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leon-grossman

Problem with underextrusion on UM2

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I submitted a support request yesterday but haven't received a response. I'm hoping someone might have an idea before the weekend.

Back when I got my UM2, I was having a ton of problems with under extrusion and it seems that the drive pulley set screw wasn't properly configured. I managed to resolve that problem.

However, my UM2 is underextruding at all but the slowest of speeds and it has pretty much been this way since I received it back in December. I thought I had resolved the issue when I fixed the drive pulley set screw. That did resolve some of the issues. Unfortunately, I've been out of town and am just now getting back to diagnosing the problem.

 

I have verified that the nozzle is not clogged and can push material through by hand with moderate force.

 

I have attached the video and image here that illustrates the problem.

Results of under extrusion

Whooping noise from over current

 

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Yes - you are definitely skipping backwards. It looks like you are printing very fast - maybe 5 cubic mm/sec? I'm not sure - I don't have a good eye for this.

Anyway, of course the quick fix is to print hotter. Or slower. What is your:

- layer height?

- print speed?

- nozzle temperature?

There's lots of discussion and fixes. I'm not sure what it is that people did to fix this issue but it seems different for everyone. One person simply got a new nozzle and bowden tube and all problems went away. I recommend:

- you put the filament on the floor in some kind of holder so the filament approaches straighter

- print at 240C (or print slower)

- if printing over 4 cubic mm/sec then even hotter - 250C (but this is too hot if you are printing slow) e.g. 100mm/sec .1mm layer

- Check for tilted Extruder motor due to the nut holding the frame together sitcking into the back - look down from above the top of the UM2 at the E motor where it touches the back of the machine

- Check knurled wheel to make sure it is touching the PLA nicely

- Try increasing the current of your extruder motor from 1.25ma to 1.5ma - this made a huge difference for some.

Unfortunately there is so much info about this topic and it is spread among 800 posts:

http://umforum.ultimaker.com/index.php?/topic/4586-can-your-um2-printer-achieve-10mm3s-test-it-here/

http://umforum.ultimaker.com/index.php?/topic/3976-almost-always-missing-layers-underextruding/

In the second thread above, post #545 by me lists all the theories as to what might cause this:

http://umforum.ultimaker.com/index.php?/topic/3976-almost-always-missing-layers-underextruding/?p=39843

 

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For this experiment, I chose to print with completely stock/easy settings with fast low quality print and stock PLA settings.

I'll check out those resources. I'm presuming somewhere in those resources it shows how to change the motor current? That was one of the first things I looked for with this problem. I'll check the mechanical stuff first.

Thanks for the response!

 

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M907 E500 - sets extruder current to 500ma. Default is 1250ma. Max is 2000ma.

Someone found 1500 was significant improvement but going to higher currents made it worse again and the stepper kind of vibrated or something strange. Any higher than 1250 and I get grinding. I guess my stepper is nice and strong.

Put the above gcode in the top of your test if you want to try it.

 

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last week, I cleaned my nozzle...

 

  • Today, I checked the seating of my bowden tube, ran at standard current and started having problems at 7mm^3/sec.
  • I upped the current to 1500 and made ti to 9mm^3/sec
  • I realized that i was printing at 220C so I upped the temperature to 230C and started a normal current test. The nozzle clogged part way through.
  • I cleaned the nozzle (again)
  • I ran at normal current and made it all the way through 100mm^3/sec

I'm confused as to why my nozzle keeps clogging. Apparently, my method is not getting enough material out. The integrated nozzle/heat cartridge is my least favorite thing about this printer. It really hampers the ability to take everything off and get in there to solve problems like this.

Oh well, at least now I have diagnostics and a lot more information about the potential issues.

@gr5 and @illuminarti, thank you for your help!

 

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What makes you think that your nozzle is clogged? :-)

To play devil's advocate here.... Lots of people talk about 'nozzle clogs' in relation to the UM2's under-extrusion, but I'm not entirely convinced that they are getting clogged nozzles, so much as they get filament stuck, or grinding and extrusion doesn't work right any more. But that's not necessarily the same as 'clogged nozzle' where the only solution is to take everything apart and physically remove something that is preventing extrusion.

As a point of reference... in two years of printing on UM1 and UM2... I have *never* had a clogged nozzle any worse than could be fixed by heating up the hot end a bit, and resuming extrusion - and that was only ever due to trying to extrude way too fast on a UM1 by using the Ulticontroller to advance the filament.

So... my question is... if your nozzle is clogging... what form does this clog take? Whereabouts is the clog forming?

 

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Sadly, I can say 100% that it was an actual nozzle clog.

