eric.s20
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SUCCESS! How I resolved my MMU2 issues (MK2S -> MK2.5 -> MMU2 upgrade path)

Jan 17, 2019 4:29 pm

Hello all,

I wanted to share my findings with others having the same, or similar, issues with the MMU2. Before reading any further, just know that my hardware upgrade path has been as follows: MK2S -> MK2.5 -> MMU2. And I have a Micro Swiss .04 hardened nozzle. No other mods/tweaks.

TL;DR

My solution was a combination of the following:

1. Switch out the heatbreak to the MK3 version: https://www.printedsolid.com/products/e3d-mk3-heatbreak
2. Definitely follow the advice in Chris Warkocki's video: https://www.youtube.com/watch?v=v1h-S7bxPEE
3. The only changes I've made to the default Slic3r Prusament PLA configuration are: "Loading Speed at Start" = 19, "Loading Speed" = 22

Please consider reading the rest of this post, as I'm sure many of you will benefit.

My Journey in Detail

Probably not unlike you, I have spent about a month trying to get my MMU2 to print reliably. I tried every combination of Slic3r settings. I watched Chris Warkocki's great Troubleshooting 101 video numerous times, and followed his advice exactly. I tried different brands of filament, including Prusament. I tried lowering the temperature as far down as 180 c., and as high as 220 c. I've read, and re-read, posts from this forum. I've monitored the MMU Github repo issues. Sound familiar?

I was at a point where I was confident that my filament path was clear of obstruction and any excess friction. And I felt I had done everything I could think of on the software side of things. I was left with the conclusion that Ramming and Cooling Steps seemed to have the most meaningful effect on the filament tips. But this is where I was stuck, and thoroughly frustrated. When I lowered the Ramming, the filament would get too stringy and inevitably jam during a load. When I raised the Ramming, the tips would come out better, but they'd be too fat causing it to jam on unload. I was damned either way.

Not wanting to give up, I recalled someone on these forums mentioning that the heatbreak on the MK2S/2.5 is slightly different than that of the MK3. Neither my MK2.5, nor MMU2 upgrade kits came with any new heatbreaks. So whatever heatbreak came with my MK2S originally is the one I had.

Whoever mentioned the heatbreak difference said they were going to try the MK3 version, and report back. I could be wrong, but I don't recall ever seeing their conclusion. Did it work for them??

What Worked for Me

Having no other option myself, I decided to give the MK3 heatbreak a try. After all, nothing else had worked. So I placed my order on Printed Solid, and it arrived the other day. I promptly installed it: https://www.printedsolid.com/products/e3d-mk3-heatbreak

I wanted to eliminate as many variables as possible with the new heatbreak. So in Slic3r I did the following:

1. Reset my copy of the Prusament PLA settings back to its defaults.
2. Changed the "Loading Speed on Start" to 19, and the "Loading Speed" to 20. (These seem to be universally accepted as the correct values to use).
3. Loaded up 4 rolls of Prusament PLA.

I have a simple model that allows me to print out a row of small blocks, each being a different color. It's what I've been using to quickly iterate on configuration changes, and seeing how it affects things. I kicked off this print, and studied it. As the MMU2 would switch colors, I'd push the recently-unloaded filament out and look at the tip. It seemed good, but I wasn't convinced yet.

I let this print finish, and to my surprise I didn't have any issues with loading/unloading. I once again pushed out each filament tip to inspect it. There was absolutely no stringing. And the tips no longer had the large bulge, which had previously been a tell-tail sign of inevitable jamming. The tips, to my surprise, actually looked... perfect.

Still not convinced, I loaded up the multi color version of the Kobayashi Fidget Cube. This is a print that I've never successfully printed before. It would typically jam during load/unload within 10 color changes. That wasn't the case this time. I monitored the tips during the print for the first couple of hours, and everything seemed to be working fine. Gaining confidence, I let it run for a couple more hours and checked again. Still fine!

I finally went to sleep and woke up this morning to a perfect print! This was two prints in a row where I didn't have a single jam or skipped layer! Clearly, something I did seemed to resolve the issues. And I am 100% convinced that one winning change, is in fact the MK3 heatbreak.

Conclusion

Will this fix your issues? Possibly. In fact, I'd venture to say "probably, yes" if my troubleshooting experience sounds anything like your own.

How can I be so confident after only a couple of prints? To that, I say, I was at the point with my troubleshooting/iterating that I could quickly tell from the shape of the tips whether or not I was going to have issues. That, and I've never had more than about 20 color changes before encountering a jam. There is a noticeable improvement in the shape of the tips after swapping in the MK3 heatbreak. No stringing, just perfectly shaped tips.

I feel like I'm FINALLY experiencing the MMU2 the way Prusa intended it! If you are at your wits end, and haven't tried this change yet, I strongly suggest doing so. It's a $20 part. And it would be great to get further confirmation from others.

