Poor dimensional accuracy, is the prusa mini is actually a bad printer?
 
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Poor dimensional accuracy, is the prusa mini is actually a bad printer?  

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defgum
(@defgum)
Active Member
Poor dimensional accuracy, is the prusa mini is actually a bad printer?

Hello

About a year ago i received my  Prusa Mini  bought on the multiple recommendations on the internet because of its touted MK3 Print quality, but alas it seems that is regular marketing hype with no substance.

Because the print quality is clearly inferior to the MK3, or is my unit defective seeing as mostly pre-assembled was the only option back then which is sad. I have googled the subject but came up empty with bad interior dimensional accuracy on the mini, i am figuring over extrusion could be an issue but i used comparable settings 0.20mm Quality Settings on both machines with the same spool of filament.

It stands mostly unused because i can sometimes use the MK3's at my local makerspace and i have other printers from less reputable vendors with far better print quality. Its been pissing me off so much that i decided to go here and see if anyone has a good idea as to whats up before i scrap it for parts. and to see if i just got a lemon or if i just have been scammed by prusa and their marketing. Since its not even close to true in my experience.

I have some example pictures attached, a test piece showing that it has poor tolerances and is unsuitable for most prints where dimensional accuracy is off importance. None of boxes that don't fit together at all when printed on the mini, in any fashion with each other or with the drawers. The test print was printed with a garbage spool but i have gotten useful and good prints off it with the Mk3's at the maker space. however with the Mini eh the finish says a lot.

Thank you in advance for responding.

.

Posted : 30/08/2021 12:10 pm
fuchsr
(@fuchsr)
Noble Member

Not sure how to respond here because "my Minis work great and are as good as my Mk3S" is not a meaningful response. But it tells me that there's certainly an issue with your specific machine. I assume you've done troubleshooting on the mechanical aspects of it. Axes correct, belt tension okay, bearings moving freely, etc. Have you contacted Prusa support? What did they say?

Posted : 30/08/2021 12:22 pm
defgum
(@defgum)
Active Member
Topic starter answered:
Reply

I have checked the belt tension yes, it did produce an XYZ Calibration cube with the appropriate dimensions.

The printer firmware has bluescreened randomly previously full with beeping like crazy in the middle of the night when just idling turned on on multiple occations. This has not been observed on the latest firmware though.

Therefor i assume its an extruder/hot-end issue or firmware/motherboard related issue, my printer is running the latest firmware now.

Seeing as prusa don't like you modifying the firmware i have tried nothing there.

With the proprietary hotend thing i have done nothing as well, seeing as it should work and i dont have spare parts that are approperiate, exept maybe a cheap nozzle.

 

Posted : 30/08/2021 1:46 pm
Sebastian Flodin
(@sebastian-flodin)
Active Member
Re : Poor dimensional accuracy, is the prusa mini is actually a bad printer?

I have started to think about the same thing, when I compare prints with my other printer printer a cheap flashforge finder so the result is much better. My first thought when I unpacked my mini was that the construction felt lean and allows a lot of movement when it only has one arm up, this should lead to lots of unwanted movement in the x arm? I almost think you can see it shaking when it prints.

Posted : 24/09/2021 8:43 am
BogdanH
(@bogdanh)
Reputable Member
RE: Poor dimensional accuracy, is the prusa mini is actually a bad printer?

Disclaimer first: I'm not a "Prusa fan" and I have no reasons to "defend" Prusa products -simply because I paid full price for my printer.

Yes, Mini looks kinda "fragile" at first sight... But if assembled properly, it's solid enough. There have been "doubts" about X-axis (vibrating, etc.), but again, if assembled well and proper settings are used, then print results are very good. Or let me put this way: if you get better prints with any other printer up to $1000, then your Mini is badly assembled or you use wrong settings.. or (can happen) you got faulty machine.
I'm about to build MK3S and I really hope it will deliver prints as good as Mini does.

