Under extrusion? Over extrusion? Clicking? Pilling? Inconsistent layers? Clogging? Unloading problems? It's probably all the same core issue...
I have a hunch this may be a thermal/creep related problem. I went through all the typical fixes, hotend scoot, extruder cleaning, etc. to notice that the PTFE tube shrank significantly, approximately 1mm. Replacing the tube seems to have fixed my issues for now.
My issues seemed to be exacerbated by an ASA print at high temp. Wonder if insufficient cooling at the heat break is causing the PTFE tubing to shrink around the filament path and trigger under extrusion.
We'll see how long I last with the updated PTFE tube.
I found exactly the same, the PTFE tube was 1 mm shorter than it should be. Because the compression fitting was already flush with the heatbreak, there was no margin to adjust. I reset the heatbreak higher up, put in the replacement tube. After hand-tightening the compression fitting then had several threads showing.
The interesting thing is that worked for a bit, but then started jamming again. I had to tighten up the compression fitting quite a bit. Since then it has been fine.
I think that supports the theory that the PTFE tube gets compressed, maybe it is designed like that. But the setup seems to very sensitive to any variation from the ideal setup.
Have you used the Prusament ASA filament?
In further support of compression, it is described in the knowledge base here, as being compressed. " We will compress the PTFE tube in a later step." When I followed these steps I made sure I compressed it.
BTW, my PTFE was only 2-3 10ths of a mm short, and I didn't have any problems, I just did the adjustments when I assembled the printer the first time.
Was some e3d ASA of decent quality. Used the recommended print temps from Prusa.
Issues really occurred once I switched back to PLA from the ASA print. I think too much heat is traveling to the tip of the filament/PTFE tube. Replacing the tube and sticking to PLA since has cleared the issue so far. *fingers crossed*.
The upgraded heat break looks like it removes some material to limit the heat flux via conduction. Hypothesizing that all the fixes in the forum are likely band aids till you upgrade the heat break.
Fullmetal is better for PETG and worse for PLA?
I'm wondering why the MK3S heatbreak has a constriction, where the Mini doesn't.
I was wondering the same thing. The Bondtech heat break has it also and Prusa designed the MK3 S with this configuration. Why change something that works? They did it for manufacturing costs?
Prusa Slicer 2.2.0
I have been successful printing with PLA, so I have been waiting for a failing test case before installing the Bondtech heatbreak. Now I have one, trying to print TPU failed completely. The prints became successively worse, by the last even the first layer was flawed. I noticed the heatsink noticeably warmer with a nozzle temp at 240 versus 215 for PLA.
So I will install the Bondtech and be able to do an A/B comparison. Unfortunately most of my test gear is inaccessible due to Covid19, otherwise I would measure the actual temperatures.
I am still waiting for dual-drive extruder to arrive, I am also ordering a new beefier fan for the hotend, and looking at new cabling arrangements. Having cables and stuff in front of the fan can't help the airflow.
Also considering a slightly more radical option : changing the hotend for a stock E3D v6 all-metal.
Here are some more threads people have started which I believe are all related to the topic of this post, the flawed hotend design:
Yeah, I think you are right, the evidence is becoming overwhelming regarding the hotend issue. It's obviously not a one-off, but an issue for a significant number of users.
Thanks @bobcousins. You did not agree my observations at first:)
I saw you also got the Bondtech heatbreak. I have been running my Mini with the Bondtech 12hrs a day for over 2 weeks now and no issues yet! Did you end up installing yours yet?
That's a lot of posts. Wish I could report in about my Bondtech heat break experience, but I got it shipped by snail mail which took way too long, then I found out I had no heat paste (and none was included...) so now I'm waiting for my heat paste which comes Tuesday!
LOL, yes waiting for thermal paste too 🙂
😀 please let me when you guys get yours installed. Very interested to know how it works for others.
By the way, the Bondtech heartbreak instructions call for 1.5nm of torque on the nozzle: https://support.bondtech.se/Guide/0.1+Heat-break+Upgrade+Kit/60#s646
I printed the 2nm torque wrench from here: https://www.prusaprinters.org/prints/24539-torque-wrench-handles-from-10nm-up-to-30nm
And evenly filed down all of the fins in order to get it down to 1.5nm. I put in a request to the author for 1.5nm and 2.5nm versions:)
One more datapoint. I rebuilt my Mini many times following various fixes on the various threads. The thing that finally fixed my problem was replacing the heatbreak with the Bondtech (which actually has a heatbreak). The thinner wall caused by the heatbreak may make it more fragile but I think it is important - any minor gap or anomaly at the PTFE-SS interface doesn't matter if the filament isn't molten there.
Sorry. I didn't realize there was two more pages to this thread when I replied. Looks like folks have already picked up on the missing heat break. It (the constriction) is what prevents too much heat from moving from the heatblock to the heatsink. It is to heat what a resistor is to current.
Installed the bond-tech heat break yesterday, and printing is going a whole lot better than before! Not all kinks are ironed out, still have some underextrusion as you can see, and the z-scar is visible (which shouldn't be the case, because linear advance is enabled by default) so I'll do a cold pull one of these days to try and clear that up.
Curious if those of you that have installed the BondTech heat break are using the PID gcode recommended in the installation guide? The guide states: add M301 P13.54 I0.98 D46.58 to the start G-code in the slicer before the ; intro line.
is that line necessary? I don’t recall that being part of the install process originally.