Consistent Feeder Grinding Issues

[geert_2 557]

If the environment is already 35°C, could it be that the filament starts softening? Or that the heat transferred from the feeder stepper motor to the feeder wheel is just too much, and it softens there? Maybe you could let a fan blow onto the feeder too?

 

Edited May 29, 2018 by geert_2
corrected typo

[whoneyc 10]

Ambient temperature of shop: ~33C

Temperature of print cores: 34C

"Off" temperature of driver: 36.6C

A plot of the temperature of the "Left" driver measured by IR thermometer for the first hour or so.

 

This print started at 3:30pm and was set to go for 15+ hours.  It failed at some point after I went to sleep (11pm).  The result was "gray" underextrusion.  

 

But I am apprehensive @gr5.  While the temperature does seem to be a valid issue, I can't reason why that would cause the grinding.  If the driver was being temporarily stopped, reason suggests that then it would just skip a step while cooling rather than pushing too hard and grinding the filament down.  

[whoneyc 10]

7 hours ago, geert_2 said:

If the environment is already 35°C, could it be that the filament starts softening? Or that the heat transferred from the feeder stepper motor to the feeder wheen is just too much, and it softens there? Maybe you could let a fan blow onto the feeder too?

 

 

This is an interesting thought.  The high temperature in conjunction with the Oklahoma humidity could be causing issues there.  I'm going to convince the girlfriend to let me do a print in the house while we are at work tomorrow (such that the sound does not keep us awake) and we can see what the AC does for it.

[whoneyc 10]

The results are in.  A 69F/20.5C environment for the printer with ample airflow was not enough to print successfully.  The print failed with underextrusion within the first 20 minutes.  

 

Suggestions?

[gr5 2,172]

23 hours ago, whoneyc said:

While the temperature does seem to be a valid issue, I can't reason why that would cause the grinding.  If the driver was being temporarily stopped, reason suggests that then it would just skip a step while cooling rather than pushing too hard and grinding the filament down.  

Doh!!

 

You are absolutely right.  More likely the stepper motor is heating the gnurled wheel and when that reaches 52C the filament is compressed as it starts to get soft right around 52C.  Without going back to page 1: is this a UM2 or UM3?  A "plus" feeder found on UM2+ and UM3 is heat isolated between feeder and gnurled wheel but I suppose it could still happen.  Not sure how to cool the gnurled shaft though.  airflow probably won't help like it would for the stepper driver.  the stepper driver needs to be cooled from around 100C but the shaft needs to be cooled below 50C.

[gr5 2,172]

Is it possible to pass the filament through a bath of ice without it getting wet before it hits the feeder?  That probably won't help if the gnurled sleeve is at 50C.  This is a tricky situation.  I think you need some kind of cooling at the feeder.  I think you should visit a neighbor who has air conditioning just long enough to verify this is the problem.

 

I guess another solution is to avoid PLA.  Almost every other material can handle 50C no problem.  Such as nGen.  PET, CPE - those are pretty easy to print and don't get soft until around 80C.

 

[whoneyc 10]

1 minute ago, gr5 said:

Is this a UM2 or UM3?  A "plus" feeder found on UM2+ and UM3 is heat isolated between feeder and gnurled wheel but I suppose it could still happen.  Not sure how to cool the gnurled shaft though.  airflow probably won't help like it would for the stepper driver.  the stepper driver needs to be cooled from around 100C but the shaft needs to be cooled below 50C.

 

UM3 Extended

 

Note that I ran a print last night in the AC (20.5C ambient) and it still failed.

[gr5 2,172]

oh.  right.  20C.  Okay this is good - you are knocking down the list to fewer and fewer possibilities.

 

 

 

#1 Okay well I don't want to discount #1.  Let's pick a print that was particularly bad and please send me the layer height, line width (all of them), speed (all printing speeds), printing temp (all of them).  Maybe a new print.  And when it gets going bad if you notice try slowing it to 1/2 speed.  As a test.  From the TUNE menu.  And a photo of the print.

 

#9 - No need to check this.  Parts of your prints are coming out perfect.  Other parts are extruding at 50% at the most.

 

#5 - Do you still have both AA cores?  Are they both doing this?  Is one worse than the other?

 

I recommend you test the feeder pull strength.  Put some filament in that does not reach into the print head.  Half way down the bowden is fine.  Go to MATERIAL/PRINTCORE menu then "Material 1", then "move".  move the material at any speed (even stopped is fine - basically we need the stepper motor powered up and it powers off after about a minute if you don't keep moving it).  Pull hard down on the filament.  Have a weight handy and try to approximate how much force you have to pull before the filament slips.  The UM3 should be able to pull 10 pounds.  Maybe even 15.  If it can only lift 5 pounds that might be the problem.

