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UM 1, second layer not extruding -> Underextrusion

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I've just moved to ABS after building my own Heatbed, but I can't print: first layer goes nice and smooth, the abs stick to the bed really well, but as soon as it goes to the 2nd layer it stop layering those "nice lines of abs" but it drops little bobbles, as underextruding, and by the 3st and fourth layer, becouse of that, it starts printing in the air, and it doesn't even extrude... Print fails. Any idea?

Heatbed temp 110

extruder 230-235 (still testing)

Ultimaker bought this early summer



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After others tries i think the problem is not underextruding, but it is that new layers don't stick on previous ones.

Becouse if I go to prepare, move axis, 1 mm, extruder, and extrude a bit it does extrude with no problem already at 230 degrees.

After the print fails i usually take my z level down a bit to remove the priint and in the mean while some abs still extrude out of the extruder.

So probably the problem is that filament sticks to heatbed but not on other filament. Is it possible?


After other experiment i managed to have a final print. Here's a picture of it


As you can see extrusion was randomly non regular, and overall quality really really really bad... I can't understand the reason of it..

Printed at 240, 110 heatbed, 125 flow ratio...


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You have severe underextrusion. You need to raise the temp or slow it down. First of all go up to 250C. 240 is a bit cold for ABS. Then also slow it down a bit. The first layer prints slower but as you get higher up extruder speeds up and the filament is like toothpaste and it takes a ton of pressure to get it to flow through that nozzle. So whatever speed you are printing - try half that speed. You can even play with the speed (feedrate) while printing in the tune menu. And you can play with temperature also.

Also check your filament that it has a nice easy path into the extruder - nice and straight. Consider putting the filament on the floor or something so it has an easy path into the extruder.


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Now i did more tests:

- No fan

- bed 110

- nozzle 250 and 260

but i noticed i have a problem with extrusion: it seems as the filament hasn't a smooth way through the extruder: while moving manually the extrusion gear ( and during prints having it moved by the stepper) the bowden tube is being pushed up instead of having the filmant smoothly go through the extruder, as if it had a hard way. Picture:


In the pic bowden is no more visible because It has benn pushed up a little

If i manually extrude and keep the bowden down it has a nice extrusion but it fells like it's limited: if I try to extrude very fast it still goes slow..


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What print speed? You may have a partial clog in your nozzle but probably not.

You seem to be missing the horse-shoe ring on the white clip that holds the bowden down - the blue clip in this picture:


McMaster sells a pack of 10 for $2.29, Part # 51055K413.


You can print one that is even better:



Be very careful. That white clip that holds the bowden - I call it the "bowden holder". It has 4 metal knives that dig into the bowden. Those knives can break or get twisted the wrong way. More likely though - you can scrape the outside of the bowden - removing the outer layer of material. The bowden may look fine but be missing a little bit of material. It's visible but you have to look very carefully. The fix for that is to cut off a tiny bit off the bottom of the bowden - 1mm or 2mm should be enough. If you do this too many times you will need a new bowden.

Normally to remove the bowden you push down on the white bowden holder and lift the bowden at the same time.


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It worked! bowden is a bit ruined and scraped but the "holder" seems to hold it anyway. My problem now is that after a while, when stil printing, the object doesn't remain attached to the heatbed (110 theorically) so the whole print (wich was going well) is ruined and pushed around the build platform by the extruder, still thinking it's printing on soething.... But i guess i should opena new topic for a different problem..


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I have serious underextrusion problem I can't fix: I've raised temp to the max (260) slowed down print speed to 20 (which is veeeeeery slow. I mean Ultimaker says it can print up to 150, I just wish I was able to reach 40....) and increased flow (but it doesn't make any real difference). Even though, abs filament extruded feels "cold". It's not that soft and it doesn nicely melt with previous layers... so as pla used to... I am using ultimaker stock abs. Is it possible it's due to the filament? I heard sometimes it's just it... because people seem to be able to print abs with UM but I guess they don't suffer of such underextrusion and print so slowly either....

I am trying to clean the hot end with acetone ( the one is used on nails.. I hope is the same)


Edit cleaning did not work. I also unmounted the hotend put that on my kitchen fire and cleaned it but it did'n work. When I put it back filament first extruded brown, then white and then underextruded. Extrusion by hand is really hard and filament does't come out of the hot end vertically but always curve to one side of the hot end, suggesting there is something blocking part of the path...


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I think I had a clog. I recleaned it all and now if I manually extrude I get "expected extrusion" (while I used to get a really slow one before).

Now I am able to print nicely over previously printed layers but things goes bad while printing on air (by on air i mean also when crossing lines printing the infill..) I have no idea why....

Temp 255

speed 20-40

height .1 .2


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