This also begs the question: Why didn't Prusa include the MK3 heatbreak in our upgrade kits? If I'm right, in this being a fundamental reason why so many of us MK2S/2.5 users are having issues, they could have really saved a lot of people from the headaches.

I hope this helps someone else out there. This forum has been of tremendous value to me. And without it, I probably wouldn't have even through to try the MK3 heatbreak.

Does anyone have a specific model they'd like me to try printing? Maybe one that you personally have had trouble with? I'm just thinking it could help validate my findings, while simultaneously showing what could be possible for those in the same boat as I was
Last edited by eric.s20 on Jan 17, 2019 11:42 pm, edited 1 time in total.

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nikolai.r
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Re: SUCCESS! How I resolved my MMU2 issues (MK2S -> MK2.5 -> MMU2 upgrade path)

Jan 17, 2019 6:33 pm

Thanks for sharing and welcome to the 20% of successful MMU2 users :D

eric.s20
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Re: SUCCESS! How I resolved my MMU2 issues (MK2S -> MK2.5 -> MMU2 upgrade path)

Jan 17, 2019 6:38 pm

nikolai.r wrote:
Jan 17, 2019 6:33 pm
Thanks for sharing and welcome to the 20% of successful MMU2 users :D
Sadly, 20% might even be optimistic! :? Luckily we have this community of people to help. I'd love to hear how others have resolved their issues, with the same hardware/upgrades I'm working with. I'm also curious to hear if anyone else has also had success with the MK3 heatbreak.

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nikolai.r
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Re: SUCCESS! How I resolved my MMU2 issues (MK2S -> MK2.5 -> MMU2 upgrade path)

Jan 17, 2019 6:52 pm

eric.s20 wrote:
Jan 17, 2019 6:38 pm
Sadly, 20% might even be optimistic! :? Luckily we have this community of people to help. I'd love to hear how others have resolved their issues, with the same hardware/upgrades I'm working with. I'm also curious to hear if anyone else has also had success with the MK3 heatbreak.
My assumption is based on this poll:
general-discussion-announcements-and-re ... 26509.html

If you rebuild a heatbreak, you're also readjusting all the extruder parts. So it's hard to tell if it's only because of this part or a more accurate rebuild.
I realized that after upgrading my MK2S to MK2.5. I paid attention to stuff which I didn't knew during my first MK2 build. Double checking the alignments, placements, paths, tubes... . The more experience you gain and more understanding you gain for the process, more accurate is your build and issues are less likely.

Your way of fixing is the same I would have go. Trying everything in software/configuration first and then looking for the hardware issues. But many people are going the other way around and replacing hardware (extruder motor, ptfe tubes...) without knowing and understanding the process. It's very hard to help those people because they don't have original hardware setup anymore and it's hard to see what is actually happening on their printer.

eric.s20
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Re: SUCCESS! How I resolved my MMU2 issues (MK2S -> MK2.5 -> MMU2 upgrade path)

Jan 17, 2019 7:08 pm

nikolai.r wrote:
Jan 17, 2019 6:52 pm
eric.s20 wrote:
Jan 17, 2019 6:38 pm
Sadly, 20% might even be optimistic! :? Luckily we have this community of people to help. I'd love to hear how others have resolved their issues, with the same hardware/upgrades I'm working with. I'm also curious to hear if anyone else has also had success with the MK3 heatbreak.
My assumption is based on this poll:
general-discussion-announcements-and-re ... 26509.html

If you rebuild a heatbreak, you're also readjusting all the extruder parts. So it's hard to tell if it's only because of this part or a more accurate rebuild.
I realized that after upgrading my MK2S to MK2.5. I paid attention to stuff which I didn't knew during my first MK2 build. Double checking the alignments, placements, paths, tubes... . The more experience you gain and more understanding you gain for the process, more accurate is your build and issues are less likely.

Your way of fixing is the same I would have go. Trying everything in software/configuration first and then looking for the hardware issues. But many people are going the other way around and replacing hardware (extruder motor, ptfe tubes...) without knowing and understanding the process. It's very hard to help those people because they don't have original hardware setup anymore and it's hard to see what is actually happening on their printer.
Oh wow, I hadn't seen that poll before. Interesting.

You hit on something. One of my hesitations in sharing my findings was basically because of something you said. I realized, that the simple act of tearing down and rebuilding the hot end with the MK3 heatbreak might have fixed my issues, for reasons other than the new heatbreak itself. I absolutely cannot rule that out entirely; it's possible.

What has me convinced that the heatbreak was the issue, is that the construction of the hot end is quite simple. There aren't a lot of variables. The heatbreak and nozzle screw in, and butt right up against each other. There are no moving parts there, just the path for the filament. I did also consider that maybe I reinserted the PTFE tube in the heatbreak differently. That is also possible. It would be hard to be sure.

