Jamming in the steel tubes  

Re: Jamming in the steel tubes

Have you tried printing one of the pre-sliced GCode files? Maybe try the gear bearing.

If you have a blockage with that, remove all festos at the top of the MUX, remove cooling tubes if possible and post a picture of the filament ends.

Peter

Re: Jamming in the steel tubes

I am having the same problem. Here is a photo of whats happening. A bldg develops preventing full retraction of the plastic. https://goo.gl/photos/gHZV8J3VzioQ37ry8

Re: Jamming in the steel tubes

Joshua.J's photo looks exactly like what's happening to mine. And yes, it's with the pre-sliced models, as well as ones that I've sent through Slic3r (The MM version).

Probably the same as Joshua's, but my plastic is small enough to enter into the steel tubes but that's where it gets stuck. The motors are unable to push it either way, forward or reverse after that.

Re: Jamming in the steel tubes

Oh, side note, is that printing on a single extruder works flawlessly. Great quality single-color prints.

Re: Jamming in the steel tubes

Try with lower temps. 200 to 205 seems to be right for most of my filaments.

Peter

Re: Jamming in the steel tubes

Think that did it... It's in the middle of a print right now that hasn't jammed yet.

Thanks!

Re: Jamming in the steel tubes

Unfortunately, it wasn't the end-all solution. Although it did work very well through multiple prints.

The jamming came back and on a very consistent basis now. I'm going to open a support ticket to see if they know any more tricks to keep the plastic flowing.

Re: Jamming in the steel tubes

2 support tickets opened on this using the online form. Not sure if the system is working, as I hadn't heard any response yet.

Re: Jamming in the steel tubes

I cant get PLA to play fair, below about 225C

none of the pre sliced files worked for me. 🙁

Joan...

Re: Jamming in the steel tubes

It could be that the unload strategy is not right for your filament type.

It took me a while to get the unloading speeds right and even now some PLAs require different speeds to others.

When you get a blockage, can you please unscrew all the festos on top of the MUX and post a photo of all filament ends.

NOTE: be careful not to lose the tubes!

Peter

Re: Jamming in the steel tubes

The issue is still continuing. I'm unable to get through any single prints without the filament forming a blob and getting stuck in the tubes. I've dropped temps to the point that it's not hot enough to melt the plastic in time and the extruder skips steps from trying to push the filament out the nozzle that's a tiny bit too cold.

The blobs still form in this instance. The pic posted earlier in the thread is an exact representation of what's still happening.

When you mention that the unload strategy may be different from the filament type, what exactly do you mean? Is it an option to change what it's doing during a purge / color change? - And if so, how? - Side note, this is just PLA rolls, nothing special. (And yes it's still happening on the Prusa supplied roll as well - so it's not simply due to the fact that I may have bad filament. All makes and mfgs of plastic are not exempt).

Please advise, it's very aggravating to come back to a printer that seemingly working just fine at the 4 hour mark - to come back a few hours later to air printing because of this issue. And now it's nearly 99.9999% of all prints this is happening.

Re: Jamming in the steel tubes

I don't usually go to third-party sites to view images; it's much better to add the pictures to a post here.

In this instance, I did have a look and it's obvious that your tension is too high. This will cause damage to the filament and prevent smooth movement through the cooling tubes. This could prevent unloading and cause blockages.

Thing with this MM upgrade is that adjustments have to be much more precise than with the single filament printer.

Regarding unload strategy; I found that PR post-processor works very well with PR filaments, so if you are having issues with that filament, then it's likely to be another issue causing the problem.

Loosen the tension so that there is almost no damage to the filament and try a print.

If that doesn't work, then I will slice a file for you to try with a different unload strategy (it's not something you can do yourself within Slic3r).

Peter

Re: Jamming in the steel tubes

First - thank you VERY much for assisting with this, you are a testament to the forums here, and it's really appreciated.

Second - Please go into depth what you mean about tension. The filament is free flowing very easily up to the extruder, then it navigates down through the bowden tube as expected up to the point it melts. No tension in the system, except what's created between the extruder and hot end.

Unless you mean tension of the bondtech drives? Apologies - but please clarify - the kit is built to specs as per the instructions and the filament stand allows easy free movement of the spool. No tension necessary, nor present.

Re: Jamming in the steel tubes

First - thank you VERY much for assisting with this, you are a testament to the forums here, and it's really appreciated.

Second - Please go into depth what you mean about tension. The filament is free flowing very easily up to the extruder, then it navigates down through the bowden tube as expected up to the point it melts. No tension in the system, except what's created between the extruder and hot end.

Unless you mean tension of the bondtech drives? Apologies - but please clarify - the kit is built to specs as per the instructions and the filament stand allows easy free movement of the spool. No tension necessary, nor present.

If you have a look at your picture, you will see that the drive gears have bitten in to the filament causing damage. This will squash the filament and cause it to become somewhat oval rather than round.

Filament is manufactured at a nominal diameter of 1.75mm, but this does vary and the parts of the filament which are manufactured at the upper diameter limits can already be tight in the cooling tubes. Add damage caused by the drive gears and the filament can become tight and even get blocked in the cooling tubes.

The tension settings as specified are for "average" spring tension and "average" filament. If you see your filament being damaged like this, you need to loosen the tension springs - maybe by a couple of millimetres - so that such damage is reduced. Softer filaments require less tension; harder filaments may require a little more.

In my experience, you need as little tension as possible, so that skipping is prevented on unloads but the filament is not damaged,

I hope that this clarifies my earlier post and thank you for your kind comments. 😀

Peter

Re: Jamming in the steel tubes

Peter, that's a very insightful comment about damaging the filament on the extruder gear with excessive pressure. I'm going to start watching for that. Prusa should hire you to write their manuals. 🙂

Re: Jamming in the steel tubes

Prusa should hire you to write their manuals. 🙂

Yeah, there have been a few things found their way into the manuals...

Thanks

Peter

Re: Jamming in the steel tubes

Update: I continued to keep getting jamming, in the same scenario as described from this thread. - Even after loosening the screws on the bondtech mounts.

Fast forward to yesterday - where I ended up accidentally contracting a horrendous jam in the nozzle that - no matter what I did - I couldn't clear it. So, it was off to the races with my used 3d printer part box, and stealing a nozzle from an older hot end.

It was cheap far-east clone nozzle, so obviously I wasn't expecting anything... But miracles happen when you don't expect them. The used "Ebay Nozzle" is filling the billet quite nicely! - After multiple tests, the blob that used to form from before isn't present in any of them, nor have I had any retraction issues when the plastic goes back through the steel tube... SO FAR.

I'll keep an eye on it for sure, but it's looking promising as I'm writing this. Just throwing the info on this forum if others run into the same problem as described in the thread here. It may not fix the problem at all, but it appears to be working in my case. I'm guessing the way the inside of the nozzle is drilled out, it allowed for the formation of the blob on the original one, where as whatever magic is happening inside the cheap one - it's not allowed to form.

Hopefully this keeps going.

Re: Jamming in the steel tubes

*Of, and of note that I forgot to mention.

The nozzle change has allowed me to hit the entire normal PLA temperature range also. Previously, it had only seemed to work at the lower side of the melting point, but I'm currently printing at 215 with no issues yet.

Re: Jamming in the steel tubes

I‘m also fighting with jamming … but in my case it starts already in front of the PTFE tube at the end of the hot-end.
It doesn’t matter if printing pre-sliced code with MM or with single extruder.
The only solution I have actually is to print with temp higher 240C. But that temp is not suitable for my PLA … so no option!

I love my Prusa i3 MK2S but I start to regret to have them upgraded to MM!!! 😕