 

My list is missing one:  brittle filament. 

19) Brittle filament.  Espciallty with older PLA but even brand new pla can do this.  If you unspool some (for example if it's in the bowden) for many hours (e.g. 10 hours) it can get extremely brittle and it can snap off into multiple pieces in the bowden.  It's not obvious if you don't look for this.  Then it starts printing just fine and at some point one of those pieces reaches the print head and gets hung up somewhere and the printer suddenly stops extruding for now apparent reason.  This usually happens within the first meter of filament - once you get to printing the filament that was recently on the spool it should be fine from then on.
 

If #1 checks out by my calculations and this feeder test checks out I think it's time to buy a 3rd core.  Weird and complex things can happen in the cores.  Some of them are defective in subtle ways.  For example, PLA can melt, then expand, in parts of the core and then cool and get stuck.  If the internal teflon piece inside the core isn't as long as it is supposed to be or if it's inner diameter is larger than it's supposed to be this can cause problems.  Or gunk can basically get permanently adhered to the inside of the bore of the nozzle turning your 0.4mm nozzle into a .25mm nozzle without you realizing it.  If the trumpet part at the top is overly crooked it can cause excess friction.  If any part is smaller than 2.85mm it can cause excess friction.  Who knows but it's easy to replace.

 

[Torgeir 242]

Hi Folks,

 

What a great analysis done here, lots of job with all this.. @gr5

 

I've been following this for sometime as this is kind of strange..

 

Just a note on your last print in here, the print you stopped before finish of first layer.

At first I thought the beginning of «filling in» was OK. However, when copying this picture and zoomed into it for more details in here, I can see that the squished first line has a leak track, meaning the feed rate is to high. At the end of this, the nozzle do not leak any more -it looks flat as it should be. Maybe the bed is just a bit closer to the nozzle and really close the outflow. At this point the filament will sure be grind-ed, and this part of the filament will slowly move into the bowden tube. You now start to see the blobs, -that’s escape from the nozzle and you see how squeezed the last part is before a total lack of extrusion. Also those two blobs seems to be burnt, but may be a visual error..

 

When the prints go on, more and more of the grind-ed filament is feed into the bowden tube and this is become a serious problem for the rest of the print as the feeder have to work against the additional forces due to friction. So this is why your print suffer for under extrusion, as the grinding will continue.. IMO.

 

The look of your nozzle also tell a story.. When everything is right, the nozzle looks great..

 

You should probably lower the first layer feed rate and also reduce the feeder 1 stepper current as this will prevent high torque when pressure is too high at the feeder side.

This is one of Gunnar's suggestion in his long check list.

 

 

Below you can see two areas magnified from your picture.

 

Anyway, good luck.

 

Thanks

 

Torgeir.

 

Edited May 30, 2018 by Torgeir
Forgot magnified parts.

[whoneyc 10]

On 5/29/2018 at 8:15 PM, gr5 said:

Let's pick a print that was particularly bad and please send me the layer height, line width (all of them), speed (all printing speeds), printing temp (all of them).  

 

I may not be able to change the flow at the moment of failure too soon.  The failure can happen at any point, and I'm not going to sit in that hot shop for 15 hours waiting for it.  It will have to appear by luck.

By looking at an exported version of my printer profile, the only changes from the default "fast" profile are:

[values]
adhesion_type = none
layer_height = 0.2

[values] <--- on the left extruder
material_print_temperature = 230

Although this minimal set of info might be useful for Ultimaker wizards, in the interest of making this post accessible for future folks having problems, I'm going to list out everything.  It's a shame this forum doesn't use [more][\more] tags.  Buckle up:

 

Layer Height: 0.2 mm

Wall thickness: 1 mm

Top/bottom thickness: 1 mm

Infill density: 20%

Print temperature: 230 C

Build Plate Temp: 60 C

Diameter: 2.85 mm

Flow: 100%

Initial Layer Flow: 100%

Enable retraction: True

Print Speed: 70 mm/s

Travel Speed: 250 mm/s

Print Accel: 4000 mm/s^2

Travel Accel: 5000 mm/s^2

Print Jerk: 25 mm/s

Travel Jerk: 30 mm/s

Enable Print cooling: True

Generate Support: False

Build Plate Adhesion Type: None

Enable Prime Tower: False

 

On 5/29/2018 at 8:15 PM, gr5 said:

#5 - Do you still have both AA cores?  Are they both doing this?  Is one worse than the other?

 

Yes.  I already tried this.  They are pretty much the same.