Mini+ with Bondtech upgrade & modified firmware...
Posted : 24/09/2021 10:27 am
bobstro
(@bobstro)
Illustrious Member
There are better ways to ask for help
Posted by: @defgum

[...] About a year ago i received my  Prusa Mini  bought on the multiple recommendations on the internet because of its touted MK3 Print quality, but alas it seems that is regular marketing hype with no substance.

Whenever I read one of these posts that open with a line like this, I really have to wonder if the poster is aware of the first impression they're making. Reading this, I can only conclude one of two things:

  1. The entire user population of the Mini are idiots, and OP is the only one brilliant enough to have noticed these fundamental product flaws, or
  2. The OP is having some problems and is awkwardly trying to ask for help with complete lack of self-awareness as to how annoying such statements are.

Given that there are literally thousands of users printing on Minis without such fundamental issues, I'm going to assume the latter. The fact that the "faulty" printer "did produce an XYZ Calibration cube with the appropriate dimensions" implies that the printer itself is capable of printing accurately. It sounds like a bit of learning and calibration may be all that's needed.

One obvious question is how well the Prusa-supplied gcode samples print. If they print well, that narrows the concerns down to slicer settings.

Save your a current 3MF project file, zip it up, and attach it to a reply here so we can see your part & settings and give better recommendations.

And please, if you're not sure what you might be doing wrong, don't go implying Prusa is crooked or that we're all just suckers. That is really off-putting and annoying.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 24/09/2021 3:19 pm
Sebastian Flodin
(@sebastian-flodin)
Active Member
Reply

Now it's not me who started this post but there was a response when I agreed and had a similar experience of the printer. I previously posted a friendly post with my perceived problems and unfortunately received no response. Everyone is right to their opinions and I think OP posts were interesting.

Posted : 25/09/2021 8:37 am
BogdanH
(@bogdanh)
Reputable Member
Posted by: @sebastian-flodin

... and had a similar experience of the printer.... Everyone is right to their opinions...

Agree with you.
Opinion is always based on some experience and as always, there are good and bad. Now, if someone says "printer XX is crap", it sounds differently than saying "printer XX is not good from my experience". I'm not targeting you.. is just an example.

When I assembled my Mini (bough as partially assembled), I was extremely sceptical, almost disappointed because of it's "fragile" appearance. It got even worse when I wasn't able to successfully finish first layer calibration. But then I though, how come big majority of Mini owners says how "great it is" and prove that with some awesome prints? So I took time and started learning "how stuff works" and searched for answers in this forum.
Yeah, now I'm happy with Mini as it is and I'm trying to help others where I can. Many of us bough Mini with hard saved money, so we deserve to be happy with our decision. At least so my thoughts.

Mini+ with Bondtech upgrade & modified firmware...
Posted : 25/09/2021 8:07 pm
defgum
(@defgum)
Active Member
Topic starter answered:
The issue has been resolved,

So the first off issue has been resolved, it involved the simple steps of disassembling the entire bowden assembly,  extruder and finally the hot end. and reassembling and changing the tubes and i changed the nozzle to a genuine e3d nozzle instead of the prusa nozzle.

In case you where feeling like accusing me of doing that it was a "mostly" pre-assabled by prusa. The only offering available in the initial stages of prusa mini sales.

As such it was not done by me, further adding to the frustration.

Works as it should now at least the few test prints i have gotten out of it.

Now with the time investment required it still is a lot less than i was expecting when i bought a prusa, its taken more time and effort that i have had to put in to any of my other printers.

The post initial post i guess was at the tip of frustration before i finally got enough frustration to do something about the printer.

As for the comment about the prusa G-Code printing fine, the USB had died and i was salty about for a while but i got the G-Code of the website and printed it a couple of times yielding seemingly "almost perfect" benchys  the finish was great except for random patches that where messed up.

As far as if it was broken

i got good help from the support and they where willing to take it back to look at it so hey. But at last i had enough fury to get through fixing it my self.

Ill post an image with 3x benchy's from left to right its Before,  After and one of my other printer under 500$ total cost. As an explanation as to my  initial and utter annoyance with the printer.

