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why does MK4 suck so bad?!  

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Thejiral
(@thejiral)
Prominent Member
RE:

If we want to focus on problem solving rather than other things what you have here is substantial layer shifts. This should only happen if there is some underlying serious issue with your machine. A very common culprit is a loose grub screw in the belt gears. I would check all of those and re-tighten all of them while at it. 

Another thing to check for is if the machine triggers crash detection. This can happen either because you have adhesion issues and the nozzle is indeed crashing into the part or it can be falsely triggered crash detection if some bearings have a bit too much friction. At least that is valid for the Mk3. The Mk4 also has this kind of crash detection, doesn't it? Anyhow, if it does, deactivate it. I found it causes more troubles than it does good. 

Last but not least. First layer adhesion. The blob of doom you had later on as well is something you can get with any printer if you have insufficient 1st layer adhesion. Usually that is because the print bed is not clean enough (fat residues from touching it with bare hands). There are tons of threads on that aspect. If you want to be basically 100% safe against blob of dooms, simply revisit your printer after the first few layers. It basically only happens if your adhesion is so poor that the object detaches already in the first few layers. If the object detaches fully later, you get a relatively harmless spaghetti monster instead. 

If the thermistor error accured after cleaning up a blob of doom, it is very likely that the undoing of that blob damaged the thermistor wires, which can happen very easily if molten plastic attaches to them. 

Posted by: @jeffl

Why does my Prusa MK4 suck so bad? I cant even print the same print without chaos. I got one good print out of 3 tries. the first try (middle print) was using fw_4_7_2_MK4, so then I changed to MK4_MK3.9_firmware_5.1.0-alpha2 and got a good print. I then I tried to print it again, bad print. I use PrusaSlicer 2.6.1+win64-202309060711

WTF!!!!!?????!!!!

 

This post was modified 3 months ago 2 times by Thejiral

Mk3s MMU2s, Voron 0.1, Voron 2.4

Posted : 07/12/2023 1:17 pm
Willemoes liked
fullmetalnozzle
(@fullmetalnozzle)
Active Member
RE: why does MK4 suck so bad?!

I had posted this reply, but it's stuck in moderation purgatory - maybe this one will make it through:

"Hmm... okay, fair enough. I suppose I need to educate myself further on disadvantages of a core-xy machine. I wasn't aware that core-xy had any significant downsides. If you care to send a link to info about the tradeoffs, I would appreciate it.  I will go away to educate myself and come back after further testing on the MK4."

Since that reply, I've done some reading.  It appears most of the CoreXY downside has to do with cost and some aspects of maintenance due to complexity.  Since the increase in cost and complexity are marginal, I have to conclude the CoreXY platform is superior to the bedsling one for all but the squattest of parts; but of course let me know what I'm missing.

Back to troubleshooting / providing more data related to the layer-shifting the OP posted about, I have a couple new pics in that google drive folder which shows another part with a much larger layer shift, akin to what the OP was showing:  https://drive.google.com/drive/folders/15dp3zOWuGWOSClgIHcVNNwGdq7QXVMx3?usp=sharing

I checked the grub screws on the pulley and they're solidly tightened and I checked the tensioning of the belt.  Since those were both to-spec, I have to assume it was a "blob of death", some build-up which caused the print-head to skip, lose its place in X.  Would all of you wiser, more experienced hands agree?  If so, how is the OP (and myself) able to avoid it?

thanks

 

Posted : 07/12/2023 3:26 pm
IPIND 3D
(@ipind-3d)
Estimable Member
RE: why does MK4 suck so bad?!

 

Posted by: @jeffl

this printer is a special type of garbage

Aside from the bed looking pretty dirty, it also looks like you didn't watch the first layer or so successfully complete.

The first layer clearly failed and then the printer was just left to run and destroy itself.

Whilst I don't doubt you have had legitimate issues, Prusa have offered to take the machine back and repair it with no cost to you on freight, etc.

Just do it and see how it goes when it comes back.

Posted : 07/12/2023 8:40 pm
Willemoes liked
Thejiral
(@thejiral)
Prominent Member
RE: why does MK4 suck so bad?!

I don't have a link at hand. One disadvantage is the much longer belt lengths compared to corexz and belts are one of the major factors for print inaccuracies. Another one ist the more complex design where more things can degrade and go wrong. Generally it is said that the bigger the printer is, the better CoreXY compared to CoreXZ. 

I am not saying corexy is bad, just that it is not the golden bullet some make it out to be. This is especially true for small printers. I do love my Voron 0 but its core xy design is hardly a rational choice for regular printing tasks. There is a reason why Bambulab designed its a own Mini also as bedslinger and it surely is not printing in inferior quality.

