Extrusion Problem  

Re: Extrusion Problem

What temperature are you printing at? Are you using Z-Lift? What retraction settings are you using?

Peter

Re: Extrusion Problem

What retraction settings (length and speed) are you using?

And when you measured the length of the extruder idler tensioning screws, was the filament in it? The length of the springs changes, they get shorter when the filament is inserted, so if you measure with the filament in, you get less pressure.

I don't understand why you conclude that it must be a temperature problem.

Re: Extrusion Problem

If you can now reproduce the problem, then try to print just that part of Benchy to save some time. When it is misbehaving, stop the print and change the filament. Then inspect the filament carefully for signs of wear. You might be able to see if the fast repeated retraction in areas with many hops between printing parts causes slipping or grinding of the filament.

I don't know if the filament would be damaged if the tensioner screws are too loose, but I would certainly try to make them a bit tighter (and then a bit looser if tightening does not help).

Re: Extrusion Problem

My failed Benchy prints are also accumulating! 😀

I tried with retraction 5mm at 80mm/s speed, and it ground the filament down until it did not move any longer.
At least I can now identify the sound it makes when this happens.

The next Benchy print is running now, retraction 5mm at 60mm/s, and this is looking promising so far at z 12.95 (fishing rod holder completed).

Re: Extrusion Problem

My failed Benchy prints are also accumulating! 😀

I tried with retraction 5mm at 80mm/s speed, and it ground the filament down until it did not move any longer.
At least I can now identify the sound it makes when this happens.

The next Benchy print is running now, retraction 5mm at 60mm/s, and this is looking promising so far at z 12.95 (fishing rod holder completed).

I don't have my MK2 yet, I hope to get it this week, but, the retraction settings seem way too high. those are number usually seen on bowden setups. try 2mm retraction at 40mm/s and see what happens.

Re: Extrusion Problem

I don't have my MK2 yet, I hope to get it this week, but, the retraction settings seem way too high. those are number usually seen on bowden setups. try 2mm retraction at 40mm/s and see what happens.

True, but I want to find the maximum setting that I can use when I again try to print what I really want to print. Nylon and PC, for relatively large objects. Too expensive to try it out with those materials.

The latest Benchy failed again in the 'invisible ghost ship' fashion, at about z8.85. No weak layers building up, just sudden complete stop of extrusion. The filament shows clearly where it has been ground away.

The idler tensioning screws were 12.8mm long with the filament in it. Now, empty, the length of the springs is 13.7mm.

I adjusted the springs to 13mm length (empty) and measured again after loading filament: 12.0mm .

Next up: Benchy with retraction 5mm at 50mm/s.

Re: Extrusion Problem

Yep, sounds like high values, at least for PLA.
I'm using 0.8mm now, and 30mm/s

Re: Extrusion Problem

If you retract more than 1mm, you should expect blockages, which is exactly what you are getting.

Generally 0.6 to 0.8mm retraction will generate good results. At this retraction distance, setting speed above 30mm/sec is rather pointless because of acceleration.

And in general there is very little point in using PLA as a test for nylon. Each filament will require different settings. You will need to learn what each filament requires as you go along.

Peter

Re: Extrusion Problem

If you retract more than 1mm, you should expect blockages, which is exactly what you are getting.

Generally 0.6 to 0.8mm retraction will generate good results. At this retraction distance, setting speed above 30mm/sec is rather pointless because of acceleration.

And in general there is very little point in using PLA as a test for nylon. Each filament will require different settings. You will need to learn what each filament requires as you go along.

Peter

Cheers, that makes sense! The notch in the filament occurs when a bit of soft filament was pulled back during a retraction and has hardened and blocks the way.

Re: Extrusion Problem

When I used the standard 0.8mm retraction at 35mm/s, there were no blockages but pretty extreme stringing. See earlier in this thread http://shop.prusa3d.com/forum/original-prusa-i3-mk2-f23/extrusion-problem-t2168-s10.html#p17740

So I'm now printing Benchy again with these settings:
SLIC3R_Settings
0.10mm_DETAIL_Quality_Brim
X3d-white-PLA-1.75mm_EMult1.099_210C
Original Prusa i3 MK2 with ZHop_2-40

The layer adhesion was poor, so I increased the temperature by 10degC, and I measured 91mm extraction instead of 100mm, so I set the extrusion multiplier to 100/91 = 1.099.