Posted : 26/09/2021 2:34 pm
defgum
(@defgum)
Active Member
Topic starter answered:
Reply to @fuchsr

Thank you for your good advice and most critically in contacting Prusa support, because if nothing else it helps to have someone to talk to with your issues, because when you talk to people you have to express your thought and you might just figure it out on your own. I have got the printer working as it should now.

Posted : 26/09/2021 2:57 pm
defgum
(@defgum)
Active Member
Topic starter answered:
Reply to @bogdanh

 

Posted by: @bogdanh

Disclaimer first: I'm not a "Prusa fan" and I have no reasons to "defend" Prusa products -simply because I paid full price for my printer.

Yes, Mini looks kinda "fragile" at first sight... But if assembled properly, it's solid enough. There have been "doubts" about X-axis (vibrating, etc.), but again, if assembled well and proper settings are used, then print results are very good. Or let me put this way: if you get better prints with any other printer up to $1000, then your Mini is badly assembled or you use wrong settings.. or (can happen) you got faulty machine.
I'm about to build MK3S and I really hope it will deliver prints as good as Mini does.

First off thanks for replying to my post, i think you will have a stellar time with the MKIII, in my experience they are almost bulletproof.

Also if you say that it prints better than any other printer under 1000$ you are severely underestimating the quality you can get with other manifacturers, however in my experience its just a matter of time before an issue crops up and stops the printer.

Seeing as you have modified your prusa mini, just a few tweaks will make almost any printer great with a few tweaks and upgrades, i mean unless its inherintly flawed in the motion system.

I have used a mendel that prints great, i mean it makes noise like nothing else, needs to run tethered, has no display a fixed mirror bed. a genuine e3d hotend. It would probably be slower than a Prusa yes, but its still going strong.

As to the mini, i still feel that its an inferior product in comparison with the MK III and that they should not be compared as its unfair to the mini. maybe i will change my opinion in the future.

Posted : 26/09/2021 3:56 pm
MysDawg
(@mysdawg)
Eminent Member
Mini Experience

I have to agree....This meets my needs at the moment and has been a joy to print with. I take my time with calibrations I print and I find that what I have designed and sliced are as accurate as I need them to be.

Posted : 26/09/2021 4:10 pm
Sebastian Flodin
(@sebastian-flodin)
Active Member
Reply

Thank you Bogdan and the rest of you for your input on your experience of your mini, I hope that I myself will be as satisfied as with mine in the future. Realize that it will be a small learning curve to get everything I want even if it was what I had hoped to avoid when I bought the mini. Unfortunately, I still have not managed to get the print with my small storage boxes, as if you or someone else has any idea what goes wrong would appreciate if you or someone had time to check my post with pictures and description about it. Also recently tested a print where I put two boxes, one at the far end of x and one so far into x and I think I see small vibrations in the print on the one that is placed far out at x. I am still looking for a new second printer but need become more convinced that it is an extra mini it will be ...

Posted : 26/09/2021 4:26 pm
BogdanH
(@bogdanh)
Reputable Member

 

Posted by: @defgum

... Also if you say that it prints better than any other printer under 1000$ ...

Actually I didn't say that. I said "if any other printer up to $1000 prints better than Mini" -means, Mini is not better, but is also not worse. Or let me be more clear what I mean:
I think that every printer that is well designed, properly assembled and adjusted, results very similar prints. In that sense, we're not limited by printer itself, but by FDM process.
And so differences among consumer printers come down to:
-material quality (bearings, print surface, etc.)
-versatility (filaments types that can be used, connectivity, etc.)
-features (auto bed leveling, display, etc)
-bed type and bed size
-software & support.

As to the mini, i still feel that its an inferior product in comparison with the MK III...

