PLA does not flow through extruder, if it does, flow is not uniform

I am using the k8200 software of repetier:

with the pretty much the same configuration as in the post

For PLA, I got the one from velleman:

When I got stumbled to the 1st problem that PLA does not flow smoothly:


I’ve played with the temperaturs from extruder (190-210C) and beds (50-60C) without too much luck. I also played a bit with the screw that fasts the PLA, not too much luck… And it looks to me that there’s not enough “push” for the PLA to go out…

May sound strange but try making the screw looser.
Check the screw that holds the small pulley on the motor make sure it’s tight.

When the extruder is heated, are you able to push filament through by hand? You should feel some resistance, but you should be able to get a clean bead of plastic if you rotate the large extruder gear by hand, or push the filament down into the hot end.

Does the extruder work if you raise the print head off the table? If your Z calibration is off, the nozzle can end up too close to the bed and the plastic cannot flow out smoothly. (I usually adjust the first layer height by turning the Z axis by hand while the skirt is printing.)

The extruder mechanism can get bound up if it is not assembled carefully. As I recall, I had to loosen the major bolts through the assembly and square it up carefully before re-tightening. As Wrong_Way points out, you want it to be bolted firmly, but not too tight.

Hi @Wrong_Way and @Dr_Vegetable,

thanks for the posts and encouragements.

It would be cool to get a better understanding about the k8200, extruder, dynamics, anything and everything.

To answer immediate questions: (1) The extruder does not let the PLA flow independent, if I raise the head off the table (1cm or more). (2) if I push the PLA somewhat forcefully, then it goes through, but of course, after some time everything stops. I’ll be experimenting with all the bolts then.

As I assembled the extruder, I really carefully placed the motor into the place, so the rotation is smooth but also the freedom/leeway between the cogs is as minimal as possible. After the complete assembly, interesting phenomenon was observed: for a complete rotaion or so, it was very easy to rotate the large cog, then it was a little bit harder.

Can you also have a look at the pictures if everything looks suspicious to you?

Which bolts should I play with (make tighter/looser)?


Try backing the motor away just a little so the gears are not to close to each other.
Just to see if anything improves.
Also just wondering are you sure you are using PLA (should smell kind of sweet)

A few things to check:

1.) Make sure the set screw in the small black gear is holding the gear to the motor shaft without any slippage.

2.) Make sure the two aluminum plates are parallel and aligned with each other. I found it worked to slightly loosen the nuts on all of the thru-bolts, then carefully move the plates around to make sure the plates align, and all plastic parts between the plates are correctly positioned and flush. Then tighten it back up, firmly but not over-tight. Try to torque them all down with the same amount of force. (It is difficult to see when things aren’t right, but not so difficult to feel it.)

3.) Inspect the knurled bolt where it grips the filament to ensure that it isn’t clogged with bits of plastic. (This is the bolt that passes through the center of the large black gear.) Make sure the nut on the knurled bolt is not too tight!

1 Like

Hi @Dr_Vegetable and @Wrong_Way,

Thanks for the updates. I’ll revisit those one more time tomorrow (as things are getting towards the night in Europe).

Update from my side: I’ve took the extrude apart, and realized that the PLA inside have bent, therefore, the big cog was not able to push the PLA downwards. I’ve took the bent part out, reinserted the PLA thingy, and enjoyed the movement as the cog moved. I’ve restarted the job, and the PLA was moving for a while. Afterwards it stopped again.

Let me come back to you tomorrow.


Could you post a video?

capital idea. Takes me forever to learn how to do it. Cause I do it with my phone, then upload to my computer , then reduce the size, then upload to youtube. Took me forever, hopefully, I’ll get faster with every next day:

1st video: (just restarted the job after the “clean up” yesterday)
2nd video:
3rd video:
4th video:
5th video:
6th video:
7th video:

heat dynamics of the last video

It says the video is not avaliable

forgot to push the “publish” button. Videos are on their way

Well, I have uploaded the videos. I’ve checked some of those, the quality is not perfect. I’ll reupload the full HD version of them tomorrow. Will be faster/beter from work. Upload connection from home is horrible (in Germany)


I have reaploaded the videos in HD quality:

From what I could see the motor is not turning at all.
The easiest thing to check would be swap the extruder driver from the X or Y to the extruder.
this is to see if the problem moves. next check the wiring to the extruder motor.
Make sure it is correct and there are no bad solder joints. since it started to move but then stopped and the bed running into the wires it kind of looks like a failing solder joint on the motor side but you should check them all.

Thanks for the tip. I really like the idea of swaping the extruder connection with the Motor X one. I suppose, if I press the HOME X button, that would be a way to test it, wouldn’t it? Is there a way to issue extruder motor command (something like: rotate clockwise for 5sec)?


1 Like

No not the connection.
Swap the driver board.
The one that you set the reference voltage on.
All 4 of those boards can be unplugged.
When you put it back in the board make sure the orientation is correct.

Hi @Wrong_Way,

Thanks for the nice picture and the clarifications. I’ve reconnected the extruder to the Z motor, and press go up/down (the PLA was heated to 190C):

Now that you mentioned, I remembered (, page 30) that once I’ve tested all the motors (PLA was not in), the motor of the extruder was working

Ok this just tested the motor.
Now you need to put everything back and swap the drivers.
Also did you adjust them to 0.55?

I did 0.5. I’ll increase it to 0.55 then. I’ll also resold the extruder cables just to be sure.

Even if I have a bunch of screws, it is bloody hard to get to the value around 0.55. What’s the tollerance there? Is it ok, if one motor has 0.555, and the other 0.547?




Are the soldering cables correct (page 339 and 372 from the asembly manual)?

Update: increase to 0.55V somehow made the printer to ignore the Y stopper. Can that be possible?

Should anything there be changed?


The wires are ok.
When you swapped the connectors and made the extruder run that was the proof.
You need to remove the driver card from the control board and swap it to the X or Y axis.
This is a picture of it off of the board.