 

On 5/29/2018 at 8:15 PM, gr5 said:

19) Brittle filament.  Espciallty with older PLA but even brand new pla can do this.

 

The filament doesn't feel brittle to me.  But, I am a bit worried that there may be other filament issues we have not explored, such as humidity.  So, I am prepping another experiment should the next ones fail, vacuum outgassing of my filament.  

 

 

The vacuum is holding at -750 torr, and ambient temperature (which gets hot out there during the day).  My hope is that this might remove any water which had adsorbed(absorbed in this case?) to the PLA.  

 

 

Additionally, despite us determining that my issues are not temperature related at the stepper drivers, I have taken the initiative to put some heat sinks on the ICs.  They are crooked as hell because I did this without looking, but hey...you get what you pay for.

 

 

I would add a computer fan, but I can't seem to find any around my shop currently.  

 

 

12 hours ago, Torgeir said:

Just a note on your last print in here, the print you stopped before finish of first layer.

At first I thought the beginning of «filling in» was OK. However, when copying this picture and zoomed into it for more details in here, I can see that the squished first line has a leak track, meaning the feed rate is to high. At the end of this, the nozzle do not leak any more -it looks flat as it should be. Maybe the bed is just a bit closer to the nozzle and really close the outflow. At this point the filament will sure be grind-ed, and this part of the filament will slowly move into the bowden tube. You now start to see the blobs, -that’s escape from the nozzle and you see how squeezed the last part is before a total lack of extrusion. Also those two blobs seems to be burnt, but may be a visual error..

 

This is actually quite the catch.  Nice job. Yes, the blobs that have dropped are slightly blackened.  I'm going to take a crack at your suggestion first.

 

I will be lowering the first layer "flow" to 75%, and I will be lowering the print "flow" to 90%.  I wish they had called it "feed rate", since that makes more sense linguistically, but from your description the values seem to be labeled "flow" in the english Cura.

 

Observation: There appears to be no adjustable current on the printer side.  I look all around in the settings, and I could not find anything that resembled the UM2 setting.  So I think I will play with the g-code.  I assume it will be M907 in the gcode according to old forum posts regarding the UMO and UM2, but if someone else knows something different, please let me know.  I will be doing tests on the flow/feed rate and stepper current separately to aid in diagnosis.

[gr5 2,172]

flow affects feeder only.  feedrate affects all 4 axes (x,y,z,e).

 

PLA does not need to be dried.  PVA, Nylon need to be dried.  PLA will be fine.  Filament that gets moisture in it will pop and sizzle while printing and it will come out all snowy and foamy and Matte.  Brittle filament is only brittle for the portion that has been off the spool for 12 hours.  The part on the spool will never get brittle.  You should be able to bend PLA with your fingers into a U turn with a curvature similar to the outside of your thumb without it snapping.  Brittle filament won't even get to 90 degrees before snapping like spaghetti.

 

Well... trying the same setting in my version of cura (it's a different version than yours but hopefully the profiles are the same) it looks like the infill is at the highest volume at 70mm/sec, 0.42mm line width, and X 0.2mm layer height - multiplying those 3 numbers together gives me 5.9 cubic mm/sec.  That's doable at 230C.  It's pushing things a bit but any UM3 should be able to do that.  Even an old tired one.

 

I personally would lower all the speeds to 35mm/sec and do a long print to see if it fails at all.

 

Please try my pull test - just put some filament in the feeder part way down the bowden and pull hard.  It should be able to take 10 pounds without slipping.

Just do it very roughly - just estimate (have a weight nearby or a scale to push on to compare).

 

 

[whoneyc 10]

@gr5 stepper motor pull test: Fail

 

The only heavy small thing I could find that would work is a cast iron meat grinder (7lbs. 5.5oz) attached with a metal clamp (4 oz).  The pull test failed with filament grinding.  Filament mush? Slipping knurled wheel?

 

 

 

On 5/30/2018 at 10:05 PM, whoneyc said:

I will be lowering the first layer "flow" to 75%, and I will be lowering the print "flow" to 90%.  I wish they had called it "feed rate", since that makes more sense linguistically, but from your description the values seem to be labeled "flow" in the english Cura.

 

@Torgeir this failed about 10 hours in with underextrusion.  I can post pictures upon request.

[gr5 2,172]

5 hours ago, whoneyc said:

The only heavy small thing I could find that would work is a cast iron meat grinder (7lbs. 5.5oz) attached with a metal clamp (4 oz).  The pull test failed with filament grinding.  Filament mush? Slipping knurled wheel?

 

Maybe we are on to something!  And no one printed any "filled" filament like glowfill or carbon fill?

