Change in print time and not wanting to actually print

[tmrevlje 1]

Hi

I have an interesting problem, which I have no clue why it happened or even worse how to fix it.

Until yesterday afternoon everything was pretty much printing as it should now all of a sudden for let's say an object which Cura says would print 2h 12mins, and when I put it on SD card and insert it into the printer, when pressing Print it initially also says 2hours, but then things change.

1.) All of a sudden it says Time left 6 hours (no matter which object I want to print).

2.) Buildplate lifts up, but the print head remains in the front left corner with material oozing out as if it started the process, but the printhead just doesn't move to position and starts to build.

Hmmm... Any suggestions? The first time this happened was yesterday 1 min till the end of a print, when it said 1 min left, and all of a sudden it went to "Time left 6 hours" and kept oozing material onto an almost finished object. I did a Factory reset yesterday evening when this first happened, but it didn't help much. I am seeing the same problem today.

Help :???:

 

[Dim3nsioneer 558]

Check the gcode file on the sdcard. Maybe the file is empty?

Always eject the sdcard before removing from your computer...

[tmrevlje 1]

Yep good call, that was the problem. Gcode being "empty". Did a swipe of all gcodes (pretty much just the default ones) generated new gcode for a model, ejected the SD card and off we go - printing again

Thanks Dim3nsioneer

EDITED: Although, I was thinking if that was the case (and it obviuosly was), why would at the final minute of my print from yesterday evening all of a sudden go from 1 min left to 6 hours remaining. Could it be that because of not ejecting the SD card properly it messed up the last part (sorry if that sounded stupid but I am no developer) of the gcode?

 

[Dim3nsioneer 558]

No, the time forecast during the last minute of a print is more or less random. Precise time forecast is difficult on the UM2 as cpu power is limited.

 

[tmrevlje 1]

Ah ok, although up till now the time was pretty much dead on, counting to the last seconds and the print actually finished on time.

On another note, just wanted to add to this post that I am experiencing the same behaviour (on the same model, the open rose from thingiverse). After it's done (time countdown wise) it goes to Time remaining 6 hours and keeps moving the head away from model for a few seconds (as if wanting it to allow to cool down a bit) then going back on the model to add a few more layers, even though in all honesty I believe the model is finished.

I have to make another rose any way, so this time I just might leave it and see how long it will be in this loop. Will report back.

 

[SandervG 1,521]

I think that is the minimal cooling time you see in play, where the head moves away and gives the layer some time to cool down. Without that the heat of the nozzle will probably melt the previous layer again creating a rather rough surface finish..

 

[tmrevlje 1]

Yea I thought it might be that since I did set it to 8 sec (Minimal layer time setting). So I think I will just leave it finish and see what happens - although the 1 min to 6 hours time change distracts me and I then think it must be a "bug" or something.

Will report back, thanks Sander Dim3nsioneer

 

[nallath 1,124]

Might also be a corrupted SD card.

 

[tmrevlje 1]

Soooo now that my third rose is finally finished, a report follows. So the print finished fine, just when the countdown got down to 6 seconds or so was a bit jumping up and down (trying to estimate I guess), but that's I'm guessing due to the print head moving out of the way for a few seconds, to let the top layer cool down it gets a bit confused.

So at the end it did again say 6 hours remaining, however the print ended well only a minute or two later, so again Sander you were right.

One thing that did bother me though and it might be that I made a setting which is doing this and I don't know about it (I am guessing something to do with retraction?) is that when the print head moves away from the print to let it cool down a bit, the material doesn't stop extruding from the nozzle, which means that of course some of it acumulates and when the print head decides it's time to continue printing it adds this small blob of material on to the layer, which results you can imagine how in unwanted artifacts. Also when the printhead moves to cool down the top layers, it drags a string with it so the end result at the very top of the print is stringiness - which can be of course cut off later.

So any ideas how to disable the extrusion of material during the "cool off period" when the print head gets away from the print for a few secs?

Aaand a nice little photo of the rose for you all

 

[pm_dude 27]

You cant prevent the material to flow. Regardless the amount of retraction the nozzle will stay hot and presure will push the material out (quote taken from many seniors here ).

I also sometimes have the remaining timer to show 6 hours remaining when its prediction passes time zero. No worries . you may also notice that you can get the predicted time to be completely wrong just by staying it the tune menu for a while. I had a 17 hour print that was showing 50 hours left today.

[gr5 2,265]

is that when the print head moves away from the print to let it cool down a bit, the material doesn't stop extruding from the nozzle, which means that of course some of it acumulates and when the print head decides it's time to continue printing it adds this small blob of material on to the layer, which results you can imagine how in unwanted artifacts. Also when the printhead moves to cool down the top layers, it drags a string with it so the end result at the very top of the print is stringiness - which can be of course cut off later.

 

It's does retract but it keeps extruding (very very slowly) anyway due to heat expansion. You can't stop it.

The best fix is to print a skinny tower on either side of the part. This will avoid the "cool head lift" feature you are talking about and keep the tips of the rose from getting too hot. But usually these cool head lift blobs are easy enough to remove/break off.