Blockage troubleshooting.  

Re: Blockage troubleshooting.

Hi guys,
I've been busy working on Multi Material as we are listening to your feedback. We've finished changes to improve the ease of assembly and I'm already going through your issues regarding print.

Please note, we aren't leaving you behind. We are already on it!

Re: Blockage troubleshooting.

Jakub very glad to read that, hope you will find a solution for the jams of fillament soon.

Re: Blockage troubleshooting. CHALLENGE

First of all my single extruder version of Prusa i3 MK2S Kit was (and hopefully will be again) a great printer.
Having problems to print with the MMU Kit at all and got a MM head-replacement from Prusa Research Team pretty fast. Thanks, but sadly the same just in a different colour, means no difference in anything. 🙄 😥 And yes i tried all i could see in any thread. The (original Prusa Silver)filament of extruder1 is not even getting through the PTE tube to be melted...
After reading all the postings here i will probably stop spending lifetime trying to solve a problem obviously caused by design.
And instead of going through even more postings about very special temperature, retraction and other settings and a lot more
I herein call for a Challenge:
Everybody who is happy with a MMU Kit post his/her story here and (more important) tell everybody else how he/she got it working.
And seriously NO. I don't want to hear about any engineering at a purchased product, special environment or temperatures.
I did NOT purchase a cheap copy of a well engineered 3D printer on purpose, because i appreciate all the work developing one. The MK2S is well worth the price and it is a great printer. The MMU Kit ruined that at least for me for now, until i changed it back to single extruder printer.

So bring it on, your success story. Show prints. Tell us how you avoided all the problems!

Will be back from a biz trip in a week. So let's see.

Re: Blockage troubleshooting. CHALLENGE

So bring it on, your success story. Show prints.

Wrong thread for this, but happy to oblige:

How to get it working? Well just spend a little time reading, learning and tweaking.

BTW, these are variable layer height prints (0.14 to 0.26mm), printed together.

@Roman - many thanks for the brilliant models!

Peter

Re: Blockage troubleshooting.

Peter , First thanks for all you've done before and after the MMU release. I think I've read most of the 13 pages here, and I'm ready to get things working as they should. First though I have a question, I've been printing a couple things in single color, one extruder mode. I get the blob forming in the heat break others have posted, and I wonder is this probably is just a temperature thing ? Or could it sill be retraction/speed related ?
Thanks !

Re: Blockage troubleshooting.

I get the blob forming in the heat break others have posted, and I wonder is this probably is just a temperature thing ? Or could it sill be retraction/speed related ?

If this is occurring during a print, it could be retraction/retraction speed or badly formed/installed PTFE tubing.

If it happens at the end of the print, then it's more likely to be a temp issue or badly formed/installed PTFE tubing.

Peter

Re: Blockage troubleshooting.

Oke this is my experience until now, blockage blockage... I did played around with the retraction settings, temp, etc, but no luck.
The printers starts with printing, but when finished the first layer, or halfway the second or the third, the extruder starts clicking because the resistance "somewhere" in the line is to high and the filament stops feeding. When I "help" the filament by pushing, it will run and after some time it runs by it self, without my help until the end.
When the printer ends, the top of the filament looks good (nice round top). So my conclusion is that the cooling procedure works fine.

I checked the voltage of the PSU. With load it was 11.70 V. So I tuned it to 12.4.

I worked my way through path of the filaments back.
I disassembled the heat block, nozzle and cooling. Nothing special. Path way is smooth. Checked with filament, hot and cool.
I bought new PTFE in America for the PTFE tube. Did the camfer en roundings and the precise length by checking the MMX sitting correct on its basis, so the PTFE tube has no tension and fits nice in the MMX. Path way is smooth. Checked with filament, hot and cool.
Checked the MMX exit to the PTFE tube. Path way is smooth. Checked with filament, hot and cool.
Checked the resistance in the metal tubes: and here is a lot of resistance. Not when the filament is smooth and untouched by the extruder. Then the resistance is low. But when the filament runs through the extruder gears, it gets this little sharp bites (I did loosen the tension screws as much as possible, to avoid the "damage" to the filament, made a gauge for the adjustments of the screws/springs). I use the prusa silver PLA.
These nasty bites causes a lot of resistance. I checked the steel tubes, they are in line. When I inspected the steel tube, I can see the are chamfered, but I think not enough). I think that the incoming side (top) of the tube should be more chamfered, then it is now.. Because it is RVS, and so pretty hard, it is tough for me to do it by myself.

