I have heard reports that loosening the 4 screws in the printhead helped, and loosening the 4 screws that hold the feeder tight also may help.
Obviously I do not mean that the printhead should start showing gabs in between the housing, but do not make it as tight as you can. Just have it reasonable tight 
(I do not believe in any manual 'reasonable tight' would be a certified way of describing tension) :wink:
There's definitely more than 1 cause for the issue, I just ran another test, and under extrusion began midway through the first section, then failed.
This time I had to clear the nozzle due the buldge issue. Are there instructions somewhere on how to remove the nozzle / hot end assembly?
Hey @Schafe! Lol, I "Liked"your post for several reasons 
. Yes D. is a reason for sure; you added a lot of detail to your post to help pin down your under-extrusion issue. I thought it was interesting that you think you are only getting 0/10 Blarp prints when it's your first print after a cold start (also Blarps for a unit of measurement is a great idea!). I was going to ask if you could provide any more details about this, but have been super busy lately and was going to ask at a later time. I suppose this is a good time. Do you always get a good cylinder after a cold start, or is it only some of the time?
I also "Liked" it simply because you were trying to add valuable content to this thread. I "Like" even seemingly off handed comments because they keep the momentum of the thread going; I like when people chime in and say what's on their minds. I also like the humor of your posts, keep them coming!! BTW your subsequent posts have definitely been impressive. I like the record keeping you are doing and think this information is invaluable to help pin down the problem.
Also, I want to add that I'm originally from Nebraska; I wasn't born there but spent a majority of my life there. I understand what it's like being from the Midwest. Personally I think Iowa is nicer to drive through and there is more stuff to do; you have better strip clubs for sure :mrgreen:! I lived in Bellevue, Omaha, and Lincoln so going over to Iowa to sample their local delights was always something I enjoyed. It sucks when you go overseas or something and people have no clue Nebraska exists. It's even worse when you travel within the country and hear all the stereotypes people associate with Nebraska and surrounding states. I think this is a pretty upstanding forum though, most people probably haven't developed these stereotypes so there is more mental equality 
.
You know, I've always wanted to see the Cedar Rapids Nice Shiny Thing!! I've only been in the US for 15 years though, and I was waiting until I'd become more fully assimilated into US culture in order to be able to appreciate it fully. And for global warming to improve the situation vis-a-vis snow. :-)
Thanks lots for taking the photos - very helpful. I've recently been fortunate to get access to a number of printers that I've been able to test, and I'm trying to identify some patterns and build up a library of reference data. Since your machine is definitely one of the more delicate souls in the Ultimaker family, I just wanted to see how it compared to some of my reference machines (almost all of which, annoyingly, work great). But no, I don't see anything in particular wrong with your printer in those photos. :-(
Apologies if my request appeared patronizing - it wasn't meant to be. I just had some half-baked theories I wanted some more data for... without muddying the debate still further by throwing out yet more 'Well, it might be....' memes, especially when I hadn't really thought any of it through. :-)
Just a thought on the loosening of the 4 main bolts.This may be ok for this particular print with no retraction, but I'm guessing if those bolts aren't tight, it'll exacerbate the issue that occurs when the bowden tube is not seated all the way into the teflon coupler, you don't want any play in here at all, or you'll create the back pressure buldge and extreme, print failing under extrusion.
I think there are two main ways that adjusting the tension on the thumbscrews in the head can affect things. Firstly, while the back of the head assembly has a thick metal spacer fixing the distance between the two flat metal plates, the front does not. Over tightening the front bolts may flex the bottom metal plate slightly, and that might put pressure on the interfaces between the nozzle, teflon, and heater block.
Secondly, there is the issue of the teflon and or bowden end deforming underlongitudinal load. Absolutely, you want the bowden tube to be mated up against the inside of the teflon piece, and unable to move. But you don't want it pressed so hard that any part of the tube starts to deform, and make it harder for the filament to pass through.
