Multiple print failures  

RE: Multiple print failures

You don't mention an enclosure. Are you using one? That seems to be the main cause of heat-creep with PLA.

If you are - leave the doors open. That is what I do with my Lack.

Also - stock up on cleaning filament. A lot easier than cold pulls.

RE: Multiple print failures

Posted by: @epzcaw

[...] There is a gap between the nozzle and the heater fan.

I assume you mean between the nozzle and heater block, correct?

[...] My last “chat” suggested applying thermal paste to the heat-sink.  This does not seem to accord with the instructions here https://help.prusa3d.com/article/cto24vjaps-heatcreep whihc says thermal paste should be applied to the heatbreak. 

You apply it to the upper end of the heatbreak that screws into the heat sink. The important part is that you do not apply it to the heatbreak where it screws into the heater block.

This requires the hotend assembly to be dismantled.  I am very reluctant to do this, as it is deemed very tricky.

Before you do that, as @robert-rmm200 notes, if you're printing in an enclosure, open that up. Also check to verify filament feeds cleanly from the top down past the Bondtech extruder gear and into the PTFE tube. Verify the Bondtech gear tuns freely and that the axle it sits on is centered and not hanging. Verify the filament path doesn't have any snags or undue friction.

If you do end up opening things up, it's a bit of work, but put it on a bench or table with good light and it's not overwhelming. The only tricky part is if the parts won't come apart easily. Have some good pliers and needle nose available. The good news is that you want to remove the heatbreak from the heat sink to apply the thermal compound, not the heater block, so you don't need to do it at temp and they're unlikely to be stuck together. Make sure the PTFE is seated properly and not deformed while you're in there. Add a collet if one is not present.

I'd recommend ordering a replacement E3D "non-Prusafied" heatbreak before doing this as the stepped heatbreak can be a source of jams under some combinations of conditions. Might as well make some improvements while you're at it. Have replacement zip ties handy to tidy it all up when done.

RE: Multiple print failures

One other easy check:  when it jams up, do a simple UNLOAD and examine the filament stub that comes out.  Post a photo here. 

Nominal diameter at the end of the filament should be 2.0 mm or less. If the stub measures 2.2 mm diameter, then you might be having a heat break jam.  Here's an example of a stub that causes jams.

And the collet Bob is talking about is actually a CLIP at the collet to better retain the PTFE tube at the top of the heatsink. And the process of checking for heatsink/heatbreak thermal paste is pretty easy; you do not need to remove the nozzle.  The heatsink/heatbreak are hand tight.

RE: Multiple print failures

Thank you all for advice.

I do not have an enclosure so that is not the problem.

I have put the printer away for a short while as I have another task to work on.  Also need a  break or may just throw it in the bin as it driving me round the bend.  I am doing this out of interest and to get my grandchildren involved and at the moment all the fun has gone out of it.

I will resume again in a few days,  implement your suggestions and return to the discussion.

Thanks again.

RE: Multiple print failures

Do not give up, my grandsons they like very much when I print them any fancy stuff. 

Can you please describe in more details your "print fails half-way through."

- does it stop extrude?

- what is the expected duration of your half way through failed prints ? 

- is the expected duration of your succesfull prints substancionaly different from failed?

- do you recognize on the filament the gears teeth marks?

- does this issue happen with your previous filament as well yet?

RE: Multiple print failures

Thanks for the encouragement!  My grandson has started designing (using Tinkercad) and making  at school.  I was hopign we ccoudl do some together when he comes for Christmas but.....

Re failures.  Sometimes, it seems to just stop extruding, but carries on moving about as if it was still doing so.

Sometimes, the last layers are not attached, and a tangle of filament forms.  If I get there in time, I stop it,  If not, I think it eventually stops extruding but carries on as if it were.

A recent one formed a solid spiral sort of pillar.

Usually, I manage to complete the PRUSA logo (20 minutes) and a small test piece I designed which only takes 7 minutes

This has been getting steadily worse since the problem started, and normally now, I can't complete anything which takes longer than that.  However, a few days ago, I managed a 1hr 50mins one.  Thought I was out of the wood, but alas no.  Some fail quite ealry on, others fail halfway or three quarters of the way through.

I went back to the original filament the the problem also occurred with it (both are PRUSA PLA)

A piece of filament which I have from unloading feels serrated on one side which I assume indicates gear marks.  The tip measures  at the maximum width 2.03mm.

What is particularly frustrating is that it was working perfectly for several weeks.  It seems as though I must have disturbed something when I changed filament, but no idea what.

I think the extruder is jammed once again so I will have to tackle that before I do anything else.

But thanks again everyone for "listening".

RE: Multiple print failures

You said you did a cold pull. Did you do them until the pull came out clean?

Did you try a new nozzle? Is the hot end temperature steady during a print?

