Nallath, you are right. I have tested the speed test cylinder and fails above 3mm3/s. I am using robert's feeder and apparently it works well, no skipping. Have performed two atomic cleanings and have tried three different spools. I have been using Roberts feeder for some weeks with success, until today.
Is there anything else to look for?
You are printing at 3.2 mm^3/sec (.4 nozzle X .2 layer height X 40mm/sec). This is a little faster than I recommend but it should be fine for most colors and brands of PLA. You can probably ignore #1 below.
Many factors can cause underextrusion. Here is a short list of the most common:
1) Print slower and hotter! Here are top recommended speeds for .2mm layers (twice as fast for .1mm layers):
20mm/sec at 200C
30mm/sec at 210C
40mm/sec at 225C
50mm/sec at 240C
The printer can do double these speeds but with huge difficulty and usually with a loss in part quality due to underextrusion.
2) Isolator - this is most common if you've printed extra hot (>240C) for a few hours or regular temps (220C) for 100 hours. It warps. It's the white part touching the heater block. Test it by removing it and passing filament though it by hand.
3) Curved filament at end of spool - if you are past half way on spool, try a fresh spool as a test.
4) curved angle feeding into feeder - put the filament on the floor -makes a MASSIVE difference.
5) Head too tight? Bizarrely MANY people loosen the 4 screws on the head by just a bit maybe 1/2 mm and suddenly they can print just fine! Has to do with pressure on the white teflon isolator.
5b) Bowden pushing too hard - for the same reason you don't want the bowden pushing too hard on the isolator.
5c) Spring pushing too hard. Although you want a gap you want as small as possible a gap between teflon isolator and steel isolator nut such that the spring is compressed as little as possible.
6) clogged nozzle - the number one problem of course - even if it seems clear. There can be build up on the inside of the nozzle that only burning with a flame can turn to ash and remove. Sometimes a grain of sand gets in there but that's more obvious (it just won't print). Atomic method (cold pull) helps but occasionally you need to remove the entire heater block/nozzle assembly and use flame.
7) feeder spring issues - too tight, too loose
8) Other feeder issues, one of the nuts holding machine together often interferes with the feeder motor tilting it enough so that it still works but not very well. Other things that tilt the feeder motor, sleeve misaligned so it doesn't get a good grip. Gunk clogging the mechanism in there.
9) Filament diameter too big - 3mm is too much. 3mm filament is usually 2.85mm nominal or sometimes 2.9mm +/- .05. But some manufacturers (especially in china) make true 3.0mm filament with a tolerance of .1mm which is useless in an Ultimaker. It will print for a few meters and then clog so tight in the bowden you will have to remove the bowden from both ends to get the filament out. Throw that filament in the trash! It will save you weeks of pain
9b) Something wedged in with the filament. I was setting up 5 printers at once and ran filament change on all of them. One was slowly moving the filament through the tube and was almost to the head when I pushed the button and it sped up and ground the filament badly. I didn't think it was a problem and went ahead and printed something but there was a ground up spot followed by a flap of filament that got jammed in the bowden tube.
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Thanks for your detailed answer!
By the way, how can I place the filament on the floor? Is there any special spool holder to this purpose ?.
Main thing is to get a more straight line of entry into the feeder, I've seen people hang a spool on a broomstick between 2 chairs...
some of my options, there are many out there...
https://www.youmagine.com/designs/ultimaker2-spool-connector (look at the pictures)
https://www.youmagine.com/designs/ultimaker2-rail-system-u2rs
@gr5: "2) Isolator - this is most common if you've printed extra hot (>240C) for a few hours or regular temps (220C) for 100 hours. It warps. It's the white part touching the heater block. Test it by removing it and passing filament though it by hand."
Actually, when in use and on the border of collapsing, it will pass the "cold" filament through hole test, but when been hot for some time collapses inward on the filament, similar like an overdose heroin strangely bends the knees and has the poor subject sink into a low stance...
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nallath 1,124
Could you add a photo? This really helps with 'debugging' the problem.
Judging from your description I believe it could be http://d33v4339jhl8k0.cloudfront.net/docs/assets/53970867e4b0c76107b1091a/images/53bbf859e4b09d13bf3cdd85/file-NJOw1Ah4bz.jpg
This is caused by under extrusion. You can find quite a bit of topics that deal with solving that problem.
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