And yes, it will be hard to assist others if they've have moved away from the stock components. There are so many variables that can impact the MMU2's operation already. When you introduce non-standard parts, it complicates things further. I'm not saying it's wrong to swap out parts, upgrade, etc. I'm mainly pointing out that, if you are determined to fix your MMU2 issues, you should go back to basics. Eliminate any variables you can.

At least the MK3 heatbreak gives others one more thing they can try. :)

eric.s20
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Re: SUCCESS! How I resolved my MMU2 issues (MK2S -> MK2.5 -> MMU2 upgrade path)

Jan 20, 2019 5:15 pm

Hey folks. I figured enough time had passed with the MK3 heatbreak, that I should post an update.

I continue to have hassle-free prints. The color changes are happening without user intervention, which is SO nice. I've printed out several more things since my first post, and none of them exhibit any skipped layers or anything like I was seeing before the new heatbreak was installed. I haven't had a single jam on load/unload. Everything is just running smoothly.

Since I've finally achieved successful prints, I AM starting to find other areas where I need to tweak things. These are in the realm of, what I would call, "the simple stuff". For example, the screws holding down the top part of the MMU2 seem to back out on their own over time. Another issue I have found is severe color bleed across certain colors. But this can be addressed via the "Purge Volumes" feature in Slic3r.

Here are a few pictures of tips/prints I've done. You can see the color bleed issue on the sheep. One has slightly less color bleed, after tweaking the Purge Volumes.
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joan.t
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Re: SUCCESS! How I resolved my MMU2 issues (MK2S -> MK2.5 -> MMU2 upgrade path)

Jan 20, 2019 6:06 pm

Hmmmm... I cheated,


I got the MMUv1 to MMUv2 upgrade, and as my MMUv1 is working well, I fitted the upgrade to the Mk3 either way, I should be Ok, because the MMUv1 heatbreak is supposed to the Mk3 heatbreak... I used a spare full size stepper for the filament drive, and a spare extruder motor foe the idler drive... that worked OK but there was a lot of wire to hide, so I swapped the extruder motor out for a pancake motor, and that seems to be working ok too... I can now use the original extruder motor for the spare mk2, whenever I get round to building it

Regards Joan
I try to make suggestions that I believe to be well founded and safe,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions,
what you do, is YOUR responsibility.

eric.s20
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Re: SUCCESS! How I resolved my MMU2 issues (MK2S -> MK2.5 -> MMU2 upgrade path)

Jan 20, 2019 7:30 pm

joan.t wrote:
Jan 20, 2019 6:06 pm
Hmmmm... I cheated,


I got the MMUv1 to MMUv2 upgrade, and as my MMUv1 is working well, I fitted the upgrade to the Mk3 either way, I should be Ok, because the MMUv1 heatbreak is supposed to the Mk3 heatbreak... I used a spare full size stepper for the filament drive, and a spare extruder motor foe the idler drive... that worked OK but there was a lot of wire to hide, so I swapped the extruder motor out for a pancake motor, and that seems to be working ok too... I can now use the original extruder motor for the spare mk2, whenever I get round to building it

Regards Joan
If I'm following correctly, does that mean users who started with MMU1, and upgraded to MMU2, should already have the correct heatbreak? If so, that would be good for that information to be spread.

In my case, MK2S -> MK2.5 -> MMU2, I never received a different heatbreak in any of my kits. I suspect Prusa just didn't account for this, but don't know that for a fact.

Joan, do you just have the one MMU kit on an MK3? I'm trying to determine if you have an alternate solution that would allow users along the same upgrade path as myself to have some success through other avenues.

eric.s20
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Re: SUCCESS! How I resolved my MMU2 issues (MK2S -> MK2.5 -> MMU2 upgrade path)

Jan 20, 2019 7:58 pm

I thought it would be good/interesting to do a side by side comparison of the MK2S heatbreak, and the MK3 heatbreak. Visually, I didn't see much if any difference. When I broke out my calipers though, I found that the hole at the bottom of the heatbreak was a different size.

Left: MK3 heatbreak with a 2.2mm hole. || Right: MK2S heatbreak with a ~2.6mm hole
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Other pictures just showing there aren't obvious visual differences, other than that bottom hole. Still MK3 heatbreak left, right is the MK2S one.
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kenny.b2
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Re: SUCCESS! How I resolved my MMU2 issues (MK2S -> MK2.5 -> MMU2 upgrade path)

Jan 20, 2019 9:35 pm

Switching to the mk3 heatbreak worked for me too. I've had other problems which have caused me grief but it was a huge difference in the tips after changing the heatbreak.

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