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Weird under extrusion

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HI All, I am new to this forum as a contributor but not as a reader,I have helped incredibly by the already posted stuff on the forum but I am now stuck.


I have been doing excellent quality prints on the Ultimaker 2 since I have had it about 8 weeks ago. I did some prints lately of 4-5 hours for a local school and now all seems to have gone wrong. I have done the Cleaning methods mentioned in the forum, Stripped the head down, Checked the Teflon white bit and tubing and all seems ok, Had the feeder in pieces Used a 0.4 needle to clean nozzle etc. But I cannot fathom out what is going wrong. I have noticed that there is a bit of a pattern. The print starts out fine for the first 6-10 layers and then it goes "stringy and rough" I have notice though that 2 sides seem to be ok and 2 not. I have attached some pictures to see if anyone can shed some light on this for me.


This is just a theory but is it possible for a gcode to get stuck in the Ultimaker, it doesn't seem to make much difference if I choose a 0.25 layer or a 0.12 layer.



Many thanks.




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You say it happens only on two sides of the object, which sides on the plate would that be?

What is the brand of the filament you're using?

Did you try the cylinder test?

You can find it here:


As for your question on the gcode, it's read on the SD Card so it should be different if you replace the gcode on the SD Card.

I'm guessing you're using good temperature/speed settings as you're an active reader of the forum!


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HI Didier,

thanks for your reply.

The left and right sides ( looking from front of printer) are fine its the Front and back that are a poor holy/stringy print.

Filament being used is Either "the3d filamentshop" own brand (not chinese made in the uk) - Ultimaker Blue and some sample of Trideus PLA all with same results.Up until now all prints have been excellent.

I have left a print running (new feeder for the back) this morning with the flow rate at 120% and the Temp at 213 Degs. All seemed ok when I left it about half an hour ago.

I shall do the cylinder test when I get back home. I did do the cylinder test about 3 weeks ago and passed with flying colours. I still have the test so I will post a pic of both ato compare.

Thanks again.


Ultimaker 2


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it's not weird to have a single side suffer from this. the original feeder is just fine, but under certain circumstances the bowden tube gets in a turn that is too tight for the stock feeder.

i would recommend replacing it with a custom feeder and trying it again.


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OK, here what I did to cure it. I did the cylinder test and failed major miserably at 5mms . I then Started again on stripping down the head and taking our the Teflon tube. I did notice a little browning on this so I shave about .5m with a craft knife. Then checked the flatness of the new face using Electronic calipers. I then heated up the hot end to 230 and used a safety pin straightened out to clean out the nozzle very thoroughly and also the edge that the Teflon tube sits on. it took about half an hour of burned fingers, a little cursing and swearing.

I then put it all back together and started again with my new feeder and hey presto back to new. In fact I am now extruding at 200 with PLA and the results are pretty spectacular.(Ignore cooling lift at the bottom, I didn't use any glue!)



Layer height 0.25

Shell thickness1.6mm

Print Speed 50mm/s

I am doing some free work printing the designs created by students at one of our local schools so I think they will be happy with this.

Thanks to all who contributed and hopefully this may help someone else out. Conclusion :Change the stock feeder and make sure you clean the nozzle really really really thoroughly. I did use some 0.4mm needles but it was the Pin from the top of the nozzle and the PTFE trimming that did the trick. :-P



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