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Robert Górski

Ultimaker 2+ decreasing extrusion over time problem

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Hello,

 

This is my first post here, so, hello everybody!

 

I own two Ultimaker 2+ printers and I stumbled upon the same problem on both of them.

When the printer is new, it prints excellent, but after about one month of heavy using (like 6+ hours per day) it begins to underextrude.

It happend to my first printer - I send it to servicing company, they lubricated it and returned with conclusion that there is not a problem with a printer.

I bought another Ultimaker 2+ and the new one works better. It prints the same gcode file as old one with much better result.

But after one month it started to do the same - underextrude. The lines of filament spilled from a nozzle get thinner from print to print and eventually they begin to not stick to the very next parrallel line of filament.

 

I can see that there is a problem right away after printing starts. At the very begining of the printing process the printer spills a "noodle" of a filament in the left close corner of the printing table (before even the moving the printing head). When the printer is new, the noodle is thick, its even twice as thick as the nozzle width (in my case is 0.4 mm). Now, the noodle diameter is about nozzle diameter width.

 

Something creates the problem and:

- its not like blocked/dirty nozzle - it happens with newly replaced nozzle also.

- its not a gcode file problem - when printer is new it prints the file with excellent quality.

- I use the same filament from the very beginning on both printers - it is not a problem with filament quality.

 

Can you point me to things I should check?

Did you have the same problem?

 

Regards,

Robert      

 

Edited by Robert Górski

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This is very common and is almost certainly the teflon part.  You should have gotten spares with your printer as they really don't last long.  They are quite inexpensive.  Get the UM ones which are a special type of teflon that is somewhat translucent and lasts longer (more temp resistant).  Don't use the completely opaque white ones.

 

A quick fix is to remove the nozzle and drill out the teflon from below.  This should improve things for a few more prints while you wait for a new teflon part to arrive.

 

There's a small possibility that your nozzle is getting a layer of gunk on the inside.  I don't think this is your issue but the easy check is to swap out the nozzle.  If you are getting this the fix is to do lots of cold pulls.  Read up on cold pulls (aka atomic pull) and watch some videos to understand it.

 

If changing the teflon and the nozzle do nothing, report back.  There are a few dozen other possibilities which I can list out but 95%, from your description, it's the teflon.

 

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Thank you very much for your answer.

I follow your advice and I did the cold pulls (atomic method). It looks like there is not much of a burned PLA, dirt or dust or whatever there (see photo).

So, I checked the diameter of the teflon coupler. After unscrewing the nozzle I tried to push the 3 mm drill from below with the blunt end, which, as I measured, has 2.9 mm diameter.

And it not fit - it wont go. I cannot say how much the coupler hole was smaller, but it was not much, maybe about 0.2 mm. So I drilled it with 3 mm drill.

After all of this cleaning and drilling I must say it got liitle better. It's not like new, but I can see positive difference.

I read somewhere here, that even 4 mm drill can be used. I wonder if I should use 4 mm drill.

 

The other printer (the older one) is still in service. I was told that the clogged nozzle was cleaned and the coupler was changed to new one. In few days I will get the printer back and check if it solved my problem.

 

Anyway, again, thanks for your help.

coldpull_u2plus.jpg

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More info. My first printer came back from service. It works OK now.

I was informed that:

- nozzle was cloggead and it was cleaned

- teflon coupler was quite OK, nevertheless it was replaced

- there was many residues of filament in printing block (above teflon coupler) and most propably it was the major problem. The service guy told me that is a case of not-so-good quality of the filament I use.

 

This last thing worries me much. Where the residues come from? Are they scratched pieces from the rear filament providing block and they travel via bowden tube?

Should I clean the printing block myself? 

Can you point me to instructions how to do this?

 

 

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I really doubt the brand of filament matters.

 

I'm not sure how filament residue gets above the teflon - that's the bowden tube.  

 

I guess if you increase retraction distance too much that could happen.  When a print is over, when the head is still hot, if you retract manually or automatically, you get a string of filament at the end.  That can end up in the bowden tube if you later pull the filament out but it breaks off in the feeder and the next piece of filament inserted pushes it back into the end of the bowden.

 

I liked the older version of the UM2 where it had a spring where the aluminum spacer is now.  You could see if there were bits of filament at the base of the bowden.  Now having said that - I've never had a problem with bits of filament at the top of the teflon part so this is a new issue on me and I've been reading this forum for about 5 years.

 

Is your "third fan" working?  The one at the rear of the print head?  It probably only turns on after the nozzle is above 40C.  When that breaks you get intermittent unexplained clogging.

 

Anyway, next time you have the problem, remove the bowden from the head and look down into the head to see if there are bits of filament at the top of the teflon coupler.

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I'm quite sure that the third fan is working. In fact, it spins so fast that its hards to see if it is rotating at all.

 

About retraction distance - I think it's set to default value in my Cura profile.

 

I don't know if the residues are parts of broken strings created while replacing filament to new spool - but it may be the case...

I think I must see it for myself.

Is there a instruction for disassembling printing block?

 

 

 

 

 

 

 

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