If the Bowden is fully inserted before the thumbscrews are done up, and held captive at the top of the head by the retaining clip, then when the thumbscrews are tightened, the available space for the bowden is going to be reduced and while that will keep pressure on the Bowden-teflon connection, it's also going to cause the tube to bend or deform somewhat - and that's going to increase resistance. I think that's probably the biggest reason why reducing the tension in the four long screws might help with extrusion issues.
The way I recommend assembling the Bowden to minimize these issues is firstly to make sure the 4 thumbscrews are fully screwed in, but not excessively tight so as to risk bending the bottom plate. Then insert the Bowden tube fully into the teflon piece, while the white retaining clip is fully pressed into the head assembly: you should then be able to move the bowden (and the clip with it) in and out by a couple of mm, without the end of the Bowden tube ever being visible above the teflon piece. (Temporarily depressing the spring with a screwdriver blade might help improve visibility, if the spring is in the way). Then you need to hold the bowden so it stays pressed in place fully inside the teflon, while lifting the white clip upwards fully, to capture the Bowden tube. Then slip the c-clip around it, to help keep it in the raised position where it will grip the tube fully.
When it's assembled like this, the bowden tube should be pressed fully against the teflon piece, but unable to move back and forth at all when pulled by hand (or by retraction), while minimizing the stresses on the end of the tube.
LOL Schafe you sound like a dangerous person, perhaps you should live in NW Washington
@Illuminarti: The second issue with the bowden pressing too hard against the teflon piece - that's something that I experienced too:
It might be hard to see, but the top of the teflon coupler is recessed a bit. I guess that's also how the lip formed inside the coupler where filament could hang on.
I'd say it isn't a smart idea to tighten the metal piece where the teflon coupler sits on. This just jams it against the bowden tube and leads to deformations.
Hi Schafe 10/10 Blarps for your printer. You are at the top in the Blarp contest!
Check your nozzle, I suspect that it will be full of black s***
250ºC for PLA is too much, this will generate a lot of burned plastic inside the nozzle. Since you have to remove the teflon coupler, you should measure that too.
Go to the supermarket and buy a six pack of comfort and acetone to clean the nozzle.
A little more anecdotal evidence... in a recent test I did, I had a machine that consistently failed at 9mm³/s when printing with a fairly tightly coiled PLA. By loosening the head screws and extruder fixing screws on the back the performance immediately improved to be able to print 12mm³/s.
I'm not convinced though that the sort of subtle mechanical problems that limit throughput in the 7-10mm³/s range are the same ones that limit some printers to 3 or 4mm³/s.
Not offended at all. Just wanted to clarify that I'm no Larry and yes, we really do have a Larry where I work. I suspect that the people who own a 3D printer are all pretty intelligent.
I was hoping I wouldn't have to disassemble any more. Blarp!
If you are seeking "talented" young women with great flexibility may I suggest Peoria or East St. Louis Illinois.
I doubt that my nozzle has any burned PLA inside. I've cleaned it since printing at 250 using the heat and stuff cool and pull technique. Henceforth this technique shall be refered to as the Has Cap technique, at least by me.
I'm not sure how much beer is in a European 6 pack, but a 6 pack for a proper Iowan just scratches the surface. More like 12 with a shot or two thrown in.
Another favorite beer quote: "In dog beers I've only had one."
Hi Schafe,
I doubt that my nozzle has any burned PLA inside. I've cleaned it since printing at 250 using the heat and stuff cool and pull technique. Henceforth this technique shall be refered to as the Has Cap technique, at least by me.
Are you sure that the Has Cap technique works? I tryed that and didn´t remove almost anything. I think it all depends on how much burned plastic you have inside your nozzle.
Once you've managed to successfully print at 10mm3/s for a few times, the first thing that I would check would be the nozzle, the teflon coupler and the filament radius. I could bet some beers that your problem is a dirty nozzle.
I'm not sure how much beer is in a European 6 pack, but a 6 pack for a proper Iowan just scratches the surface. More like 12 with a shot or two thrown in.
