6-CF). I have been having many extrusion problems with this filament, and I have no idea why. I had thoroughly cleaned the nozzle with cleaning filament, increased the temperature to the maximum recommended temp, increased and decreased the tension on the system, upgraded the firmware for what it was worth, and completely cleaned and oiled the feeders, in which I found quite a bit of said CF filament which I think is due from when I increased the tension. 

When printing with this filament, it will print for almost exactly four hours each time until I get an under-extrusion error of about 0.3 units under the minimum threshold. disabling the flow sensor results in a print where some parts of the print have been normally extruded, and others have only the first few layers that were successful. To me, this means that it is somewhat extruding, but it's spotty and works only about 1/4 of the time. When I remove the filament, it is obvious in some locations that it was ground in the feeder, but in others, it is relatively smooth. 
The only thing that will get the print working again is to abort it and then restart it. Doing so will result in a perfect print for four hours until it completely stops, and then nothing can get extruded again. 

During this print, I try unloading and reloading that filament, cutting off the ground parts of the material. It comes out of the hot end fine and has a good, smooth flow. But the instant that I resume the print, I get a flow error and am forced to abort the print. 
Any help would be greatly appreciated since I've tried to print this part about 20 times and it has never gotten past four hours out of a 12 hour print

Edited March 14 by madest

[gr5 2,230]

Is the front fan working?  The symptoms you describe sound like what happens when the front fan is not spinning.  Not the side fans on the print head - the fan in the door of the print head.

[madest 0]

yes the fan is going

[Dadkitess 19]

Do you happen to have something specific at this 4 hours threshold ? Maybe some fast contours for instance ?

 

You might be close to the max flow rate allowed for that given material, and UMS5 is really really bad at flow rate extrusion. If it always happen at a given spot of your print, it's maybe because of a geometry that is eager to go faster / wider / thicker layer.

 

You say "I get an under-extrusion error of about 0.3 units under the minimum threshold" : I don't get it, what is this "0.3 units" ? Do you have some kind of feedback I don't have, when it comes to UnderExtrusion sensor error ? Maybe it's in the LOG file ?

 

I really really often face this under extrusion sensor trigger... Be it with PVA on BBCore, or PETG / PLAtough on AACore, when I print "fast".

[PizzaTijd 14]

You might want to try turning the maximum amount of retractions down, or even try turning retractions off completely just to test.

When and how the feeders grind into material can feel a bit random sometimes - but I've found that it helps with materials where the feeders really like to dig into it (mostly TPU on my end).

The moment that the feeders dig into filament enough will also be the moment that your printer will start showing you the flow rate error.

[Torgeir 264]

Hi @madest,

 

Printing with this type of filament means we are in "experimental" mode. Nylon with 20% added chopped carbon fiber is one of the strongest filaments we can find. Normal print temperatures are: 280 deg C., - to max - 300 deg C. As you say you print with the highest possible temperature, how high a temperature do you use? In your case, you should take a closer look at the cooling fan in the front, which should cool both sides. Like @gr5 said, the cooling fan must be working and in your case it's very important. Also make sure that there is no collected filament "strings" in the inlet side of the fan.

All of what you're describing pointing to the cooling of the upper part of the nozzle.

 

Are you using any support filament during this printing?

If not, you might be able to improve the air flow "a little" to core no 1..

 

Thanks

Torgeir.