Mk3s MMU2s, Voron 0.1, Voron 2.4

Posted : 08/12/2023 8:23 am
Thejiral
(@thejiral)
Prominent Member
RE:

One more point. The weight of the X-axis beam is affecting a fast moving axis in the case of a corexy. With a bed slinger it doesnt. On the other side , the weight of bed and printed part doe not affect a fast moving axis on corexy. For a smaller printer that can mean that for many jobs a corexy has to push around more weight than a bedslinger. For larger prints on larger printers obviously core xy is lighter.

This post was modified 3 months ago by Thejiral

Mk3s MMU2s, Voron 0.1, Voron 2.4

Posted : 08/12/2023 8:29 am
Thejiral
(@thejiral)
Prominent Member
RE: why does MK4 suck so bad?!

Regarding blob of doom. Like Ipind 3D said, watch the first few layers. You don't have to babysit the printer but if you want to ban the risk of blob of dooms, have a quick look at the print bed after a few layers. If something is not right abort.

Learn how to ensure good bed adhesion, especially how to clean the bed and how to keep it clean.

I have never seen a report of a blob of doom to date that was not caused by a very early bed adhesion failure.

This is the case for any printer btw, no matter if  Prusa, Bambulab or Ender. CoreXY or CorXZ.

 

Mk3s MMU2s, Voron 0.1, Voron 2.4

Posted : 08/12/2023 8:39 am
Willemoes and Zappes liked
fullmetalnozzle
(@fullmetalnozzle)
Active Member
RE: why does MK4 suck so bad?!

so, I don't get this argument.  it doesn't take much of a part volume to be much larger in mass than the hot-end assembly of a core-xy.  The point is that, in the case of the core-xy, you have a predictable mass you have to sling around, rather than variable and typically increasing (over a print) mass of something you have to sling around on a bedslinger.  that, right there, for me, kills the proposition that a bedslinger is a good platform.  Just for the simple fact you can start with a near-zero mass (at start of print) and end up with, depending on your print, 1kg of plastic you need to sling around in Y, make a bedslinger an awful platform.

really, the belts required for a corex-y machine are not much longer and not much more complex.  Look at tons of industrial machines which are much more complex and operate 24/7.  Our very simple core-xy printing machines are not very complex in comparison.  Is a bedslinger more simple?  sure, but you're talking about simple differences in construction with a very big difference in performance.  That you can predict the mass you're moving about is so much more valuable than decreasing belt length by some small amount.  I appreciate all the thought you've put into this, but you're missing the forest for the trees.  Bedslingers are fundamentally flawed.  It's only by controlling a defined mass that you can really have a high-speed and well-controlled nozzle.  Have the 3d-printer manufacturers done a good job with this?  That's debatable, but one thing is clear:  only the CoreXY platforms will be successful over time in high-performance, high-speed and high-accuracy solutions.  Bedslingers were a platform of necessity wrt cost, but they can't possibly succeed in all the above areas.

 

 

Posted : 09/12/2023 4:26 am
Thejiral
(@thejiral)
Prominent Member
RE: why does MK4 suck so bad?!

I am all for discussing the impact of certain differences but its a bit weird to discuss facts away. Belts for corexy are much longer and their path is much more complex than in a corexz machine. I mean I just bulit a Voron 2.4 and that fact is plain obvious. Now you can say it doesn't matter much but don't talk facts away. A 350mm V2.4 needs almost 5m of belts for A and B alone and involves how many pulleys? Was it 10 for A and B? All of that can add to artifacts and inaccuracies. No, I am not saying it is a terminal flaw of CoreXY design but it definitely is a disadvantage. So is the larger weight of the moved Y axis when you are printing light objects. Yes with heavy objects things turn around. Like always the usage case is important for evaluating machines.

Is Bambulab incompetent or did it for cost cutting purposes build an inferior machine with the A1 Mini? I would say no to those questions. You wouldn't?

Mk3s MMU2s, Voron 0.1, Voron 2.4

Posted : 09/12/2023 9:41 am
fullmetalnozzle
(@fullmetalnozzle)
Active Member
RE: why does MK4 suck so bad?!

I don't know why I keep going on about CoreXY v bedslinger.  I think I'm just frustrated with some of the early results out of the MK4 and I'm seeking vent-paths for my frustration!

I yield to your superior knowledge on the subject and will heretofore have more respect for the bedslinger platform.