Was not my intention to doubt from the capacity of Iowan people, but a European six pack it will put you drunk real fast. So my Iowan friend, it doesn't matter the quantity but the quality, didn't you know that size doesn't matter? :mrgreen:
Cheers,
now I'm thirsty...
Additional note: The nozzle interior is dificult to inspect due to the small size, but make sure that you really cleaned it. In my very first experiments with the UM2, I noticed that after a few prints the filament wasn´t "dripping" during the heating process like in the begining. I made a extrusion test and only reached to 6mm3/s. after the nozzle clean I started to achieve 10mm3/s again.
Follow illuminarti's procedure (post#133) to assemble the Bowden.
Another test last night. This was done with a small segment of filament cut off, not on the spool. Although it has a fairly tight radius, there should be no resistance. This suggests to me that the feeder only plays a small role in the under extrusion issue.
I didn't answer an earlier question. Many of my cylinder prints that were conducted with a "cold" printer failed. It is all just very random. I can never get the same result twice.
I've had 2 more thoughts neither of which I think make a difference.
My first 20 hours of printing used Ultimaker white ABS at 260C. I printed almost all of the objects that came on the SD card using ABS. I have no idea what those objects have for an extrusion rate, but they all came out perfect.
My printer did not come with the glass plate. I used an 1/4 inch aluminum plate modified at the corners to accept the clips. I now have the glass plate from Ultimaker, but I never stopped using the aluminum plate. It seems to be working and I have no adhesion problems when the aluminum is covered with blue masking tape.
I don't think either of these is what is making my printer behave so poorly.
Would someone verify for me that the brass nozzle unscrews from the silver cylinder with the perimeter holes. I'll get the acetone tomorrow and begin the soak. I just want to make sure about the unscrewing part before I destroy something.
I remembered that beer in Iowa is required to have a lower alcohol content than normal. No wonder we have to drink so much. A recent Google search did not give me a solid answer. Its something like 3.2%. I'm sure that if I were in Europe, and drank as fast there as I do at home, I would be flat in no time. It normally takes about 5-6 hours for me to transform from happy, giggly, life of the party Schafe that everyone wants to be with to mellow, quiet Schafe to angry, throwing cans, get out of my house Schafe to creepy, blacked out naked guy. My wife hates creepy naked guy. I once fell down on a pile of bricks, pants around my ankles, in front of her parents. Europe wins - this time.
You guys are going to be sad when I finally get my printer going - if that ever happens.
Braddock - the natural curve of the filament in your photo would be to the right, while the Bowden tube is curving to the left and away - I imagine there's quite a lot of resistance generated. It would be interesting to unhook the Bowden just above the extruder and try feeding another length of that same filament into it, while keeping it in that same orientation as in your photo.
The extruder has quite a bit of force, and feeling the spring of the curled filament in my hand, it really isn't that tight, not when it's just hanging loose like that, it's just difficult to imagine that it causes that much of an issue. This is also with Inox still lubricating the bowden.
Braddock - the natural curve of the filament in your photo would be to the right, while the Bowden tube is curving to the left and away - I imagine there's quite a lot of resistance generated. It would be interesting to unhook the Bowden just above the extruder and try feeding another length of that same filament into it, while keeping it in that same orientation as in your photo.
I also tried your test braddock, but slightly differently. When selecting an object to print the screen says how much filament is required. My thought was to measure and cut off that amount plus a little more for safety. Then cut the filament right where it enters the feeder. Use the manual feed option to run the new filament into the feeder then start the print. Didn't work.
Hi braddock,
There are several things that can cause under extrusion, it's not caused by only a little devil, the devil has several little friends.
Thought that your problems were solved!?
Man, that filament has really tight radius!! there should be a lot of resistance in bowden tube and in the teflon coupler.
It's so random... problem not solved, just momentarily reduced.
Anyone want to buy a slightly used UM2?
Hi braddock,
There are several things that can cause under extrusion, it's not caused by only a little devil, the devil has several little friends.
