Knocking sound in extruder 1 during retraction

[kmanstudios 1,120]

This is something that just started happening, but during retractions on print core 1, I hear a knocking sound with each retraction beep. It is not there during the print core 2 retractions. I am doing a lot of prints right now that have a lot of spot details and I did a series of actions to remedy this last night to no avail. I have also had some issues with grinding. I had heard the sound before, but thought it was the filament pulling on something in the back. My filament rolls are too large sometimes and I let the guide hang and allow the gravity to help with keeping the filament from pulling oddly. So, I did think at one point that it was the feeder guide being pulled into the table top. But I have a standard roll on the spool holder now and the feeder guide is mounted as usual.

1. Took feeder off the back of the printer for print core 1
2. Cleaned the heck out of it.....Brushed off the knurled wheel. Could have made a sandbox with all the ground up filament in there, mostly from the raw plastic edge where the grommet use to be.
3. blew out the bowden tube as it did have a lot of dust
4. I lost the grommet on that feeder a while back so I printed a replacement to smooth the entrance into the feeder housing. It had really ground up the edges of the entrance to the feeder.
5. Did hot and cold pulls
6. Reset the core by removing and reseating to make sure it was not loose in the printhead

 

All of this improved the feeding of the filament, but still has the knocking sound. I am doing a test print without the major retractions right now and if needed, I will make a recording of the knocking sound. But hopefully someone will have an idea of what I am speaking.

 

Edit: I did print out a 'grommet replacement' to smooth out the transition from outside the feeder box to inside the feeder box. Just something to help it not catch edges and guide the filament without grinding as before. Here is the grommet replacement I made for that.

GrommetReplacement.STL

Edited January 11, 2018 by kmanstudios

[geert_2 558]

I do not have an UM3. But a knocking sound seems like some play somewhere in the system. For example screws of the stepper motor coming loose, or something similar. Or something loose in the nozzle.

 

Have you tried removing the bowden tube, but leave a little piece of filament in the feeder? And then manually move that piece of filament up and down? Next, idem for the nozzle: manually dial up temperature, manually feed a bit of filament, and manually retract it? Then Maybe you could feel where the problem is?

 

[SandervG 1,521]

Is there any difference in feeder tension or filament diameter between feeder 1 and 2? 

[kmanstudios 1,120]

4 minutes ago, SandervG said:

Is there any difference in feeder tension or filament diameter between feeder 1 and 2? 

Maybe on the dimensions...but it is polymaker or colorfabb PLA/PHA. Why the confusion? Well, it is a clear spool with no branding on it.....Grrrrrr......

 

Been playing w3ith it. I am thinking I may have to swap out a core to see if that alleviates the problem. I am doing test prints and they seem crappy all of a sudden too. I was getting perfect prints before, and without priming tower! So, I will have to endeavor to persevere.

[kmanstudios 1,120]

You know, now that I think about it....this print core has been working solid for almost 7 months straight......when I took it out, I did notice that it seemed to have some slop in the way the top tube would move when pushing on the tab.

 

 

Edit:

I am thinking that changing print core should be top of the list for checking. I do have a new AA core.....

 

I also did some printing with fillamentum's glittery filament. I was told it is not supposed to be abrasive, but.........

Edited January 11, 2018 by kmanstudios

[kmanstudios 1,120]

Ok...changed the AA core out, printing a test box and getting really pretty infill, even with the default cura speeds for infill.

 

I have a print with a gazillion retractions in it so I will be able to tell if all this worked out or not. But, I can say that before changing the core, I was not getting this nice of line.

 

I think it is one of those things that as the months go on, the nozzle may be wearing out. You do not see it because you sort of adapt to it over the slow time period involved. But, we shall see.

 

I will have to go to @gr5's youtube channel and checkout how to change a nozzle in a standard core. I have a few spare 0.4 brass nozzles. I wonder if it was the nozzle or the whole core. Actually, I wonder if I fixed it or not......

[kmanstudios 1,120]

Well, changed the nozzle and the knocking sound is mostly gone now and getting good extrusions. But, it is still there. Unfortunately my hearing is not that good and I cannot tell if it is coming from the printhead or the feeder box.