Everything about your problem description points to contamination  in the hot end or nozzle damage. Maybe.

RE: Multiple print failures

Yes, cold pull came out clean - image attached.  That was several days ago.

I don't have a replacement nozzle.  I can get one - but it is very annoying how expensive gteh delivery charges are.  Coudl I get one in the UK rather than having it sent from Czech R?

Yes, I think I will have to take the whole thing apart but not looking forward to that.

I haven't closely observed the hotend temperature, but am fairly sure it remains within a few degree of 215.

RE: Multiple print failures

Posted by: @epzcaw

Thanks for the encouragement!  My grandson has started designing (using Tinkercad) and making  at school.  I was hopign we ccoudl do some together when he comes for Christmas but.....

You've got time. My sons are out of the house and I've got nobody to print with. Wish I'd had this when they were in school. It's always hard to be the "cool" (relevant) parent/grandparent. I managed to repair their broken Power Rangers toys (I was the "plastic surgeon") and would have had endless fun printing improvements. Stick with it! You'll be a superhero.

Re failures.  Sometimes, it seems to just stop extruding, but carries on moving about as if it was still doing so.

Sounds like a typical jam, so we need to figure out the root cause. The suggestion for a nozzle swap and/or the more labor-intensive (but not that bad) heatbreak swap and thermal paste application are probably worthwhile. I didn't build mine from a kit and still found the extruder tear-down and part replacement a 1 hour job the 1st time. The 2nd time took less than 30 minutes. You've probably spent more time trying to figure out a VHS timer in the past!

If you do decide to do the teardown, I'd replace the heatbreak just to be sure. There's a more expensive titanium version that I opted for that is supposed to be better at preventing heat working up past the heatbreak into the cold end. I haven't had any problems since installing it, though I didn't really have issues before. Don't forget that thermal paste at the top between the heatbreak and heat sink.

Sometimes, the last layers are not attached, and a tangle of filament forms.  If I get there in time, I stop it,  If not, I think it eventually stops extruding but carries on as if it were. A recent one formed a solid spiral sort of pillar. 

If things detach and you get the spaghetti or the dreaded Blob of Doom, you've got adhesion issues. The part is popping loose mid-print. That's important, but a different issue than the jam.

[...] I went back to the original filament the the problem also occurred with it (both are PRUSA PLA)

This really sounds like something mechanical like a partial jam in the hotend or nozzle. Again, a nozzle swap is easy (if you follow the guides). 

One question just to c0nfirm: Are you getting these jams when printing the pre-sliced parts on the SD card? If not, we should look at slicer settings.

A piece of filament which I have from unloading feels serrated on one side which I assume indicates gear marks.  The tip measures  at the maximum width 2.03mm.

That would tend to point away from the "stepped heatbreak" then as it has a 2.2mm step. The gear marks are from the Bondtech extruder, so are normal. However, if they're too deep, it may indicate an overly-tight extruder tension screw which could explain all of this.

What is particularly frustrating is that it was working perfectly for several weeks.  It seems as though I must have disturbed something when I changed filament, but no idea what.

Going into winter, I wouldn't expect it to be related to increasing ambient temps like we saw moving into summer. Are you running a space heater or anything that might account for more heat and/or reduced air circulation? Changing filament should obviously not cause problems, but perhaps something changed or shifted. Definitely check your filament feed path from spool to nozzle! One common recommendation is to always heat and feed a bit of filament before removing. This can help avoid jams further up in the extruder.

I think the extruder is jammed once again so I will have to tackle that before I do anything else.

One trick I learned with a jammed extruder: Open the extruder door, heat the nozzle up to 285C and use a 1.5mm rod (available at hobby stores) to push down past the Bondtech extruder gears, into the PTFE, down into the hotend and nozzle. The hex wrench will work but only goes so far. You want 6in/15cm ideally. With any luck, you can push stuck filament through without a tear-down. You might also remove the nozzle to clear anything out as you do this. I also recommend cleaning filament for feeding through and cold pulls.

But thanks again everyone for "listening".

A few years back I realized I was exhibiting signs of getting old: I know how to fix things.  Stick with it! There are good lessons here for your grandkids, so be sure to let them know what happened and how you worked through it. They may end up loving the process as much as the toys. Get to it. Santa's workshop is depending on you.

RE: Multiple print failures

I guarantee this will beat Prusa's price, and free delivery:

https://www.amazon.com/Genuine-E3D-Extra-Nozzle-V6-NOZZLE-175-400/dp/B00NAK9TWM/ref=sr_1_1?keywords=e3d+nozzle&qid=1573944316&s=electronics&sr=1-1-catcorr

Amazon UK must have something similar. Note: don't get one of the brass E3D clones. It is not worth it.