Thought that your problems were solved!?
Man, that filament has really tight radius!! there should be a lot of resistance in bowden tube and in the teflon coupler.
My first 20 hours of printing used Ultimaker white ABS at 260C. I printed almost all of the objects that came on the SD card using ABS. I have no idea what those objects have for an extrusion rate, but they all came out perfect.
.
Abs is a different animal (like someone said here in the forum ) it's easier to extrude
I don't think either of these is what is making my printer behave so poorly.
I agree with you...
Would someone verify for me that the brass nozzle unscrews from the silver cylinder with the perimeter holes. I'll get the acetone tomorrow and begin the soak. I just want to make sure about the unscrewing part before I destroy something.
Yes, it's correct, just unscrew the "silver cylinder with the perimeter holes" from the nozzle.
After soaking the nozzle you have to use something to remove the crap. Last time I used a match and (not sure if is the correct term) a tooth stick!?
I remembered that beer in Iowa is required to have a lower alcohol content than normal. No wonder we have to drink so much. A recent Google search did not give me a solid answer. Its something like 3.2%. I'm sure that if I were in Europe, and drank as fast there as I do at home, I would be flat in no time. It normally takes about 5-6 hours for me to transform from happy, giggly, life of the party Schafe that everyone wants to be with to mellow, quiet Schafe to angry, throwing cans, get out of my house Schafe to creepy, blacked out naked guy. My wife hates creepy naked guy. I once fell down on a pile of bricks, pants around my ankles, in front of her parents. Europe wins - this time.
:smile: :grin: :lol:
I will miss your humor, that's for sure.
Almost all beers have 4,5% and the good stuff has 5,5% :blink: :blink:
Hey Shafe,
Tell Larry to be gentle with the Pt100 probe and the fan's wiring
there's a small hexagonal screw that fix the probe and the heater
...and tell Larry to use R/C hex wrenches, so awesome they rocks my socks!!
The extruder has quite a bit of force, and feeling the spring of the curled filament in my hand, it really isn't that tight, not when it's just hanging loose like that, it's just difficult to imagine that it causes that much of an issue. This is also with Inox still lubricating the bowden.
The reason I ask is that I *have* done that test several times - and if you're pushing the filament against its natural curvature, it can be almost impossible to get it to slide through the Bowden tube. The filament will usually try to realign itself into a better arrangement, by rotating, so it slides more easily. However, when the filament is fixed in place by the extruder mechanism, and unable to rotate, then it can't be realigned.
Remember that the whole reason that the filament slips is for no more, and no less, reason than that the extruder can no longer push the filament hard enough. The pressures in the head get really high when extruding; any additional resistance can be enough to push it over the limit. Yesterday I was running tests at 9mm³/s, on a printer that was getting very close to its limit. The lightest pinch of the filament that I could feel between my index finger and thumb was enough extra resistance to make the extruder slip.
The issue is not so much the absolute amount of force the extruder can deliver, so much as how much force is left over once the natural resistance in the system has been overcome. :smile:
I totally understand your frustration, but I'm also pretty confident that UM will figure this out, and when they do I expect they'll make sure that everyone gets a suitable fix.
Thanks Illuminarti,
I've just installed a new Bowden tube, and assembled the print head as you suggested. I took a lot of care not to damage the new tube, and make sure it's nested properly, without excess pressure.
I then ran another test, and used another cut off filament, with a similarly tight radius, and it completed perfectly, other than that I miss calculated how much filament I needed, and it ran out just before the end.
So, after another re assemble and a new bowden tube... testing perfectly again. Blue one actually ran out of material at the top, was a cut off piece with a tight radius.
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Just a thought on the loosening of the 4 main bolts.This may be ok for this particular print with no retraction, but I'm guessing if those bolts aren't tight, it'll exacerbate the issue that occurs when the bowden tube is not seated all the way into the teflon coupler, you don't want any play in here at all, or you'll create the back pressure buldge and extreme, print failing under extrusion.
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