 

Was this 7 pounds in addition to printing?  Or was the 7 pounds the only load on the filament?  Because just normal printing will put 5 to 10 pounds of force on the filament and the additional 7 would of course put it over the edge.  No surprises there.

 

Well maybe when you took the feeder apart (or am I thinking of someone else) you put it back together wrong?

 

Maybe something is wrong with the feeder gears - maybe something is slipping in there?  No - it grinds.  You are going to have to take this feeder apart maybe.  If you don't find anything obvious you can just get another one from your supplier.

 

Feel the gnurls on the gurled shaft and see if they are no longer sharp.  Or something is wrong with the spring tension.  Or maybe I misundertood your test.

 

Make sure you do this test with virgin filament that hasn't been ground down flat already.

[whoneyc 10]

@gr5 The 7 pounds was pulled while applying a moderate pace to the feeder with the "Move" function.  

 

The feeder is back together matching how it was originally.  I matched a picture.  

 

No grinding in the gears that I am aware of.  No damage to the gears. 

 

Virgin filament (unless Colorfabb screwed me).  The recycle stuff is waiting for when I fix this issue.  Also, there has been no "fill" filament.  (haha filllament)

 

I will check the knurled gear later. I'm a few beers deep.

 

 

[geert_2 557]

Could a misaligned feeder cause such issues? For example if it is mounted a bit too far to the left or right, so that the clamping of the filament doesn't work well due to misalignment? Or if the knurled wheel is sitting too deep, so it grips the filament only partially (=on the edge of the knurls, or halfway off), and has not enough traction? Just guessing...

 

[gr5 2,172]

 

If you look at the first post in the above link, this is for the old black UM2 feeder (not the plus feeder) which notoriously was on the weak end of things and even the worst of the 3 feeders tested there was at least 4.5kg or 10 pounds.  I have to tell you I am very happy that we have narrowed this down to your feeder.  Please repeat that 7 pound experiment now that the feeder has been rebuilt or look at how the experiment was done in the above link to get more accurate results.

 

I urge you to get a new feeder.  The amount of work to figure this out versus just getting a new one...

 

Especially if your business is paying your wage versus the cost of a new feeder.  I think at this point you should just get a new feeder.

[gr5 2,172]

On 6/4/2018 at 7:33 AM, geert_2 said:

Or if the knurled wheel is sitting too deep, so it grips the filament only partially (=on the edge of the knurls, or halfway off), and has not enough traction?

I really don't know.  I don't have enough experience to form an opinion.  I've seen this exact problem on UMO and UM2 but I don't know the plus feeder as well.  I've only taken it apart 2 times.  Most of the stuff in there isn't very adjustable.  I did have a feeder where one of the parts (gear) kept sliding off the motor.  fbrc8 sent me a replacement.  I think they sent the entire stepper motor and gear assembly.  They service USA customers.

 

If you do get a new feeder, look at the sharpness of those little pyramids on the gnurled wheel and compare the new versus the old.  Maybe post a picture if they are different.

 

FYI - the UM2 plus feeder is identical to the UM3 feeder.  I have both printers.

 

[geert_2 557]

On 6/4/2018 at 1:33 PM, geert_2 said:

Could a misaligned feeder cause such issues? For example if it is mounted a bit too far to the left or right, so that the clamping of the filament doesn't work well due to misalignment? Or if the knurled wheel is sitting too deep, so it grips the filament only partially (=on the edge of the knurls, or halfway off), and has not enough traction? Just guessing...

 

The reason why I wrote this is because in one of my UM2 (non-plus) there is a little bit of play when fixing the 4 mounting screws of the feeder. If I push the feeder totally to one direction, and then fix the 4 screws, it is nearly impossible to insert filament afterwards. If I center the feeder or push it to the other side and then fix the screws, inserting filament goes easy. I have to get the right balance. This is only a few tenths of a mm difference, but since PLA is not very compressible, it seems to make a difference. So I could imagine that the opposite might also occur: not enough grip, and slipping? But as said, this is guessing, trying to find a direction...

 

[whoneyc 10]

1 hour ago, gr5 said:

I have to tell you I am very happy that we have narrowed this down to your feeder.  

 

I urge you to get a new feeder.  The amount of work to figure this out versus just getting a new one.

 

 

I am happy we have narrowed this down as well.  I did some confirmation testing that there are no filament issues by using the second feeder to make a print with no underextrusion issues.  

 

I am contacting Ultimaker NA Support.  We shall see if they can provide a new feeder (still under warranty)

 

1 hour ago, gr5 said:

Especially if your business is paying your wage versus the cost of a new feeder.

