Prusa i3MK3s extruder blocked  

RE: Prusa i3MK3s extruder blocked

I saw that the forum lost the second picture link, here is https://photos.app.goo.gl/1G7DfWRY1ABiToEs9

RE: Prusa i3MK3s extruder blocked

Were there a lot of retractions (e.g. hops from place to place) in the offending prints? Your explanation sounds like an issue I was running into prior to adding my MMU (and I haven't got back to trying to get that print to work yet). There is a theory that the custom heat break Prusa uses on the MK3 can clog up on prints with lots of retractions.

As far as the sensors not noticing a problem, the IR sensor is just detecting the presence of filament, not if it is moving. This is a significant downgrade from the MK3 laser sensor in my opinion. Yes many people had issues with the laser, but there are options to make it work and instead they decided to remove functionality.

To get you back up and running I would suggest the following steps:

1. Move the extruder to the center of the X axis
2. Raise the extruder so you have plenty of room to work on it from all angles.
3. Open the idler door
4. Run the extruder temp up well above the filament you used (e.g. 240+ for PLA)
5. Pull the filament out (I've had to use vise grips a couple of times to get a good hold).
6. Remove the nozzle
7. Manually feed filament (I suggest a different color so you can clearly identify any plug that comes out) through the extruder in the normal path (top down).
8. Pull the filament back out.
9. Clean or replace the nozzle
10. Reinstall the nozzle
11. Perform cold pulls until it's clean
12. You should re-calculate your Live Z because the nozzle was off, but I never do...

If 5 takes too much force or the filament breaks you'll have to disassemble the extruder to clean things up.

If that does appear to clean things up, you continue to have these issues, and you do not plan to add a MMU, then you can replace the heat break with a standard straight through heat break (the custom break is to support the MMU).

RE: Prusa i3MK3s extruder blocked

Hi,

nothing worked. Heating the extruder and trying to pull out the the filament did not worked. The filament was so blocked in the PTFE that could break the extruder or bend the axes if I had to apply more force. So I had to dismantle all the extruder, to completely free the E3D v6, then heat the hot end, and when hot, screw the hot-end block from the aluminium cooler with the PTFE inside. After that I waited it cooled down, and tried to remove the PTFE with the filament, but again was completely blocked. The small black ring over the PTFE tube on the top of the cooler, prevent the tube to go in up direction. The only way to remove it is pushing it down, so pushing down the PTFE tube, I was able to remove it, and the piece of the filament.

Don't ask me how, but the bottom filament part was larger than the diameter of the PTFE tube, and couldn't be fitted in, so it could not be slide out in normal condition. Only when I dismounted the PTFE, I was able to extract the filament from the bottom.

Here is how the filament appears: Image A Image B

- How it was possible for the filament to take that shape ?
- Can it be that the PTFE tube was not fitted till the end ?
- The diameter of the filament is 1.75, while the final part is 2.18 !!

I am studying some schemes of the E3D V6......

RE: Prusa i3MK3s extruder blocked

I have the exact same error as you described: Extruder clicking, not extruding, and about 1.5mm above the rest of the print. Just like you, I always had to disassemble the extruder to get the filament out. I tried the same and a different model already and, so far, I didn’t find a solution... 

Here is my post:

https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-hardware-firmware-and-software-help/print-stops-extruding-at-exactly-the-same-layer-every-time-layer-height-0-1/

Maybe together we can find a solution because right now, I am a bit annoyed by that problem...

RE: Prusa i3MK3s extruder blocked

I'm not exactly an old pro, so this is worth what you are paying for it. I've recently been through some similar experiences, and here is what I concluded.

After replacing hot end parts over the preceding months, many not from Prusa, I had some mis-matches. In particular, some coolers (the large aluminum cylinder with the cooling fins) have a neck near the bottom that is too small for the PTFE tube to fit through. Some heat breaks have PTFE inserts in the top, apparently to go with the coolers that do not allow the PTFE tube all the way down to the restriction near the bottom of the heat break, where the heat break screws into the block. With any combination that leaves a void inside the heat break that has a larger diameter than the filament, that void will trap whatever filament was last used - even when a cold pull is applied. This material can degrade from long exposure to heat, which is even more likely if it is low temperature stuff left over when the printer is working with higher temperature stuff. Such degraded stuff can plug the path.

