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Very sparse and brittle prints due to under-extrusion! Help!

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Posted · Very sparse and brittle prints due to under-extrusion! Help!

Hello all,

I received my new (assembled) Ultimaker last week, and after 5 flawless prints, I went to check my 6th print to find that it was extremely sparse and was about as strong as paper. Every print thereafter has either started extremely sparse with lines not overlapping, or started with a decent first layer only to have extrusion slow to a crawl after a few minutes. I have tried everything I can think of, but just cannot get the flow to be consistent. I would appreciate any insight!!

My problem seems very similar to this one: http://umforum.ultimaker.com/index.php?/topic/1812-my-prints-are-now-very-brittle/ . But the solution there has not helped me. I believe I have the V2 hotend, and they even now include the machines with a bracket that holds the bowden tube/white tightener down to prevent the bowden tube from popping out.

Here is a summary of what I have tried, and it is long to help answer any questions you might have, and to provide as much info as possible.:

- I have printed with 3 different types of filament, Ultimaker Yellow, and Ultimachine Red and White. It seems like no matter what I do, I still have an under-extrusion problem. I have attached picture 1 to show you an example of the prints I am getting (it is actually one of the better ones, but still breaks very easily).

Pic 1

- I tried varying printing temperature at 210, 220, 230, and even 240 for each of the PLA, all printing at 40-50 mm/s. While 230 worked a bit better than I had been getting at 220 or so, it still had the same issues with under-extrusion that I have been having. Many times the first layer will work reasonably well, but will quickly get much worse after the first layer.

- I checked the extrusion mechanism, and tightened the screw on the spring on the back. It seems to be working properly. The filament has the impressions from the mechanism, but is not smashed into an oval shape. I checked with my calilpers and it is all between 2.82 and 2.93 mm. The only time I notice any grinding is when a plug of some sort has formed in the hot end, and extrusion has slowed very much. The large extruder gear does not seem to be lined up perfectly with the small black gear, but I do not think it is missing any steps that would cause slippage or under extrusion.

- I tried heating up to 245 and feeding as much filament as I could through the hot end to clear any plugs. However, after some extrusion a plug developed, and I had to disassemble the hot end. When I have had visible plugs (which is not all the time), they have not been forming in the bowden tube, but have been forming in the bottom of the peek. I can't tell if some of the plugs have been forming upon removing the filament from the bowden tube some of the time either. Is there a preferred method for removing filament to avoid causing any plugs? I have been preheating for PLA, extruding a little filament, and then pulling the filament out of the tube by hand.

- Although I am disassembling, and assembling the hot end the same as I was with my previous ultimaker (which would fix plugs after I put it back together), perhaps there is an error in the way I am reassembling. Here is the process I have followed: First preheat the hot end, then remove the blue horseshoe clip and push the white tightener down and remove the bowden tube. As I said before, plugs seen to have been forming in the teflon tube rather than the bowden tube. Then I begin to unscrew the 4 long screws, and remove the fan assembly and let it dangle. Finally, I pull the hot end assembly down, and separate the aluminum block /peek/nozzle assembly from the teflon tube and remove any material I find in either piece. Picture 2 is of the disassembled hot end.

Pic 2

- Is there an error in the way I have reassembled the hot end? I have not taken the nozzle itself apart. I have heard it is rare to have a plug in there, and I have heard it is easy to damage the nozzle. Typically, when I reassemble the hot end, I first put the nozzle/aluminum block/peek part and push it up into the teflon tube, and then push the bowden tube down through the white tightener into the teflon tube as a last step. I also tried pushing the bowden tube into the teflon tube before reassembling the 4 screws into the nozzle/aluminum block assembly, but I did not notice a difference. Pictures 3, 4, and 5 are of the assembled hot end.

Pic 3

Pic 4

Pic 5

If anyone can offer any help, I would greatly appreciate it! Thanks in advance.


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    Posted · Very sparse and brittle prints due to under-extrusion! Help!

    I have never had this problem so I am not the best person to ask but I have 2 theories:

    1) Maybe there is something wrong with the thermocouple. Maybe the temp is much lower than you think. Maybe try setting the temp to 101C exactly and see if it boils a drop of water? Maybe try 260C? (careful as you shouldn't let peek get to 300C).

    2) Maybe there is a piece of metal or wood chip in the print head. Look in the feeder and see if there are any splinters - take the filament out and use a flashlight and look carefully for chipped/broken wood. Maybe you work in a dusty room? I think it's time to heat the head and unscrew the nozzle - perhaps by hand with an oven mitt? I doubt you will break it if you don't use a wrench. Then heat it up enough to burn any potential wood or dust in the nozzle maybe with flame?

    Hopefully someone who's done this will reply.


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    Posted · Very sparse and brittle prints due to under-extrusion! Help!

