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mariem

So much grinding!

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Hey guys!

I'm back with more question,

I use to have literally no issue with my printer, and then slowly started getting grinded filament once in a while,

then the fan issue (loose connection), got myself a new fan, pm_dude was nice enough to install it for me.

Nozzle was now clogged, unclogged it twice. And since then all of my print fail because of grinding issue.

Any idea why I am having so many grinded filament issue?

Some people suggested me to print a new feeder (https://www.youmagine.com/designs/alternative-um2-feeder-version-two#!design-information)

but I'm not even sure I'll be able to print it since it usually fail quite early in the print.

Help?

 

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1) Some people have grinding issues due to the feeder servo getting too hot and softening the PLA. Especially in warm climates except that you are currently in a cold climate, right? Anyway some brands of PLA are much softer. Did you change filament recently?

2) Another possibility is that you are getting near the end of your spool and the curvature of the filament makes it difficult to get through both the bowden and the isolator inside the head.

3) With the recent firmware change in Marlin (have you changed firmware before the grinding started?) there is a change in the temperature stability of the nozzle. When the nozzle gets too cold you can get grinding.

I have a few other theories but these 3 seem most likely.

 

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1)

my appartement is really not too hot in any way (it's usually around 20C inside and the printer isn't close to any heating source.) I had grinding issue when using a colorfabb filament so I just changed back to a filament I got directly from the ultimaker store (those are the one I used at the beginning when I had no grinding issue) and still It just chewed my filament right away!

2) I was close enough of the end of a spool when that happened so I just changed for a bring new one the other day and still had that issue couple of layers in. The spool is pretty much full!

3) About the firmware update I did it yersterday.

I had grinding issue so I figured I would do the firmware update in case that might help and.... grinding still, I'm quite lost.

You say there is an issue witht he firmware?

4) all 3 of them seem to be working fine. Also just got my back one replaced.

5) I dont know, haven't notice that kind of change in the filament.

 

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When I had that same issue, I took apart the hot end and found plastic stuck to the Teflon fitting around the rim and it was also deformed. This caused the entrance to the nozzle to shrink and the filament could not get past the fitting.

Heating up the nozzle did not work.

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Chrisp, You mean that no filament came out at all anymore? when you heated and move the filament?

because if this is the case its still working fine on my side most of the time. when I move filament I still get a nice string of filament (until it grinds)

 

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I am a brand new UM2 owner and have made half a dozen very nice prints the last couple days. Then I decided to do a "torture test" kind of print of a dodecahedron chain. Print should have taken 6 hours, but after an hour the extruder was failing due to grinding of the filament. Tried increasing the extruder tension, but got another failed print. Then I realized the part was doing an excessive amount of retracts. The constant retracts were chewing up the filament to the point it would no longer feed.

I went into the advance settings in Cura and changed the retract minimum from the (apparently) default setting of 1.5mm to 5mm. Now I am re-running the print and it is performing much, much better. There is a slight amount of stringing in a couple of places, but the reduction in the amount of retracts has allowed the print to succeed without grinding.

So much to learn.

 

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IMHO the pressure of the drive teeth on the filament come into play on the retraction point. If that is what "increasing the extruder tension" means then you probably want to reduce the tension not increase it. Anyways I had a similar problem a couple of months back and reducing the pressure did the job for me; I am assuming that it is adjustable on the UM.

 

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Yellowshark, thanks for clarifying. Yes, once I realized retraction was grinding the filament I went back and loosened the extruder to the original factory setting best I could. My last print with the reduced retraction settings made it much further along before grinding.

I saw another post where it mentioned that lots of retraction over time will allow heat to build up in the colder part of the hot end and the filament can soften causing extra resistance, and subsequent grinding. This does not appear to be the issue with the OP's extruder, but possibly mine. Guess the final test will be to completely disable retraction and see what happens.

Thanks for your help.

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Chrisp, You mean that no filament came out at all anymore? when you heated and move the filament?

because if this is the case its still working fine on my side most of the time. when I move filament I still get a nice string of filament (until it grinds)

 

Yes, that is exactly what I meant. If you still have filament coming out then this is not your problem.

 

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@u2fletch - it's great that you narrowed down your issue and have a work around but I've done a 30 hour print with 109k retractions (that's half a kilometer!) no problem. So eventually you might want to figure out what's going on - I suspect the extruder motor is hotter than mine.