Therefore, it seemed to me, the solution is either to avoid any such cavities, or to fill them with PTFE tubing. If there is no restriction in the cooler, then the PTFE tube can extend all the way from just below the feed gears to the bottom of the heat break, leaving no voids to collect molten plastic. If there is a restriction in the cooler, then if there is not a PTFE tube inside the heat break, put one there, and make sure it butts up tightly against the underside of the restriction in the cooler.

I think the original Prusa cooler for my printer had no restriction, so it was possible for a single PTFE tube to extend all the way down to the restriction in the heat break, leaving no void diameter larger than the filament. That was by design. But if one pushed down on the lock ring, then pulled up a bit on the PTFE tube, that would open up a void the diameter of the PTFE OD ... 

There must be a clear path all the way down to the nozzle for the filament, obviously. Easiest way to keep that path clear is to make sure no molten plastic gets outside the PTFE tube except at the end, and all of that has to go through the nozzle.

RE: Prusa i3MK3s extruder blocked

The Prusa version of the E3D-V6 Heat Break has a milled diameter of 2.2 mm for most of the length, but right at the cold-hot transition zone it necks down to 2.0 mm.   

Printing with a high percentage of retract/z-lift operations seems to cause melt to back up into the transition zone where it cools and then is impossible to extrude. Can't get 2.2 mm filament into a 2.0 mm hole.

Replacing the heat break works for a lot of people and totally changes the print experience.   While Prusa states the mod is needed for the MMU user, many MMU users claim to have no issues with the stock E3D-V6 heat break.

RE: Prusa i3MK3s extruder blocked

I have a new build MK3S. I ordered a genuine ED3V6 all metal heat break and some socks. Not fitted yet.(Following 3D Printing Nerds (Joel) video over on Youtube.  I notice when the part cooling fan kicks in it can drop the hotend temp up to 10 degrees but it does recover after a while. No blocks for me yet.  So I leave well alone for now.

RE: Prusa i3MK3s extruder blocked

I guess a redesign of the part cooling fan flow maybe needed. The part cooling fan should cool the part and not the hotend/nozzle. 

RE: Prusa i3MK3s extruder blocked

I cleaned the PTFE tube (dismounting and reassembling everything), and took the opportunity to make the MMU2S upgrade to the Extruder part.

Then I reprinted the same, gcode, and after some layers, I got a message on the display saying something like "Remove the filament immediately". I pressed the  button and the filament was ejected.

The display said "Press to load the filament". I inserted the filament again, it was loaded, and after few seconds, I heard the gear shifting, and no PLA was expelled. I unloaded the filament, but unfortunately it was blocked and jammed again.  The filament message should be the effect of the new MMU2S sensor.

I was using Prusament Galaxy black. Now I will need to dismount it again. 🙁 

This will give me the opportunity to do some verifications:

They exist several versions of Prusa cooler design. As Prusa support told me, the latest printers have a larger PTFE tube, (2.0mm hole instead of the usual 1.80). I am not sure what PTFE tube version my Prusa i3MK3S has. It was assembled and shipped by Prusa in late April, so it should have the 2.0.
However they asked me if I updated the tube, and I did not, since the one I found on the MMU2S+Extruder Kit, I though that was a spare part. 🤨 
I verify this info comparing the PTFE tube found on the MMU2S kit with a spare old one found on the original MK3S box, and I can confirm that the new has a bigger diameter that should allow the larger top of plastic to pass through the PTFE tube and not to block the filament. This means that is probable my printer still has the small diameter PTFE tube.

Your E3D drawing does not correspond to the Prusa shipped. The drawing shows a continuous drilled hole filled with PTFE. Prusa has ORIGINAL E3D parts, and my Prusa has a metal funnel shape inside just before the 4mm intermediate section, so no PTFE con enter inside the intermediate section, and the funnel shape of one side of the PTFE just matches the metal shape. Exactly like the original E3D part
I will take drawing, measures, and picturesof mine as soon as I dismount it again.

• If the previous point is true, the filament is directly exposed on the intermediate metal, and that is not an issue in normal conditions since the temperature is not enough to melt it, but with retractions, the melted material suddenly become cold in contact the metal, and hardens, blocking the extraction from the PTFE tube.
• Today I have seen a strange picture on the Prusa shop, where the new intermediate metal part is coated with red silicon to protect the metal from the air and keep the temperature higher and the filament still soft, to avoid it can stuck inside !! If this is the case I could cover mine with some silicon high temperature gum.
• I took some closeup photos of the hotend, and what surprise me, was the position of the cooler: it is exactly in the middle, blowing air 50% on the HOT END (!!!!) and 50% on the NOZZLE (!!).
  You can see here a photo that is taken parallel to the hot end (I removed the fan to take it).  You can see that is straight toward the hot end. Very strange design. That means 50% of the air can go to to cool the "intermediate" tube section, just over the hot end block, and cool it down quickly, cooling down the filament melted inside. I could expect the nozzle to be  lower at least 8-10mm.

