Question mark on LCD display after time remaining estimate
I just had a question mark show up after the time remaining display on the LCD while running a print on my new MK3S. I hadn't seen that before and I didn't get any hits searching the forums. I noticed this print job ran 4:22 instead of the initial 3:36 prediction.
Any information on the question mark display?
Maybe that is what happens when the estimated time runs out, I haven’t ever seen that before though.
That sounds like a very good theory. By the time I checked it, the remaining estimate was about right, but I hadn't paid attention during the middle part of the run to see what happened as the original predicted time passed.
Something to keep an eye on in the future.
Is your speed (">>") anything other than 100%? That will do exactly this.
Estimated time cannot "run out". It's not a real timer, it's controlled by special gcode lines and not a real timer.
I've always left the speed on 100% on the LCD, so that shouldn't have been the cause this time.
I just got the printer and have only run half a dozen prints. Still getting used to things.
That's a good thing to be aware of, though. Thanks for mentioning it.
Once in a while, randomly on my printer, the SPEED adjustment becomes active, any use of the knob will change it. It's one of those "bump in the night" firmware issues that pops up from time to time. When the knob is active, and you do something like look at another menu, you can turn it a notch just by pushing in; and that trips the ? feature.
That's certainly possible. I've been scrolling around looking at things while printing because this printer's new to me. I could maybe have bumped that. Next time I see a question mark there I'll certainly look at the speed setting. Thanks for adding to my knowledge of this printer.
I see this happening as well. It doesn't always happen, but sometimes it does. The question mark is there right at the start of the print, so it's not time running out issue, and I'm pretty sure I'm not touching the speed control. Mostly I print through Octoprint, so not sure if this could be related to that. Anyone figure what that question mark means?
I have always taken the question mark to mean the printer has no idea how much time is remaining.
As I recall, slicing with Cura will give that result.
PrusaSlicer makes the time guesstimate part of the GCode file name. That is good enough for me.
And a best guess is all it is. Don't use it to time your eggs.
It is very easy to bump the dial when printing. Pretty sure I've seen the default action is increment or decrement print speed, so it is easy to get the ?
If you deliberately or intentionally adjust speed during a print with the front knob, the time estimate will be off and it will display a question mark. It will retain that setting between prints until you set it back or cycle power. I've added a gcode command to the start of every print to reset it to 100.
To be 100% positive, post a pic of the front panel.
I did read the manual when I built the printer and started using it. They did mention using the knob to adjust the speed while printing, but I confused that with having to be in the Tune menu, which they had mentioned elsewhere. Re-reading I see that it's also true in the main display mode. The reason I didn't notice it while playing with the knob and seeing the filename scroll is because if I turn the knob slowly it doesn't start adjusting the speed right away, while the file name scrolling is immediate. If I spin the dial faster, or further, it then starts adjusting the speed as intended by the developers.
And when you do that, you get the question mark after the time estimate, which makes sense. Or sort of makes sense. Really, it seems the software should be able to just scale the time remaining according to the speed ratio. By the way, my time remaining estimates seem to be right on the money in general.
[...] Really, it seems the software should be able to just scale the time remaining according to the speed ratio. By the way, my time remaining estimates seem to be right on the money in general.
Keep in mind that "the software" in this case is being executed by an 8 bit controller that is busily trying to keep up with the actual print job, so taking the time to recalculate a displayed value of questionable value on every clock of the knob is not particularly desirable. Add to that the complication of scaling in any meaningful way -- do we want an 8 bit controller interpreting the gcode to determine the impact of acceleration and jerk in addition to cumulative moves? -- and I wouldn't consider this much of a priority.
Excellent points. Makes perfect sense. I forgot about the tiny brain inside the box and the subtleties of truly estimating the printing time:-)
Actually I don't think the machine works out the time at all. I think those times are inserted into the gcode by Prusa Slicer. The machine just updates the display when it gets to those lines. When you change the print speed via the interface all it can tell is that they aren't valid any more so adds the question marks.
Its also why if you use other slicers that don't insert the time codes you don't get any time remaining values at all.
Just checked and its the M73 commands in the gcode file from the looks of it. Parameters are stored in seconds I think so all the printer is doing is converting seconds remaining as listed in the sliced file and displaying it as days, hours, minutes.
I did a check. Indeed, turning the knob while printing will change the print speed and add a question mark to the time remaining estimate (I had no idea that turning the knob on the Info screen did anything). If you turn the knob back to roughly where it originally was, the question mark goes away.
And changing the speed via the dial does in fact adjust the time remaining; but the time shown with the ? is less accurate due to machine limitations. Some things are firmware limited for speed and the gcode is where the times originate (the slicer does the calculation). Errors between displayed time and actual print time at increased speeds are expected.