My conclusion for my situation is that if I a push manually not "extruded" filament there is low resistance all the way from top to bottom. But when I use filament that has been extruded by the gears, the resistance is high.

I have good faith it will be solved, with all you people there on this beautiful forum and the support of PRUSA.
Frans

Re: Blockage troubleshooting.

But when I use filament that has been extruded by the gears, the resistance is high.

With regular PLA, the filament should not be damaged so much by the extruder gears. If you are getting this much damage on all extruders, then there is too much tension or the filaments are over-sized.

Try printing a simple object with a single extruder and while it is printing, loosen the tension springs until the filament stops extruding and then tighten them again by half a turn.

Peter

Re: Blockage troubleshooting.

Peter, I'm the one that asked about single color/extruder problems, forming a blob in the heat break. You said in your reply it could still be retraction or speed related. If you get a minute, could you explain how ? Still trying to learn to make this work well .............................Thanks !

Re: Blockage troubleshooting.

Peter, I'm the one that asked about single color/extruder problems, forming a blob in the heat break. You said in your reply it could still be retraction or speed related. If you get a minute, could you explain how ? Still trying to learn to make this work well .............................Thanks !

Yeah. There are just so many things which can cause issues; a lot of it comes down to bad PTFE (or installation thereof) or temperature.

If it's not one of those things then you have to start looking at other possible causes.

Retraction on this system is significantly higher than E3D recommends. Michael Hackney has an excellent post regarding retraction here: http://www.sublimelayers.com/2016/10/some-musings-on-retracts.html

If you have a model which requires lots of quick retractions, if the speed is too high, you leave a lot of filament behind in the nozzle. Furthermore, the extruder is not a sealed system. The filament is nominally 1.75mm in diameter, yet the heat break is 2.1/2.0 mm diameter. Those retractions can cause the melted filament to be forced upwards into the heat break and solidify.

Basically, you need to set retraction as low and slow as possible. Which is why "Linear Advance" - when it is working - is a very good system. It allows retraction to be significantly reduced. I have been printing with the KISS "PreloadVE" which is a similar (slicer-based) system and also allows retraction to be reduced to as little as 1mm - more in line with E3D recommendations - and helps preventing retraction-created blockages.

Sorry, it's a bit of a rambling explanation, but I hope it helps!

Peter

Re: Blockage troubleshooting.

WOW ! Good reading. So do you have a personal recommendation for amount and speed of retraction on PLA ? I'm using the Prusa edition of Slic3r, which I know you don't use, and I don't have a clue what the default setting is. I also don't have a clue how to change it. But I'll find it, or ask the people much smarter than me on Facebook where to go. Thanks !

Re: Blockage troubleshooting.

WOW ! Good reading. So do you have a personal recommendation for amount and speed of retraction on PLA ? I'm using the Prusa edition of Slic3r, which I know you don't use, and I don't have a clue what the default setting is. I also don't have a clue how to change it. But I'll find it, or ask the people much smarter than me on Facebook where to go. Thanks !

Are there people on Facebook that are smarter than you? You are here and that makes you very smart!

Slic3r - Printer/Extruder n/Retraction

Probable settings: 4mm, 80mm/s, 50mm/s (smiling at the terms used... "deretraction" - is that really an English word? Surely "Retraction Suck" and "Retraction Prime" are better terms)

Peter

Re: Blockage troubleshooting.

Prusa facebook has WAY smarter people than me 😉 But I'm learning. Default setting is 4mm 50 mm/s. Seems like a lot of retraction after reading the link you gave me. I was feeling the filament during the last print, and I'd have guessed it was more like 6 mm. It felt like a lot. Should I try 2 mm and 25 mm/s ? Or is that to drastic ? My last print failed BTW, blob in the heat sink, heat break. Only seems to happen with white. But temp changes don't seem to change anything. Thanks !