After those considerations, I will go to maintain the printer and see what is inside the cooler.

That explains why several videos on youtube claimed to have solved the clogging issues using the silicon cover of the E3D block. If the block does not cool with the air against it, it is hotter, and also the intermediate tube is hotter, keeping the filament inside soft. Then the latest Prusa intermediate tube as in addion silicone on that section.

RE: Prusa i3MK3s extruder blocked

One clarification, since I can not edit posts in this new forum: I was wrong on the PTFE measure when I compared the two PTFE tubes.

I have rechecked them and they are exactly the same hole diameter size. I have four of them. I can't say the exact measure, since PTFE is flexible and it is very difficult to measure very small diameters inside the tubes with a calliper. I got always a different sizes around 1.75, but I can say that all them must be the same size.
Looking at them, a PLA filament fits inside perfectly, so they should be either just around 1.75. This Prusa page has the specification, and the hole seems exactly 1.85 mm, but I don't think mine are. Prusa Shop is not clear. It has two different PTFE tubes page products (A and B), but they say only "compatible with selected Original Prusa i3 printers at 1.75 mm ", and this is confusing.

Dismounting my hot-end, I found again the filament blocked with the usual blob at the end, not passing through the PTFE tube as you can see here.

May be now I have the nozzle partially blocked, and this cause the PLA to go up in the tube. I tried to clean it with the special 0.35mm needle. I hope it solve the issue. If it happens again I will change the nozzle. I did not had a single issue for 3 weeks and then suddenly two in a day....

RE: Prusa i3MK3s extruder blocked

Antimix - that drawing is from E3D - and properly represents the modifed Prusa heat break.  PTFE extends into the very top of the heat break, followed by a 2.2 mm channel, then the 2.0 mm  channel at the transition zone.

Here's a standard E3D-V6 heat break.

That photo of a heat break with a color at the neck is a marking to let users know it is a modified E3D-V6 ...

RE: Prusa i3MK3s extruder blocked

Tim-m30,

my Prusa cooler does not allow a single PTFE tube to extend till the end. As you can see in the photo, it has a funnel shape just before the narrow section, and the PTFE stops just before the level of the narrow section. In this photo you can see it when I just removed the PTFE tube, and the filament is still blocked inside the small hole of the full metal separation section, that it is around 2.0mm diameter (larger than the PTFE). From that position i think is all metal till the contact with the nozzle.
The hole that you see is NOT the nozzle part but the bottom separator part in the PTFE high section tube.

I have done the following changes:

A) I covered with Kapton tape the front, top, right of the heating block and central tube separation as you see in the photos. I hope it helps better to maintain the constant temperature.

B) I realize that decision of Prusa design to have NO PTFE tube in the lower part of the tube (just after the separator is all metal) is due to have with MK3S the possibility to print very high temperature materials (HT) around 280/300° C.  At such temperature PTFE has problem. If you never plan to print models that should resist to high temperature (100°) with high temperature filaments, then the all size tube version is fine for you, otherwise you will need the mk3S as it is now. For this reason I expect there is no PTFE tube in the lower section. When I will change the nozzle I will see, may be I am wrong.

C) I realized that the real cause of the issue was a partially blocked nozzle that now is completely blocked, killed by a bad filament spool.
I had big difficulties even to unblock it with a needle. Is jammed and blocked. So when I changed the filament, the nozzle was already partially blocked, and the pressure blocked it again at all, even with Prusament PLA. The pressure bring up the melted PLA that blocked the filament under the PTFE tube. Easy ! So in normal condition (e.g. good filament) this cooler section should not give issues.

Tomorrow I will replace the nozzle, hoping that the block with bad material does not extend either into the metal separator, and in that case I need to buy also a new separator.

I will need to build a nozzle cleaner: a device built with arduino and LCD, that stays over a table, and has a small heater block where the blocked nozzle can be screw, heated and cleaned cold pull, a needle, a brush, without the uncomfortable position under the printer X-Axe. I don't want to throw away the blocked nozzles.

