3D print time remaining keeps going up?


I’m new and just got my Snapmaker 2.0 yesterday. Super excited to finally get making.
I successfully printed a Benchy yesterday and am very impressed.

Earlier today I started a larger print which when it started was estimated to take 23 hours.
It has now been printing for over 7 hours and the time remaining is now showing 27 hours remaining.

Is this normal that the time estimate is that wrong and keeps going up?

Wow, that’s a big difference. Unfortunately estimating print times accurately is quite a difficult problem, but there are some tricks that can help the estimator give a more meaningful estimation.

Print time is sometimes estimated simply by looking at all the gcode yet to run in a file and adding up all of the moves based on length and speed and calculating time that way. Unfortunately a simple approach like that will not account for the printer’s acceleration limiting and jerk limiting functionality (which help to minimize ripples and other distortions from trying to change directions too fast).

If you happened to be printing something with a very fast maximum print speed that happens to be limited by the acceleration settings of the printer, then you’ll end up slowing way down on the corners of every move. This will result in each line of gcode taking slightly longer to perform than the simple estimator guessed it might.

I’m sure there may be other factors at play also, but the answer to your question is yes, print times are usually wrong, to some degree at least. How wrong depends on many things, and your example is pretty extreme, so maybe someone else can chime in with some other factors that may be contributing.

Some of the tricks I’m aware of to trick the estimator into being more accurate involve telling a slicer more information so that it can generate moves that won’t ask the printer to violate any programmed limits, minimizing the estimated error of each line of gcode’s execution time. Cura is capable of this, for more information see here: http://lokspace.eu/how-to-make-cura-accurately-estimate-the-print-time/

Glad to hear your Benchy turned out well! That’s always very exciting.

Now that this long print completed and I’ve also printed a few more prints to have some more experience I’ve found that the original estimate right as the print starts so far was actually pretty spot on and correct, but basically once it starts and keeps counting it just get’s wonky.

So for the long print that I mentioned above, it did actually finish in a bit over 23 hours as the original estimate said.