Re: Extrusion Problem

First layer @ 215; remainder @ 200 (or 195). 210 may cause stringing. Most PLAs will print as low as 180 degrees without problem (depending on print speed)

Try without Z-Lift as that too can cause strings.

Increase bed temp to 60 (or 65 degrees).

Increase non-printing move speeds.

Use a different filament type.

Reduce retraction to 0.5mm.

Reduce print speed.

Peter

Re: Extrusion Problem

What temperature are you printing at? Are you using Z-Lift? What retraction settings are you using?

Hi Peter, I am using the preloaded PrusaPLA settings in Slic3r for the benchy model. I have been bale to print a successful benchy model before with these exact settings. On top of that, this issue is also happening with Prusa supplied GCode (as mentioned in my last post edit with the adalinda dragon). For the benchy, yes I am using z-lift.

Re: Extrusion Problem

Here is a video of the jam as it is happening. I thought I could predict it happening during the parts of the model with more travel time after it happened twice in a row, but it looks like I was wrong. This benchy failed much earlier in the print as you can see.

Re: Extrusion Problem

I should not have replied to this topic, because I now have my printer (just arrived today 🙂 ), it seems to have caught the same bug.

second print after assembly, calibrated, printing with included brass PLA.

Some layers at least in the outer perimeters are missing. Its still printing, so I assume it still has some infill, and it happens as well in the small areas as in the large parts.

Model is the dragon (analinda?) unaltered from the included SDcard. Started print in high-power mode had some fails in the arms of the dragon, switched to silent (because its getting late) , still have some errors in the later parts.

The first print was the Prusa logo, which went fine.

I'll post some pictures tomorow, its currently still printing.

My money is on the spool holder design. Thats the first thing I'm going to change.
On my last printer I had much improved prints by using a reverse-bowden or filament guide setup.

Complete guess, no idea if this is even remotely the problem!

Because the spool is full, and quite heavy, I bet the problem is that fast movement leads to pulling on the spool and rocking it.
Because its full and has 1kg of mass, it starts oscillating and pulls leads to missed stepps in the extruder.
Same thing on small perimeters, due to the small retract/push movements of the extruder it shakes the filament roll, and leads to misstepps.

So, I'll retry the print with the exact same original gcode supplied on the SDcard tomorrow, with the exact same roll of filament and a PTFE guide installed.

{please don't make me clean my hotend, I hate doing that}

Re: Extrusion Problem

So, what I did:

1 cold pull of the filament. (heatup to 220, let cool down to 85, yank out filament.)

McGuyvered a filament guide by drilling a 2mm hole into one of the supplied spool holders, eyeballing a length of PTFE tube and commissioned a spool stand built in lego from my kids. PTFE tube just sits between extruder and top mounted spool holder with hole.

poked the nozzle with the included needle.

brushed the nozzle with some robot's toothbrush. (wire brush)

Tightened extruder idler screws. Springs are now about 13mm long with filament inside.

analinda is currently printing, and looking good! no missing layers yet. (printing in silent mode from the start.)

Re: Extrusion Problem

Marco

Don't know if you have seen this video (PR Print Farm): with all the printers using the supplied spool holder and with no problems. Having said that, the printers used to create the parts for our printers are tuned in by people who really do know what they are doing (unlike us...).

I think your issue was probably mainly due to the filament tension springs not quite set correctly for your filament and environment.

Peter

Re: Extrusion Problem

Marco

Don't know if you have seen this video (PR Print Farm): with all the printers using the supplied spool holder and with no problems. Having said that, the printers used to create the parts for our printers are tuned in by people who really do know what they are doing (unlike us...).

I think your issue was probably mainly due to the filament tension springs not quite set correctly for your filament and environment.

Peter

Yes, you are probably right that it was the tension springs.

Still, I dislike this spool-on-top thin:

- it puts an unneccessary swingable (?) weight on the highest leverage pint on the printer.
- X-Axis movement from the middle out pulls a lot of filament from the spool, which can lead to tangling.
- X movements jerk the spool, and can possibly lead to uneven extrusion. (very minor, possibly not noticable on this printer, but on my old cheap malyan m150, it was very noticable.)
- most important: I don't like it 😛

I do like the "tidiness" of the filament guide, and the smooth unrolling of the spool you get by decoupling hotend-movement from the spool.

Also, if you print yourself a couple of spool rollers, you can have the spools always sitting there, and just pick the filament you want to use, without rearranging everything.

But, yes, in the end, mostly a matter of taste. At least on such a well built printer as the MK2.