Can you tell whats going wrong from this photo?

Printing with the printer shown in my Avatar.

Approximately 1,700 hours on the printer
This is a 5 hour print.
PLA
3 Processes......Process 1 = 0 - .3mm Process 2 = .3mm - 12mm Process 3 = 12mm to end of print
Max movement speed 2700mm / min.
Temp 190C /Bed 60C

The print starts out fine. About 50-75% through the print (or approximately 3-4 hours into the print....it starts getting little "lint balls" of filament.
That progresses until it's just a total mess.

I completely disassembled the extruder hot end, thoroughly cleaned all the gears and the nozzle and checked it. Installed a new teflon guide tube. Reassembled. Flowed like a champ immediately after reassembly. I thought I was good to go.

However after starting a new print, exact same same thing.

Here's one clue......when the problem starts...if I end the build and if I immediately go to "LOAD Filament"....the filament does not come out properly. It's as though it's clogged again? Very little filament comes out.
This is obviously what's causing the print failure...but what's causing this apparent clogging?

My guesses......
1). Power supply is dropping power to the nozzle heater.
2). Hot end heating element is going bad.
3). Stepper motor for hot end is going bad

Attachment 11146

Well,
I apologize to anyone in the future who finds this thread because they have the same issue. I was hoping more information might be posted.

Through further investigation, I have found that the other extruder assembly (Right Extruder) prints the exact same x3g file flawlessly.
So at least I can rule out any problem with file itself and confirm that the issue is somewhere in the chain between the power supply and the Left extruder.

I did a quick check of the coils on the Left Extruder stepper motor by checking the resistance of it's two coils, indicated by the set of orange arrows and the set of green arrows in the photo below.

The resistance was 6.9 ohms on both. For comparison, I checked the OHMs on the stepper motor on the RIGHT Extruder and found the coils resistance to be 7.3 and 7.4 ohms respectively.
Since the resistance on the stepper motor coils on the working extruder were slightly higher than the values from the stepper motor on the non working extruder, this preliminary test suggests that it may not be the stepper motor.

What I really need to do is run the stepper motor for over an hour to simulate the conditions during a build and monitor the temperature of the motor.

Attachment 11151

Note that the front panel indicator for the temperature of the Left Extruder hot end showed normal and stable temps on the malfunctioning extruder during the build.....at least during the glances I made. However, it's very possible that at some point the temps dropped but I didn't see it. Too bad there's no temperature alarm. So at this point I do not suspect the thermister or heating element of the malfunctioning Left Extruder.

I'm leaning towards a power supply issue or Left Extruder hot end failing.

Anyone? Please?

Are you using a PTFE lined filament Throat.

If so I would say that the PTFE is deformed causing low filament extrusion.

Roberts_Cliff
Thank you for the reply ! Was getting really lonely in here all alone.

In the posts above I mentioned replacing the PTFE tube in the malfunctioning extruder with a brand new one but that did help.

Still....nice to have a reply ;)

Missed that somehow. "Installed a new teflon guide tube" thought this the tube leading to the extruder!

Have you checked the Stepper current, is the Spring tension weak.
Do not know if this applies, thou on my printer when I was using a new slicer and somehow it managed to change the configuration, in order to correct the problem.
I had to restore firmware settings using M502 "reverts to the 'factory defaults" and M500 to save the 'factory defaults'.

I feel your loneliness. diy forums all over the place seem to be dying :(. Unfortunately, I don't have the knowledge required to help you with your problem.

Although I doubt it's the stepper motor, and if you think it is, the obvious thing is to switch it with the other motor and see what happens. Then try swapping the drivers to see what happens. What would the filament cost be to run those tests? 3 to 4 hours into it, wow. Such a random thing.

I don't own a filament printer, so like I said, I don't have this specific knowledge to help you. What does a new print head cost?

Heat creep causing the filament to soften and then the extruder motor failing to push through reliably?

I had some poor filament that was causing the extruder hobbed gear to become clogged, which then led to the odd failed print.

Have you thoroughly cleaned the extruder drive? Use a craft knife to clean each spline fully, scrape any residue from the idler and lightly oil the bearing. Try changing the nozzle and again, scrape away any burned residue.

I doubt the stepper has gone bad and the difference in resistance is very small. A failing heater also sounds unlikely, as this would manifest itself in slow heating.

My experience is that most failures are mechanical, followed by cable faults. Even the bargain basement parts used by many manufacturers tend to last quite well and failures tend to be total rather than partial.

Have you used the same filament in the other extruder as well? Otherwise you are not ruling out issues with the filament.
Some cheap filaments start to bead up above certain temperatures. Rather than a continuous stream they become stringy with the occassional bead.
Also it can be containing too much water - look if the extrudate contains small bubbles or steam develops.