Can Cura go stupid and double extrude?

[Mozella 0]

I've been using Cura 3.6.0 with Octoprint and a Tevo Black Widow for a while now.  I spent a lot of time upgrading the printer and fine tuning nearly everything over a long period of time.  Eventually I achieved near perfect results under nearly all circumstances.  My rig is so reliable and versatile that I can't remember the last time I changed anything either hardware or firmware.

 

However, three days ago without warning, the print quality became horrible.  It looked like massive over extrusion, but to an extent that was so severe, that I suspected something else must be defective.  The print nozzle was plowing through the print to a degree I've never seen before.  My first guess was a Z axis fault.

I checked the obvious mechanical things like set screws, belt tension, etc.  I re-calibrated my Z axis and calibrated the Extruder as well........ all OK.

Thinking it might be a driver, I did some driver swapping between a spare, the extruder, the Z axis and the Y axis with no change to the problem. 

I experimented with some settings and discovered that I could make a good test print if I dialed the filament flow down to 50%.  What's up with that?  It made no sense. I started thinking how could my printer suddenly double the feed rate without warning and without having changed anything.  The fact that my extruder calibration was perfect added to the confusion.

 

A year ago I had what I thought was a driver overheating problem which, after a LOT of fiddling around, turned out to be a defective main board, so I ordered a new board and a fresh set of drivers just to be on the safe side.  I'd rather spend 50 bucks than spend another full day pulling my hair out chasing a mystery.

While waiting for the parts I re flashed the Marlin firmware............ no joy.

 

A few hours ago I upgraded to Cura 4.0 and now the printer is behaving perfectly, just like it used to do.  I'm partly happy, but not completely thrilled because I hate it when things go wrong without explanation and I also don't like it when the repair doesn't make sense.

 

I'm not sure Cura was at fault, but upgrading did in fact fix my problem.  How could the older version of Cura suddenly double the extrusion speed?  Or am I barking up the wrong tree?

 

S

[smartavionics 288]

Hello @Mozella, if you use 2.85mm filament and, somehow, the old Cura thought it should be using 1.7mm filament, that would probably account for it. Just guessing, really.

Edited April 20 by smartavionics

[Mozella 0]

I've never had anything other than 1.75 filament near this printer; nevertheless, it's something that crossed my mind so I checked the label as well as measuring the filament itself just to be sure.