Cura time prediction wrong?


#1

I’m printing something that was sliced in Cura and the time it said it would take was 2h10min. 2h54min have passed and the printing is still in half, which leads me to believe that the printing will take about 4 hours, instead of 2.

Is there anything I can do to make Cura times more precise for the Snapmaker? I’m using the “Fast print” profile that I copied from Snapmaker 3D.


#2

Hi Guz

I too have struck this issue. I just did a Google search with “cura time estimate on print” and it came up with many hits; we may have to sift through these for hints.

As an example have a look at this link https://github.com/Ultimaker/Cura/issues/2414

Doug


#3

The way it was explained to me is that slicers assume that the printer is able to do exactly what it says for it to do. This can include accelerate at insane rates. The reality of the matter is there are limits to how fast the printer can accelerate. SnapMaker is using lead screws and its components are not light. As such it does not have the fastest acceleration when compared to a delta or a CoreXY style printer. As such if your print requires a ton of quick direction changes of the print head it will take considerably longer than what Cura thinks it will take.


#4

That makes sense. I wonder if not having a preset printer profile in Cura makes a difference too. At work we have a Ultimaker 2+, and speeds on that thing is fast; 70mm/s print, 120mm/s travel. And eventhough Cura is made for Ultimaker printers, the print times are not accurate either. But they are much more accurate than the estimates for the Snapmaker.


#5

As I’m having over 100% difference from predicted to actual when using Cura (Cura on PC, sending to Octopi), I’m trying to “calibrate” cura engine so it can better predict.

Following this link http://lokspace.eu/how-to-make-cura-accurately-estimate-the-print-time/, it is suggested to set acceleration speeds and retraction speeds. But its says:

 "In Marlin’s Configuration.h, this parameter is called “DEFAULT_MAX_ACCELERATION”.
You can also view your current limits from the printer’s menu: Control -> Motion -> Acceleration -> Amax X (and Amax Y)."

How can I get these values from Snapmaker (and others firmware values)?

Thanks!


#6

Answering my own question, http://marlinfw.org/docs/gcode/M201.html

And the default acceleration in my Cura version was up to 3 times larger than the max. set in Snapmaker firmware. Testing with new settings to see how accurate it will be. Next steps would be to try out faster accelerations to improve printing time :wink:

Results of M503 commad, showing my firmware defaults:

Send: N89370 M503*32
Recv: echo:Steps per unit:
Recv: echo:  M92 X400.00 Y400.00 Z400.00 E92.60
Recv: echo:Maximum feedrates (mm/s):
Recv: echo:  M203 X300.00 Y300.00 Z5.00 E25.00
Recv: echo:Maximum Acceleration (mm/s2):
Recv: echo:  M201 X1000 Y1000 Z100 E10000 X_CNC100 Y_CNC100 Z_CNC100 E_CNC100 X_LASER3600 Y_LASER3600 Z_LASER3600
Recv: echo:Accelerations: P=printing, R=retract and T=travel
Recv: echo:  M204 P1000.00 R1000.00 T1000.00
Recv: echo:Advanced variables: S=Min feedrate (mm/s), T=Min travel feedrate (mm/s), B=minimum segment time (ms), X=maximum XY jerk (mm/s),  Z=maximum Z jerk (mm/s),  E=maximum E jerk (mm/s)
Recv: echo:  M205 S0.00 T0.00 B20000 X20.00 Z0.40 E5.00

#7

@rgriffogoes Did you find the proper acceleration values to set in Cura for more accurate time estimates? It seems like you almost got the answer and it would help the community a lot!


#8

I didn’t explore it further, so my current setup is using Snapmaker’s firmware values and still gives some incorrect prediction (but around 20%, not 100% as before).

I think after setting up OctoPi with a camera, I stopped caring too much about printing time (I’m also not printing much these days… somehow busy with custom laser engraved wood key fobs and “leather”/plastic phone cases).