Agree! As from above, Mini is inferior at least in versatility, in bed size and in cantilever design (there might be more depending on personal preferences). But I can hardly imagine print results would be noticeable better on MK3... same nozzle, same temperature, same precision. But hey, let me be surprised when I have it 🤩 

@sebastian-flodin
Mini is not perfect machine. To be honest, I never printed benchy or any other "test object" -that is, I don't to search for it's flaws. I print stuff I need and as long I succeed on that, I'm happy.
The only reason why I decided to add MK3S is bed size. Yes, I was looking among other (cheaper) brands, but I always found (in reviews or in specifications) something that disturbed me: no flex bed sheet, questionable auto bed leveling solution, lack of support, non-open software, etc.

Just sharing my thoughts...

Mini+ with Bondtech upgrade & modified firmware...
Posted : 26/09/2021 8:28 pm
Sebastian Flodin
(@sebastian-flodin)
Active Member
Reply

The quality of the prints are for the most part very good. I have recently started selling products so the prints need to be very good every time, when they have not always been I started looking for reasons why, think that sometimes the seams can be unnecessarily large in layer changes and thought that it may be because x the shoulder "swings out a little" but has no idea if it has anything to do with it.

Now it's not a big problem, just a problem that I discover and that may be the same in other printers. Now I just want to understand why my little boxes print so badly.

Attach pictures printed on the small box that does not work. It is thin, 0.5mm, do not know if that is the problem in combination with PETG. Have always printed it perfectly in PLA on my Flashforge. 

I print in PETG with 0.2 Quality and have not made any changes to the program, just sliced and printed ...

White printed on flashforge, black on Mini. It is not just stinging but large plastic hooks that occur in the seam when changing layers

 

 

Posted : 27/09/2021 8:57 am
BogdanH
(@bogdanh)
Reputable Member

@sebastian-flodin

..yeah, that looks ugly.
Would be nice if you could upload 3mf file of this box, which would reduce the amount of questions & answers (zip 3mf for uploading).
Is your Mini stock, or you did some upgrades? What firmware and slicer version are you using?

Mini+ with Bondtech upgrade & modified firmware...
Posted : 27/09/2021 9:18 am
fuchsr
(@fuchsr)
Noble Member

How did it print with PETG on the flashforge? Also, wall thickness of 0.5 mm is not great if you're using the standard extrusion width of 0.45 mm. 

Posted : 27/09/2021 1:07 pm
Sebastian Flodin
(@sebastian-flodin)
Active Member
Reply

@Bodgan

yes my mini is stock and pre-assembled, f.m 4.2.1-final+2072 and slicer 2.3.3.

@fuchsr 

my flashforge is and old finder and can only print PLA, ok maybe I try 0,45 instead?

Posted : 27/09/2021 2:07 pm
Sebastian Flodin
(@sebastian-flodin)
Active Member
zip

Forgot the mf3.zip 

Attachment removed
Posted : 27/09/2021 2:16 pm
BogdanH
(@bogdanh)
Reputable Member

3mf file you sent is not from box shown on photo.. so it's kinda useless. Still, before you decide to make "serial" prints, it's always good idea to print single (one) object at first. Once you're sure it's printed well, you can merge more together. And just a remark: if multiple objects are printed at once, try to position them closer to center of the bed (print head has shorter travel) .. keeping objects 1cm apart is enough.

I took a closer look on your photo again and I see there's not only corners where you have troubles -walls look bad as well. Assuming that your Mini is built as it should be (screws tightened, nothing lose or  rattles), then you have extrusion problem.
You can try to print with another PETG filament brand (if you have by hand)... but I suspect there's a problem with hotend. As usual in this case: take hotend apart, clean inside heat break and nozzle, check length of PTFE tube inside heat break and change it if needed. Maybe you think I'm exaggerating, but if you don't do that, you will most probably have same troubles if you go back to PLA (even it was printed fine with PLA before you started using PETG).
Finally, make sure you assemble hotend properly!

As usual in this case (Mini & PETG), I recommend you consider upgrading to Bondtech heat break (is only about 16€).

Mini+ with Bondtech upgrade & modified firmware...
Posted : 27/09/2021 4:37 pm
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