RE: Multiple print failures

Before doing ANY mechanical work, please do check the tip of the filament after a jam;  it is an easy check and virtually proves the jam is coming from the heat break.

RE: Multiple print failures

@epzcaw

Your printer is rather new one and still under warranty.

You bought the hot end already pre-assembled you just installed it. Unless you cut some of the wires 😊 it should be under warranty.

Let me advice you to contact the support chat - you can open it connected and logged in on prusa e-shope page. Describe them in detail what did you encounter. They should be able to help you and when you and the support mutually discover and agree it is the hot end issue, they might under the warranty send you the replacement for free.

Edit: warranty is valid provided that you have bought the printer in shorter time period that 2 years ago 😊 

RE: Multiple print failures

@tim-m30

Is this as in the picture you showed before?

I know it is definitely jammed now as I cannot unload the filament.

I will not be doing anything for a few days, but will need to remind myself first how to unjam- I've had to do this already.

I've ordered two nozzles and will try to replace the current one. I will also add thermal paste to the heat break.

We will see what happens...

Thank you

RE: Multiple print failures

Btw. At the moment your print is going without extruding the filament what nozzle temperature is shown on the printer's display?

RE: Multiple print failures

@zoltan

I haven't checked this.  Last time I tried to use it, it wouldn't unload filament so I assume it is blocked.

I am having a few days off -  I'm doing some old technology manufacturing, i.e. sewing  a costume for my granddaughter's drama performance.

When I resume, I will have to remind myself how to unblock the system (replace PTFE tube???).  I have ordered tow new nozzles, and will therefore replace the nozzle, and apply thermal paste to the heatbreak.  Perhaps all will be well them.  If so, I will report back.

If not, I will pay more attention to the various points mentioned here, and return for more assistance.

Cheers and thanks.

RE: Multiple print failures

A total blockage where filament won't unload is rather rare.  Lack of thermal grease on the heat break is not the first place I'd look for problems.

Also - the threads of the heat break where grease is applied go into the heat sink.  So folk interchange saying grease the heat break with grease the heat sink.

RE: Multiple print failures

Hi all. 

I am hoping you can help me as to how to proceed.

As I explained earlier, I printed lots of parts successfully, but when I changed filament Ione PRUSA  PLA to another), I started having problems with parts failing to be completed. I have had several "chats" with PRUSA  advisors. Here is a summary of these.

__________________________________

15^th  October

Under –extrusion suggested as the problem. Advised to check gears.

30^th October

Adviser suggested it could be a problem with the model. (But was not just one model that was failing).

Adviser suggested I do a cold pull.  Did this successfully

1^st November

Unloading filament was now not working.  Adviser suggested checking if filament was stuck in PTFE tube.  It was, so replaced PTFE tube.  Advisor also mentioned heat creep as a possible issue

8^th November

PRUSA logo was now starting off, but failing partway through.  Advisor suggested PID calibration. I did this and it was fine.  Advisor also suggested heat creep as a problem.

14^th November

Adviser said definitely looks like heat creep.  Suggested adding thermal paste to the heat sink.  Also suggested doing several cold pulls.  Also referred me to the article on clogged hotend.  I was somewhat alarmed by the statement there relating to dismantling the hotend.  – “We do not recommend doing this on your own unless you are absolutely sure about what you're doing.”.  Adviser said I should first try thermal paste on the heatsink but might need to dismantle the hotend and clean it all.

____________________________________________

18^th November

After a few days off, I started up the printer. I uploaded the clogged hotend sheet.

The first step was to unload the filament but I couldn’t do this- it was totally jammed.

I went to the next step in the clogged hotend sheet, and heated up the nozzle to 280. No filament came pouring out.  I don’t have an acupuncture needs but tried with a sewing needle – still nothing came out.

Tried to unload filament again and got some movement.  After several goes, and a lot of brute force, it came out.  It looks very similar to the picture by tim-m30, suggesting a heatbreak jam.

So what should I do next?  I’ve  ordered replacement nozzles but do not have these yet.  Advice welcome

RE: Multiple print failures

I should also add that it has not been a continuous process of deterioration,  Each time I followed an instruction, I would usually be able to print a few small parts and even a bigger one.  And before the last failure, I managed to do a 1hr 50 min print which was a 45mm high box with several slots which had failed several times before.

There is a good chance that if I load the filament now, and do the first layer calibration, I may get a perfect PRUSA logo.  BUt when I move on to something bigger and more interesting, it will fail again.

RE: Multiple print failures

Sounds like multiple issues are cropping up.  It's best to deal with them one at a time. 

Starting with the basics, I'd like to see what your axis friction is because the photo above shows a very direct layer shift.  A layer shift is nothing nefarious, I suspect friction is your enemy in long duration prints; and there are simple cures.

Perform a SELF TEST, then report the BELT TENSION numbers -- make no adjustments, just report the numbers.