Material Feed problem

[markjme 2]

Printer: Ultimaker 2+

Material: Ultimaker tough PLA (but have tried different materials)

Problem: Material ceases to extrude leaving only the first few layers printed. Cannot remove the material without dissassemby of the print head where I find that material is folded at the back of the nozzel which is why the material cannot be removed. The drive cog ultimately wears away the filament. There would appear to be a mismatch between the filament feed and the rate of extrusion.

This has happened on the last 5 prints which have all been unsuccessful.

Actions taken:

1) All the drive cog has been dismantled and cleaned.

2) Replaced nozzel

3) Tried using an earlier version of Cura

4) Reset to factory settings on the printer

5) Installed latest Firmware

6) Tried printing other files (same result)

 

In photo the bottom of the filament is from the nozzle, the knot is from the back highlighted in red.

 

Any suggestions please.

 

[gr5 2,235]

Your bowden needs to go all the way down into the white teflon part.  The part below the red circle.

 

The bowden can catch a few places on the way down.  Because of this I hate that aluminum cylinder that you circled.  I recommend maybe drilling a few holes in it so you can see when the bowden passes through there.

 

Alternatively, because the white collet that holds the bowden in has sharp knives inside, you can look carefully (with reading glasses maybe) and find all the marks on the bowden.  Use a sharpie to mark the farthest mark from the end.  And when you insert the bowden make sure that mark gets down to the blades in the collet.

 

Or maybe measure the distance from the top of the head to the white teflon part top.  Mark the same distance onto the bowden and use that to be sure the bowden is all the way in.

[gr5 2,235]

By the way, I know this is the problem because your filament on the left is filling that space inside the metal cylinder you circled.  Which you are clearly aware of.  The bowden shouldn't let it fold up like that.  The pressures are intense (typical 10 to 20 pounds of force on the filament) even in normal printing.

[markjme 2]

Thank You gr5

Over the years the bowden tube as cut up from the knives and as a result when I measured how far it was inserting it was falling short. Had to cut off about an inch off but now seems to be fully home.

Back printing so fingers crossed.

[markjme 2]

Hi gr5

 

Now tried twice printing the same file twice. Both stopped extruding material. 

Cannot perform a remove material as the drive cog has eroded the filament away. Cut the filament and removed the bowden tube both ends. Photo below. 

It is clear that although the bowden tube was fitted correctly at the nozzle end and material could not be backed up the filament has still swelled inside the tube and jammed. I do have a noisey fan so maybe not cooling the rear of the extruder head sufficiently?

 

Of all the recent failed prints only 3 had the crunched up material.

[gr5 2,235]

No need to cut a whole inch off the end of the bowden!  3mm is plenty!  Plus if the bowden is slipping you would know.  So don't cut the bowden unless it is coming out of the print head (or feeder).

 

I think you figured it out.  You had 2 problems:

1) Bowden not all the way inserted properly.  Sometimes it takes a lot of frustrating effort to get it into that aluminum cylinder.

2) Rear fan not spinning.

 

There are 3 fans on the print head.  Not 2.  There are 2 on the side and one on the rear.  The rear fan should come on as soon as the head passes 60C.  Anytime the head is above 60C the rear fan should be on.

 

Sometimes threads of filament can clog the fan.  This is kind of uncommon (the threads are common - but usually the fan doesn't care).

 

Sometimes the fan just dies.

 

Most often one of the wires breaks or a connector pulls out.  The problem is usually inside the print head or in the few inches above the print head.  There is a connection in there - typically just above the print head hiding inside the cable sleeving.

 

Anyway, manually heat the print head to 80C and make sure the rear fan spins up once the temp passes above 60C.

[markjme 2]

Hi gr5

 

Fan still spins but i expect the output is low.

Fan is always on even below 60C.

I feel sure the problem lies here.

Thanks for your help, very much appreciated.

 

Mark

 

[gr5 2,235]

Well I simplified.  I think it might be 40C on UM2.  On S3/S5/S7/UM3 the fan comes on above 40C if the heater is on and turns off when below 60C when heater is off.

 

The fan can be VERY quiet and it works just fine.  I don't think that's it.

 

So summarizing:

1) The pla still softens but it stays in the bowden now you don't have to take the head completely apart?

2) It still stops extruding and it still gets stuck but only in the bowden now?