@mariem Chrisp's comment implied that "this is not your problem" but it could still be contributing. I still recommend you try taking apart the head as he suggests. Also:

1) Do you have lots of retractions? As u2fletch says it increases the risk of grinding/flattening even though my printer is fine.

2) I still recommend removing the back left cover (only 2 screws) and blowing a window fan on the feeder from the front of the machine - it makes a huge difference for some and narrows down the problem so we don't have wildly varying theories.

3) You possibly do have some kind of partial clog or restriction in the nozzle or head so taking it apart would be wise as you might learn something. Particularly consider burning out the nozzle with gas flame so it's once again nice and clean and consider sliding a piece of filament through the white section (the isolator) to see if there is any resistance there. If so you can order a new one or simply drill out the existing. The isolator tends to get deformed after many months of use.

 

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I don't really know how to know if my print required a lof of ''retraction'' I was printing very simple stuff recently. something that look like a flower pot. So basically just a cylindrical shape. My minimum travel is 1.5

and minimal extrusion before retracting 0.02 I think those are the default setting

Once again I'm very not a very ''handy'' and manual person and I'm really not comfortable about having to do so many maintenance and stuff like taking the head and nozzle apart all the time. :(

I'm currently wondering If I should sell the machine to somebody that could get a use of it better than I can...

 

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Update,

Once again I had help from the very generous pm_dude.

He installed me a new feeder to help my grinding issue.

He also checked my teflon piece wich was fine and not burned, deformed etc.

He also blow torch my nozzle.

The nozzle long screw (or whatever that is) cannot be completly removed tho (pm_dude had the same issue on his)

Will need to get it replaced at a later date.

So far the machine did a full print without grinding. I'm hoping this has fixed the issue.

 

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Hi Mariem,

Could be a multitude of issues unfortunately. You'll generally get grinding if:

 

  • Your nozzle is starting to clog, so that the feeder needs to push harder but can't and instead grinds into the filament:
    Solution: Try to print an underextrusion cone, you can find them on the forum. Also try the atomic method to clean your nozzle.
  • Your teflon is deformed, so that the same thing happens
    Solution: Open up your head and inspect the teflon, replace if needed.
  • You do a print with alot of retractions (the material is moving back and forth alot)
    Solution: Tinker with your retraction settings
  • The material you're using is too soft
    Solution: Try a different brand of material, or a different type
  • Your feeder axis becomes too hot and heats the filament, which then loses stiffness and gives way
    Solution: Put a fan or it, or try a feeder design with a gear reduction

 

And if you're unlucky:

 

  • A combination of the above
    Solution: Reserve a sunday and stock up on pizza :)

 

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Yes the set screw on the nozzle was very stiff. I managed to unscrew a few turns but didn't manage to remove enough to free the sensor (heater got out ok). I would have replaced the nozzle if I could but didn't wanted to have to use vise-grips to take it out like on mine.

We did blow a butane torch a little but didn't wanted to damage the sensor so that was very light.

Hope it will last more than a few prints.

Side question: How much should one expect to get a clean/ get the dark stuff off the nozzle when using a torch? That one has only printed PLA.

 

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I've done a 30 hour print with 109k retractions (that's half a kilometer!) no problem.

 

Can you post your retraction settings, and any modifications to your UM2? I've just gotten started with mine and I am having the same issues with grinding during prints with retractions (and even on some without any), and with the filament and/or knurled wheel slipping off. I plan on printing and installing IRobertI's feeder this afternoon and seeing how it work. Also I will try messing around with retraction settings.

 

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Hi CCW1984

I was using (and still am) using the default retraction parameter. (My minimum travel is 1.5

and minimal extrusion before retracting 0.02 I think those are the default setting )

Since the new feeder and the cleaning of the nozzle I haven't had experienced any issue yet, I'm hoping this fixed the issue.

Here my 3 latests prints, pretty much 25h/each printed one after another, no issue

image1 (2)

 

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Those look great! And I'm glad it appears to have fixed your problems, hopefully it will work for mine as well. I was actually wondering what settings @gr5 is using though for his 30h long print with 109k retractions. I'm wondering if he has the stock feeder or perhaps IRobertI's upgrade. I think for something like that I would also put a small fan blowing on the feeder from behind to hopefully keep the shaft cool.

 

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Hi everyone, would you be able to advise as to the best way to remove filament that has been caught inside the material feeder due to grinding? It looks like it's ground to a point where trying to pull it out with pliers does not work.

Taking the feeder out is a big hassle each time and makes the motor inside fall down, so often I take the entire left side out. Would be great to avoid this. Thank you!

 

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