Sudden Temperature Change - Prusa Mini  

Sudden Temperature Change - Prusa Mini

Hello All,

I have just faced something very weird (for me). I got my Mini last year sometime and since then I have only used (partially) one filament spool (eSun PLA+). Haven't printed a lot but every time I did, it worked perfectly fine. Then, since about early June this year, I just left it sitting on the table and not printing anything.

In the meanwhile, I had to re-do my computer (didn't backup any profile etc. from prusa slicer). I just installed the latest version when I re-installed windows (I am on 2.3.3.+win64). Yesterday I wanted to print a couple of files, so thought to upgrade the firmware first to the latest release. (I was on 4.3.0 before). 

Did the upgrade, used the default profiles to export the gcode, it worked for one part I guess but then suddenly I started to hear clicking sounds and no filament coming out at all. From there, I tried a lot of things:

1- Tried purging (nothing came out)

2- Tried unloading filament (it was jammed so didn't even move out of the hot/heat end

3- Then I detached the long PTFE tube, filament was still stuck inside, even on heating the nozzle couldn't pull it out. 

4- Got the smaller PTFE tube out from the hot end, the filament was stuck quite bad there but after wrestling with it for some time I was able to get it out eventually. 

5- Re-tried after unloading-reloading the filament, same thing happened. jammed almost instantly.

6- Tried a couple old g-code files (that I had exported earlier using last whatever version of the slicer I was using a few months back), same result, jam. 

7- Then I thought maybe the filament has gone bad since it has been sitting on the table for some time now, so got another brand new spool of the same brand (esun PLA+), and tried again. Same result. Instant jam.

8- I checked the old gcode files, the temperature being set was 210/60 which I was using now as well. But it just won't print. 

9- Then I tried the original prusament (that came with the printer, had it lying around). Well, it printed perfectly fine. 

10- Tried the eSun again, same problem again. 

11-Back to prusament, perfect print again.

12- Tried to go through forums, looking for possible explanations, saw a couple of posts where people said that eSun required 20-30 degrees above regular temps, thought to give it a try.

13- tried a few temperature settings, and finally got 250/60 to work. Anything below this would cause the filament jam or under extrusion now. 

14- Rolled back the latest firmware back to 4.3.0 to see if anything changes, but it changed nothing. Lower temps are still causing jams with this filament. 

15- Now I have got it working on this temperature, tried a couple of test prints all good (except I couldn't calibrate first layer using this filament as it just jams on the first layer calibration temperature settings, as a workaround I measured the calibration on a normal print, then used prusament filament to actually calibrate using the same z-height, so now it works fine for eSun Filament). 

My question is, can someone please explain what could have caused this? All of a sudden the temperature which was working absolutely fine stopped to work and now I have to use additional 40 degrees for it to work properly. Can't understand what is going on at all.

I would have thought the filament went bad, but then exactly the same is happening with a brand new out of the sealed box filament so something definitely changed with the printer/firmware/slicer but I can't understand. I am just glad that after about a whole day of constant experimentation I finally got it working again but would love to have your comments on the possible causes.

Thanks.