Last week, with the nozzle dismounted, I could heat it up and push as hard as possible and no flow would come out. So I used a variant of someone else's cleaning technique here.

 

  1. Dismount nozzle assembly
  2. Heat to 260
  3. Push white abs plastic into nozzle
  4. Push a small bit of wire up into the nozzle
  5. Lower temperature to 110 (the recommended 90 was too low)
  6. Pull the plug of material out, using the wire as a structural support so that all of the material comes out of the nozzle

Today, the nozzle started extruding at a smaller diameter. I repeated the process of cleaning and now I'm able to print at 10. I can't say where the clog came from as I've only ever used UM materials in the printer and I have yet to even make it through a full roll because we haven't used it that much yet.

I haven't had clogging problems in my home printer and I never had problems on my old Thing-O-Matic but I can't seem to make them go away on this printer.

 

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Personally I wouldn't put ABS in the nozzle if I didn't have to; since it melts at a much higher temperature, any ABS that doesn't get cleaned out is just going to thermally insulate the melt zone and/or risk causing a blockage when printing at PLA temps.

Some users have suggested not switching between PLA and ABS in the same hot end. I'm not sure I'd go that far, but you certainly need to be very careful to fully purge any ABS when switching to PLA.

 

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Hmm, I've used three other printers and not a single one has ever had a problem switching between PLA and ABS. The melt temperatures of each is close enough that the ABS is soft enough to flow well even at 220C and the PLA shouldn't crystalize that quickly during a changeover at 260C. However, I can't substantiate that later statement.

 

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Are you printing in a dusty environment? Most dust will not melt or burn until much hotter than 260C. If it gets on the filament it can get carried through the feeder, through the bowden and get stuck in the nozzle.

Alternatively the ABS that the feeder is made out of can get ground down by the PLA filament and tiny flecks of black ABS can also make it's way to the nozzle. Usually 260C is needed to get that ABS out. I don't know if it is "high temp" ABS or what but I have a theory that it causes many clogs that people have been seeing with UM2.

 

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When I mentioned earlier about black stuff coming out of the nozzle, this is a good example. I was printing this guy at fast/low/ABS default settings and he printed for a large portion of the print before starting to spit garbage out of the nozzle and then it was clean again for awhile beofre doing it again near the end of the print.

Debris Top

Debris Side

 

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Looks like black ABS from the feeder. If you take the feeder apart I think you will see it is getting ground up.

Consider building a filament holder on the floor. I spent 10 minutes and used spare chunks of wood for this one:

spool On floor

 

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@leon - I don't know how much you are following things but UM is hard at work designing new feeders that won't have this issue. For example one of *their* new designs has the bowden slip much further in from the top so that the filament doesn't touch ABS after the gear and they added a metal gromet at the bottom of the feeder so it doesn't touch there either. This is still all experimental but you can request your own grommet and print out the current design if you want and they will send you a free grommet. Or you can print many other community redesigns.

Ian's design:

Ian? Where is it?

Geek's design:

https://www.youmagine.com/designs/extruder-um2-version-2

 

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OK, I'm bringing this topic back from the dead.

Shortly after @gr5 posted about Geeks' design, the heat bed suffered a failure on the thermister and had to be replaced. FWIW, the connector would go to open connection with moderate pressure.

When the new bed came in, I finished printing Geek's design and installed it but PLA still frequently clogs. As a result, I inspected the original cold end and the amount of material wearing off of the inside is not enough to produce the material I was seeing.

My current working theory is that the ABS doesn't flush completely from the nozzle when switching to PLA. I have a lot more investigation to do and I'll keep everyone updated when I figure it out.

 

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UM2 FEEDER DESIGNS

Ian's design is secret for now.

Geek's design for UM2 feeder:

https://www.youmagine.com/designs/extruder-um2-version-2

Robert's design is here:

http://umforum.ultimaker.com/index.php?/topic/4393-ultimaker2-feeder-system-improvements-and-ideas/?p=45758

Post #402. Read Robert's post #409 below that one for more details on assembly and such.

Ultimaker's design is in these three posts

post #500:

http://umforum.ultimaker.com/index.php?/topic/4393-ultimaker2-feeder-system-improvements-and-ideas/?p=50304

Post #279:

http://umforum.ultimaker.com/index.php?/topic/4393-ultimaker2-feeder-system-improvements-and-ideas/?p=42330

post #268

http://umforum.ultimaker.com/index.php?/topic/4393-ultimaker2-feeder-system-improvements-and-ideas/?p=42162

I think this second post is more useful. Anyway, contact Bas for a free metal grommet.

Takei Naodar's design won't fit on the back of the UM2 so you need to also print his very clever spool holder:

https://www.youmagine.com/users/takei-naodar

 

 

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