Filament extruder always knocking when printing

My printer’s filament extruder always knocking when printing. And I am getting models with lines of air, “dry” layers where the filament seemed like sand, and weak adhesion of layers.
It’s the same problem as Filament Oiler/Filter
I also tried the Universal Filament Filter
But the knocking still happen.
Is there anyone out there experiencing same problem?
Or can someone give me some help.

What stopped my knocking besides the oil/filter. I 'm using an external filament holder, I bought the hatchbox one from Amazon for $10.00 and the knocking went away. This worked for me.


@pmbroth, to clarify, do you mean just changing the filament supplier to Hatchbox stopped your knocking?

Actually I don’t think the knocking problem can be solved by using external filament holder.
Once I put a little pressure on the filament to force it feed into the filament extruder, then the knocking noise JUST disappear.
This is strange when I have used oil/filter.

I believe the angle which the filament is feeding into the flux changed, so that the filament is being fed at an angle that is aligned with the feeding mechanism. All I know is that I do not get knocking using the external holder at this angle. I also believe that there is less resistance on the spool so that it turns easier than being at the horizontal position in the machine.


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I also have similar experience with external holder, the feed angle, the friction of spool have an effect also, as @bmw760liamd mentioned, slightly pushing in the filament stops the knocking. Presently I have occasional knocking when the speed is around 50-60mm/s. The problem could be due to gear teeth skipping or maybe under powered stepper motor. It can also be due to stepper motor thermal shut down, related to occasional heavy loading ( ). Hard to say how hot the stepper is running since the top is covered.
Does anybody have an idea which screws are holding the top cover? I see 11 screws but some may be holding the sensor and USB connector. Is there a drawing or instructions somewhere on how to take the top off?

Be careful, remove the printing plate and the print head and bars. When you remove the screws, carefully turn over, and lift the top, there is a cable attached so be careful

B rian

Thanks, so there is only 5 screws holding the cover. I will wait until the knocking gets more frequent, my intention is to attach a thermocouple to the stepper to monitor the heat. I have another home assembled 3D printer, its stepper gets really hot and attaching a heatsink to the motor helped that case.

yes only 5 holding the cover. I had to replace a board they sent me and that came from their instruction. sheet.


Did you take a picture of the inside while the top was open?

In the doc they sent me here is the only other pic,

Found this in one of the topics

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So do you think my problem caused by filament feeding angle? Or is caused by heating problem?

How fast are you printing? What you describe appears to be underextrusion. That happens when you try to push more filament through the nozzle than it can handle. Have you tried to print at a slower pace, and has that made a difference? Also, you can print at a slightly higher temperature. What are your slicer settings?

I spent a lot of time watching my printer when having these exact issues. The knocking for me was caused by resistance in feeding the filament through the extruder. I took the bottom apart and removed the brass nozzle and my nozzle was defective (the aperture was not centered on the interior side) causing resistance which resulted in the feeding mechanism rightly skipping.

My issue resulted in the same under extrusion at some times during printing but not others as it seemed to manage to feed smoothly enough to succeed when printing at certain speeds.

Worth checking for a clog or a problematic nozzle.

I have that knocking problem too.
Tried a lot of things and some did help a bit (like moving the external spool holder on top of Flux to feed in a better angle) but still there are some point in the printing process when it’s knocking.

I put the plastic down where the stepper motor is on top and watch how the filament is coming in. It knocks when the filament is pushed back in then in again. At the point when it’s pushed in, it knocks.
What is the main reason for this? How to solve it?
I tried with different temperatures, filament angles, bridged the switch there too.
Even if I push it in, it sometimes knocks.

Thanks for all these tips. I’ll try them tonight and give you a response.

My printer was running with the top off for about a year, and with the filament sensor bypassed, and that was working fine. I did that to be able to print flexible filament at the time (ninjaflex and filaflex).Today, I installed the extruder upgrade (that should be able to drive flexible filament) and reinstalled the top.

And I had that knocking noise ! A lot of them. And inserting the filament was a pain. And one print had the filament completely blocked.

So I removed the top again, re-shunted the filament sensor, and I’m back printing.

My diagnostic is that the plastic part with the filament sensor has a wrong angle.

I might put the top back in place at some time in the future, but without the the filament sensor and support.

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lucky you, sensor or no sensor I get extruder knocking at speeds between 50-60 mm/s

did try loads of things (like chabging ptfe tube, temperature,…) nothing really helped, so now I print at max 45 ish mm/s

I noticed recently the the flux precision seems to suffer quite a bit at somewhat high wall speeds, about max 30 mm/s seems ok.

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I’m getting that issue. Before all this upgrading, the printer worked great. I was getting nice prints every time. I only upgraded with the hope that maybe it’d get even better, but it went downhill from there. I’ve actually removed the stepper motor and let the printer go as if it were printing. After just a short amount of time, that knocking noise starts. Looking at the stepper motor, it’s like it gets hung up and won’t continue to rotate. It will process faster rotations and turn, but once it gets down to the slower continuous feed, it starts skipping. Putting it back together and running filament, it loads and prints up until that certain point then it just stops feeding filament. You can press down the lever and push filament through seeing it come out from the extruder, but the stepper stops feeding it. Any solutions to this yet? I had set the machine aside until new upgrades occurred thinking that would help it, but it didn’t do a thing for it.