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Probably Under Extrusion...Help

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Hi Forums,

This is my first post as I have only had my Ultimaker for a couple of weeks. In those weekes everything has gone great, it worked perfectly after being assembled, no under extrusion, accuracy was bang on and apart from retraction blobs everything looked awesome.

Now I am having a few issues and would like some opinions (in all the photos the part on the left is what I am printing now, the identical part on the right is what I printed only a few days ago):

Sparse first layer and what I think is low nozzle pressure


I am having issues with a very sparse first layer, the infill doesn't touch the walls very well. I think the main reason for this is that I have been having to set my z-axis very slightly higher than specified with the nozzle just slightly higher than the bed (probably 0.05mm or something). I know this isn't what is supposed to be done but if I set the z=0mm during bed levelling the print will work fine for the walls but stop extruding on the infill. Then if I lower the bed very slightly a whole load of material comes out.then it works fine. I think I might have a partial blockage :sad: any tips on how to unblock...?

Far Far more warping than before




The part is warping more than ever and I don't see why. Perhaps this is a symptom of under extruding.. Also on the side photo you can see something that I think is retraction blobs and overhangs when the print is doing a top fill...weird.


My Settings

Note that though the screenshot shows 240C I have been using 220C typically, 240C was me doing a manual feed through the hot end.


Basic Settings

Advanced Settings

Expert Settings

Hot End and Extruder

because I know you guys ask for pics of these from time to time :smile:. On the hot end you can see residues frmo when my brass part wasnt fully tight into the alumium block cause it to leak. This has been sorted now.

Hot End


Thanks for any help!



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It's definitely over-extruding. You can tell by the ridges between your infill on the top layer. Over extruding also just tanks your print quality because retraction never works properly. It does sound like you might have some dirty nozzle/clogging issues, but those could also be due to the overextrusion which may have been grinding your filament, which can then cause clogs when it makes it to the hotend. If I were in your situation, I would:

- Change your filament diameter in Cura to reduce extrusion by around 20% (It's much easier to work your way up from under-extrusion than it is to work your way down from over-extrusion, because unless you're measuring your parts with calipers, slight over-extrusion is hard to detect)

- Open up the filament drive and pull out all of the filament that is in the bowden and hotend, discard it.

- Reassemble the filament drive with fresh filament, and increase drive spring tension 1-2 full turns.

- Reduce your initial layer thickness to .2 or .15. Too thick of a first layer will make it harder to diagnose other problems.

- Send a print with a large skirt with many lines. Adjust the bed height by manually turning the Z screw until you get good skirt lines coming down, and then micro-adjust with the leveling screws until the skirt layers are uniform across the bed.

If none of that worked, I would probably try to clean out the nozzle. But, speaking from experience, hot end disassembly is a can of worms that often leaves you in a worse place than you started. So be careful.


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You have 4 problems caused by 2 thing.

First the minor thing:

You levelled slightly lower on the newer print so the first layer is underextruded. This also means the first layer didn't make as good contact so the part was able to warp a little. These are not a big deal and can be fixed by levelling more carefully probably with the nozzle hot (the nozzle expands when it is hot).

The major problem:

Well you have over extrusion on one of the lower layers -0 maybe layer 5 or so, and then you have it again on the layer at the first "top" section about 1/3 of the way up the part. ALL of the other areas look pretty good. This overextrusion causes blobs when the filament explodes out of the over pressurized nozzle and also causes extra stringing due to too much pressure in the nozzle.

So what causes the overextrusion? And why only in two vertical areas? It's almost certainly related to the Z screw.

Home the Z axis, then disable the servos and turn the z screw by hand. Turn it until you have moved at least the height of this part. Notice if there is a sticky spot. Turn the Z screw back the other way until you're head touches the limit switch and repeat a few times. Try to notice:

1) Is there a sticky spot or two?

2) Watch the Z Nut carefully - that big huge nut that is embedded into the Z stage. Does it slip around suddenly at all?

3) Consider putting more grease on the Z stage

4) Does the Z stage hit anything? Is there something that the stage hits on it's way down? Maybe some wires? Look all around the edge and under the Z stage for any obstacles that might slow it down briefly.

If none of this shows you anything you could try experimenting with pronterface or cura to move the Z stage with the stepper. Listen carefully for any noise changes. Consider 1-4 above during this.

A good test print for you would be a rectangular box that is 2cm by 2 cm in X and Y and 20cm tall. Slice and print that at .1mm layers (to show off the problem more) and also make darn sure your layer cooling time is enabled and set to at least 5 seconds.

Basically you need to fix the Z but if you are in a rush you could simply change your layer height to .2mm and you might not get such severe overextrusion.


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Excellent photos by the way. I should also mention that Z screw issues often repeat every 3mm vertically (the vertical movement for one rotation). Often the Z screw has a huge wobble which causes the Z nut to slide around which can cause these kinds of issues. Also did I mention to try adding more grease? The green tube that came with the UM.


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Hi Nick, gr5,

I didn't realise this post had gotten past the moderators...it was taking a long time ;-)

So I performed an operation or two during the weekend before seeing your posts so I think some things have been solved.


  • I disassembled the hot end using my gas hob as a heat source and found a 'collar' of PLA inside the PEEK insulator. I suspect this may have been my source of poor extrusion. I cleaned this out.
  • I also noticed that my z-axis couldn't reach the bottom end stop and ended up making a loud grinding noise with the z stepper. This was due to my bed not being properly assembled. This also made it hard to level my bed as the plywood parts of the z-stage were at a severe angle. This has now been solved, the bed is much more level and I have the full range of z-axis :-)
  • I also cracked out the calipers and had a look at the filament. It measured 3.3mm!!! this is the Ultimaker silver PLA filament you get as default with the unit. So I have adjusted the filament diameter to suit. This may be the source of the over extrusion?

So tonight I just printed a 20mm cube and here are the results.

Isometric View

20mm cube

Top Infill

20mm cube

This is the bottom, i had the head too tight to the bed and had to adjust on the fly. The gap is an area that didn't extrude at all :-(

20mm cube


Looks like the z-axis issues have been resolved. I am still having trouble with bed leveling and extrusion but this is something I shall play with.



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First of all you should "follow" this topic (button on the top right corner). In fact follow any topic you post.

Looking much better. I think you have some "backlash" aka "play". You should tighten up your belts just a little. Probably the short belts (the ones connected to the x,y motors) which fortunately are the easiest to tighten (slide the motor down with more pressure).

I can tell by the pattern in the top of your cube.


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Thanks gr5, new to forums :)

I am doing a print right now so can't tighten up the short belts but will once it's finished. looking at it while it is running, the X-motor belt looks slightly loose so will make sure to get that tight.

I also increased the retraction speed to 45 which seems to have help the blobbing issue when it is moving between print areas.


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OK so here are some results of the short belt tightening.

The companion cube on the left is the one I mentioned I was printing in my last post, I then tightened the short belts and printed the one on the right.

  • Top infil looks much better with belts tightened.
  • Sides look amazing, this is 0.2mm layer height and it looks injection molded!
  • Bottom shows better infill, you can't see the "honeycomb" inside with the belts tightened.




All in all very pleased with the improvements. Nearly there! :)


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Interesting thread, I am still refining my bed leveling on my Ultimaker. I noticed one of the springs slid between the nuts at an angle, so its not allowing me to level with the other ones correctly.

I'm noticing close to no extrusion at lower temps (under 200) but at higher, I flow fine. I'll have to check a few things you pointed out.


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