Retraction Issue

[eric-rea 3]

Hi, I have an Ultimaker 2 and I am printing PLA at 100mm/s and 200c temperature.

I have had my printer since March and only tried a few overnight prints. All but one time the filament got bound up and choked off the feed making the print unable to finish. When this happens the feeder chews through the filament until it breaks and I have to disassemble the feeder to remove the broken filament.

After the last time this happened I seem to be having an issue where, every time the print retracts the filament during printing, the material stops extruding for a couple seconds leaving little beads instead of a line. It's possible that its not related to the issue above but i thought i would mention it just in case.

Does anyone have any suggestions?

Thanks!

[danilius 118]

PLA at 100mm/s and 200c temperature is like trying to pedal a bicycle at 100mph. You can do that going straight down a cliff, but the ride is going to be bumpy, and the finish might not be what you expected.

At 200C, expect to print around 30mm/s depending on your filament of course. To print at 100mm/s you would have to go up to 240C or even higher, and the print quality will be simply horrible.

[neotko 1,417]

But at 240C if the first layer it's slow (as it should to make it stick) you might burn pla. Try to adjust the temperature of the first layer so it doesn't burn pla and adjust it at layer 2. Etcetc

[danilius 118]

Good point. What I usually do is set the PLA on the UM2 to 200C, and then in CURA use the TweakAtLayer plugin to raise the temperature to 240C at the first layer. Sorry, should have thought about that!

[cloakfiend 995]

Also, for the general user expecting anything of a decent shell quality don't even waste your time printing faster than 50mm/s. For speeds of 50+ for me is more for prototyping use as speed of realisation is more important than actual finish quality. 3D printing at the moment is like pouring a Guinness. Good things come to those that wait.... etc. Doing things as quickly as possible can result in many problems, one of which is the printhead knocking into the print potentially ruining it depending on the structure and solidity of it. My average speed of printing PLA is 35mm/s at 208c (depending on filament brand) BTW.

Edited July 2, 2015 by Guest

[eric-rea 3]

Thanks for the tips all! I will try and tweak the settings and see if my retraction issue is solved.

[cloakfiend 995]

Also make sure to do atomic pulls. other wise that clicking noise will haunt you for ever!

[gr5 2,181]

200C at 100mm/sec is fine as long as the layers are then enough: 0.04mm thick.

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. Different colors print best at quite different temperatures and due to imperfect temp sensors, some printers print 10C cool so use these values as an initial starting guideline and if you are still underextruding try raising the temp. But don't go over 240C with PLA.

[eric-rea 3]

Thanks for the tips y'all. I tried doing the atomic pull and a few other tips but am experiencing the same issue. Here's a video of a print starting from the beginning printing just the brim. At :15s you can hear it 'chirp'. Unfortunately the print head is in the way of the extrusion, but when that chirp happens, it stops extruding for a few seconds. When the head moves out of the way, you can see where it missed. It does it again at about :29s.

 

[gr5 2,181]

That's very common. You are seeing it skip back on that first layer. The feeder has limited current - it's supposed to skip back rather than grind the filament to dust. The feeder can put out about 5kg (10 pounds) of force but in your case that's still not enough to overcome all the various resistances (pulling on filament from spool, friction in bowden, friction in teflon coupler, pressure in head). Normally at 1mm^3/sec you would expect only about 1 pound of force needed. So something is causing massive friction.

Now it's hard to say for sure because sometimes it only does this on the bottom layer - the bottom layer is typically .3mm thick so you may be printing 3x more volume there although it looks to be moving slowly (around 30mm/sec?) also sometimes the head is too close to the glass and it slowly builds up pressure because there is no place for the filament to go. So I guess I would wonder if it does this on layer 2 also.

Anyway I'm going to assume your leveling is fine. That means you have serious underextrusion. Check to see if filament tangled first - heck here's a list...

#10 is not your issue as that doesn't do the skip back. #1 through #6 are most likely. Try to rule these out one at a time.

CAUSES FOR UNDEREXTRUSION AND HOW TO TEST FOR THEM AND REMEDY THEM

As far as underextrusion causes - there's just so damn many. none of the issues seem to cause more than 20% of problems so you need to know the top 5 issues to cover 75% of the possibilities and 1/4 people still won't have the right issue. Some of the top issues:

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. Different colors print best at quite different temperatures and due to imperfect temp sensors, some printers print 10C cool so use these values as an initial starting guideline and if you are still underextruding try raising the temp. But don't go over 240C with PLA.

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.

10) Hot weather. If air is above 30C or even possibly 25C, the air temperature combined with the extruder temperature can soften the filament inside the feeder such that it is getting squeezed flat as it passes through the feeder - this is obvious as you can see the problem in the bowden. The fix is to add a desk fan blowing on the back of the printer.

[cloakfiend 995]

I'd say try the atomic pull again, and dont stop doing it until the end comes out perfectly shaped like the insode of the nozzle. then go from there. I used to get that damn ticking sound all the time and was ready to throw my machine onto the floor as that sound drove me crazy....then i learnt that i needed to do atomic pulls and print off the roll and i've never heard it since. Good Atomic pulls are ESSENTIAL. printing off the roll is optional but DOES eliminate the ticking sound if all else is fine as the wieght of it pulling the roll of filament round is sometimes too much for the feeder and its causes the clicking. This is how i print everything.

[eric-rea 3]

Good stuff. Thanks guys!

[cloakfiend 995]

How I do atomic pulls, in case you where wandering...(but feel free to do them however works best for you) as everyone does them slightly differently.

 

Edited July 27, 2015 by Guest