Regards

RE: Prusa i3MK3s extruder blocked

Have you looked at the drawing?  lol.  Sorry - but the drawing is 100% clear the PTFE does NOT extend down the length.  The 4.2 mm section for the PTFE is about 4 mm deep into the cold end of the heat break.  Best of luck finding your problem.

RE: Prusa i3MK3s extruder blocked

I encountered a similar problem but I am pretty sure it is the filament. I was using a ColorFabb PLA/PHA blue filament (came in the same shipment as my i3MK3s kit)  on my XYZ da Vinci MiniMaker when it displayed the same problem being described by the OP. Thinking it was a one off, I transferred the filament to my brand new PRUSA i3MK3s, only the have the same issue come up. They both were set to the prescribed temperature for the nozzle. Both prints stopped mid project, about 50% complete, 3 hours into the run. I now have two blocked nozzles, two unusable printers.

RE: Prusa i3MK3s extruder blocked

I just had a similar problem with matterhackers pro black filament. running a long job overnight last week ,  came in to the printer jammed and not extruding. removed the filament and the end was ground down at the extruder bondtech gears. cutting back the and and trying to reload didn't succeed. the broken end was down inside the PTFE so i heated the hotend up to 280 to remover the nozzle and decided to try one more reload. the reload worked and i was able to purge the jam by slowly manually extruding about 40mm of filament. once the bad chunk was cleared everything was back to normal. since then i have run the print nonstop almost 60 hours with no problems. I think there was a chunk of something with a higher melting point in the filament that jammed the hot end . once that was purged all was good.  also i have noted  that that particular filament runs around 1.70-1.71mm in diameter

RE: Prusa i3MK3s extruder blocked

So, yeah, I've printed 3 pieces, it was fine running 20 hours prior with PETG and another PLA material. My conclusion is this: There is a problem with the ColorFabb PLA filament.

RE: Prusa i3MK3s extruder blocked

Update: I've taken the extruder apart and removed the stuck filament. I'm never conna touch colorfabb again.

RE: Prusa i3MK3s extruder blocked

UPDATE:

Yesterday I dismounted all the E-parts, and cleaned it again after it failed also with the Prusa Galaxy Black. Same issue.

But then I decided to make some changes to avoid the issue in the future:

1. I took the two pieces of PLA that blocked the tube (that I did not throw away) as referral.
2. I decided to put a PTFE tube with the same internal diameter of the hole in the final metal part of the separator.
3. I checked all my Prusa spare PTFE tubes, but I noticed that they had all the same small hole diameter size around 1.80.
   Then for chance, I noticed than one just ONE PTFE tube coming from the MMU2 multi material kit (to be used to connect the MMU to the buffer) was around 2.0 mm in diameter 🙂 . It was only that tube ! The size was big enough that all the plastic heads bubbles coming from my filaments that caused the blocks in the tube, can pass through it with no issues. 🤗 
4. I decided to cut a pieces of that PTFE tube and use it inside the cooler aluminium section.
5. I cut it a little longer, to allow precisely to position it just under the gear, and allowing to have the cooler a little screwed out, so that the hot block may be 2mm far down from the plastic parts.
6. I carefully shaped the PTFE piece on the two parts as the original.
7. I re-assembled all, and re-aligned the PINDA. Then I  performed a XYZ axes and first layer alignment.
8. I performed firmware upgrade to 3.7.1, and  switched to PrusaSlicer 2.0
9. I re-sliced the piece and printed it using Sunlu Black PLA (with a little high temperature 200)

Now, after 2 hrs it has finished with no issue. Just luck ? I will see.

PS:

I have a very old white PLA spool, that I tested just before all the mess. I think it was the cause of the first nozzle block. After that, I tested a new orange PLA, and then the nozzle become blocked. However since the orange started to print I already noticed an irregular extrusion. I am not sure which of the two was the culprit for now. Once I receive the new set of nozzle from Prusa, I will test them again, and if is is the case I will drop away the old PLA.

Regards

RE: Prusa i3MK3s extruder blocked

1. When switching from a higher temp filament to a lower temp filament, run some cleaning filament through at the higher temp material's melt point. Then, perform an atomic pull to clear out the flakes of higher temp material lurking above your nozzle.

2. Have a collet clip installed to lock the PTFE tube in position. You don't want PTFE backing out and leaving a large diameter gap.