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

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

@bobstro

Those "temporary fixes" only work if everything is repeatable. I print across 3-4 different filaments within a week. This change alone requires a lot of fine adjustment. Adding Z height leveling for every single print is ridiculous. I spend less time on my cheapo "Anycubic i3 Mega" printer for similar results. 

We are expecting Prusa Quality ($350-400 printer) and are getting china-esque quality. 

The main issue Prusa has is the cult-following of their early-reviewers. They should be working with people who have experience, use multiple materials,  and are honest. I've printed hundreds of prints on my mini with PLA, PLA+, PETG, ASA and more. The only time I don't have to adjust the Z height is when printing PLA and setting the initial layer height to 0.30 ±0.02mm as the variance of ±0.080mm at that temperature range won't destroy those prints.

My goal when buying the Mini was to buy a fleet for a mini print farm as that's how I'm starting a small business. However I'm still relying on my cheap Chinese printers and may be building yet another until the mini issue is fixed.

Lastly, if you think I'm not invested in solving this issue, I have countless forum posts and have the equivalent of half a Prusa Mini in spare parts + tons of build plates, the removable build plates alone keep me reluctantly waiting for the Mk2. I have a printer rack just waiting for 8 more Mini's once the problems are fixed.

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

I have noticed one thing trying to reproduce the problem listed in this thread and while testing filament.  I cannot get the mini to print some filaments.  They readily print on the MK3S and will just not print at all on the Mini without jamming or under extruding. One brand out thus far, Jesse by Printed Solid.   I dehydrated it and it worked a little better but still poor quality.  

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

@charles-h13

EXACTLY my experience - sorted by fitting the same hot end as the Mk3 as per my previous posts on this thread.

Thats got to say something

G

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

@graham-l2

Now I understand.  I did not grasp the problem.  I am happy.  I just won’t use those filaments.  

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

Posted by: @charles-h13

@graham-l2

Now I understand.  I did not grasp the problem.  I am happy.  I just won’t use those filaments.  

How far does your heat break protrude from the heat sink? I started getting underextrusion on my mini recently and after troubleshooting with support it *appears* to have been resolved by slightly shortening the PTFE so that the heatbreak sits as far up into the heatsink as possible when the PTFE and coupler are *removed*. I suspect my melt zone was extending up and leading to partial heat creep jams - the break neck was measuring 60C and higher several mm above the block. 

You will need to cut a custom PTFE 2-3mm shorter than the factory recommended 43mm to get the right amount of pretension on the PTFE tube. 

After the change, I have only a very small piece of the unthreaded portion of the break visible, vs 2-3mm beforehand. 

MINDA adjustment required after, of course. 

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

@vintagepc

I will check tonight.  What has prusa not fixed that?  Seems like an easy fix to have an officIAL RECOMMENDED CHANGE.  

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

Gotta say, I don't understand why Prusa wanted to create their own hotend design for the Mini. It does sound to be one of the two main contributors to issues. I would've thought they'd learn a lesson after the Mk3 heartbreak mod problems.

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

@bobstro

That Makes perfect sense.  I will probably modify it to run a V6 or J head.  

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

@bobstro

Almost certainly it's cheaper  (in the short-term)

🙁

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

@bobstro

I don't know, maybe it's not the heatbreak as much as cooling? OK maybe heatbreak too, but 3D printers are around where computers were 20 years ago when it comes to heat dissipation systems, so we may be at the very beginning of evolution here. Sometimes tiny fan blowing air through piece of aluminium is good enough, sometimes it's not. I have a nagging feeling it's not sufficient with MINI, but I can't put my finger on it, few people reported improvements after they changed the fan.

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

I'm not sure I understand it either, especially since the heatsink is machined with a step that naturally lets the assembly sit at this full depth - the only thing preventing it is the length of the PTFE. 

-- And I checked, my stock PTFE was not longer than the official recommendation, it did come in at 43mm. 

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

Posted by: @graham-l2

@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

 

Unfortunately I have to agree with Graham's conclusions. The design IS flawed. After a week of testing I can confirm that the printer can't handle long PLA prints reliably. It will start the print, go for over an hour (or two) without any problems and then it starts either underextruding (if the tension on the extruder screw is low) or stops extruding abruptly with clicking (if the tension is higher). And it happens each time I try. I can print PETG or ASA for a long time and nothing bad happens, but PLA is failing. Sad day for me, as I was very, very impressed by the printer initially. And what's important - neither extruder upgrade nor heatbreak upgrade to Bondtech fixes the issue. I know, because I have both upgrades installed and still cannot print PLA reliably.

Now I think the only possible solution is to buy the V6 hotend 🙁

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

@goszu

Yes very annoying.

I bought a genuine V6 which cost about £65 if I recall I learned later that there are MUCH cheaper clones out there for around £12 when I searched and if I was doing it again I gamble £12.   I added this note to that pdf recently:   

"Cheaper alternatives can be found if you search for ‘ Hotend J head’ but I have not tested these.
Remember you only need the heat sink, heat break & block, all the other bits you already have and that makes the upgrade easier as there is no rewiring required."

If you have success with one let me know & I will update that pdf for others to learn more from.

Graham

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

Posted by: @graham-l2

@goszu

Yes very annoying.

I bought a genuine V6 which cost about £65 if I recall I learned later that there are MUCH cheaper clones out there for around £12 when I searched and if I was doing it again I gamble £12.   I added this note to that pdf recently:   

"Cheaper alternatives can be found if you search for ‘ Hotend J head’ but I have not tested these.
Remember you only need the heat sink, heat break & block, all the other bits you already have and that makes the upgrade easier as there is no rewiring required."

If you have success with one let me know & I will update that pdf for others to learn more from.

Graham

I made a strong statement, but still have that small bit of hope in the stock hotend left. And as I would like my opinions to be honest and truthful I will do some more multi hour tests in the next days and play with different options. I'll check bowden tubing setup and connectors, a few different PLA materials and print/retraction speeds. I'll report back with my results before I move to the new hotend.

BTW. How is the E3D performing ? Is it "fully" reliable ? Can you put a fresh spool of filament and leave the printer for 2 days of printing with confidence ?

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

@goszu

The new E3D V6 transformed it, I don't do extremely long prints on the Mini it is a backup to my trusty Mk3.  But the odd longish runs on the Mini  ( 6+ hrs) have been flawless where before on third party PLA it was hopeless.

G

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

90% of my prints are 1 hour or less and are near 100% reliable.  

Even my clone is successful  about 95% of the time.  

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

Well even though I believe that the design needs improvements I was lucky enough not to have any problems with the hotend. My main and most frustrating problem is the MINDA. I hate waiting 5 mins every time and I hate that every now and then my first layer is just off. Then I have to stop the print and wait for another 5 minutes and maybe if the MINDA values dont change then I ll get a good print. I mean its ridiculous. Despite that I have used other brands of PLA and PETG and never had problems with clogging. Except from the TPU which needed adjustment with the tension. Also I went for the MINI because of its capabilities but still waiting on those too...