    Sorry to read that you're having a difficult time.

    I've only had my (kit) Ulitmaker a few weeks but I have some loss of extrusion experience already (far too much,in fact).

    The first was obvious - the bowden tube had come out at the hot end. Eventually fixed (with the help of advice from this forum) with a new retaining collar (collet). This problem may have been largely my poor assembling - and, perhaps, a substandard retaining collet.

    About a week later, lost extrusion again. Bowden tube OK (both ends), absolutely no sign of leakage.Looked up the Wiki and followed the advice to try 240C, 250C. No good. Searched the forums and found a note from Daid suggesting 260C - and, once the nozzle was clear, then making something at 260C. Wound up to 260C, waited a couple of minutes, and then pushed the filament by hand. After a while the nozzle coughed and spluttered and material started coming out, after another minute or so it looked as though it was coming out at the right rate. Given the strong words in the Wiki about only a few minutes at 250C I wasn't keen to continue at 260C - which may well have been a mistake. Dropped the temperature to 210C and all seemed well. Started making something, all fine for quite a while then extrusion stopped again. Once again Bowden OK and no leaks. Couldn't push filament through by hand.

    Fully disassembled the hot end. Very hard to see into the nozzle. Put it into our electric oven inverted at 250C for quarter of an hour and black stuff came out. But not clear. Could find nothing to push through the 0.4mm hole and have ordered some 0.3 and 0.4 drills (with plain ends so I won't have to put a cutting edge through the nozzle).

    Reassembled, but broke the brass tube when doing so. Yes, I was using a wrench on the PEEK. A complication is that the the PEEK lower end had swollen and kept jamming in the Aluminium plate.

    Fed up with this I've ordered a new nozzle, PEEK and brass tube.

    In the meantime I've filed down the swollen PEEK so that it no longer jams.

    Once the drills arrive I'll clear the nozzle (using a butane torch) though without being able to clean it thoroughly internally I'm worried about residual carbonised PLA. If (when) I have this problem again I'll follow through with the 'make something at 260C advice'.

    Sorry that I can't offer you an easy solution to your problem - only the consolation of knowing that you're not the only one suffering!


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    Posted · Very sparse and brittle prints due to under-extrusion! Help!

    Although blockages can be due to mechanical issues, a very common cause is trying to extrude at too high of a flow rate. The standard head can handle at most 8 - 10 cubic mm of plastic per second. Any more will cause a build-up of pressure in the hot end, and result in the filament grinding at the extruder end, and/or molten plastic squirting up into the cooler parts of the hot end, and solidifying there.

    The volume per second can be calculated as layer height x nozzle width x print speed. E.g., with a 0.4 mm nozzle width and 0.2mm layer height, printing at 50mm/s, the volume per second is 0.4 x 0.2 x 50 = 4mm³/s.

    Some things to watch out for are that increasing layer height - say to 0.3mm - can quickly increase the volume per second. Also, in Cura if you set a wall width that is not an exact multiple of your nozzle width then Cura will adjust your effective nozzle width (see my blog post for details - although the specific bugs discussed there are supposedly fixed in Cura 14.04 - such that the print path spacing is now correct).

    So fo instance, if you have a nozzle width of 0.4mm but specify a wall width of 0.6mm, and a layer height of 0.3mm - then at 50mm/s the volume per second is now 0.6 x 0.3 x 50 = 9mm³/s - enough to potentially cause problems.

    Another thing to watch out for is if you use the ulticontroller to advance the filament when changing filaments - the Ulticontroller tends to also advance the filament at a rate that is too fast for the nozzle to handle, and can cause instant jamming in my experience. I recommend advancing the filament by turning the gear wheel by hand - that way you will be able to feel the resistance when you try to turn too fast, and can adjust accordingly.

    These issues may not be anything to do with the problems that you are both reporting, but it's something to be aware of, so I thought I'd mention it. :-)


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    Posted · Very sparse and brittle prints due to under-extrusion! Help!

    Ok, I managed to solve the issue. It was a plug in my (brand new) nozzle! After checking just about everything else I could think of, I removed the nozzle, held it to a candle, and ran a heated copper wire through it a few times. Then I placed the nozzle standing in the oven at 400 for half an hour. Finally I ran the copper wire through a few times again, and replaced the nozzle on the hot end. The change was instant.

    I have still been having some black gunk come out randomly during prints (on my 4th now), but other than that the difference was night and day!


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    Posted · Very sparse and brittle prints due to under-extrusion! Help!

    That's good. I'm also new and have had a similar experience. Because of the onerous postage cost to Australia I've looked for alternative sources of nozzles and found this:http://www.ebay.com.au/itm/251261994682?var=550230700985&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

    I've one in the machine now and it seems fine.


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