Prusa Mini is a flawed design – urgent action from Prusa required.
 

Prusa Mini is a flawed design – urgent action from Prusa required.  

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benji
(@benji)
Estimable Member

I have run my own tests a few months ago on the MBL. I could then, and now, consistently get inconsistent results. For what it's worth, I created a simple spreadsheet with real data from several runs: https://docs.google.com/spreadsheets/d/1n3qKVI80dKMmc-eSm6O3HZD5gDbHZ-0_29ghAAEJTq8/edit?usp=sharing

As you can see, after about 5min of preheat, the returned values stable out a bit. But YMMV, for example depending on the position of the hotend to the bed during preheat, or ambient temperature.

This post was modified 1 month ago 3 times by benji
Prusa Mini Silicone Bed Leveling Mod: https://bbbenji.github.io/PMSBLM/...
Posted : 22/09/2020 9:19 am
mcjamez liked
gordon.w
(@gordon-w)
Reputable Member

@benji

Unless I'm being really stupid (again  😀 ) your headings in column I to J are 'one off' ( I is the 'sample number' not value of x) and you're not comparing the right cells. Not sure that it makes a lot of difference for the point you are making though.

Posted : 22/09/2020 12:11 pm
benji
(@benji)
Estimable Member

Looks like it might have gotten a bit mixed up over the months. I'll take a closer look when I find a moment or maybe just run some new tests. Thanks for pointing that out.

Prusa Mini Silicone Bed Leveling Mod: https://bbbenji.github.io/PMSBLM/...
Posted : 22/09/2020 12:20 pm
graham.l2
(@graham-l2)
Active Member

Hi - Some good news I've had acknowledgement from Prusa support that the stability of the  Z axis offset is indeed an issue and announcement will be made soon on how it is to be addressed.  Fingers crossed.

I also ran into the common problem of the poor performance of filaments other than Prusas own Prusament product and Bob is correct the issue revolves more around the design of the hot end not the extruder as I originally suspected.  (but IMO is still a bit marginal).

Ive created a pdf with photos on the journey I went on and how I also resolved his albeit at some cost but it should save you some excessive spend.

Please read this....  Prusa Mini Issues

Graham

Posted : 25/09/2020 12:44 pm
Karl Herbert
(@karl-herbert)
Famed Member

@graham-l2

Thanks for the detailed feedback! I have already installed an self-designed E3D V6 hotend and another extruder  when assembling the Mini:

I also replaced the compression fittings with PC4-M8. So far the mini runs fine.

PC4-M8

 

 

 
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 25/09/2020 1:03 pm
stevensmith
(@stevensmith)
Estimable Member

@graham-l2

Can you share what Prusa support said?

Posted : 25/09/2020 1:22 pm
graham.l2
(@graham-l2)
Active Member

yes: quote from Prusa support onn 24/9/20 in regard to Z height stability:

"We are working on the solution of this issue. There will be probably a newsletter update then, so make sure you are subscribed (at the bottom of the page)."

Posted : 25/09/2020 2:35 pm
jason.e.joyner
(@jason-e-joyner)
New Member

New Prusa mini here. I have to agree with the original user at this point.  I bought a Prusa because I wanted to concentrate more on printing and less on tweaking and experimenting on the hardware. Perhaps I was being naive. 

Wanted to add something else to the design "flaw(s)", I read a post but can not find it now but have not seen it mentioned in the comments here. The bowden brass connectors have a crazy small tolerance and it being well ... brass, any malformation caused by the extruder or hotend (for unload) causes the filament to get stuck.  When printing anything causing the extruder to skip(click), can create a flaw in the filament, this may slow and cause resistance. This basically creates a feed back loop until it's catastrophic. 

I have a MP Select Mini with ~2017 tech that uses pretty much any filament (under 230 temp) that I throw at it.  It does not have a fancy hotend or extruder.

Prusa mini seems to be super picky on the quality and hardness. It prints great when it prints but the margin for error is so small with the stock components its ridiculous when it's calling it self a "print farm work horse".

People seem happy with the bondtech extruder or e3d6 hotend which leads me to believe that is more complicated than just 1 thing. However, I do believe Prusa could easily make some improvements if they would test with other filament.

Something like https://www.3djake.uk/3djake/ecopla-matt-red (not sure if allowed to provide links).  This matt pla is a little soft on the spool. Printed it's nice and matt with a little give, more like PETG.

I have tightened the extruder idler as much as possible before deforming the filament and I am currently experimenting with printing the retractions slower.  

 

Posted : 28/09/2020 1:48 pm
jason.e.joyner
(@jason-e-joyner)
New Member

After talking to support and re-setting the ptfe for what must be 7 or 8 times, things seemed to be working ok. They had me push the heating block as high as it can go, screw in the grub screws, and then put the bowden tube back on.

Got about ~24 hours of printing, a few good prints a long the way. Starting feeling pretty good and fired up a 20 hour print and then a clog in the nozzle half way through. Just depressing, I have had more clogs and failed prints then I have in over 2 years of printing. 

Another interesting thing is the backup ptfe tube that was longer than the one installed, is now the same size. Must be the temp/pressure, not saying this is the issue just something I noticed when troubleshooting with support.

Posted : 01/10/2020 9:21 pm
graham.l2
(@graham-l2)
Active Member

@jason-e-joyner

Hi Jason

before you buy any new bits read this - my conclusions at the end I think you might find interesting...

....  Prusa Mini Issues

Best

Graham

 

Posted : 02/10/2020 9:30 am
charles.h13
(@charles-h13)
Famed Member

I believe the flaw is there for some.  I am unable to recreate it.  

Posted : 02/10/2020 12:13 pm
Karl Herbert
(@karl-herbert)
Famed Member

@graham-l2

Thanks for the list and your efforts! I haven't had any problems of this kind so far, but to be fair I have to say that my Mini is not quite original anymore. However, I would like to optimize the MINDA according to the MK3 model. I mainly print ABS/ASA (100 Grad C. bedtemp.) and there the missing temperature compensation becomes noticeable.

 
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 02/10/2020 12:57 pm
graham.l2
(@graham-l2)
Active Member

@charles-h13

Your a lucky lad  🙂

 

Posted : 02/10/2020 1:20 pm
Karl Herbert
(@karl-herbert)
Famed Member

@graham-l2

From time to time you may also have some luck in life 👍 

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 02/10/2020 2:47 pm
charles.h13
(@charles-h13)
Famed Member

@graham-l2

Heck, I just ordered a second.  

Posted : 02/10/2020 5:24 pm
graham.l2
(@graham-l2)
Active Member

@charles-h13

I thought I saw you thinking of ordering a Chinese version?

At least with the money saved you can afford to get a better 3rd party hot end 🙂

 

Posted : 02/10/2020 5:32 pm
charles.h13
(@charles-h13)
Famed Member

I talked the team into buying the Prusa Verision instead.  

Posted : 02/10/2020 5:35 pm
graham.l2
(@graham-l2)
Active Member

I hope your luck stays good.

Graham

Posted : 02/10/2020 5:47 pm
charles.h13
(@charles-h13)
Famed Member

@graham-l2

Me too.  I hope yours is fixed.  

Posted : 02/10/2020 5:49 pm
graham.l2
(@graham-l2)
Active Member

@charles-h13

With the exception of the Z level stability yes but at some expense, that I could have done without.

I don't have space for another Mk3 and the Mini is a perfect fit besides my Mk3 but its ... well just not as good.

Graham

Posted : 02/10/2020 5:53 pm
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