Constant under extrusion and filament grinding

Question

I sadly have a big problem since a couple of weeks and I cant fix it myself. For over 20 prints, I had the same problems: At the start, everything goes well but at some point of time, my Creality CR-10 starts under extruding and after like 1 minute, NO filament is extruded anymore and the 3D printer moves over the printing bed without extruding anything. After that, I have to pull out the filament and the feeder always grinds into it.

Some problem with the hotend (so the feeder works well but it cant push the filament through somehow - I cleaned the nozzle and couldn't find anything wrong there. When I push the filament through by hand it gets extruded but after a failed print, it is VERY hard to pull it back (because of the filament being slightly bigger at the nozzle - hard to remove! -

That could be the problem:

I just tried to remove the filament from the printer (another failed print) I had to use two tongs because the filament was so hard to pull back. I noticed that the diameter of the PLA close to the hotend was a lot bigger (way over 1.75 mm) For about 5 cm that's a very long distance - that's the reason why it's hard to pull back (and also push through?) But I don't know why that happens... If I get an answer for that, I think that I have solved my problem

I already tried printing at 50 % which didn't work.

• Creality CR-10 with 0.4 mm nozzle,
• 1.75 mm PLA filament used (white)
• 0.27 mm layer height
• 45 mm/s printing speed at 220° (I can easily push the filament through at 200° by hand)
• 60° bed temp

And here some pictures of the failed prints:

I think I can exclude these:

It could be: (the things I can imagine but don't have a solution for)

• The feeder being too strong/my new PLA filament being too soft
• Maybe a software problem? I'm using the newest Cura version and I don't know what could be wrong there.

The filament seems to run out of the hotend. Something is really broken here. I tried to lower the print temperature and don't have an issue (at least not that big) with pulling out the filament but instead, the feeder started grinding into the filament again.

I'm very happy for any answer and possible solutions.

Answer 1

Grinding is due to attempts to advance filament faster than it can be melted and dispensed. Try one or more of the following:

• Raise the head temperature (to meet current throughput demand)
• Lower the print speed (to reduce throughput demand)
• Slice for thinner layers (to reduce throughput demand)

Answer 2

I have had this problem for several reasons. I can not say what your reason is, but these have been mine. From your symptoms, I suspect the first problem, but I've listed others in case they are helpful

1. I had this problem to most with a "Thing-o-Matic" printer. The problem was that there wasn't a clean enough break between the heater and the filament. To fix this, I added a fan on the metal tube above the melt zone. When the filament was sitting, it would soften and expand. It was then harder to push, and it would cause these vertical strings like you have in your picture. The Thing-o-Matic extruder was direct rather than Bowden, but the same problem could exist. I see that the CR-10 has a fan attached to the extruder. Be sure it continues to run, and that the airflow cools the region right above the hot-end, even when the head is an inch above the bed.

   One more thought on this topic: retracting pulls filament out of the melt zone into the space above the melt zone, bringing the heat with it. Lowering the retraction settings may reduce the heating of the space above the melt-zone.

2. Bad connection to the heater, so that the temperature drops while printing.

3. Too much pressure on the filament by the extruder pressure roller. One pass through is fine, but a pattern of short extrusions with frequent retraction caused the filament to pass repeatedly through the roller, and become flattened so that it had difficulty feeding through the rest of the mechanism.

4. Jammed filament on the spool, preventing the extruder from smoothly pulling.

Some other problems which could cause this, and I have looked for but haven't been the problem in my cases:

1. Weak power supply. Check the +12 or +24 voltage while the problem is occurring.

2. Overheated or defective extruder driver chip that fails to drive one or more stepper motor phases with sufficient current. This can allow good behavior much of the time, but if anything happens that adds load to the motor, it can stop turning.

Answer 3

There are many reasons why that could be happening. The simplest one:

1. The nozzle may be clogged/has debris. Push the filament down into the hot end with your hand to see if more force will cause a better flow rate. Also, if the filament tries to curl as it's coming out of the nozzle (in any direction) there is is most likely a blockage in the nozzle.

2. There is a gap between the teflon tube and nozzle, resulting in a larger melt zone which makes it harder to push the filament through.

3. The extruder cooling fan isn't working which allows the heat to travel up heat brake, extending the melt zone.

4. The extruder gear may be dirty with plastic debris/dust/rust. This will cause slipping. The fact that the print starts working but then fails seems to indicate that the problem is progressive, indicative of slipping.

5. The motor is under-powered, resulting in step loss and a cumulative error during printing.

6. The filament is poor. Voids and inconsistent diameters used to be a problem that caused print fails long ago, but not so much these days.

7. The stepper motor drivers are over heating and shutting down intermittently during printing, resulting in cumulative errors. Use a house fan/ or other suitable fan to cool the board. I had one Anet A8 mainboard die on me due to over heating.

Answer 4

Under-extrusion after some time printing sounds like heat-creep. If the cold side of the extruder is getting warm, even up to 60°C (the glass transition temperature), then the un-heated filament will start to soften and fill out to block the tube. As this happens, there is more pressure above the hot-end and less extrusion (but even more force to make the situation worse).

The best solution to this is better cooling of the extruder/stepper, and a good heat-break with a sharp transition between solid and well-melted (but something has presumably triggered this failure on your setup, rather than a fundamental design problem).

Other things you could try are:

• Less retract distance (to reduce the variables)
• Lower print temperature (and speed, but this will increase pressure in the nozzle)
• Reduce the extrusion multiplier (if your filament is a bit thick, the pressure might be a bit high)

Answer 5

A 0.27 mm layer height is not correct for any printer, any nozzle/hotend, any file, and should never be used as a layer height variable for any FDM printer.

Layer height should be a factor of the diameter of your nozzle size. i.e. Your nozzle is 0.4 mm, so depending on your printer, your range of resolutions/layer heights could start as low as 0.04 mm, but is monumentally more likely to begin at 0.08 or 0.12 mm, with a maximum value being 0.28 mm, and maybe 0.32 mm if you're doing some risky/experimental spiralized vase printing.

Answer 6

Sadly, this isnt true: "I finally found the solution! It was the spring being slightly too loose at the feeder. That was it. Such a small thing. I thought that I checked it at least twice."

I bought a new Hotend for my 3D-Printer. I hope that solves the problem. I think that the PTFE Tube doesnt sit tightly on the nozzle so that some filament leaks through. And maybe the fan doesnt work properly. At least I can say that the problem is the Hotend. -the cooling of the filament I guess. Thats because the filament always became larger near the nozzle because it melted. That's also the reason why it was so hard to pull out.

Answer 7

Fixed this by replacing the hotend.