Also, I apologize to everyone for hijacking this thread and taking up mind-space on something so banal.  My only defense is that I started out talking about something close to on-topic: the layer-shifting, as was shown in OP's pics.  My following opinions as to cause, primarily centered around bedsling v not-bedsling platforms, threw me down the slippery slope of off-topic-ness.  Lesson learned.  I continue to have layer-shift issues, so I'll create a new thread and avoid ignorantly positing judgements on the MK4 platform.

 

Posted : 09/12/2023 1:42 pm
IPIND 3D and Zappes liked
Willemoes
(@willemoes)
Member
RE: why does MK4 suck so bad?!

I just want to say that I really appreciate comments like these that try to problem solve the issue. I totally relate to the author of the post as well since working with stuff like this can be incredibly infuriating when you don't get the results you were hoping for. I think it encourages turning the attention toward something constructive, which to someone like me who is completely new to 3D printing is such a huge help to read. I'm still at the assembly stage of my printer, but I can totally see why everybody says that the community here is very strong.
I look forward to posting my own frustrations here haha 

Posted by: @thejiral

If we want to focus on problem solving rather than other things what you have here is substantial layer shifts. This should only happen if there is some underlying serious issue with your machine. A very common culprit is a loose grub screw in the belt gears. I would check all of those and re-tighten all of them while at it. 

Another thing to check for is if the machine triggers crash detection. This can happen either because you have adhesion issues and the nozzle is indeed crashing into the part or it can be falsely triggered crash detection if some bearings have a bit too much friction. At least that is valid for the Mk3. The Mk4 also has this kind of crash detection, doesn't it? Anyhow, if it does, deactivate it. I found it causes more troubles than it does good. 

Last but not least. First layer adhesion. The blob of doom you had later on as well is something you can get with any printer if you have insufficient 1st layer adhesion. Usually that is because the print bed is not clean enough (fat residues from touching it with bare hands). There are tons of threads on that aspect. If you want to be basically 100% safe against blob of dooms, simply revisit your printer after the first few layers. It basically only happens if your adhesion is so poor that the object detaches already in the first few layers. If the object detaches fully later, you get a relatively harmless spaghetti monster instead. 

If the thermistor error accured after cleaning up a blob of doom, it is very likely that the undoing of that blob damaged the thermistor wires, which can happen very easily if molten plastic attaches to them. 

Posted by: @jeffl

Why does my Prusa MK4 suck so bad? I cant even print the same print without chaos. I got one good print out of 3 tries. the first try (middle print) was using fw_4_7_2_MK4, so then I changed to MK4_MK3.9_firmware_5.1.0-alpha2 and got a good print. I then I tried to print it again, bad print. I use PrusaSlicer 2.6.1+win64-202309060711

WTF!!!!!?????!!!!

 

 

Posted : 11/01/2024 9:49 pm
ssmith liked
Mike B
(@mike-b-3)
Active Member
RE: why does MK4 suck so bad?!

Almost a year since the original post, I'd like to post a comment now that the MK4 seems to have its teething problems sorted out.  I'm completely new to 3D printing, received my MK4 in mid-January of 2024.  I spent 13 hours assembling the kit, and my first 3 test prints went perfectly!  I then spent another 5 hours putting it in the enclosure, and since then have completely 31 prints, and I have had only one bed adhesion failure (on a wipe tower, not the print itself) that I caught immediately and managed to clean up and continue the print successfully.  My initial assessment of the MK4 is that it is an extremely well thought out product, and the assembly instructions online are top-notch!  I'd love to know if the original poster resolved the issues he had (and how)...

Posted : 05/02/2024 5:51 pm
Oregun liked
Brian
(@brian-12)
Trusted Member
RE: why does MK4 suck so bad?!

Not to downplay your issues but I've been running my MK4 pretty much daily for 6 months without issue.

Early on I had the ball of death and I discovered it happens if you don't clean the nozzle before your print starts, especially if you print filament that oozes like Petg.  If you leave buildup on the nozzle and don't clean it before the print the nozzle will pick up the bed incorrectly due to the buildup.

If you make sure the bed and nozzle are clean before the print you shouldn't have issues.  I clean the nozzle and bed before every print and the 1st layer is always perfect, and the .9 stepper motors make beautiful prints. 

Posted : 06/02/2024 1:58 am
Oregun liked
LarryMcCutchan
(@larrymccutchan)
Member
RE: why does MK4 suck so bad?!

I had layer shift issues (like the ones shown in the picture). I did a belt tuning/tightening of the X axis and it is gone. Belts stretch a bit from manufacturing to use over time. I woudl suggest that.

Posted : 09/02/2024 3:35 pm
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