Re: Blockage troubleshooting.

PJR, Thank you sooooo much for your time and attention to this matter. I have finally gotten my MMU working in single mode at least, printing a part out now and looking forward to the full use of the MMU. Again, I cannot express my gratitude enough!!

Re: Blockage troubleshooting.

Prusa facebook has WAY smarter people than me 😉

So why are they not here helping out (and learning)?

Seems like a lot of retraction after reading the link you gave me.

Yes, it is a lot, but 3 to 4 mm retraction is needed without linear advance. Hence the requirement for the hardware to be working near-perfectly.

Should I try 2 mm and 25 mm/s ?

Maybe 3 or 3.5 and 25mm/s, but only change one setting at a time, then you will know what works. Regarding the white, you may need to lower the temperature even further. The different pigments can change the filament properties quite significantly.

Sorry, but this really is trial and error. I could try slicing a model for you to see how that goes...

Peter

Re: Blockage troubleshooting.

PJR, Thank you sooooo much for your time and attention to this matter. I have finally gotten my MMU working in single mode at least, printing a part out now and looking forward to the full use of the MMU. Again, I cannot express my gratitude enough!!

Nicholas.

Thanks for your kind comments - makes it all worthwhile!

As you will no doubt have read, it seems that each printer has its own peculiarities which does make diagnosing issues quite difficult. If you have the patience, you will be printing some very nice models.

Peter

Re: Blockage troubleshooting.

I am not very experienced, and just as I got the my single extruder prusa working properly I bought the multi material. Like all of you, I have been experiencing issues with blockage. However, after reading these posts I have been trying new things for each print. First, I don't know why, but the fan was running backwards. It was wired properly, but I had to flip it around. Not sure if that is my own mistake or not, it doesn't make much since to me. After fixing that issue, I still had blockage. I tried running at cooler temperatures, and it still blocked. This morning I took the same print I have been using, and changed the retraction distance from 4mm to 2mm for each extruder. It has finally printed successfully! This may not be true once I try it again, but this print has 3 different colors (PLA) plus soluble scaffolding. So I am hoping that a shorter retract distance is a solution to blockage. It seems everyone has slightly different issues, but perhaps this may help some. I will try some other prints with these settings to see if they will print successfully as well. Thank you to all who have posted in here, it has helped me troubleshoot these issues.

Re: Blockage troubleshooting.

The 3D Maker Noob published a Video "How I Reduced Filament Jams On The Prusa Multimaterial Upgrade" on youtube.

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Maybe it helps the one or other 😉

Re: Blockage troubleshooting.

The 3D Maker Noob published a Video "How I Reduced Filament Jams On The Prusa Multimaterial Upgrade" on youtube.

-->

Maybe it helps the one or other 😉

The PTFE tubing should come pre-formed with the correct tapers and chamfer. If it doesn't, then please contact PR support and request a replacement...

Peter

Re: Blockage troubleshooting.

Oke before opening a ticket by Prusa, I will ask the forum for suggestions. I have noticed and tried all the suggestions on this forum:
spring tension, temperature, new PTFE tube (chamfered my self with the correct ID PTFE), retraction, speed, flow, etc

This is the case:
Until now not capable of printing MM. To determine what is happening, I first start with MM in single mode, to get that running reliable.

MM in single mode:
When I start with fresh cut (45 degrees cut) filament by hand, the printers prints (with oneven first layer, but that is for later to be solved) fine. All 4 extruders work fine this way in single mode. No skipping of extruders
When I start a print with the same extruder, that ended the last print correctly, the print starts oke, going out of the printing area with pushing filament out, then starts with the brim and/or skirt (with pushing filament out) and then when laying the first layer the extruder starts to skip. If I help the filament by pushing by hand some time, the skipping of the extruder stops and the print continues to the end.

So my conclusion is that in the proces by ending the former print somethings goes wrong, but what?

When printing fine after I helped the extruder, and the printer is working fine, the power of pulling the filament is great and is capable of dragging my filament out of the filament on top of the enclosure of the printer.

The rond top of the filament looks fine when the print ends.

I use prusa silver filament but same issues with copper from prusa and filright filament

Any ideas?

Frans