I need stronger, solid infill Carbon Fiber type parts and enclosures and have the upgraded hardened steel 0.4mm nozzle. I have been attempting to calibrate on a more basic specialty filament (3DXTECH PETG-CF) within the MK4 Prusa enclosure and I use the recommended NANO polymer adhesive advertised by 3DXTECH.

Issues:

- critical thermistor failure requiring replacement within the first 25 attempted prints.

- z calibration has been poor, requiring manual adjustment in prusa slicer to prevent the nozzle from scraping and accumulating petg gunk on the nozzle during prints

- complete failure to print supports correctly. This has been the main issue. For context I am talking about small rectangular box enclosures for electronics that have holes for antenna ports screws, power ports ect. These are not complicated prints. I've watched the MK4 basically attempt to print supports in mid air before my eyes. I continue to try almost every possible combination of support type, speed, flow rate, interface distance.. ect with no success.

These 4 machines just kept having problems on problems. First the Prusa flashdrives just went corrupt really shortly after we started using them. 
We tried Prusa connect and prusa link which were great on paper, but way too slow from time to time (and we are not hobbyists so we need a repeatable process, we can't just use prusa connect on mondays and do something else the rest of the week). So we bought brand new sandisk usb drives but problems kept arriving, blue screens at startup or during prints, prints failing due to various temp or fan issues, shitty quality prints out of nowhere even using PLA on simple prints. We tried input shaper but I felt like that got things worse quality wise so we quickly went back to trying normal printing.

We contacted Prusa support, not really knowing were to start, we sent them videos, photos, they keep asking us for more pictures, asking more questions but it just feels like a never ending list of problem that we really don't have the time to deal with. Really, it's like they are asking "what's the problem, exactly ? " and I feel embarassed because I don't even know where to start since my staff reports problems with the printers almost every day. I feel like investigating on so many issues on brand new machines is a waste of time for me and my staff. It's a shame because 3D printers were some of the least problematic machines in the shop and everyone used to love using them. Nowadays we do everything we can to avoid having to use them. My staff recently took the MK3s off their storage boxes and restarted using them instead of the MK4.

Some of you might think this is a fake review to make prusa look bad online. I wish it were (at least I'd be making money from the chinese or sthing), but no. The worst thing is, we hesitated a lot as some other printer from some other brand had just come out when we made the choice to go with the MK4, we had been long time lovers of the MK3s and of the Prusa Spirit and we thought maybe we aren't buying the best printer, but at least it will be reliable, but it's been anything but reliable... and I must say I deeply regret my choice. 

Roman, CEO of  Get-quark pegboards

Posted by: @m3d-2

Guys I wrote a topic but I haven't received any feedback yet, I'll write it here maybe someone has a solution, when I insert magnets or something else into the prints when restarting from the break the filament is not under pressure, has this happened to you?

- PEI sheet delaminated immediately. Replaced with a spare sheet from my MK3 stock. Maybe a bad batch? I'm ordering more and testing.

- Fan self-test always failed, although fans appear to be working properly. The official support worked with me to resolve it (thanks!).

- The cable for the touch screen module was a little too short for the instructions of the official enclosure.

The previous MK3+ arrived with a chunk of PLA in the hot end as usual: they test-print and then cut the filament. When I tried to unload it, it broke under the gears and turned into a big mess. I had to disassemble the hot end almost completely in order to take that out and continue with the commissioning of the printer. But the MK4 unloaded that PLA with no issue.

Been reading this thread mostly to figure out if I am getting in trouble or truly getting a next generation machine.... Obviously, I might get biased questions here.

Also own a A1 Mini and it is quite impressive.

I really want to like this printer and hopefully this has solved issue and I can work on printing and not the printer.