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!
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.
Thank you, I'll try that.
BTW, I think GR5 means:
M907 E1500
E500 would cut the current dramatically, and probably not work well. Or at least, don't take that example literally and put it in your gcode as is. :-)
last week, I cleaned my nozzle...
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!
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?
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.
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.
You're printing ABS?
I can see how my statements could be confusing. I have a lot of ABS to print with but I'm currently printing with PLA.
I'm using the ABS to clean the nozzle with because it's white, I can see the black stuff coming out of the nozzle and because I can dissolve the ABS in acetone as a last resort.
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.
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.
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.
I'm printing in an office environment so there is minimal dust. The UM ABS I'm using can be manually pushed through pretty easily at 240.
I will, however, make an SOP to flush the ABS at 260 and see if that helps.
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.
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:
I hadn't considered that. I'll take a look!
bingo... I think George hit the nail on the head... your printing black courtesy of your ABS feeder mechanism !
Ian :-)
I confirmed it. There's little black specks of plastic traveling up the bowden tube. I've relocated the roll to the floor but I'm still seeing a small amount of the debris. I don't yet know whether it's leftover or new so It looks like I'll be disassembling the feed mechanism this afternoon.
@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
@gr5,
I wasn't aware of that. I've been following the old internet tradition of whining on the board to get people to help me with my problem. 
Fortunately, you are all way too nice and have been helping me out.
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.
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:
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:
Post #279:
post #268
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
Looking at the print I'm doing today, I swapped white ABS for silver PLA. There are white ABS flakes in the bowden tube, presumably from being ground off by the drive wheel and no black flakes.
This indicates that my problem is not the plastic cold end housing but, instead, the drive wheel.
ArunC posted a topic in UltiMaker Cura,
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Dustin posted a topic in Firmware,
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gr5 2,173
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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