 

This seems very unusual.  What temp are you printing at?  What is your printing speed - please tell me:

layer height

print "speed"

line width

 

(I multiply these together to get volume/sec and that's what I sometimes mean by printing speed)

 

The grinding by the feeder is normal if things get clogged.

 

You shouldn't get expansion in the bowden.  Sometimes it happens for prints with tens of thousands of retractions.  Prints that have maybe 100 islands per layer.  This is common in architectural parts that have lots of banisters where you are printing 100 of those posts on the same layer.  It's also common on "voronoi" prints (google it).  But overall it's extremely rare to have a print that has too many retractions per layer.

 

With every retraction you are pulling the heat up higher towards the bowden.  Still - it's usually not a problem - it depends on your model.

 

Another thing that makes the filament swell is if you get a jam and the filament is now no longer moving through the nozzle and no longer moving the heat down and out the nozzle.

 

So it's possible the whole problem is the jam and all the things you are noticing are the side effect.

 

Here's a good test - heat the nozzle and do "move" or "move material" or whatever the menu item is.  Try to extrude as fast as possible which means not going too fast as you go too fast it then slows down.  Make a kink or something in the filament and time how long it takes to get down to the glass bed.  10 seconds is typical for a UM2+

[markjme 2]

Hi gr5

With PLA I am never tempted to stray from default settings.

 

1) Yes PLA softens in the Bowden tube and jams.

2) Yes

 

Layer height: 0.15

Print speed: 60mm/s

*Line width:0.35

 

* I am using a Raft which I can see hs different line widths, base=0.8, middle=0.7, top=0.35

 

With Move material it takes about 7 seconds. 

 

I did replace the nozzle already as I thought this maybe the cause.

 

I agree the problem is in the all in the bowden tube to extract the material I have to remove it at the print head end which is why on a coulpe of occasions I failed to insert it far enough.

[Slashee_the_Cow 438]

10 hours ago, markjme said:

* I am using a Raft which I can see hs different line widths, base=0.8, middle=0.7, top=0.35

I don't know what size the nozzle the UM2+ comes with (cue @gr5 coming in to correct me) but if it's the (fairly common) 0.4mm I'd start to worry about whether it can actually push out enough material for lines that thick, especially if your raft uses thicker layers than your main print. If it's trying to push more out than there's physical room for, that definitely puts you on the road to clog city.

[gr5 2,235]

slashee, yes it's 0.4mm by default but the "plus" should have come with a .25, .6 and .8 as well.

 

I'd ditch the raft.  You don't need a raft for PLA.  The raft technology is a very old technology that isn't used much in the last 10 years.  It was before we had heated beds and before we had PLA.  If you have PLA *or* a heated bed you don't need raft.

 

However you do need some glue on that bed.  The printer should have a glue stick.  Put just a little bit on there and spread it around even thinner with a wet tissue and let dry (by the time the bed hits 60C, it should be dry.

 

What brand PLA are you using?  What temperature is there in the default settings for the nozzle?  This is all just weird.

 

I'm thinking it's not the bowden that is the problem.  The bowden NEVER gets filament stuck in it.  No matter what.  Even if the fan fails in the print head.  I mean it's possible there is some problem that makes the filament get too wide in the teflon part but by the time you get up into the bowden the diameter is now larger and things are usually too cool to cause the filament to widen like that.  Maybe this is some weird extra soft PLA?

 

(a) Instead I suspect the white teflon part but I'm not certain.  It's just... weird.  I'm very tempted to tell you to replace the teflon part.  It can go bad with a mere 500 hours of printing.

 

You didn't answer about if your STL has thousands of retractions.  Like railings or voronoi for example.  If you look at any individual slice, how many separate islands are there?  (You need one retraction for each island).

 

(b) Also a 0.8mm wide line width is very difficult for a 0.4 nozzle especially the first layer.  That alone can cause the whole problem.

 

Perhaps you are leveling too close to the bed - I'd love to see what your first layer looks like.

 

Right now I'm leaning to "a" or "b".

[markjme 2]

Thank you gr5 and slashee.

 

Also happened without using a raft.

 

Single island part with a large footprint (140x88mm)

 

Teflon part looks ok.

 

Now cleaned everything and re levelled and i'll see what happens.

 

Still think my fan is the problem.

 

I guess I will know in the next hour.

[markjme 2]

Still 10 hours to go on this print but so far have been printing for nearly 8 hours and all ok.

 

Thank you gr5 and slashee

[gr5 2,235]

So what was the cause?