 

What specifically should I look for via the parts that may be loosened?

[kmanstudios 1,120]

9 hours ago, SandervG said:

Is there any difference in feeder tension or filament diameter between feeder 1 and 2? 

Diameters are the same (should be but I do not have calipers to check it) and the feeder tension is restored to a normalish mid position now that that I have implemented the previously mentioned maintenance on the feeder box.

[exforma23 12]

I have a UM3 ext. Recently, I have also been hearing a knocking sound. On my machine, the sound is from the knurled feeder wheel slipping and grinding the filament. This is especially pronounced while doing infill layers. I too will be looking into changing the nozzles. Are the UM3 nozzles sold anywhere? I have hardcore nozzles but I’d like to find ones with the little rubber o-ring just like the stock ones. Also,  have a Bondtech DDG kit on the way to help with this problem and chronic underextrusion with infill.

[gr5 2,230]

The nozzles are not sold anywhere.  UM considers cores expendable.  I believe they make almost no profit on them (not sure though).  The nozzles are standard M6 thread but much much longer than the UM2 nozzles or e3dv6 nozzles.  So, no.  I don't think anyone sells them.

 

Well infill layers tend to be done at a crazy speed.  Cura I think decides to print so fast that you get some underextrusion or slipping.  I don't like that personally so I set infill speeds to the same as the other printing speeds normally.

 

Is it possible that you printed CF filament or glowfill filament at some time in the past?  And now the gnurled sleeve of the feeder wheel is no longer pointy and is now smoothed out a bit by the filament grinding the points down?  Just a thought.

[exforma23 12]

It feels like such a shame to pitch the entire printcore. However, I'm a user that would prefer to spend more time printing and less time tinkering. So, I suppose that I should get with the program and replace a printcore or two when needed. Although, I'm pretty sure that's not my trouble here.

 

This is what brought me to this thread. 

 

I have been happily printing for almost a year with no trouble. The problem that I now have is a large shape with a lot of infill relative to the amount surrounding wall thickness (see photo)

 

The feeder wheel is shiny and new like the day it was born. So, I can check that off the list.

I cleared out the feeder. 

I did about 10 cold pulls to clear out the nozzle (after it got pretty mucked up) so I'm confident clogging is no problem.

I also removed my filament from my dry box (I though the dry box was adding friction to the works) and let it feed off the spool holder.

After doing all this the print failed quicker than ever before with a PLA print (the one in the photo)

 

I will say that I have always seen under-extrusion on infill layers. Usually, this is a fairly short duration of time before it moves on to wall or next layer. So, it doesn't lead to grinding. On this particular shape the first few solid layers are perfect. It's when the infill starts that I see trouble.

So, I believe that the knocking and grinding is caused by the feeder wheel just not able to keep up with the faster speeds on infills. I will crank up the tension and see if that helps.

 

Other than that, I have high hopes for the Bondtech DDG kit

[gr5 2,230]

I agree with all your analysis.  This all makes sense.  Consider lowering the infill speed and using the "gradual infill" feature in cura to save time overall (faster print, less underextrusion).

 

Anyway for setting tension with PLA, the example on the left is not tight enough.  The example on the right is too tight at the feeder.  Either condition can cause filament to grind up and cause a print to fail particularly when you have lots of retractions (sometimes on a retraction heavy print the same point of filament might go back and forth 30 times through the feeder)

 

 

[kmanstudios 1,120]

I have to admit I am doing super heavy retraction prints like this:

It is like printing lace.......

[exforma23 12]

So, I slowed the infill rate from 70mm/sec to 50mm/sec. Bumped the PLA  print temp to 210 C. Slightly increased the tension at the feeder. 

All appears to be well. No more knocking and grinding and the infill is nice and robust.

[exforma23 12]

2 hours ago, kmanstudios said:

I have to admit I am doing super heavy retraction prints like this:

 

It is like printing lace.......

Holy Cow! That looks tricky!

[kmanstudios 1,120]

8 minutes ago, exforma23 said:

Holy Cow! That looks tricky!

I have been pushing the limits of the machine since day one.