First impressions on Prusa MINI

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Although I bought the unit back in October 2019, it seems I was not the only one, so it has been a while until I have received my unit, but just last week, during the lockdown, I was pleased my new printer arrived.

The main goal was for this printer to be a tiny 3D printer to have on my desk at home. I have been very pleased with Prusa's MK3 printer that provided me with reliable prints every time I need it. I just thought a smaller printer would be ok at home, as most of the time I do not need the extra volume the MK3 can do.

Building the Prusa MINI was quite straightforward and it took me less than one hour. I guess it can be done much faster once you are familiar with the model.

The new LCD graphic color display is one step forward from the older LCD used in the MK3. It is kind of small so I did not miss it was not touch-sensitive.

Once it was built and working, I checked the firmware version and it was, indeed, running the latest version.  So the next step was to print something, like the 3DBenchy file that came with the printer. And there is when the trouble started:  I have got the printer with the two types of coverings for the spring steel sheet, but I started with my favorite one: the textured PEI. The first two attempts, after calibrating the first layer refused to stick to the base. After cleaning the surface I have got almost 7 millimeters of height before the base released the part while printing and I was forced, once again, to stop the print.

So I changed the steel sheet by the smooth one, repeated first layer calibration and started a new 3Dbenchy attempt. This time it seemed bed adhesion was good, so I left the room. When I checked it minutes later it was making clicking sounds, so I reduced the print speed (I was using Galaxy Black Prusament) to 50% and it seemed the clicking went away. But when I came back again to the room it was printing in mid-air. No filament was coming out of the nozzle at all. No more clicking sound as the extruder had already bite onto the filament.

Not being experienced on this printer I went online to customer support chat and, after 20 minutes I was told to send a picture of my heat block. It was suggested that I move it upwards all the way in, But once I did that I was not able to feed any filament at all. The hotend seemed totally clogged.
Another 20 minutes wait for the chat and this time I was told to do a cold-pull. After a couple of them, the hotend was operational again.

After all this, I was able to finally print the 3Dbenchy, but I was a bit disappointed about all this trouble, especially when I think that a newbie might have not been able to go through it.  Then I read a bit on the Internet about this particular problem and it seems some users have it and it all seems to be connected to how well the PFTE tube and the heatbreak fit inside of the new Prusa hotend. My guess is that if there is any gap, the melted filament can crop in creating almost a barrier that will prevent any new filament to enter the heatbreak.

The MINI is slightly noisier than the MK3, though I just read some of the changes in the new 4.0.5 firmware version is to reduce some of it. Still, quite acceptable, retraction moves, in my opinion, being the noisiest of it all.

So after looking at the printed part, I would say output quality is almost as good as an MK3 and much better than, for example, an Ender 3.

I still have to figure out why the textured PEI sheet that works great on my MK3 is not holding the parts here. I tried first with the sheet just out of the manufacturing packaging. Later I cleaned the surface with IPA but that did not help much and the printed part was released mid-print.

By the way, the firmware the printer came with, 4.0.4, did not support the Ethernet port. So when I connected it to my network I could not see any new device. The new version, luckily, gets the new Prusa Connect page back to life.


My second printing attempt, the PRUSA tag, is not going ok either, as the extruder is struggling to push the filament through the nozzle, skipping every now and then. Reducing the speed to 50% was not enough for the problem to go away, and raising the temperature from 210 to 230 helped but that is not the expected behavior so I guess I have to contact customer support again. So far this is my worst printer experience and it makes me wonder if the new hotend design is not so well thought out (or manufactured). I am printing PLA all the time, not sure if another type of filament might give me a better experience.

Update:

Again, after maybe more than 20 minutes of waiting for a customer service representative on Prusa's chat I have been told maybe my original PTFE tube is a bit too short, but moving the heatbreak up should help. So I have cut a slightly longer (45mm) tube from a piece I had at home and tried again with it (in my case just moving it up did not entirely fix the problem).


This time, I have been able to print without a problem the PRUSA logo model, at its intended speed and temperature. So, for now, it all seems good. And, once again, while the wait was long, I can tell you that I received good and friendly support that focused on solving my problem and getting my printer working. Kudos to PR for that.

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