 

Hah.  I'm just a nutter with design experience, a science PhD, and a shop full of weird toys.  Very few of my contract projects pay money instead of beer.  

 

1 hour ago, gr5 said:

If you do get a new feeder, look at the sharpness of those little pyramids on the gnurled wheel and compare the new versus the old.  Maybe post a picture if they are different.

 

I will test rigorously and report back.

 

1 hour ago, geert_2 said:

The reason why I wrote this is because in one of my UM2 (non-plus) there is a little bit of play when fixing the 4 mounting screws of the feeder. If I push the feeder totally to one direction, and then fix the 4 screws, it is nearly impossible to insert filament afterwards. If I center the feeder or push it to the other side and then fix the screws, inserting filament goes easy. I have to get the right balance. This is only a few tenths of a mm difference, but since PLA is not very compressible, it seems to make a difference. So I could imagine that the opposite might also occur: not enough grip, and slipping? But as said, this is guessing, trying to find a direction...

 

 

This is interesting.  The feeder in question does have a few issues getting the filament in correctly.  I have to bend the filament slightly to get it into the bowden.  However, I either have never observed what you are talking about, or I am not picturing it correctly.  The screws and screw plate seem to fit very naturally.  I have taken that blasted think apart and reassembled it so many times to clean out filament grindings, I could do it in my sleep, blind, with one hand behind my back.  Do you have or can you direct me to any illustration or other description of the issue you are referring to?

[whoneyc 10]

Update:

 

So I did some more testing.  I wanted to make absolutely certain that it was occurring only on the Feeder 1 and not due to other issues.  So I ran some prints on Feeder 2.

 

Feeder 2 with spare core and new filament: success

Feeder 2 with spare core and old gray filament: success

Feeder 2 with primary core and new filament: success

 

This doublechecking increases my confidence that the issue is in the feeder, even with the previous evidence we have collected.

 

Now that I am confident in the location of the issue, I recontacted the Ultimaker Support team.  Our work here really narrowed down the potential issues, but they had one more to check.  This is something that I had not heard of, so I think it is important for the folks that are able to offer advice on the forums to hear ( @gr5, @geert_2, @Torgeir, @Dim3nsioneer, @XYZDesignPro, @kmanstudios, @fbrc8-erin, @neotko).  The support guys have observed a groove which forms on the lever in the feeder that can cause alignment issues and grinding.  Sure enough, that appears to be what my lever has.

 

 

 

I have not seen this reported on the forums in my cursory searches.  A picture which was attached to the support email showed that I am not the first person to see this problem, and I doubt I will be the last.  

 

Of course, this does not mean my problem is fixed, but I have some hope.  The support guys are sending me a new one.

 

[fbrc8-erin 272]

It's a spot where wear and tear can occur on the lever if the filament isn't quite sitting straight on the bearing; it's not super common but we've seen a few cases. I just put the label on the box actually about 5 minutes ago, and you should have the part in a day or two, with tracking information in your email. There's also an update on your support ticket with assembly instructions for installing it in your feeder.

[whoneyc 10]

Bad news folks.  It appears the damaged lever was more of a symptom rather than the disease.  My first print failed.

 

 

I tried to push it by giving it a large design with multiple colors and retractions.  It is still underextruding.  I have sent an email to the support guys, but they won't be in the office until Monday.

[gr5 2,172]

Do the pull test to be sure.  It *might* be unrelated.  I doubt it but it might be unrelated.  Did fbrc8 send you only the lever?  Maybe they should send you the whole feeder if it still fails my pull test.

[gr5 2,172]

You could also by a pair of DDG feeders from my store ?

 

https://thegr5store.com/store/index.php/um3-up.html

[whoneyc 10]

 

53 minutes ago, gr5 said:

Do the pull test to be sure.  It *might* be unrelated.  I doubt it but it might be unrelated.  Did fbrc8 send you only the lever?  Maybe they should send you the whole feeder if it still fails my pull test.

 

Was this the pull test I tried with ~7lbs and failed?  I'd be happy to replicate (although I still need to find a better source of weight).  

 

43 minutes ago, gr5 said:

You could also by a pair of DDG feeders from my store ?

 

https://thegr5store.com/store/index.php/um3-up.html

 

No harm in a little shameless promotion.  The parts sent from fbrc8 were paid for by the NA support folks.  I haven't heard back from them, but I'm guessing they aren't too into doing a full upgrade.

 

I'm just a little curious about the Bondtech feeders you have as a side note.  I see a two-part feeder gear, and that is the only real difference.  Is the rest of the kit really necessary if I can't print my own custom lever?  Do the 1.75mm feeders work well on the UM3?  That would be a nice side-grade to consider in the future.