Posts: 134
Joined: Tue Mar 29, 2016 7:47 pm

I think I figured out why S3D print times are so off and how to fix it

Sat Feb 09, 2019 10:21 pm

Well I can't fix it but I think I know how YOU guys can fix it :-)

I have a 200mm print going right now. S3D says 7 hours. its been over 7 hours and I am at 28% so estimating actual print time of 30hrs or so.

I think I know WHY its so "off"

jerk and acceleration. I don't think S3D is calculating jerk and acceleration properly into the equation AND I am pretty sure its not accounting for my Start Code script where I alter the Jerk and Acceleration with M205 commands.

basically the less "turns and changes" the print has the more accurate simplify 3d seems to be form me.

the current print I am making (the happy pilot gcode file is 83mb!!) with no infill 4 perimeters. but the "surface" detail on the model is simply ridiculous!

I set my Jerk to X5 and my acceleration to P500 T1000

so I Have these lines in my start script

M205 X5
M204 P500 T1000

I don't think this is being factored into the print time estimate calculations.

ALSO some of these machines have firmware hard ceilings (values they won't go beyond)

for example on older creality machines (not sure about newer) Retraction speed for the extruder was hard set at 25mm/s no matter how high a value I put in the slicer it was going to be 25mm/s

same with movement speed. my flashforge guider II appears to be hard set for travel speed at around 80-100mm/s

I set it for 150mm/s no change in print speed which made the slicer prediction that much more inaccurate.

SO for a partial fix end users can try and find out what they maxes are and do not program higher than that in the slicer (which will make it more accurate)

but you guys might also need to account for manual jerk and acceleration settings. OR have an entry box where we can specify these values so they are calculated properly in your print time estimations math.

it would also be nice if I COULD in fact enter these values for jerk and acceleration and S3D inputs the M205 and M204 commands itself and of course accounts for them in its calculations. even let me CHANGE it for different processes ie big round circles high acceleration and jerk. sharp corners LOW jerk and acc etc..

I can't upload a Factory file. its too large but its easy enough to make

scale to 195mm tall. 3 bottoms 3 tops 4 perimeters 0 infill 60mm/s 80% under 30% first layer under.

slicer predicts something around 7 hrs.

actual print time estimate based on current status of ongoing print 28-32 hrs. now higher up the model there are fewer "fine details" for it to apply jerk and acceleration changes too so it might actually end up faster but I doubt less than 20hrs. we shall see in 14-20 hrs :-)

Two Tree Sapphire S 200mm cubed core xy machine 0.4mm nozzle.

gcode analyzer is telling me 15hrs. we shall see. either way we are past S3D's prediction and only at 28%

Posts: 420
Joined: Wed Jun 20, 2018 11:45 am

Re: I think I figured out why S3D print times are so off and how to fix it

Mon Feb 11, 2019 11:41 am

Our print time estimates are based on preset jerk and acceleration settings. During our extended testing period we tested numerous popular printers to decide which values to use that would fit with a majority of our user's printers. You're correct that at this time we're not scraping the manual start code lines to grab manually specified jerk and acceleration values. Perhaps in the future we may move to a manual input system. And that's why I've moved this topic to feature requests.

Please let me know here if manual entry of your machine's accel and jerk values is something you'd be excited for!
"A bird does not sing because it has an answer. It sings because it has a song."

Posts: 251
Joined: Mon Feb 01, 2016 11:36 am

Re: I think I figured out why S3D print times are so off and how to fix it

Mon Feb 11, 2019 11:52 am

I would love to see accel and jerk settings for different build features and moves integrated in to the UI.

Posts: 134
Joined: Tue Mar 29, 2016 7:47 pm

Re: I think I figured out why S3D print times are so off and how to fix it

Mon Feb 11, 2019 11:59 am

Hopefully this is a feature that will be added because it is the reason pretty good times are so off for a large number of prints and for any printers that have default values that are different from the defaults that your slicer assumes

Proper integration of jerk and acceleration and find control over it would be nice but I think as a minimum just account for it for example slice the sample file that I included with the settings I specified and then adjust your internal algorithm to account for a jerk of 5 and a print acceleration of 500 and see what your time estimate changes to

By the way the print ended up taking a bit over 27 hours 20 more hours than predicted but this was a worst-case scenario maximum number of acceleration changes so all of these small errors greatly over time

Of course the print came out fantastic image attached :-)

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